Although the Czochralski method for large-size crystal growth has been developed for over a century, the in-situ acquisition of interface states becomes a challenge due to the extreme environment of high temperature, high pressure, strong electromagnetic interference, and the coexistence of solid, liquid, and gas phases. To address the challenge of real-time monitoring of interface instability during the growth of large lithium niobate crystals, we combined the temporal evolution of key process parameters such as pulling rate, rotation rate, and power-of a 4-inch optical-grade lithium niobate crystal with the synchronous time of its growth interface's intrinsic growth interface electromotive force (GEMF). This integration enabled a full-process in-situ analysis of how growth conditions affect the growth interface. The GEMF analysis revealed pronounced interface instability phenomena, which sensitively, quantitatively, and in real time reflect temperature fluctuations at the interface and the inversion phenomena during shoulder growth, thus filling the detection blind spots left by conventional load-cell sensors and thermocouples. In this work, a correlation model between GEMF and interfacial heat and mass transfer was established, and an in-situ method was proposed to evaluate the stability of the crystal growth interface, providing a crucial theoretical foundation and an innovative technical approach for the preparation of high-quality, large-size crystals.

For the synthesis of CLN polycrystalline powder, high purity (99.99%) materials of Li₂CO₃ and Nb₂O₅ in a molar ratio of 0.946 were mixed, ground and calcined. Afterwards, the ground mixture was molten in a platinum crucible in a CZ furnace. The key process parameters such as pulling rate, rotation rate and power of 4 in optical grade lithium niobate crystal were synchronously recorded together with the intrinsic growth interface electromotive force (GEMF), thereby establishing a quantitative correlation between GEMF signals and heat-mass transport. This approach enabled in-situ detection and real-time feedback control of interface instabilities, including temperature fluctuations and interface inversion, during the shoulder growth stage. The seed temperature (T_s) and crucible temperature (T_l) were monitored by thermocouples connected to a model Eurotherm 2404 thermometer (±0.1 ℃). Platinum wires were employed as leads and electrodes, with a positive electrode affixed to the seed and a negative electrode to the base of the platinum crucible. The GEMF between the growing crystal and the melt was measured by a model Keithley 2100 micro-voltmeter (±0.1 µV).

The pronounced interface fluctuations and the intense interface inversion during the shouldering stage phenomena that are difficult to detect using conventional methods can be clearly determined. The validation with extensive production data from large-size crystals demonstrates that compared with conventional detection techniques, GEMF can provide real-time and valuable information on the interface state. Furthermore, a quantitative relationship between GEMF deviation and crystal mass loss is established and a feedback strategy for regulating interface stability is proposed via integrating GEMF measurements with time-series analysis of crystal growth parameters.

Based on real-time trajectory analysis of heat and mass transfer during interface inversion, a control criterion for maintaining stable interface growth is established. During LN crystal growth, the GEMF trajectory can evolve smoothly along the reference trend represented by the Seebeck baseline, avoiding sharp deviations. When the G-T_s curve exhibits a tendency to deviate from the Seebeck baseline, it indicates that interface inversion is imminent. At this stage, reducing the rotation rate or enhancing the radial temperature gradient can suppress interface inversion and stabilize crystal growth.

In this study, the growth interface electromotive force (GEMF) technique was combined with the key process parameters such as pulling rate, crystal rotation rate and heating power to enable the in-situ diagnostics of the 4-inch lithium niobate (LN) crystal growth process. The results showed that the supercooling electromotive force component of the GEMF signal could accurately reflect the periodic temperature fluctuations at the crystal growth interface, which were identified as the primary cause of diameter deviations during the constant-diameter stage. Furthermore, GEMF measurements precisely captured the interface flipping phenomenon during the shouldering process. The quantitative relationships among electrical signal deviation, temperature fluctuation, and mass response were elucidated via establishing a simplified one-dimensional heat-mass transport model for the boundary layer. Local fluctuations in heat flux could induce thermal-equilibrium shifts at the interface, thereby affecting crystallization rate and mass stability. Compared with conventional monitoring methods, the proposed model enabled real-time mapping from electrical signals to the physical growth state, providing an effective technical approach for elucidating interface instability mechanisms, predicting crystallization quality deviations, and constructing closed-loop feedback control systems for the interface. This methodology could have a significant promise for the controllable growth of large-size, high-quality crystals.

Mid-infrared (MIR) lasers operating within a spectral region of 2.7-3.0 μm have a significant importance in applications such as laser surgery and remote sensing. Trivalent erbium (Er³⁺) ions are among the most efficient activators for MIR lasers, leveraging the ⁴I_11/2→⁴I_13/2 transition. Nevertheless, the realization of high-power and efficient laser output is often hindered due to the self-terminating effect and substantial thermal loading in Er³⁺-doped gain medium. This study was to investigate the high-performance Er³⁺-doped Gd₃Ga₅O₁₂ (GGG) and Lu₃Ga₅O₁₂ (LuGG) laser crystals with the low phonon energy and high thermal conductivity.

High-quality single crystals of Er: GGG, Er/Pr: GGG, and Er: LuGG were grown by the Czochralski method in an optimized atmosphere (i.e., 98% N₂ + 2% O₂) with iridium crucibles and (111)-oriented seeds. Raw materials underwent multi-step sintering to guarantee the phase purity. Comprehensive spectroscopic analysis was conducted on the polished samples. The room-temperature absorption spectra were determined by a model Lambda 900 spectrophotometer. The fluorescence spectra at the mid-infrared (MIR: 2500-3000 nm), near-infrared (NIR: 950-1750 nm) and upconversion (UC: 500-700 nm) bands were measured under 965/967 nm excitation by an optical parametric oscillator (OPO) or a xenon lamp using models FLS920 and FSP920 fluorescence spectrometers. The fluorescence decay curves for the ⁴I_11/2 and ⁴I_13/2 energy levels were recorded to determine the fluorescence lifetime. The laser performance was assessed under two pumping schemes (i.e., a xenon lamp and a 965 nm fiber-coupled laser diode (LD)). The crystals were fabricated into laser gain media of various sizes and doping profiles, including a bonded configuration (undoped GGG/56% Er: GGG) to alleviate thermal lensing. The continuous-wave (CW) performance was evaluated via input-output power curves, slope efficiency, laser threshold, and beam quality factor (M²). The passive Q-switching was implemented with two-dimensional materials (i.e., graphene and a Bi₂Te₃/graphene heterostructure) as saturable absorbers. The main pulsed laser metrics (i.e., pulse train profile, average output power, pulse width, repetition rate, and peak power) were systematically determined.

The as-grown crystals display a high optical quality with intense and broad absorption bands centered at 965 nm. The 30% Er, 0.5% Pr: GGG composition has a notably high absorption cross-section of 5.13×10^-21 cm² and a full width at half maximum (FWHM) of 15 nm, indicating a superior spectral overlap with commercial 980 nm InGaAs laser diodes and enabling efficient pump coupling. The incorporation of Pr³⁺ ions can enhance the MIR fluorescence emission based on a cross-relaxation energy transfer mechanism, i.e., ⁴I_13/2 (Er³⁺) + ³H₄ (Pr³⁺) → ⁴I_15/2 (Er³⁺) + ³F₄ (Pr³⁺). This process effectively depopulates the lower laser level (⁴I_13/2), leading to a reversal of the intrinsic lifetime ratio between metastable states. Specifically, a ratio of τ(⁴I_11/2)/τ(⁴I_13/2) of 2.348 appears in the sample 30% Er, 0.5% Pr:GGG, which is critical for overcoming the self-termination barrier in Er³⁺ -based~3 μm lasers.

Under 965 nm LD pumping, a CW laser emission at 2.75 μm is attained. The 56% Er: GGG crystal has a maximum output power of 325 mW with a slope efficiency of 16.15%. The bonded GGG/56% Er: GGG structure improves the thermal management, increasing the maximum power to 453 mW and the slope efficiency to 17.1%, while also improving beam quality (i.e., M² reduces from 1.68 to 1.48). The Er/Pr: GGG crystal (11% Er, 0.4% Pr) shows a superior thermal performance, reaching 372 mW output and a higher damage threshold, due to the lower Er³⁺ concentration and efficient energy transfer.

The passive Q-switching with graphene and Bi₂Te₃/graphene absorbers produce impressive pulsed outcomes. The graphene-based Q-switched bonded GGG/Er, Pr: GGG/GGG crystal has a maximum average power of 186 mW, a pulse width of 360 ns, and a repetition rate of 120.5 kHz, corresponding to a pulse energy of 1.54 μJ and a peak power exceeding 4.28 W. The Bi₂Te₃/graphene Q-switched Er: LuGG laser can deliver a higher average power of 274 mW with a shorter pulse width of 340 ns at 135 kHz, yielding a pulse energy of 2.03 μJ and a peak power of > 5.97 W. These findings affirm a potential of these materials in high-performance pulsed MIR lasers.

This work established Er³⁺-doped GGG and LuGG crystals as highly promising gain media for efficient ~2.75 μm mid-infrared lasers. The strategies of Pr³⁺ co-doping and crystal bonding proved effective in mitigating the self-terminating effect and thermal load, leading to the improvement of substantial performance. The effective operation in both continuous-wave and passively Q-switched regimes could underscore the applicability of these crystals in practical high-power MIR laser systems.

Visible-light lasers have applications in biology, medicine, and detection. Compared to conventional nonlinear frequency doubling methods for obtaining visible light lasers, it is possible to prepare laser crystals that directly emit a visible light via doping with rare-earth elements such as Pr³⁺, Sm³⁺, Tb³⁺, and Dy³⁺. For yellow light lasers, doping with Dy³⁺ is more suitable. The existing Dy³⁺-doped laser crystals are still at the theoretical stage, with a few experimental cases. Recently, a high-quality Dy³⁺-doped borate crystal GdMgB₅O₁₀ (Dy³⁺:GMB) is prepared to produce a yellow light laser at a wavelength of 580 nm. In this study, a plane-plane cavity laser was assembled using a 3 mm×3 mm×20 mm Y-cut Dy³⁺:GMB crystal with a 444 nm blue LD pump, achieving a laser output at 579.3 nm. The maximum output power reached 161 mW with a slope efficiency of 3.7% as using different output couplers at different transmission rates.

In this experiment, a 444 nm blue LD with a maximum power of 12 W was used as a pump source. The model of the blue LD pump was LSR444CP4-12W. The pump output a spatial light directly without fiber coupling and used air cooling to maintain a temperature of 25 ℃. The beam size at the output of the pump was 4.3 mm horizontally and 4.1 mm vertically. The beam remained parallel within 0.5 m and could be approximated as a parallel light. A plano-convex lens with a focal length of 150 mm was used. A Y-cut Dy:GMB crystal with the dimensions of 3 mm×3 mm×20 mm was used. The doping concentration of Dy³⁺ in the crystal was 6.08%, and the end faces of the crystal were polished but not coated for the blue wavelength band. The Dy:GMB crystal was wrapped in indium foil and placed in a water-cooled copper block, with the copper block's water cooling set to 20 ℃. The polarization direction of the pump light was vertical. Based on the polarization bsorption efficiency of the Dy:GMB crystal along different axes, the crystal was positioned in an optical path. The pump light absorption efficiency of the crystal was measured under non-lasing conditions. When the crystal was placed, the pump light absorption efficiency was 55%. The laser resonator consisted of two coated plane mirrors. IM was the input mirror for the pump light, with coating arameters that could reduce reflection and increase transmission at 444 nm. The measured transmission at 444 nm was 96%. It also had a high reflectivity at 579 nm with a reflectivity of≥99.8%. OC was the output coupler mirror, and the coated mirrors with 579 nm transmission rates of 1% and 2% were used. A long-pass edge filter with a cutoff wavelength of 450 nm was placed at the laser output to effectively reduce the impact of pump light on power measurements. After the output power measurement, a Glan prism was used to analyze the polarization of the output laser.

The output wavelength of the experimental laser is 579.3 nm, without other wavelengths detected. In the experiment with an OC transmission rate of 1%, a laser generation begins when the crystal absorbes 1.94 W of pump power, achieving a maximum output power of 161 mW and a slope efficiency of 3.7%. In the experiment with an OC transmission rate of 2%, a laser generation starts at an absorption power of 2.81 W, having a maximum output power of 129 mW with a slightly lower slope efficiency of 3.6%. No saturation in laser output power occurs in either set of experiments. The laser threshold and output power using an OC transmission rate of 1% are slightly greater than those using an OC transmission rate of 2%, which is consistent with the results reported in a previous study. Based on the slope efficiency, it is estimated that under the same pump absorption power, the maximum output power of the laser in this experiment can exceed 628 mW. There are three methods to improve the output power and slope efficiency of the laser via comparing the performance of the crystal in two separate experiments. The first method is to use a higher-power and higher-quality pump to enhance the absorption efficiency of the Dy:GMB crystal. The second method is to employ different types of laser cavities and optimize the coating parameters of the IM and OC, as well as shape the pump beam to achieve better spatial mode matching between the pump light and the laser cavity. The third method is to optimize the growth process to obtain X-cut or Z-cut crystals of sufficient length with varying Dy doping concentrations, as the emission cross-section of the Dy:GMB crystal is maximum at 578.5 nm along the E//Y direction.

A 579.3 nm yellow laser output with a maximum power of 161 mW and a slope efficiency of 3.7% was obtained using a plane-plane cavity laser setup with Dy:GMB crystal pumped by a 444 nm blue LD. An application potential of the crystal could be achieved via comparing the initial laser experiments with the same crystal using blue LDs at different wavelengths. This study could provide insights for future improvements in the output power and slope efficiency of lasers constructed with Dy:GMB crystals.

Lithium niobate crystal exhibits versatile properties including piezoelectric, nonlinear and birefringence. Its stable physicochemical characteristics, doping amenability, and suitability for high-quality optical waveguide fabrication make it promising for integrated optics. However, the growth of large-size lithium niobate crystals presents significant challenges, with several critical issues remaining unresolved. Firstly, its low thermal conductivity causes a heat accumulation at the crystal-melt interface due to mismatched latent heat transport and release rates. This leads to eccentric growth and interface remelting. Secondly, the large crucible required for large-size crystal growth results in a reduced radial temperature gradient across the melt surface and an oversized cold core, which complicates necking initiation and shouldering control, ultimately compromising crystallinity. Finally, fixed thermal field configurations fail to accommodate divergent thermal requirements across different growth stages as crystal size increases. In this study, the fixed thermal field configuration and methodologies for mitigating eccentric crystal growth were investigated. In addition, the impact of dynamic thermal fields on stage-specific thermal requirements during crystal growth was also analyzed.

This work conducted the Czochralski growth of 6 in CLN (congruent lithium niobate) crystals in a fixed thermal field. A preliminary 6 in thermal field was firstly designed according to the CLN crystal growth requirements, and then by root-cause analysis of eccentric growth and thermal field optimization. The crucible position relative to the induction coil was gradually elevated, while maintaining identical growth parameters. Subsequently, comparative experiments of fixed crucible position and constant process conditions with the diminished upper insulation assessed their impact on the eccentric growth. To resolve conflicting thermal requirements across growth stages, a dynamic thermal field Czochralski technique was developed via integrating an active afterheater. This enabled real-time regulation of the temperature gradient by adjusting power to the main heater and active afterheater. Comparative analysis of the constant-diameter lengths in grown crystals could demonstrate the efficacy of the dynamic thermal field technique.

In a fixed thermal field, the causes of eccentric growth during the late constant-diameter growth stage are analyzed. During the actual crystal growth, the melt level progressively decreases as the constant-diameter length increases, gradually revealing an exposed crucible wall effect. This reduces the radial temperature gradient across the melt surface. Simultaneously, a radiative influence from the crucible wall appears on the crystal intensifies. When crystallization latent heat cannot be efficiently transported from the crystal, a heat accumulation occurs, triggering random protrusions at the solid-liquid interface that radiate heat directly upward, resulting in eccentric growth. Thermal field optimization is achieved via elevating the crucible position relative to the induction coil and reducing upper insulation. Consequently, the constant-diameter length increases from 15 mm to approximately 70 mm, effectively mitigating an eccentric growth.

The development of a dynamic thermal field crystal growth technique, enabled by the introduction of an active afterheater, demonstrates critical advantages over conventional fixed thermal fields, i.e., 1) Fixed thermal fields exhibit temperature gradients solely determined by structural design, precluding manual intervention during growth. Conversely, dynamic thermal fields facilitate different temperature gradient control in different stages through coordinated power modulation of the primary and secondary heaters, thereby altering system heat dissipation, 2) Large-size crystal growth requires substantial melt volumes with a high thermal mass, resulting in prolonged adjustment response time and significant thermal hysteresis. The dynamic approach achieves a superior diameter control via directly manipulating furnace heat dissipation by an active afterheater power. This rapidly modifies temperature gradients within the crystal bulk and near the solid-liquid interface, reducing hysteresis and enabling diameter precision, and 3) Unlike fixed configurations necessitating furnace shutdowns due to thermal design failures, dynamic systems resolve thermal incompatibilities control through power adjustments to the MF (Medium-Frequency) Power Supply and active afterheater. This eliminates costly interruptions, saving both time and cost.

This work designed a fixed thermal field for 6 in CLN crystal growth. The analysis revealed that the primary cause of eccentric growth in 6 in CLN crystal was an insufficient radial temperature gradient across the melt surface during the late constant-diameter growth stage. The thermal field optimization was achieved via elevating the crucible position relative to the induction coil and reducing upper insulation, extending the constant-diameter length from 15 mm to approximately 70 mm.

To address limitations in fixed thermal field optimization, a dynamic thermal field Czochralski technique was developed, which enabled real-time regulation of temperature gradients during crystal growth. This approach could accommodate divergent thermal requirements across different growth stages, significantly mitigating an eccentric growth in 6 in CLN crystal and further increasing the constant-diameter length from 70 mm to 90 mm, thus establishing a novel paradigm for large-sizer crystal growth.

Lasers operating within a spectral range of 1.5-1.7 μm are essential for eye-safe applications like laser ranging, lidar, and optical communications, etc.. Nevertheless, conventional laser crystals such as Er:YAG and Er:LuYO₃ have limitations in emission cross-sections or attainable crystal dimensions, thereby constraining their utilization in high-power, large-scale laser systems. To address these challenges, the development of novel laser crystals with substantial crystal sizes and high emission cross-sections is thus imperative. Yttria-stabilized zirconia (YSZ) doped with rare-earth ions emerges as a promising candidate due to its disordered crystalline structure that enables a broader wavelength tunability and a reduced thermal loading under resonant pumping conditions. Specifically, erbium (Er³⁺) doped YSZ crystals have a significant potential due to its intense emission at 1.5 μm (⁴I_13/2→⁴F_15/2 transition) for eye-safe laser. This study was to investigate the growth of large-scale Er³⁺-doped YSZ crystals by a skull melting technique, and the optical and spectral properties were systematically investigated to explore a novel laser gain medium in the infra-red region.

Pure YSZ and Er³⁺-doped YSZ crystals (i.e., 0.36%, 1.60% and 2.54% in mole) were grown by a skull melting method (or a cold crucible technique), and a radio frequency (RF) generator was used to heat up the charges. A large-scale furnace with a diameter of approximately 150 cm was employed to accommodate the spontaneous nucleation. Graphite electrodes were used for initial arcing due to the poor conductivity of ZrO₂ at < 1200 ℃. At >1200 ℃, raw materials became an electric conductor to form the melting pool. The lowering mechanism started to work at a lowering rate of 2 mm/h, and the melt crystallized from the bottom to the top. After the growth, annealing process was performed to release the internal stresses. The phase and crystal structures of as-grown crystals were characterized by X-ray diffraction (XRD). The transmittance and absorption properties were analyzed by UV-Vis-NIR spectroscopy. The luminescence and decay curve were also systematically evaluated.

The results show that Large-sized YSZ and Er-doped YSZ crystals with the diameters and lengths of exceeding 150 mm (6 inches) are grown, representing the largest YSZ single crystals reported. The XRD patterns indicate the cubic structure with a preferred <111> preferred orientation. The lattice parameters increase slightly with Er³⁺ concentration, indicating the effective incorporation of Er³⁺ into the YSZ lattice. The transmission of exceeding 74% in the range of 400-1650 nm occurs for pure YSZ crystals, confirming relatively high crystalline qualities. The absorption spectra for Er-doped crystals show some characteristic peaks at 378, 408, 451, 489, 518, 546, 654, 971, 1460 nm and 1530 nm, corresponding to Er³⁺ transitions from the ground state ⁴F_15/2 to excited states such as ⁴G_11/2 and ⁴F_11/2. The most intense absorption band occurs at 971 nm, which is attributed to the ⁴F_15/2→⁴F_11/2 transition. Under 971 nm excitation, the emission spectra exhibit a dominant peak at 1530 nm for the ⁴I_13/2→⁴F_15/2 transition, which is ideal for eye-safe lasers. The great emission intensity appears at an Er³⁺ mole concentration of 1.60%, with an emission cross-section of 4.811×10^-20 cm², which is significantly higher than that of Er:YAG (i.e., 0.6×10^-20 cm²) and Er:LuYO₃ (i.e., 0.261×10^-20 cm²). Correspondingly, the decay time of YSZ: 0.36, YSZ: 1.60and YSZ: 2.54 crystals is 1.836 ms, 1.149 ms and 0.797 ms, respectively.

This study demonstrated the effective growth of large-scale (6-inch) YSZ and Er-doped YSZ crystals by a skull melting method. YSZ: Er crystals exhibited an intense emission at 1530 nm under 971 nm excitation. In particular, a high emission cross-section of 4.811×10^-20 cm² and suitable fluorescence lifetime of 1.149 ms appeared for Er³⁺ of 1.60% in mole. YSZ:Er crystals could be used as a highly promising gain medium for high-power, eye-safe lasers at 1.5 μm due to the ultra-large crystal size and relatively large emission cross-section.

This review represents a comprehensive and in-depth summary of the La₃Ga_5.5Nb_0.5O₁₄ (LGN) crystal, covering important achievements in various key aspects, such as crystal structure and basic properties, large-size growth technology, nonlinear optical properties, mid-infrared nonlinear optical properties, and applications. In terms of large-size crystal growth, some technical problems of thermal stress cracking and component segregation during the growth of LGN are solved, and the preparation of large-size single crystals with the diameters of 60-80 mm is stablized. Meanwhile, the LGN crystal has nonlinear optical properties and applications, which provides a support for the development of high-power mid-infrared laser systems.

In the future, we need to optimize the crystal growth to obtain more accurate temperature regulation, further shorten the growth cycle, improve the growth efficiency, reduce the internal defects, and improve the annealing process, to obtain larger size (≥4 inches) high-quality LGN crystal, providing a better material base for high-performance mid-infrared laser. In addition, it is also necessary to investigate the performance regulation mechanism of LGN hybrid crystals in depth, and further optimize their nonlinear optical properties via utilizing elemental doping and structural fine-tuning, such as improving the nonlinear coefficient and broadening the gain bandwidth, to provide nonlinear optics crystals with excellent performances for the realization of high-power OPCPA applications. Developing mid-infrared laser sources and optoelectronic devices can meet a demand for mid-infrared wavelength lasers in biomedicine, environmental monitoring, national defense, security, and etc..

This review analyzes critical oxygen control strategies in CZ silicon growth, essential for achieving substrate specifications across diverse applications. The primary approaches focus on reducing oxygen dissolution through thermal field design and crucible modification, optimizing melt convection and oxygen transport via rotation and magnetic fields, and enhancing free surface volatilization by controlling argon atmosphere.

Some challenges persist, requiring a further research to clarify fundamental mechanisms. Key uncertainties include the temperature dependence of oxygen solubility and the precise mechanism relating crucible temperature reduction to lower crystal oxygen levels (primarily due to reduced dissolution or altered flow patterns). Understanding the complex coupling among detailed magnetic field distributions, resulting melt flow patterns and oxygen transport also requires a further investigation. Quantifying the influence of argon shear stress interacting with Marangoni forces on the melt surface is equally essential for refining volatilization models.

Furthermore, complicating these challenges is the multi-variable, strongly coupled nature of the CZ system, which makes conventional trial-and-error optimization approaches time-consuming and costly. A future research should therefore prioritize the developing intelligent control systems that leverage artificial intelligence (AI) and machine learning for data-driven modeling, prediction, and efficient multi-parameter optimization.

The key formation mechanisms and electrical properties of oxygen-related defects remain some challenges. The crystal growth for 300 mm wafers involves complex multi-physics (i.e., thermal, flow, electromagnetic fields) in large systems (i.e., 34-37 in crucibles, 300-450 kg charge). Maintaining radial uniformity is difficult due to the V/G criterion (where V is pull rate, and G is axial temperature gradient). Deviations lead to vacancy-rich (V) or interstitial-rich (I) regions, with a transition zone prone to forming a ring of "P-band" native oxygen-related defects. This causes a radial non-uniformity in oxygen clustering during device processing, concerning the radial defect non-uniformity and nucleation anomalies in 300 mm crystals. We should also focus on the interaction between oxygen-related defects and metallic impurities in Cz-Si used for solar cells.

We can benefit from effective control of oxygen-related defect in Large-diameter Cz-Si. The effective control requires a multi-pronged approach, i.e., sophisticated crystal growth optimization (thermal/flow fields, magnetic fields, doping), strategic impurity engineering (nitrogen, isovalent dopants), and tailored thermal processing. A further research into defect interactions, advanced characterization, and multi-scale modeling is essential for pushing the performance limits of next-generation silicon devices.

For a challenge of global water scarcity, the development of efficient and sustainable freshwater production technologies is urgently needed. Solar-driven interfacial water evaporation (SIE) technology has attracted recent attention due to its eco-friendly and low-energy-consumption characteristics. However, the inherent intermittency of solar energy availability, both temporally and spatially, prevents SIE systems to maintain a high efficiency during nighttime, severely limiting further performance improvements. The introduction of phase change materials (i.e., PCMs) is generally considered as an effective approach to address the intermittency of solar water evaporation systems and enhance evaporation efficiency. Nevertheless, leakage issues associated with PCMs during their phase transition process significantly restrict their application scope. To overcome this problem, researchers are dedicated to developing porous mineral-based supporting materials. However, the performance of mineral carriers encapsulating PCMs in some existing studies still requires a further enhancement. Furthermore, the problem of low thermal conductivity in composite PCMs also hinders their application progress in SIE systems.

Halloysite-based aerogels represent a highly promising supporting material capable of preparing composite PCMs with high loading rates, good stability, and large thermal energy storage density. Carbon fiber can be incorporated at different ratios to enhance the thermal conductivity of the composite PCMs. This study was to investigate the thermal properties, photothermal conversion efficiency, and water evaporation rate within an SIE system for the composite PCMs, and analyze the enhancement mechanisms responsible for the improved water evaporation performance.

Dopamine was firstly used to coat halloysite to obtain dopamine-coated halloysite powder (HNTP), and then 1 g of the prepared HNTP powder was added into 40 mL of deionized water. After stirring uniformly, the mixture was ultrasonicated for 30 min. Afterwards, 1 g of sodium alginate (SA) was added to the resulting suspension under continuous stirring until the SA was completely dissolved. The mixture was evenly divided into four portions and transferred into molds. The samples were snap-frozen in a freezer until completely solidified and then freeze-dried (lyophilized) for 72 h. The aerogels were then washed with anhydrous ethanol and dried in an oven, ultimately yielding the halloysite-based aerogel HA. Halloysite-based aerogels with different carbon fiber contents were prepared via replacing HNTs proportionally with carbon fiber (CF). These aerogels were named as HCA 4∶1 and HCA 3∶2 based on a mass ratio of halloysite to carbon fiber.

The composite phase change materials (PCMs) were fabricated by a vacuum impregnation method. Myristic acid (MA) was placed in an oven and heated beyond its phase transition temperature until it completely melted into its liquid state. The prepared aerogels (i.e., HA, HCA 4∶1, HCA 3∶2) were then submerged in a liquid MA. Under vacuum conditions, the MA gradually infiltrated into the pores of the aerogels. After complete adsorption, the composite phase change materials (i.e., MA@HA, MA@HCA 4∶1, and MA@HCA 3∶2) were obtained.

The SEM images of the halloysite aerogel (HA) clearly reveal its abundant porous structure. HNTs are uniformly distributed within the three-dimensional network framework. This highly porous structure provides ample space for encapsulating the phase change material. The results of leakage tests confirm a high phase change material loading rate of up to 84% within the composite. A significant supercooling reduction also occurs. The latent heat of the sample MA@HCA 3∶2 measured is 140.65 J/g. The XRD patterns and FTIR spectra show no emergence of new peaks, indicating a superior compatibility between the MA and the aerogel without chemical reactions. This ensures the core thermal energy storage functionality of the MA remains unaffected. To enhance the thermal conductivity of MA@HA, carbon fiber (CF) is introduced as a thermal conductivity enhancer. The results measured by a thermal conductivity analyzer demonstrate that compared to MA@HA, the thermal conductivity of the composites with the incorporation of carbon fiber is increased by 158%. This significant improvement is attributed to a high intrinsic thermal conductivity of carbon fiber, which forms a continuous and oriented thermally conductive network within the composite, providing highly efficient pathways for heat transfer.

The composite PCMs can efficiently store thermal energy through sunlight absorption during the day and release this stored heat to drive water evaporation during the night due to their superior photothermal conversion and thermal conductivity properties. This effectively mitigates the bottleneck of conventional SIE technology, which relies solely on daytime solar energy for high-efficiency water production. Based on this principle, a novel SIE evaporator incorporating the halloysite aerogel composite PCMs can be designed. The results show that under one sun illumination after 3-h energy storage, the water evaporation rate of the MA@HCA 3∶2 sample is 4.21 times greater than that of pure water. The mechanisms behind this enhanced water evaporation performance are investigated. This work provides valuable insights and a reference basis for enhancing the efficiency of solar energy utilization and improving the effectiveness of seawater desalination.

This study fabricated a highly porous aerogel using halloysite for encapsulating myristic acid (MA). Carbon fiber was incorporated as a thermal conductivity enhancer to modify the composite phase change materials (PCMs). The resulting composite PCMs exhibited a high loading rate, significantly reduced supercooling, and markedly improved photothermal conversion and thermal conductivity properties. The photothermal conversion model designed based on this strategy ensured that more of the heat stored within the PCMs could be utilized for water evaporation. This enabled an efficient operation under various conditions, including nighttime and low-light environments, achieving all-weather high-efficiency evaporation in the solar-driven interfacial evaporator. These results could demonstrate promising applications for enhancing solar energy utilization efficiency and seawater desalination performance.

This paper was to prepare amino-modified porous geopolymer (NH₂-3HGeo) based on geopolymer via acid treatment and post-grafting, and investigate its adsorption performance and mechanism for lead in water. Acid treatment increased the specific surface area of the geopolymer and optimized its pore structure. The maximum adsorption capacity of NH₂-3HGeo for Pb²⁺ reached 521.6 mg·g^-1. The adsorption process followed the pseudo-second-order kinetics and the Langmuir model, indicating a monolayer chemical adsorption. Geopolymer could mainly adsorb Pb²⁺ through ion exchange, while NH₂-3HGeo primarily complexe with Pb²⁺ through functional groups. After five cycles, the Pb²⁺ removal rate of NH₂-3HGeo still reached 90.6%, demonstrating a good recyclability. The results indicated that the material could have a great potential in the field of heavy metal pollution control in water bodies.

In the preparation process of amino-modified porous geopolymer, 400 g of metakaolin and 100 g of white carbon black were uniformly mixed, and then put in a sodium hydroxide solution prepared via dissolving 200 g of NaOH in 400 mL of deionized water as an alkaline activator and 10 mL of hydrogen peroxide solution under stirring. The resulting slurry was cast into polypropylene cubic molds and finally cured in an oven at 80 ℃ for 24 h to obtain the geopolymer (Geo). Subsequently, Geo was crushed and sieved to a fine powder with the sizes of 20-40 mesh. 80 g of Geo was added into 400 mL of nitric acid solutions at different concentrations (i.e., 1, 2, 3, and 4 mol·L^-1). The mixtures were placed in a constant temperature oscillator and agitated in 200 r·min^-1 at 80 ℃ for 5 h. After the reaction, the mixtures were filtered through a 0.45 μm membrane, and the products were collected, washed until neutral, and dried in an oven at 105 ℃ for 12 h, resulting in acid-treated porous geopolymers (i.e., 1HGeo, 2HGeo, 3HGeo, and 4HGeo). Finally, 20 g of acid-treated porous geopolymer was placed in a round-bottom flask containing 100 mL of xylene and stirred for 30 min. Afterwars, 20 mL of aminopropyltriethoxysilane (APTES) dissolved in 100 mL of xylene was added to a flask and stirred with 200 r·min^-1 at 80 ℃ for 12 h. The solid product was collected, cleaned with xylene, and dried at 80 ℃ for 12 h to obtain the amino-modified porous geopolymers (i.e., NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo). In addition, the control sample NH₂-Geo was also prepared by the same procedure.

This study prepares amino-modified porous geopolymers via acid treatment and post-grafting with porous geopolymers as a base material. The results of the BET specific surface area measurement indicate that acid treatment significantly increases the BET specific surface area of the geopolymer material. The specific surface area of sample 3HGeo (i.e., 343.87 m²·g^-1) and pore volume (i.e., 0.1679 cm³·g^-1) are 12.94 times and 3.29 times greater than the specific surface area (i.e., 26.57 m²·g^-1) and pore volume (i.e., 0.0511 cm³·g^-1) of sample Geo, respectively. The XRD patterns, FTIR spectra, and thermogravimetric analysis show that acid treatment increases the porosity and silanol content of the porous geopolymers, thereby increasing the grafting amount of amino groups. The amino groups are grafted onto the geopolymers. The results of adsorption test show that the adsorption amount is positively correlated to the BET specific surface area and amino content. The adsorption rate of NH₂-3HGeo for Pb²⁺ rapidly increases and stabilize as the adsorbent dosage increases. of adsorption time, the removal rates of NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo for Pb²⁺ are 48.1%, 70.1%, and 99.9% at 360 min, 300 min, and 240 min, respectively, with the increase of adsorption time. The adsorption amount of Pb²⁺ increases as the temperature increases. The adsorption capacities of NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo increase as the initial Pb²⁺ concentration increases from 100 mg·L^-1 to 700 mg·L^-1. The adsorption amount continuously increases as the solution pH vale increases. Different coexisting ions (i.e., K⁺, Na⁺, Ca²⁺, and Mg²⁺) affect the adsorption performance of NH₂-3HGeo for Pb²⁺, with divalent cations having a greater impact than monovalent cations. The adsorption kinetics follows the pseudo-second-order model, indicating the chemical adsorption. The results of adsorption isotherm indicate that the adsorption process involves monolayer adsorption. The adsorption thermodynamic results show that moderately increasing the temperature is beneficial to adsorption. The results of recycling experiment show that after five cycles of adsorption-desorption, the adsorption rate of NH₂-3HGeo remains 90.2%, having a good recyclability. The contribution of different adsorption mechanisms indicates that Geo mainly adsorbs Pb²⁺ through ion exchange, while NH₂-3HGeo primarily relies on a functional group chelation.

Amino-modified porous geopolymers with a high specific surface area and a multi-pore structure were prepared by acid treatment and amino modification with porous geopolymers as a base material. The results of nitrogen adsorption showed that acid treatment significantly increased the specific surface area of the geopolymer and effectively improved the pore structure. The thermogravimetric analysis indicated that acid treatment created more active sites on the surface of the geopolymer (such as silanol groups Si—OH), which could act as active centers for subsequent grafting reactions. The prepared NH₂-3HGeo sample had a high adsorption capacity for Pb²⁺ and a good recyclability, with a maximum adsorption capacity for Pb²⁺ of 521.6 mg·g^-1. After five adsorption-desorption cycles, the adsorption rate was still 90.2%, providing an effective approach for the application of geopolymer materials in the treatment of heavy metal-containing wastewater. The results of XPS analysis showed that the complexation between—NH₂ and Pb²⁺ essentially involved the protonation of —NH₂ to form —NH₃⁺. The adsorption mechanisms indicated that Geo mainly adsorbed Pb²⁺ through ion exchange, while NH₂-3HGeo primarily did that through functional group chelation. This work could lay a certain theoretical foundation for understanding the microstructure of geopolymers and modified geopolymers, as well as the mechanism of their adsorption of heavy metal ions.

The increasing risk of heavy metals causes many concerns as one of the nonnegligible problems in modern environmental conservation. As one of the most common heavy metals, copper (II) has a dominant effect in such a pollution. The accumulation of copper (II) in water can eventually give rise to the overexpression of copper in humans, showing to be directly associated with Alzheimer's, Parkinson's, Menkes, and Wilson's disease. As a result, the residue of copper (II) in wastewater becomes a ubiquitous environmental challenge. The development of smart materials that are capable of detecting and removing copper (II) simultaneously can pave an effective approach to solving this puzzling issue. Halloysite nanotubes (HNTs) are natural hollow aluminosilicate clays with a chemical composition similar to kaolin (i.e., Al₂Si₂O₅(OH)₄·nH₂O). HNTs display a superior water dispersibility due to the large cavity volume and surface charge repulsion. The attractive properties including low-cost, environmental friendliness, biocompatibility, good stability, and ease of surface modification also make HNTs promising composite materials in the fields of environmental protection, catalysts, bio-medical materials, and sensors.. In this study, tetraphenylethene (TPE) moiety was immobilized on aminated HNTs with oxalyl chloride for the preparation of TPE-functionalized HNTs (HNTs-TPE-NH₂).

TPE-2NH₂ (184 mg, 0.5 mmol), HNTs-COCl, mL and and 10 N,N-Dimethylformamide (DMF) were mixed in a flask. The system was stirred at room temperature to make nanoparticles well-dispersed and then reacted at 60 ℃ for 8 h. After cooling to ambient temperature, the suspension was centrifugated and the obtained residue was washed by DMF, tetrahydrofuran (THF), and ethanol.

The coumarin unit was bonded to the HNTs-TPE-NH₂ via a condensation reaction by treating 7-hydroxy-2-oxo-2H-chromene-5-carbaldehyde with HNTs-TPE-NH₂ to afford the Schiff base-containing product (HNTs-TPE-Cou). HNTs-TPE-NH₂ (1.0 g) and compound M1 (50 mg, 0.25 mmol) were added to a flask containing absolute ethanol (15 mL), and vacuum-filled with argon gas was repeated for three times. The mixture was refluxed and stirred at 70 ℃ for 12 h. After cooling to ambient temperature, the suspension was centrifugated and the obtained residue was washed sequentially by THF and ethanol. After vacuum-drying, the product HNTs-TPE-Cou was obtained as a faint yellow solid. The obtained HNTs-TPE-Cou was then deposited on the surface of polyurethane foam (PUF) to afford the composite PUF@HNTs-TPE-Cou based on the surface charge of the nanotubes. The obtained product HNTs-TPE-Cou was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state nuclear magnetic resonance spectroscopy, thermogravimetric analysis, transmission electron microscopy, respectively.

HNTs-TPE-Cou aqueous solution has a fluorescence emission peak at a wavelength of 560 nm. The chelation between Cu²⁺ and HNTs-TPE-Cou can destroy the aggregation state of TPE units and give rise to a "turn off" effect on the fluorescence intensity of HNTs-TPE-Cou aqueous solution. he maximum fluorescence intensity of HNTs-TPE-Cou appears as the Cu²⁺ ion concentration is 0 μmol/L. The fluorescence intensity of HNTs-TPE-Cou decreases gradually with the increase of Cu²⁺ ion concentration, showing a typical concentration-dependent manner. F₀ and F represent the fluorescent intensities at 560 nm without and with different concentrations of Cu²⁺ ion, respectively. The F₀/F of HNTs-TPE-Cou at 560 nm has a good linear correlation to the concentration of Cu²⁺ ion when the Cu²⁺ ion concentration in the solution to be measured is between 0.2 μmol/L and 0.6 μmol/L. Other metal ions, including Ni²⁺, Mg²⁺, Ca²⁺, Co²⁺, Mn²⁺, Al³⁺, Ba²⁺, Na⁺, K⁺, Zn²⁺, and Cd²⁺, do not exhibit the quenching phenomenon with the addition to HNTs-TPE-Cou aqueous solution.

The yielded PUF@HNTs-TPE-Cou composites are cut into special shapes to fill the glass columns. A Gel-like separation column is prepared, which can be used to retain Cu²⁺ ions selectively. Moreover, the fluorescence intensity can serve as a nake-eyes identified indicator, which is useful to display the degree of usage. When the fluorescence intensity changes to non-emission, it means the end of useful life, and new columns are needed. The column (20 cm × 2 cm) is used to purify the Cu²⁺-containing water ([Cu²⁺] = 1×10^-4 mol/L). The concentration of Cu²⁺ effluent water is detected. The results indicate the concentration of Cu²⁺ is lower than LOD calculated in the first 100 mL eluting water, having a high purification efficiency.

In this study, HNTs were used as scaffolds and surface modified with tetraphenylethylene and coumarin moieties. The obtained product HNTs-TPE-Cou could be used to detect and separate of Cu²⁺ ions in water solution. HNTs-TPE-Cou displayed an intense fluorescence emission peak at a wavelength of 560 nm in water under the excitation of 365 nm light, while a repaid "turn off" effect on fluorescence appeared, showing a chelation behavior after the addition of Cu²⁺ ions. The as-prepared HNTs-TPE-Cou had high specificity and precision in detecting and removing Cu²⁺ without the recourse to energy consumption. Furthermore, HNTs-TPE-Cou was developed as composite materials by a facile deposition method, which could be further used as gel-like separation columns. The established method could pave a path on the simultaneously detecting and removing metal ions in aqueous solution.

UiO-66-NH₂ is used as a photocatalyst for CO₂ reduction, but it still faces some problems such as a narrow light absorption range, easy agglomeration, and a high recombination rate of electron-hole pairs. Various modification strategies (i.e., metal doping, introducing cocatalysts, and constructing heterojunctions with semiconductors) are proposed to enhance their photocatalytic efficiency. Although these methods can effectively improve the performance of the catalysts, the high synthesis cost of MOFs still restricts their practical application. Using widely available and low-cost natural non-metallic minerals as supports to develop high-performance composite catalysts can significantly reduce the production and application costs of catalysts and effectively enhance their application performance. Compared to conventional three-dimensional porous materials, diatomite has abundant active hydroxyl groups on its surface, which are the main reaction sites for surface grafting and coordination, having a good affinity for organic ligands. In addition, the alkaline centers on the surface of diatomite also have a certain catalytic assistance effect. In this paper, a purified diatomite was used as a support, and UiO-66-NH₂ was anchored on the surface and in the pores of diatomite by an one-step hydrothermal method to prepare UiO-66-NH₂/diatomite composite, thereby providing an idea for the development of low-cost and high-performance photocatalytic CO₂ reduction materials.

In the synthesis of pure UiO-66-NH₂, ZrCl₄ (0.170 g) and 2-aminoterephthalic acid (0.132 g) were dissolved in a mixed solvent of 24 mL of DMF (N,N-Dimethylformamide) and 6 mL of CH₃COOH. After magnetic stirring for 2 h, the solution was transferred to a 100 mL autoclave and reacted at 120 ℃ for 24 h. After reaction completion, the sample was cooled naturally to room temperature. Subsequently, the product was centrifugally washed for three times with DMF and for three times with C₂H₅OH. Finally, the washed sample was dried in a vacuum oven at 60 ℃ for 8 h to obtain the UiO-66-NH₂ catalyst, designated as UN (UiO-66-NH₂). In the purification via acid leaching, the refined diatomite was employed as a catalyst support. The synthesis method of UND (UiO-66-NH₂/diatomite) composite was as folllows, i.e., a similar method to UN synthesis was employed, with the sole difference at varying masses of diatomite during synthesis. The composites were named as UND-X (where X denotes the theoretical loading of UN).

A 5 mg sample of the photocatalyst was dispersed in 10 mL deionized water. The mixture was vacuum-filtered, and the resulting catalyst-loaded mixed cellulose filter membrane was dried at 40 ℃ for overnight . The membrane was then positioned in a 115 mL photoreactor with 1 mL deionized water added as a sacrificial agent. High-purity CO₂ (99.999%) served as a feedstock gas. In dark adsorption equilibrium, irradiation was performed using a 300 W xenon lamp (i.e., at 320 ≤ λ ≤ 780 nm). Gaseous products were quantified by gas chromatography (GC). The product identification was established through retention time matching, with quantification calibrated against standard curves generated with certified gas mixtures. The photocatalytic CO₂ reduction performance was evaluated via calculating the yield of reduction products per unit mass of catalyst per unit time.

UiO-66-NH₂/diatomite composite catalysts with different theoretical loadings are prepared by a hydrothermal method. The results indicate that UND-60% composite demonstrates the maximum CO production rate of 6.69 μmol·g^-1·h^-1, which is 46% higher than that of UN (i.e., 4.57 μmol·g^-1·h^-1). In addition, the results of cyclic experiments also demonstrate that UND-60% composite has a superior stability. After five cycles, the production rate of CO remains >6.30 μmol·g^-1·h^-1. From the images of scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM), octahedral UiO-66-NH₂ particles are uniformly dispersed on the surface and pores of diatomite. Based on the energy dispersive spectrometer (EDS) elemental mapping images, the presence of Si, O, and Zr elements in the composite indicates the effective preparation of UND-60% composite. According to the X-Ray photoelectron spectroscopy (XPS) analysis, the increased surface hydroxyl groups in the UND-60% composite, stemming from the abundant hydroxyl groups on diatomite, enhance its photocatalytic CO₂ reduction performance. The results of ultraviolet-visible spectroscopy (UV-Vis) spectra, fluorescence spectra, electrochemical impedance spectra, transient photocurrent response spectra and Mott-Schottky curves indicate that UND-60% composite broadens the absorption range of the solar spectrum, and diatomite introduces an promoted separation efficiency of photogenerated carriers, thus improving the photocatalytic performance.

The results of In-situ DRIFTs reveal the photocatalytic CO₂ reduction mechanism in the UND-60% composite, i.e., CO₂ and H₂O adsorb onto the photocatalyst surface, where photo-generated electrons activate CO₂ to form bent anionic radicals (*CO₂^-). Subsequently, *CO₂^- undergoes proton-coupled electron transfer to generate a carboxylate intermediate (*COOH), follows by further protonation and reduction to yield *CO and H₂O. This *CO formation step is rate-limiting. Finally, *CO desorbs from the catalyst surface as gaseous CO, completing the reduction pathway.

The UiO-66-NH₂/diatomite composite was synthesized by a one-step hydrothermal method. UND-60% composite demonstrated a superior photocatalytic CO₂ reduction performance, achieving a CO generation rate of 6.69 umol·g^-1·h^-1. This represented a 1.46-fold enhancement over pristine UiO-66-NH₂ (4.57 umol·g^-1·h^-1). The results of cyclic testing indicated a superior photostability of the composite. Compared to pure UiO-66-NH₂, diatomite incorporation imparted an optimized specific surface area and pore structure, while enhancing catalyst dispersion. This synergistic effect exposed additional active sites and facilitated an improved CO₂ photoreduction performance. Furthermore, the composite had an expanded light absorption range and enhanced photoinduced charge carrier separation efficiency. The results of In-situ DRIFTs analysis on the UND-60% composite revealed the dynamic evolution of surface functional groups during CO₂ photoreduction, establishing the reaction pathway: CO₂ → *CO₂ → CO₂^- → COOH → *CO → CO. These findings could provide valuable insights for designing cost-effective photocatalytic systems for CO₂ reduction.

In the context of "carbon peak and carbon neutrality," the expansion of the solar photovoltaic industry leads to an increased demand for high-purity quartz. High-purity quartz sand with SiO₂ content of > 99.998% becomes a challenge in the industry. Some impurities in quartz mainly exist in the form of associated minerals, inclusions, and lattice impurities, and the degree of separation between associated minerals and quartz during the purification process has a dominant impact on the purity of quartz. In nature, quartz often coexists with minerals such as muscovite, and most high-quality quartz ores contain muscovite. Therefore, the effective separation of muscovite from quartz is a key to producing high-purity quartz sand.

The purification process for muscovite-bearing quartz ores typically involves high-temperature roasting, water quenching, grinding, and flotation. For quartz ores with a high degree of muscovite intergrowth, roasting and water quenching are a necessity. During the roasting and water quenching process, muscovite undergoes a series of reactions, such as dehydroxylation and oxidation, significantly affecting the flotation separation of quartz and muscovite. The existing research on muscovite and quartz flotation focuses on the mechanisms of flotation reagents and their interactions with minerals, as well as the influence of single metal ions on mineral flotation. However, the changes in muscovite after high-temperature roasting and their relationship with flotation processes have not been well integrated in the quartz purification process, and the mechanisms of the flotation separation of quartz and muscovite are unclear yet. It is thus of great significance for the purification of high-quality high-purity quartz materials to explore the impact of high-temperature roasting on the flotation separation of quartz and muscovite. This study was to investigate the flotation behavior of different associated minerals after high-temperature roasting during the quartz purification process and offer some ideas for improving the purification process of high-purity quartz sand.

In this work, quartz samples after high-temperature roasting at different time from muscovite-bearing quartz from India as a raw material were subjected to grinding, sieving, and flotation, ultimately obtaining quartz concentrates (i.e., quartz) and flotation tailings (i.e., muscovite). The chemical composition of the raw material was determined by X-ray fluorescence spectroscopy (XRF). The phase composition of the raw material and muscovite samples after flotation was characterized by X-ray diffraction (XRD). The content of impurity elements in the quartz concentration and the elements K and Fe in the flotation slurry were measured by inductively coupled plasma (ICP). The microstructure of the muscovite samples in the flotation tailings was determined by scanning electron microscopy (SEM), and the micro-composition of the samples was analyzed by energy-dispersive X-ray spectroscopy (EDS). The micro-phase composition of muscovite was determined by Raman spectroscopy, and the contact angle of muscovite in water was tested to characterize its hydrophilicity and hydrophobicity.

The XRD patterns of muscovite after different roasting times show that the interlayer distance (d₀₀₂) of muscovite increases from 9.9316 Å to 10.0387 Å with the increase in roasting time, and the peak intensity gradually reduces. The SEM images reveal that the interlayer distance of muscovite expands as the roasting time increases, and this expansion phenomenon is associated with the high-temperature dehydroxylation of muscovite.

The analysis by SEM-EDS shows that after 90-min roasting, the surface of muscovite becomes fractured and brittle, with Fe accumulation in the muscovite layers. Based on the Raman spectra, the Fe accumulation between the muscovite layers is hematite.

The XPS spectra indicate that Fe in muscovite exists in both Fe²⁺ and Fe³⁺ ions, and the content of Fe³⁺ increases as the roasting time extends. This suggests that Fe oxidation occurs during the roasting process.

The flotation results show that the flotation separation efficiency between quartz and muscovite firstly improves and then deteriorates with increasing roasting time, achieving the optimal performance at 10 min.

The K and Fe contents in the flotation slurry indicate the congruence of K and Fe leaching. The contents of elements K and Fe in the slurry first increase and then decrease as the roasting time increases, which is related to the dehydroxylation of muscovite and the increasing disorder in its structure at high temperatures.

This study investigated the effect of structural changes in muscovite during high-temperature roasting and water quenching on the flotation separation of quartz and muscovite, using muscovite-bearing vein quartz from India as a raw material. The results indicated that it could be necessary for quartz ores with tightly set quartz and muscovite to treat by high-temperature calcination water quenching. At a short calcination time, the muscovite dehydroxylation reaction was incomplete, in which caused a limited reduction of the binding energy of quartz-mica interface and a poor separation of muscovite and quartz, thus resulting in a low flotation efficiency. Muscovite underwent a high-temperature dehydroxylation reaction as the calcination time increased, leading to the increased distance between its sheets, the oxidation and enrichment of Fe, the increased aqueous nature of the muscovite mother, and the decreased floatability, which could affect the separation efficiency from quartz particles. SiO₂ content in quartz concentrate firstly increased and then decreased as the calcination time increased, and the flotation recovery reached the maximum value of 99.974% at the calcination time of 10 min. The distance between the muscovite sheets gradually increased as the calcination time increased, resulting in an increase in the dissolution amount of element K, and exposing more active sites of Al-O and Si-O, which increased the aqueous nature of the muscovite and reduced the flotation separation efficiency with quartz. The oxidation of Fe after high-temperature calcination weakened the electronegativity of muscovite, hindering the electrostatic adsorption between muscovite and dodecadecamine. Also, the presence of hematite in muscovite could occupy the adsorption site of muscovite and dodecamine, thereby reducing the effect of flotation separation between quartz and muscovite.

Cobalt aluminate (CoAl₂O₄) is one of the most common transition metal catalysts and is widely used in the persulfate advanced oxidation process. To improve the dispersion of the cobalt aluminate (CoAl₂O₄) catalyst and enhance its catalytic activity, exfoliated montmorillonite nanosheets (EMMT) as a support were prepared by a freeze-thaw-ultrasonic method. The CoAl₂O₄/EMMT composite material was synthesized by a sol-gel method, and then CoAl₂O₄/EMMT was reduced to the Co-CoAl₂O₄/EMMT composite material. The degradation performance and cycle stability of Co-CoAl₂O₄/EMMT for methyl orange were investigated, and the mechanism of catalytic degradation of methyl orange was discussed.

An appropriate quantity of montmorillonite (MMT) was uniformly dispersed in 50 mL of deionized water. After continuous stirring for 12 h, a well-dispersed MMT suspension was obtained. Subsequently, the MMT suspension was transferred into a refrigerator at -20 ℃ for 12 h. In the freezing process, the frozen MMT suspension was placed at an ambient temperature for 8 h to ensure complete thawing. After thawing, the suspension was thoroughly stirred to achieve a homogeneous state, and then ultrasonic treatment was carried out for 8 min to yield an exfoliated montmorillonite nanosheet (EMMT) suspension. Afterwards, 750 mg of aluminum nitrate nonahydrate (Al(NO₃)₃·9H₂O) and 353 mg of cobalt nitrate hexahydrate (Co(NO₃)₃·6H₂O) in a molar ratio of 2∶1 were added to the EMMT suspension. The mixture was vigorously stirred for 40 min to guarantee the well-dispersion. 384 mg of citric acid and 4.5 mg of sodium dodecyl benzene sulfonate (SDBS) as organic additives were introduced into the above-mentioned solution. The solution was then heated in a water-bath at 70 ℃ for 4 h to form a sol, and the heating process was continued for 2 h to transform the sol into a wet gel. The wet gel was subsequently freeze-dried for 24 h to obtain a dry gel, which was then finely ground. An appropriate amount of the dry-gel powder was weighed and placed in a muffle furnace. The temperature increased at a heating rate of 5 ℃/min, and followed by calcination for 3 h to synthesize CoAl₂O₄/EMMT composite material. The microstructure of the CoAl₂O₄/EMMT composite material was optimized via precisely regulating the calcination temperature. Finally, the Co-CoAl₂O₄/EMMT composite material was synthesized through reduction roasting.

At a ultrasonic power of 600 W, the lamellar thickness of the exfoliated EMMT decreases from 303 nm to 7.6 nm. The Co-CoAl₂O₄/EMMT composite material synthesized at a calcination temperature of 650 ℃ and a reduction temperature of 670 ℃ exhibits the optimal catalytic performance. Its degradation rate of methyl orange reaches 87.5% within 70 min, which is greater than the catalytic performance of Co-CoAl₂O₄ (79.3%) or CoAl₂O₄/EMMT (76.8%) composite materials. Co-CoAl₂O₄/EMMT composite material has a good stability, and the degradation rate of methyl orange still remains at 77.8% after four cycles.

Exfoliated montmorillonite nanosheets (EMMT) as a carrier were prepared by a freezing-thawing-ultrasonication method, and then Co-CoAl₂O₄/EMMT composite was synthesized by a sol-gel reduction approach. Co-CoAl₂O₄/EMMT material prepared at a calcination temperature of 650 ℃ and a reduction temperature of 670 ℃ exhibited the optimal catalytic performance. After activating peroxydisulfate (PDS), the degradation rate of Co-CoAl₂O₄/EMMT for 50 mg/L methyl orange could reach 87.5% within 70 min, accompanied by a superior cycle stability. The results of radical quenching experiments confirmed that SO₄^•- and •OH radicals were the dominant reactive species contributing to methyl orange degradation.

The large-scale mining and processing of coal resources inevitably result in the continuous generation and accumulation of solid wastes such as fly ash and coal gasification slag. However, their utilization rate remains low, with primary dependence on open-air stockpiling, leading to substantial resource depletion and ecological hazards. The existing resource utilization of fly ash and coal gasification slag is still confined to low-value-added fields like construction materials and agriculture. It is critically necessary to explore their inherent resource properties and develop high-value utilization pathways, thereby addressing environmental challenges, while enhancing economic benefits. Some researches reveal that fly ash and coal gasification slag both contain abundant silicon components in their phase compositions. This characteristic endows them with significant potential as precursors for synthesizing silicon anode materials. This study was to fabricate silicon/carbon composites with fly ash and coal gasification slag as precursors, provide novel insights into the high-value application of coal-based solid waste resources and expand the methodology for low-cost preparation of silicon-based materials for lithium-ion batteries.

In the fabrication of distinct silicon-carbon composites, a fly ash-derived silicon material was prepared via uniformly grinding a mixture with 1 g of fly ash, 1 g of magnesium powder and 2 g of sodium chloride. Afterwards, the ground mixture was heated in argon atmosphere by magnesiothermic reduction at 750 ℃ for 8 h. A purified silicon material was obtained after sequential washing with hydrochloric acid and hydrofluoric acid. For the fly ash-derived silicon-carbon composite, this silicon material was dispersed with phenolic resin at an equal mass ratio, modified via cetyltrimethylammonium bromide assistance, and carbonized at 800 ℃ for 2 h to form a carbon-coated structure. In contrast, the coal gasification slag-derived composite was synthesized in a single step via subjecting 1 g of coal gasification slag, 0.6 g of magnesium powder, and 2 g of sodium chloride to identical magnesiothermic reduction conditions, thereby retaining inherent carbon to generate an interconnected silicon-carbon architecture.

The morphologies and microcrystalline structures of all the obtained samples were analyzed by X-ray diffraction, Raman spectroscopy, X-ray energy dispersive spectroscopy, scanning electron microscopy, and transmission electron microscopy. The thermal behavior was evaluated by thermogravimetric analysis, and the microstructures were characterized via BET specific surface area and pore size distribution measurements. The two composite materials were assembled into lithium-ion half-cells for charge-discharge cycling, cyclic voltammetry, and impedance testing to evaluate their lithium storage performance.

Silicon materials obtained via the magnesiothermic reduction process with fly ash as a precursor exhibit a high crystallinity, primarily composed of densely packed crystalline particles. The corresponding fly ash-based silicon-carbon composite fabricated via a carbon-coating strategy exhibits a "core-shell structure" with a carbon content of 28.1%. This carbon layer predominantly consists of amorphous carbon enriched with abundant sp³-hybridized structural defects and edge disorders, significantly affecting the interfacial charge transfer dynamics. In contrast, the coal gasification slag-derived composite synthesized via one-step magnesiothermic reduction demonstrates a distinctive mosaic architecture incorporating 36.9% carbon with substantially enhanced sp²-hybridized carbon domains, thus facilitating a superior electrical conductivity.

Fly ash-based silicon-carbon composite and coal gasification slag-derived composite both have high specific surface areas (i.e., 215.7 and 274.8 m²·g^-1) and rich hierarchical pore structures (i.e., synergistic distribution of microporous and mesoporous pores). As lithium-ion battery anodes, fly ash-derived silicon-carbon composite and coal gasification slag-derived silicon-carbon composite exhibit reversible capacities of 800 and 420 mA·h·g^-1 at 50 mA·g^-1, respectively. These composites maintain reversible capacities of 348 and 334 mA·h·g^-1 after 300 cycles at 500 mA·g^-1, respectively, showing superior rate capability and cycling stability. This study demonstrates that silicon-carbon composites with high-performance lithium storage characteristics can be prepared by using low-cost coal-based solid waste-fly ash and coal gasification slag as precursors, which is helpful for promoting the development and application of low-cost, high-performance energy storage materials.

A silicon-carbon composite with a "core-shell structure" was synthesized by using fly ash as a precursor through a magnesia-based reduction process combined with a carbon coating strategy. Also, a silicon-carbon intergrown composite exhibiting an "mosaic architecture" was prepared by using coal gasification slag as a precursor by a one-step magnesia-based reduction process. The abundant sp³ structural defects and edge defects in fly ash-based silicon-carbon composite could enhance its lithium storage capacity, while the significant sp² carbon in the coal gasification slag-based composite could improve its structural stability. Consequently, the composites both exhibited excellent rate performance and cycling stability when used as anodes in lithium-ion batteries. This study could provide some insights for the high-value utilization of coal-based solid waste resources and expand avenues for low-cost preparation of silicon-based materials for lithium-ion batteries.

Lithium-ion batteries (LIBs) are widely applied in electric vehicles and portable electronics due to their high energy density and environmentally friendly characteristics. However, large numbers of LIBs would be retired in the future because of their limited lifespan (5-8 a). Used batteries contain numerous organic materials and valuable elements. They cause serious pollution and resource waste in the absence of suitable treatment. Therefore, typical pre-treatments are carried out to obtain used cathode or anode materials. A series of recycling methods are explored to utilize spent electrode materials, such as element-extracting leaching and direct regeneration. Compared to element-extracting leaching, direct regeneration displays lower energy consumption and higher element recovery, making it regarded as a next-generation approach. In the pre-treatment process, however, the obtained electrode materials are mixed (e.g., LiFePO₄ and graphite), resulting in low leaching efficiency and inferior regeneration performance. Also, direct regeneration processes still suffer from long treatment durations and high energy requirements. It is thus important for recycling used batteries to explore highly effective separation and regeneration methods.

Based on the particle size of raw material, three graded products involved coarse fraction (i.e., +0.21 mm), medium fraction (i.e., -0.21 mm - +0.15 mm), and fine fraction (i.e., -0.15 mm). Magnetic separation experiments on each fraction were conducted, separately. The coarse fraction was processed at a pulsation frequency of 200 times/min and a background magnetic field intensity of 1.0 T, the medium fraction at 240 times/min and 1.2 T, and the fine fraction at 260 times/min and 1.6 T. 5 g of pre-heating waste graphite was placed in 20 mL of hydrochloric acid solution as a stripping solution. After stirring for 5 h, the mixture was washed for three times with deionized water and then further cleaned for three times with an ethanol solution, enabling the short-process regeneration of graphite material.

The pre-classification, magnetic separation, and "surface peeling" regeneration are applied to transform mixed electrode materials into regenerated products. Used LiFePO₄ typically exhibits large bulk sizes, while used graphite particles are comparatively smaller. At the particle size of < 0.075 mm, the carbon content reaches 86.35%. Evidently, simple sieving effectively separates the mixed components. The resulting tailings primarily consist of carbonaceous material (96.53%) and impurities after magnetic separation. To address the detrimental effects of residual impurities, a "surface peeling" regeneration method is developed for used graphite. Increasing the number of treatment cycles progressively tailors surface/near-surface properties, while removing impurities. The related analysis reveals that high-temperature active atmospheres promote an impurity evolution, while acid solutions facilitate their removal. Based on the water-gas shift reaction principles, active carbon atoms react with water, eliminating degraded surface/near-surface layers to yield regenerated graphite. The physicochemical characterization indicates that the regenerated samples exhibit high graphitization, smooth surfaces, and reduced particle sizes. As LIB anodes, these materials deliver a capacity of 320 mA·h·g^-1 at 1.0 C after 300 cycles, with an initial Coulombic efficiency of >80%. At 2.0 C, a capacity retention remains 280 mA·h·g^-1 for over 300 cycles. Increased "surface peeling" cycles shortens activation time due to the optimized surface/near-surface properties, enhancing lithium-ion diffusion. The kinetic analysis indicates that excessive "surface peeling" treatments damage surface structures, while increasing pseudocapacitive contributions. At 0.9 mV·s^-1, pseudocapacitive contributions reach 75%, with a lithium-ion diffusion coefficient of 4.0 × 10^-11 cm²·s^-1, demonstrating a significant physicochemical evolution.

For the promising potential of used LIB graphite, effective recovery methods (i.e., from separation of mixed materials to graphite regeneration) were used. Used LIB materials consisted of large LiFePO₄ bulks and small graphite particles. For pre-classification, the mixed materials were segregated by particle size ranges, i.e., larger fractions were predominantly LiFePO₄, while smaller fractions were primarily graphite. At particle sizes of < 0.075 mm, carbon content reached 86.35%, with LiFePO₄ (12.03%) and some impurities. The magnetic separation increased carbon content to >96%, achieving an effective separation of mixed electrode materials. Subsequently, used graphite was regenerated by "surface peeling" strategie, removing impurities (i.e., conductive carbon, Al, Cu, and LiFePO₄) and tailoring surface/near-surface properties. The optimized sample with a reduced particle size exhibited smooth surfaces and high graphitization. As LIB anodes, these materials delivered the electrochemical performance up to 323 mA·h·g^-1 at 1.0 C. The analysis revealed that tailored diffusion channels played a key role in enhancing reversible lithium-ion storage and deep insertion behaviors. This work could provide effective all-process recycling strategies from pre-classification and separation to regeneration, while elucidating the regeneration mechanism of used graphite.

It is well known that crude oil is one of the most important energy sources. The oil-in-water emulsion is often produced during oil exploitation due to waterflooding and groundwater. This emulsion causes damage to the transmission pipeline and environment. Therefore, the separation of oil and water is an essential step in the petroleum industry. Chemical demulsification is currently the most widely employed due to its convenient operation and quick response. However, the extensive use of chemical emulsifiers has brought potential harm to the environment, so it is necessary to explore novel environmentally friendly demulsifiers. Recently, nanoparticle (NP) demulsifiers have been widely concerned in the application of demulsification for crude oil emulsion. NP demulsifiers usually refer to chemically synthesized nanoparticles or modified natural nanoparticle minerals. While graphene oxide and reduced graphene oxide are reported to exhibit an excellent demulsification performance of more than 99.9%, the high cost of raw materials limits their widespread use. As a result, economical mineral materials such as attapulgite, kaolinite, and nano-silica are employed to develop NP demulsifiers.

Ordinary mineral nanomaterials typically consist of a single hydrophilic part (e.g., quartz, silicate, etc.). Therefore, they require complex surface modifications to adjust their hydrophilicity and hydrophobicity, enabling them to be excellent demulsifiers. Recently, researchers found a novel mineral material called Micro-nano silicon-carbon ore (Si-C). The Si-C particles consist primarily of hydrophilic quartz and hydrophobic carbon, so it is expected that they can be used to prepare a novel NP demulsifier.

The Nano silicon-carbon ore utilized was sourced from a mining site named Shilukeng in Fengcheng City, Jiangxi Province, China. Initially, bulk samples of Si-C were ground, and the resulting mineral particles were subsequently screened to obtain samples less than about 1 um. The demulsifiers (OSi-C) were prepared through a simple oxidation treatment.

The major elemental composition of the Si-C includes O (40.35%), Si (35.33%), C (9.15%), Al (2.18%), Fe (1.3%), K (0.33%), and the loss on ignition is 9.57%. The average particle size of Si-C was 343.4 nm. The Zeta potential of OSi-C was considerably lower than that of the Si-C for all pH conditions. This is due to the introduction of oxygen-containing functional groups on the OSi-C surface after oxidation treatment. The content of C-OH, C-O-C, and O=C-O increased compared to that of the Si-C, suggesting that the OSi-C was successfully oxidized, resulting in increasing oxygen-containing functional groups. After oxidation, the obtained OSi-C nanoparticles showed good amphiphilicity, interfacial activity, and low interfacial tension (IFT) properties, which enable the particles easily to arrive at the oil-water interface. And it was believed that the self-assembly behavior of OSi-C at the oil-water interface is due to its good interfacial activity and the ability to reduce the oil-water IFT. At a demulsifier dosage of 1000 mg/L, OSi-C exhibited a demulsification efficiency exceeding 98.94% at pH 6, with the oil concentration in the separated water less than 97.33 mg/L.

An OSi-C nanoparticle demulsifier was prepared by a simple oxidation treatment of natural Si-C nanoparticles to achieve highly efficient demulsification for the crude oil-in-water emulsion at room temperature (25 ℃). The OSi-C nanoparticles exhibit superior demulsification performance than the original Si-C at the optimal conditions, and have a demulsification efficiency of 98.94% at pH 6. The mechanism behind emulsion breaking was revealed through analyses of Zeta potential, interfacial activity, surface wettability, dynamic IFT, self-assembling at the oil-water interface, and microscopic observation of the demulsification process. On the one hand, the OSi-C nanoparticles have good amphiphilicity, interfacial activity and the ability to self-assembly at the oil-water interface, which makes it easy to arrive at the oil-water interface. On the other hand, the OSi-C material has abundant Oxygen-containing functional groups and aromatic ring structures, which can promote the binding of nanoparticles with emulsified molecules of asphaltenes and resins at the oil-water interface through hydrogen bonding and π-π interactions. Furthermore, with the help of external forces such as stirring and oscillation, the protective film at the oil-water interface ruptures, thereby achieving oil-water separation. Therefore, the OSi-C nanoparticles can rapidly break the emulsion with high efficiency at room temperature. Due to the natural composition advantage and nontoxicity of the raw Si-C, this work provides a new approach for synthesizing environmentally friendly natural mineral NP demulsifiers.

Lithium extraction from salt lake is essential for ensuring lithium resource security in China, but the design of high-performance lithium extraction membranes from salt lake faces significant challenges. Two-dimensional (2D) membranes with oriented nanochannels consist of 2D nanosheets stacked layer by layer. These membranes have nanoscale channel heights that can be precisely controlled at the sub-nanometer level, making them suitable for the selective separation of lithium (Li) and magnesium (Mg) ions. Typically, the Li⁺/Mg²⁺ selectivity of membrane requires surface modification with positive charge due to the inherent charge differences between Li⁺ and Mg²⁺. Interfacial polymerization (IP) is commonly used for the membrane surface modification. However, the excessive IP reactions can result in excess positive charge, reducing the Li⁺ transport efficiency. Therefore, the design and development of 2D selective membranes with optimized IP reactions while maintaining high lithium-ion transport efficiency is of great significance. Layered montmorillonite (MMT) mineral has natural layered structure and it can be easily exfoliated into 2D nanosheets, which are ideal building blocks for the assembly of 2D membranes. In this work, hydrophilic tannic acid (TA) with negative charge is applied to modify the surface of 2D MMT nanosheets, enabling an enhanced Mg²⁺ rejection and suppressed transport resistance of Li⁺ transport. Our results provide a valuable reference for the design and fabrication of novel 2D membranes with high Li⁺/Mg²⁺ selectivity.

The MMT nanosheet suspension was prepared by ultrasonic exfoliation. The suspension mixed with auxiliary membrane-forming agents were scraped coated and dried on a substrate to obtain 2D MMT membranes. For the preparation of TA-modified membranes, TA was added to the MMT nanosheet suspension and coated on substrate using the same protocol. As-prepared membranes were then used for IP reactions. The membranes were first immersed in a PEI solution 45 s. After washing and drying, the membranes were then immersed in a TMC solution for 15 s. As-obtained membranes were dried in an oven for subsequent nanofiltration and characterizations. The morphology and surface roughness of the 2D MMT membranes were characterized by a JSM 7100F scanning electron microscope (SEM) and a Multi Mode 8 atomic force microscope (AFM). The surface chemical analyses was conducted by a K-Alpha X-ray photoelectron spectroscopy (XPS). The alignment and orientation of internal 2D nanochannels of the MMT membrane were analyzed by a D8 ADVANCE X-ray diffractometer (XRD) and Xeuss 2.0 X-ray wide-angle diffractometer (WAXS).

According to the morphological and structural characterizations, the 2D membranes fabricated with bare 2D MMT nanosheets exhibit a well-oriented 2D nanochannel structure. The alignment of TA-modified 2D MMT nanosheets were unaffected during IP reaction, generating a well-preserved membrane structure according to the cross-sectional SEM and WAXS.

With the increasing content of TA, the rejection of Mg²⁺ increased simultaneously and reached up to almost 100% with 1.5% addition of TA. A negative Li⁺ rejection was also achieved correspondingly. However, excess amount of TA resulted in a deterioration of both the rejection of Mg²⁺ and selective transport of Li⁺. In addition to the selectivity, the TA modification significantly promoted the membrane flux up to 22.5 L·m^-2·h^-1, which was 49% higher than that of bare MMT membrane. The TA modified MMT membrane exhibited consistently high Mg²⁺ rejection under various feed conditions and high performance stability during a 120 h long-term operation.

The enhancement in membrane selectivity and flux through TA modification was due to the promoted IP reaction and a narrowed pore size distribution, validated by XPS measurements and molecular weight cut off (MWCO) tests. Furthermore, the role of TA in membrane formation was revealed by AFM and XPS measurements. The TA molecules can connect the adjacent MMT nanosheets via hydrogen bonding between its phenolic hydroxyl groups and the Al-OH on edge surface of MMT. The negative charge on TA provides more anchoring site for the PEI monomers, thereby promoting the IP reaction. Energy barrier calculated by Arrhenius equation further validated that the TA modification can reduce the Li⁺ transport resistance from 20.91 kJ·mol^-1 to 18.38 kJ·mol^-1 in the 2D nanochannels.

In this work, a TA-modification method was applied to enhance the separation performance of a 2D MMT membrane system. The Mg²⁺ rejection of the modified MMT membrane with optimized TA content reached almost 100%, with a corresponding negative Li⁺ rejection of -9%. The membrane flux was 22.5 L·m^-2·h^-1, after TA modification, which was 49% higher than that of bare MMT membrane. Moreover, the TA-modified membranes exhibited consistently high Mg²⁺/Li⁺ selectivity and flux under various feed conditions and excellent stability during long-term operation.

Topographical and surface chemical characterizations revealed the role of TA molecules in forming hydrogen bonding with the hydroxyl groups on edge surface of MMT nanosheets. The enhancement mechanism of membrane selectivity via TA modification was attributed to the additional negative charge from TA. The addition of TA enabled efficient PEI monomers adsorption, which can promote the IP reaction and reduce the average pore size. Conductivity test and energy barrier calculations further validated that the TA modification was able to reduce the transport resistance of Li⁺, thus realizing the enrichment of Li⁺.

Layered silicate mineral-based composite solid electrolytes have an immense potential for advancing solid-state battery technologies. However, several scientific and technical challenges remain. First, the complexity of material composition and structural stability are key factors that restrict the performance. Variations in the batch-to-batch properties of layered silicate minerals result in compositional inhomogeneity. Furthermore, their high surface energy leads to agglomeration, disrupting ion conduction channels and stress distribution, which negatively impacts ionic conductivity and interfacial compatibility. The presence of impurities in the minerals, which are difficult to eliminate, may also induce side reactions that degrade the electrolyte-electrode interface, hindering performance improvement. Second, ion transport in these materials is constrained by small interlayer spacings and suboptimal interface compatibility, leading to a low ionic conductivity at room and low temperatures. This limits the realization of high conductivity. Moreover, the trade-off between mechanical properties and ionic conductivity complicates the simultaneous enhancement. The electrolyte stability under extreme conditions (such as low temperatures and high-voltage environments) is also a challenge. Polymer crystallization and interlayer contraction at low temperatures significantly reduce conductivity, while high-voltage conditions lead to electrolyte decomposition and electrode compatibility issues.

To overcome these challenges, a future research should focus on the following aspects, i.e., i) Multistage purification and interface modification to address heterogeneity and agglomeration, improving ionic conductivity and stability through interdisciplinary collaboration; ii) Control of interlayer spacing and surface modification, using ionic liquids and silane coupling agents to expand interlayer spacing and enhance interface properties, thereby improving ion transport efficiency; iii) Design of three-dimensional network structures, integrating layered silicate minerals with various morphologies to construct ordered 3D networks, enhancing both the mechanical and electrochemical properties of the composite material; iv) Extreme-condition adaptability, developing stable electrolytes for low-temperature and high-voltage environments through functionalization and additive optimization; and v) Scalable, environmentally friendly fabrication techniques, such as water-based dispersion and UV curing, to reduce production costs and improve batch-to-batch consistency. Layered silicate mineral-based composite solid electrolytes will play a crucial role in the development of solid-state battery technologies and accelerate their commercialization via advancing research in these aspects.

Functional coal-based carbon materials demonstrate an enormous application potential in the field of electrochemical energy/matter conversion and storage due to their abundant raw materials, low cost, and adjustable structure. This review systematically summarizes the research progress on the preparation methods and electrochemical applications of functional coal-based carbon materials, and explores the intrinsic relationships between material structure and electrochemical performance. Based on the existing research status of the preparations and electrochemical applications of functional coal-based carbon materials, we propose some prospects for their future research directions, i.e., 1) Simple and environmental-friendly physical activation methods need to be developed, such as supercritical CO₂-assisted activation and microwave carbonization, which achieve controllable pore structure construction through radical reactions and interfacial energy regulation. Low-energy technologies such as photothermal-driven carbonization and plasma pulse activation should be developed to utilize non-equilibrium thermodynamics to regulate the degree of graphitization and defect quantity of carbon layers, thereby reducing carbon emissions from the preparation process. In addition, machine learning can be also used to optimize preparation parameters (such as temperature field, pressure field, atmosphere composition, etc.) to achieve accurate prediction and targeted control of materials' morphology, structure, and chemical composition, 2) The structure-property relationship and performance improvement mechanism of materials need to be analyzed. In-situ characterization techniques (such as electrochemical-synchrotron radiation coupling technology and in-situ aberration-corrected electron microscopy) can analyze the material structure and composition during electrochemical processes, clarify the mechanisms of material performance degradation under complex conditions, and develop modification strategies. In addition, it is also necessary to develop kilowatt-scale industrial electrochemical devices suitable for functional coal-based carbon materials to promote the practical application of coal-based carbon materials and 3) Some precise coal quality analysis methods and standardized coal processing methods need to be establised and the continuous, large-scale production equipment needs to be developed, thereby addressing the impact of coal raw materials on product structure and performance consistency. For instance, establishing a rapid analysis of coal quality (i.e., combining near-infrared spectroscopy with Raman spectroscopy)-three-dimensional structural simulation (i.e., Material Studio)-process parameter feedback system ensures that the structural parameters of coal raw materials from different production areas remain within a certain range. The design of a modular mobile doping-activation-pyrolysis integrated system is expected to enable the continuous conversion of coal raw materials into functional coal-based carbon materials, thus addressing the impact of conventional batch preparation process on the product performance. These technologies can contribute to the large-scale production and application of high-performance functional coal-based carbon materials.

Hardness testing is crucial for evaluating the mechanical properties of ceramics, especially in applications involving wear and scratch resistance. The widely used Vickers hardness test is often affected by an indentation size effect (ISE), resulting in hardness values deviating from their true values under lower loads. Moreover, significant discrepancies in hardness values obtained between the Vickers hardness testers and micro-/nano-indentation instruments at low loads for identical samples persistently cause a confusion. The conventional theories presume that the ceramic materials' indentation dimensions remain unaltered before and after unloading. However, these dimensions often exhibit variations in practice. The existing models and methodologies fail to universally accommodate diverse materials, making it essential to clarify these issues for the accurate assessment of ceramic material hardness. This study was to explore the origins of the Indentation Size Effect (ISE) and the patterns of indentation deformation via comparing the Vickers hardness data with micro-/nano-indentation results under varying loads, thereby furnishing a theoretical foundation for the standardization of ceramic hardness testing.

Three representative ceramic materials (i.e., Al₂O₃, ZrO₂, and (Hf_0.5Zr_0.5)C) were investigated to evaluate their load-dependent mechanical responses. After being sequentially sectioned, ground, and polished, the specimens were subjected to a series of Vickers hardness tests at different loads. The Vickers hardness values were determined via optically measuring the diagonal dimensions of residual indentations using a metallographic microscope. Simultaneously, micro-/nano-indentation tests were performed by a nanoindenter equipped with a Vickers indenter. The pre-unloading hardness values were calculated based on the changes in depth after loading. Subsequently, the post-unloading hardness values were obtained via measuring the indentation sizes after unloading using scanning electron microscopy (SEM). Through a comprehensive analysis of the variations in indentation sizes before and after unloading, this study could elucidate the characteristics of load-dependent mechanical responses in those ceramic materials.

The three ceramic specimens display pronounced load-dependent characteristics according to the Vickers hardness data. Three specimens exhibit significant hardness declines in a low-load regime (i.e., decreased by 3 4.44% for Al₂O₃, decreased by 22.85% for ZrO₂, and decreased by 29.44% for (Hf_0.5Zr_0.5)C), and stabilize at characteristic plateau values (i.e., 15.6 GPa, 12.9 GPa, and 18.6 GPa, respectively) beyond critical threshold loads (i.e., 3-5 N) as the load increases. This behavior is attributed to the predominance of elastic recovery mechanisms during low-load indentation, which results in measured values that exceed the true hardness of the materials. As the load further increases, the plastic deformation becomes a dominant mechanism, leading to stabilized indentation dimensions and hardness values that more accurately reflect the intrinsic properties of the ceramics.

A comparative study is conducted to evaluate the pre-unloading hardness values derived from depth changes during loading and the post-unloading hardness values calculated from residual indentation dimensions as using the micro-/nano-indentation system. This investigation reveals three distinct types of indentation behavior among the materials tested. For Al₂O₃, the Vickers hardness tester obtains significantly higher results than the micro-/nano-indentation tester at low loads. This discrepancy is since the indentation diagonal exhibits a rebound pattern after unloading, resulting in a minimal residual deformation and consequently an overestimated hardness value. In contrast, ZrO₂ demonstrates the opposite trend. Ceramic materials exhibit a localized microplastic deformation at indentation edges. For ZrO₂ under low loads, the phase transformation-induced expansion at an indentation periphery creates an extrusion effect, increasing residual indentation dimensions and resulting in extrusion-type morphology. The results of Vickers hardness values measured by the tester that are lower than those obtained from micro-/nano-indentation tests. For (Hf_0.5Zr_0.5)C, a stress is alleviated due to the formation of micro-cracks around the indentation. Since there is no significant change in indentation size after unloading, the testing methods both yield comparable hardness results.

A further analysis indicates that minor deviations in indentation size (Δd) have a significant effect on the low-load hardness calculations. For instance, in the case of ZrO₂ at a load of 0.01 N, a small Δd of only 0.24 μm can lead to a relative error of 20%, due to the extremely small indentation size of 1.20 μm, which results in a substantial 57% deviation in hardness measurements. The critical load is the threshold above, which the plastic deformation dominates and elastic recovery is negligible, leading to stable test results. The differences between the results by the Vickers hardness testers and by the micro-/nano-indentation testers can be attributed to several factors, i.e., a) indenter precision: Nano-indenters have sharper tips, allowing for more accurate contact area calculations at low loads; b) load range: Nano-indenters are designed for ultralow loads (< 1 N), but are more prone to ISE. The Vickers testers require loads of 5 N or greater to minimize errors; and c) test objective: Nano-indentation primarily reflects the properties of individual grains, while Vickers testing reflects a combined response of multiple grains and their grain boundaries. These factors contribute to the differences in hardness results obtained from the two testing methods, highlighting the importance of choosing an appropriate technique based on the specific material characteristics and testing goals.

For reliable mechanical characterization of advanced ceramics, an empirical minimum applied load of 5 N was established as a critical threshold in Vickers hardness testing. This threshold was essential for eliminating load-dependent artifacts and ensuring the reproducibility of measurements. This protocol effectively suppressed elastic recovery contributions to indentation work, obtaining the hardness values that accurately reflected a bulk plastic deformation behavior. Three distinct indentation morphologies were categorized based on the systematic analysis of dimensional recovery characteristics, a) stable type: This could align with conventional assumptions regarding indentation behavior; b) rebound type: This morphology resulted in higher Vickers hardness values due to the rebound effect during unloading; and c) extrusion type: This morphology resulted in lower Vickers hardness values. At low loads, elastic deformation could dominate, while plastic deformation could remain minimal. This scenario caused the calculated hardness that was greater than the true value. As the load further increased, the irreversible residual indentation size became significantly larger than the minor elastic recovery deformation, leading to a stabilization of the calculated hardness value. This phenomenon could be a primary reason for the load effects obtained in hardness testing.

Refrigeration technology is widely used in military, commercial, industrial, and civilian fields. However, the existing mechanical compression refrigeration technology faces limitations such as large volume, high energy consumption, low cooling efficiency, and environmental unfriendliness, making it unable to meet the growing demands of emerging technological fields. The electrocaloric effect (ECE), which refers to the alignment of dipoles in polar materials under an electric field, leading to changes in entropy (ΔS) and temperature (ΔT), offers a promising alternative. Solid-state electrocaloric coolers based on the ECE are directly driven by electrical energy, which can achieve heat transfer and cooling. They exhibit some advantages such as high energy efficiency, ease of miniaturization and integration, and environmental friendliness, making them a highly potential and efficient refrigeration technology. Barium titanate (BaTiO₃)-based ceramics have attracted extensive research attention in the electrocaloric field due to their excellent polarization strength and rich phase structures. However, some challenges such as low breakdown electric fields, high sintering temperatures, and the inability to simultaneously optimize working temperature ranges and polarization strength hinder their practical applications. To address these issues, this work was to incorporate sintering additives CuO/Li₂CO₃ into lead-free Ba_0.97Ca_0.03Sn_0.1Ti_0.9O₃ ceramics to promote dense grain growth and optimize the breakdown electric field. The dielectric constant was improved, while maintaining the broad temperature range and continuous phase transition characteristics of BCST ceramics, ultimately achieving a large electrocaloric temperature change of 3.37 K (@55 ℃, 160 kV·cm^-1).

Ba_0.97Ca_0.03Sn_0.1Ti_0.9O₃ powder was synthesized by a conventional solid-state reaction sintering method at 1200 ℃ with BaCO₃, CaCO₃, SnO₂, and TiO₂ as raw materials in a stoichiometric ratio. The ceramic powder was then pressed into disks with the dimensions of φ13 mm×1 mm and sintered at 1350-1500 ℃ for 3 h to obtain dense ceramic samples. After sintering, the ceramic samples were polished, and gold electrodes were sputtered onto their surfaces. The polarization-electric field hysteresis loops (P−E loop) at room temperature were recorded by a model FETS-2000 ferroelectric tester (Wuhan Yanhe Technology Co., Ltd., China) under a frequency of 10 Hz. The values of ΔT were tested through a model RdF P/N 27134-3 heat flux sensor. The dielectric properties were obtained by a model PK-CPT1705 test system (PolyK Technologies Co., USA) with a testing temperature range from 25 to 150 ℃ and a frequency range from 100 Hz to 100 kHz. The microstructure of the grain was determined by a model GeminiSEM 300 scanning electron microscope (SEM) (Zeiss Co., Germany) and a model 7000 S/L X-ray diffractometer (XRD) (Shimadzu Corp., Japan).

The XRD patterns reveal that all ceramic samples exhibit a pure perovskite structure, indicating that Cu²⁺ and Li⁺ ions diffuse into the BCST lattice to form a solid solution. The addition of CuO/Li₂CO₃ causes the XRD diffraction peaks shifting to lower angles, indicating that Li⁺(the radius of 0.73 Å) and Cu²⁺(0.71 Å) substitute the B-site Ti⁴⁺(0.61 Å) and Sn⁴⁺(0.71 Å), leading to a lattice expansion. The SEM images demonstrate that the incorporation of CuO/Li₂CO₃ results in significant grain growth and well-developed, highly dense microstructures in the ceramic samples. The grain size increases from 7 μm to 46 μm due to the low melting points of CuO/Li₂CO₃, which induces liquid-phase sintering effects during the early stages of the sintering process, thus promoting mass transfer and facilitating grain growth and ceramic densification. Dielectric temperature spectra indicate that the addition of CuO/Li₂CO₃ significantly enhances the dielectric constant of BCST ceramics. This improvement can be attributed to two factors, i.e., the increase in grain size; second, the aliovalent acceptor doping of Cu²⁺ and Li⁺ substituting Ti⁴⁺ and Sn⁴⁺, which generates lattice defects and oxygen vacancies . These defects coupled to form dipole clusters, thereby enhancing the dielectric constant. Also, the local random electric fields caused by the charge mismatch between Cu²⁺/Li⁺ and Ti⁴⁺/Sn⁴⁺, as well as the average ionic size effect, due to the reduction in the phase transition temperature. Polarization-electric field (P-E) loops show a significant increase in the polarization strength of the ceramic samples with the addition of CuO/Li₂CO₃, which can also be attributed to the role of dipole clusters. The electrocaloric performance of the material is greatly enhanced, with the BCST-CL ceramic achieving a giant electrocaloric temperature change of ΔT = 3.37 K (i.e., at 55 ℃, E = 160 kV·cm^-1).

The Ba_0.97Ca_0.03Sn_0.1Ti_0.9O₃ (BCST) ceramic samples with varying amounts of CuO/Li₂CO₃ sintering additives exhibited a single perovskite structure, characterized by large, well-developed grains and a dense microstructure. The addition of CuO/Li₂CO₃ sintering agents enhanced the dielectric constant of the material, while preserving the broad continuous phase transition temperature range of BCST. During the sintering process, Cu²⁺ and Li⁺ ions entered the grains, leading to lattice expansion and increased ferroelectric displacement. Also, as acceptor dopants, they formed defect dipole clusters with oxygen vacancies, thereby improving the material's polarization strength. The direct measurement tests demonstrated a significant enhancement in the electrocaloric temperature change (ΔT) of the ceramic samples, while maintaining excellent operational stability. The BCST-CL composition achieved a maximum ΔT of 3.37 K (at 55 ℃, 160 kV·cm^-1), providing a feasible strategy for further improving the performance of electrocaloric ceramic materials.

Formaldehyde as a volatile organic compound (VOCs) is one of the main indoor gas pollutants produced by building materials, furniture and interior decoration industry. The excessive exposure to formaldehyde can affect human-being health, and lead to nerve damage. Inhaling lower concentrations of formaldehyde can cause cough, allergies, headaches and other symptoms. It is thus of great significance to monitor formaldehyde efficiently, control indoor environmental pollution and maintain human health. In recent years, spinel oxides have some potential application prospects in the field of gas sensing due to their stable crystal structure and good gas sensing performance. CdGa₂O₄ is a kind of wide-band gap semiconductor spinel structure oxide, which has a good gas sensitivity to formaldehyde gas, but it has some problems such as complex preparation process, low yield, high working temperature and low response. Some studies show that metal oxides modified with two-dimensional materials can effectively improve the performance of gas sensors. MXene, represented by Ti₃C₂T_x, is a class of two-dimensional transition metal carbides or carbonitrides, which is widely concerned because of its unique layered structure, large specific surface area, rich functional groups and good electrical conductivity. In this paper, CdGa₂O₄ nanomaterials were prepared by a solvothermal method. On this basis, Ti₃C₂T_x-CdGa₂O₄ composites with different proportions were prepared by a hydrothermal method. The morphology, surface chemical composition and valence state of the elements were investigated, and the gas-sensitive properties of the composite were analyzed.

Ti₃C₂T_x was prepared by using the mixed solution of concentrated hydrochloric acid and LiF (AR, Shanghai Aladdin Reagent Co., China) as an etching agent, and the Al atomic layer in Ti₃AlC₂ was removed by HF generated. CdGa₂O₄ was prepared from Cd (NO₃)₂·4H₂O (AR, Shanghai Sarn Chemical Technology Co., China) and Ga (NO₃)₃·xH₂O (AR, Shanghai Maclin Chemical Technology Co., LTD., China). The Ti₃C₂T_x-CdGa₂O₄ composite was prepared by mixing CdGa₂O₄ with Ti₃C₂T_x magnetically in different proportions, and then reacting at 180 ℃ for 12 h by a hydrothermal method. The phase composition of the materials was analyzed by a model D8 Advance X-ray diffractometer (XRD, Bruker Co., Germany, 40 kV, 40 mA, Cu K_α, λ=0.154 06 nm, 5°-70°) and analyzed by a model JSM-7800F scanning electron microscope (SEM, accelerated voltage 15 kV). The elemental composition of the material was analyzed by a model ESCALAB 250 XI X-ray photoelectron spectrometer (XPS, Thermo Co., USA, accelerated voltage 15 kV), and the specific surface area and pore size distribution of the material were determined by a model ASAP2010C nitrogen adsorption and desorption instrument (Micromeritics Co., USA, accelerated voltage 15kV).

To determine the gas-sensitive properties of Ti₃C₂T_x-CdGa₂O₄ composite material, the sample was ground into a pulp with turpentine permeation alcohol, uniformly coated on the outer wall of alumina ceramic tube. After drying, Ni-Cr heating wire was installed and welded into para-heated components. The working temperature was controlled via adjusting the power added at the both ends of the heating wire and tested after calcination at 170 ℃ for 4 h. The sensitivity was defined as a ratio of the material stability resistances in air and a target gas, and the relative humidity of the test environment was constant (i.e., 50%).

The SEM images show that granular CdGa₂O₄ accumulates on the surface of Ti₃C₂T_x with a layered structure. The EDS spectra show that there are elements Cd, Ga and O in the composites, and the ratio is 1∶2∶5∶7, which may be caused in the presence of Ga₂O₃ components in the composites. According to the adsorption desorption isotherm analysis of XPS and N₂, the functional groups (—O, —OH, —F) in Ti₃C₂T_x provide additional active sites for the adsorption of gas molecules. The addition of Ti₃C₂T_x builds the mesoporous structure, and also increases the specific surface area of the composite, exposing more gas adsorption active sites, thus improving the gas sensitive performance of the sensor. The maximum response value of sample TC-3 to 0.01% formaldehyde at 110 ℃ is 105, which is 9.4 times greater than that of pure CdGa₂O₄. The selectivity and sensitivity of the sensor to different gases at 110 ℃ are investigated. The results show that the sample TC-3 has good selectivity and detection limit for formaldehyde, and the lowest detection limit is 0.00001%, which proves that the prepared sensor TC-3 has a great practical application potential.

In this paper, CdGa₂O₄ nanomaterial was prepared by a solvothermal method, Ti₃C₂T_x with a layered structure was prepared with LiF and concentrated hydrochloric acid system, and then Ti₃C₂T_x-CdGa₂O₄ composite was prepared by a hydrothermal method. The gas sensitive properties of CdGa₂O₄ and a series of Ti₃C₂T_x-CdGa₂O₄ composites were investigated. The results showed that at 110 ℃, the response value of sample TC-3(7% Ti₃C₂T_x-CdGa₂O₄) composite to 0.01% formaldehyde gas was 105, the lowest detection limit was 0.00001%, compared with pure CdGa₂O₄, thus improving the sensitivity and reducing the operating temperature. The combination of appropriate amount of Ti₃C₂T_x could be conducive to improving the gas sensitivity of CdGa₂O₄ material to formaldehyde gas.

Solar energy as a sustainable energy source has attracted much attention, and the development of highly efficient photothermal conversion materials becomes a key to coping with the energy crisis due to an increase in global energy consumption and demand. Conventional photothermal materials generally have some bottlenecks such as complication preparation process, high cost, and lack of durability, and there is an urgent need to develop novel and efficient materials. As a crystallization of Chinese ceramic craftsmanship inherited for thousands of years, black porcelain glaze with its rabbit hair, oil drop and other classic glazes show a unique artistic value due to the low cost of raw materials, mature and stable technology, especially for the solar spectra of the wide-area absorption characteristics in photothermal conversion to show a significant advantage. However, there is still controversy in the academic community regarding the coloring mechanism of black glaze, and there is a lack of systematic research on its photothermal properties. In this work, we investigated a relationship between the iron oxide content and the glaze layer by using a basic glaze of SiO₂-Al₂O₃-CaO-MgO-Na₂O-ZnO-Fe₂O₃ in the microstructure and glaze color, revealing the mechanism of its black color formation and photothermal conversion properties.

The raw materials were mixed in a ratio of 1.0∶1.3 and ground in a ball mill, and the ground slurry was sieved through a 200-mesh sieve. Afterwards, the glaze paste was dipped and coated on a 40 mm diameter billet for several times, keeping its thickness of approximately 1 mm. The samples were dried in an oven at 75 ℃ for 12 h, and then fired in an electric furnace in air according to the following firing procedure, i.e., the temperature increased to 400 ℃ at a rate of 2.5 ℃/min and kept warm for 30 min, then increased to 1250 ℃ at a rate of 4 ℃/min and kept warm for 90 min, and then decreased to 1100 ℃ at a rate of 2.5 ℃/min and kept warm for 30 min. Finally, the glaze sample was naturally cooled to room temperature in the furnace.

The parameters such as L*, a* and b* values in the CIE space of the samples were determined by a model WSD-3C whiteness meter. The light reflection spectra of the glaze were analyzed by a model Lambda 850 UV/Vis diffuse reflection spectrometer. The Raman spectra was characterized by a model InVia type Raman spectroscope (Renishaw Co., UK) with an excitation wavelength of 532 nm. The physical phase of the glaze was detected by a model D8-Advance X-ray diffractometer (XRD, Bruker Co., Germany), with a 2θ of 10°-80°. The glaze samples were firstly etched with 10% hydrofluoric acid solution for 30 min, and then the microstructure was determined by a model SU8010 scanning electron microscope (SEM, Hitachi Co., Japan). The elemental composition was determined by a model 550I energy dispersive X-ray spectroscope (EDS) . The morphology and structure were analyzed by a model JEM2100F transmission electron microscopy (TEM, JEOL Co., Japan) at a voltage of 200 kV, and the surface temperature of the glaze samples was tested by a model UT320D high-precision K/J dual-purpose thermocouple thermometer (UNI-T Co., China). The thermograms of the samples were obtained by a Ti400+ thermal infrared image analyser (FLUKE Co., USA).

The experiment results show that the color of the glaze changes with the increase of iron oxide content. The glaze is transparent when the iron oxide content is 0.0%. The glaze surface turns brownish yellow when the iron oxide content increases to 2.5%. The glaze surface appears dark black when the content further increases 6.5%. A micro-/nano- array structure of resembling zinc ferrite crystals forms when the excess of iron oxide reaches 9.5%, which affects the color of the glaze surface. Clearly, the iron oxide goes through the process of participating in the network structure of the glaze layer and precipitating from the glaze layer. The in-depth analysis of the ink-black colored glaze samples reveals that a large number of iron-rich agglomerates or even crystal nuclei of approximately 3 nm are precipitated from the glaze layer, and the glaze samples are characterized by an increase in the refractive index gradient from the glaze surface to the billet. This special micronaire structure can strengthen the glaze layer's absorption of the incident light, resulting in the glaze with a black color effect and also greatly improving the performance of its photothermal conversion.

This study investigated the effect of iron oxide variation on the microstructure and color of the glaze layer in the SiO₂-Al₂O₃-CaO-MgO-Na₂O-ZnO-Fe₂O₃ multicomponent glaze system. The results indicated that when the content of iron oxide was low, the trivalent iron ions could participate in the network structure of the glaze layer in the form of [FeO4] tetrahedra, and the glaze surface dominated due to the chemical coloring of Fe ions, presenting a brownish-yellow color. A large number of iron-rich aggregates and even crystal nuclei of approximately 3 nm could precipitate from the glaze layer when the content of iron oxide increased to 6.5%, and the glaze layer exhibited a structural characteristic of increasing refractive index gradient from top to bottom. The special micro-/nano-structure of this glaze layer could greatly increase the absorption and consumption of sunlight, and the glaze surface had a black effect and structural coloring characteristics. The results of photothermal performance test showed that the glaze could have the maximum temperature difference of 12.2 ℃ with the blank color, indicating its good photothermal conversion characteristics and a great potential in the green utilization of solar energy.

Silicon nitride (Si₃N₄) ceramic materials are widely used in industries due to their excellent high temperature resistance and corrosion resistance. With the increasing application of Si₃N₄ ceramic materials, the research on the service in various extreme environments has attracted recent attention, especially the corrosion resistance of Si₃N₄ ceramics in corrosive liquids (i.e., the corrosion behavior of HF on Si₃N₄ ceramics).

Si₃N₄ ceramics have a superior acid corrosion resistance. A prolonged contact with HF solution leads to a decrease in the stability of Si₃N₄ ceramics, thus damaging the overall function. For porous Si₃N₄ ceramics, its unique structure aggravates the corrosion of acid solution. In some special applications, porous Si₃N₄ ceramics are required to have sufficient strength and acid resistance to ensure application stability and life. However, the existing reports mostly focus on Si₃N₄ composite ceramics or dense Si₃N₄ ceramics with sintering aids. Little work on the preparation of Si₃N₄ ceramics using pure Si powder as a raw material for nitridation sintering, specifically the corrosion behavior of porous Si₃N₄ ceramics in HF, has not been reported yet. In this work, Si₃N₄ ceramics were prepared via nitridation reaction sintering using a pure Si powder as a raw material without any sintering additives. The acid corrosion resistance of Si₃N₄ ceramic materials with a porosity of up to 30% prepared was investigated to explore the corrosion behaviors of and time on Si₃N₄ ceramic samples at different HF concentrations.

High-purity porous Si₃N₄ ceramics with a porosity of 30% were prepared via nitridation reaction sintering using Si powder with a purity of 99.99% (in mass fraction) as a raw material. After cold isostatic pressing at 200 MPa, the ceramics were processed into the samples with appropriate sizes, and their density, flexural strength, and phase composition were analyzed. The HF solutions with different mass fractions of 20%, 30%, and 40% were prepared, respectively. In the first group, the same amount of HF solution with different mass fractions was taken, put into plastic containers with the ceramic samples, and corroded at room temperature for 200 h. In the second group, the HF solution with a mass fraction of 40% was used as an etching solution, and the samples were placed for corrosion. The corrosion time was 100, 200, 300 h, and 400 h, respectively. Each group of samples was sealed and placed in dark. Afterwards, the samples were cleaned, dried and tested, and the changes of mass, density phase composition and other properties before and after the corrosion were analyzed.

As the mass fraction of HF solution increases from 20% to 40%, the ceramic sample reacts with HF to form a corrosion product (NH₄)₂SiF₆ phase, which attaches to the surface of the sample to form a loose corrosion layer, and gradually fells off and dissolves in the acid solution, resulting in an increase in the mass loss rate. Simultaneously, the increase of pores caused by corrosion reaction also results in a higher porosity, lower density, and reduced flexural strength of the ceramic samples as the HF concentration increases. The change in the microstructures of the samples before and after the corrosion indicates that the Si₃N₄ ceramic sample is immersed in HF solution to produce (NH₄)₂SiF₆, which causes the loss of Si and N, leading to an increased porosity and a reduced density within the sample, and thereby degrading the performance of the ceramic sample.

The mass loss rate and porosity of ceramic samples increase, while density and flexural strength decrease as the corrosion time increases from 100 h to 400 h. From the perspective of corrosion rate, the corrosion rate decreases after 200-h corrosion. This is because the corrosion products of (NH₄)₂SiF₆ formed on the sample surface can block a direct contact between HF and the ceramic sample at a constant HF solution concentration. The extension of the corrosion time does not lead to an increase in the corrosion rate, indicating that the corrosion layer plays a significant role in maintaining the stability of Si₃N₄ ceramics in a corrosive environment.

Si₃N₄ ceramic materials prepared by nitridation reaction sintering with pure Si powder were corroded in HF solution for 200 h. The results showed that the mass, density and bending strength of ceramic samples decreased gradually, and the porosity increased with the increase of HF concentration and corrosion time. The Si₃N₄ ceramic sample was immersed in HF solution and reacted with HF to form a phase of (NH₄)₂SiF₆, leading to a loose corrosion layer on the surface of the sample. The mass loss and density of Si₃N₄ ceramic samples were reduced due to the corrosion reaction, and the presence of the corrosion layer reduced the corrosion rate, indicating that the high-purity porous Si₃N₄ ceramics were more stable in HF solution, and could maintain a better corrosion-resistant performance.

Pure NBT exhibits the frequency-dependent Curie temperature, indicating that its dielectric properties are affected by temperature, measurement frequency, and material processing condition. To enhance the dielectric and relaxor properties of NBT, various dopants such as Sr, K, Li and Bi are incorporated into the NBT structure. These modifications significantly alter the dielectric constant and relaxation behavior, demonstrating a dominant influence of dopant on the material properties. Among these, the solid solution of BaTiO₃ (BT) with NBT is widely investigated due to its ability to stabilize the perovskite structure and improve dielectric performance. However, the temperature-dependent stability of dielectric properties remains a critical challenge for high-temperature applications.

In this study, (1-x)(0.75Na_0.5Bi_0.5TiO₃-0.25BaTiO₃) -xBaZrO₃ (NBT-BT-xBZ, x = 0, 0.08, 0.14, and 0.20) ceramics were prepared by a solid-state reaction method. The effect of BaZrO₃ (BZ) addition on the structural, dielectric, and energy storage properties was systematically investigated. In addition, the phase transition and relaxation behaviors were also analyzed based on the modified Curie-Weiss law, Vogel-Fulcher relation, and Lorentz-type empirical law.

The starting materials were powders of high purity Na₂CO₃, Bi₂O₃, TiO₂, BaCO₃, and ZrO₂. The powders were weighed according to a stoichiometric ratio (with 1% excess of Na and Bi) and ground with ethanol in a ball mill at 300 r/min for more than 12 h, and the weight ratio of raw material to ethanol and zirconium balls was 1∶1∶2. The dried material was heat-treated at 850 ℃ for 2 h to promote the formation of NBT-BT-BZ. After further grinding for 12 h, the samples were mixed with a small amount of polyvinyl alcohol (PVA). The samples were sintered in air at 1150 ℃ for 2 h and cooled to room temperature.

The phase composition of the ceramic samples was determined by an model D8 ADVANDCE X-ray diffractometer (D8 ADVANDCEXRD, Bruker AXS Ltd., Germany) with Cu target Kα rays, at X-ray wavelength λ of 1.540 6 Å, 2θ in the range of 10° to 80°, applied voltage of 40 kV, and a current of 500 mA. A silver paste was coated on the two surfaces as electrodes and heat-treated at 700℃ for 10 min. The dielectric properties of the ceramic samples were determined at different frequencies by a model DMS-1000 high-temperature dielectric temperature spectroscope (BALAB Tech. Co., China) with at a ramp rate of 3(°)/min in a temperature range from room temperature to 450 ℃. The overdamped (200 Ω) discharge tests for bulk ceramic samples were performed by a model CFD-005 discharge tester (Gogo (GG) Instruments Technology, China)).

The XRD patterns indicate that all the ceramic samples have a perovskite structure without any detectable secondary phase, proving that zirconium ions can completely enter the lattice and form a solid solution. Based on the locally magnified XRD peaks, the XRD peak shape shifts towards lower angles as a whole as the BZ content increases. This indicates that the overall volume of the crystal cell shows an expansion as the Zr ions replace Ti ions due to different ionic radii of Zr and Ti ions. The SEM images show that the grain size gradually increases with increasing the BZ content. The addition of BZ promotes the grain growth. However, this gradually slows down with the increase of content up to x of 0.20. The limited grain size variation appears in the latter two samples. All the samples show a relatively dense morphology.

The Curie temperature of the NBT-0.25BT ceramic samples is 256 ℃, which is similar to the reported results. The Curie temperature decreases gradually with the increase of BZ additive, and the dielectric temperature spectrum flattens out, indicating that the enhanced structural and temperature stability of the NBT-BT-BZ ceramics. The maximum values of all dielectric constants correspond to temperatures that increase with frequency, indicating a dielectric relaxor behavior. A frequency dispersion is accompanied at near the Curie temperature, which can be ascribed to the thermal evolution of the tetragonal polar nanoregions (PNRs) and the mixing effect of the transition from tripartite to tetragonal PNRs.

The γ values obtained from the experimental data at 100 kHz are 1.79, 1.83, 1.89, and 1.92 for NBT-BT, NBT-BT-0.08BZ, NBT-BT-0.14BZ, and NBT-BT-0.20BZ, respectively. The γ value increases gradually with the addition of the BZ content, showing an enhanced relaxation of the NBT-BT-BZ ceramics. The comparison of discharge current curves and energy density of all the ceramics indicate that the addition of BZ significantly improves the discharge current and energy storage performance. A high discharging energy density (W_d) of 1.6 J·cm^-3 with a fast discharging speed (τ_0.9) of 75 ns is obtained for the ceramic samples with x of 0.14. This can be attributed to an increased relaxation as the BZ content increases.

NBT-BT-BZ ceramics were prepared by a solid-state reaction method. The XRD patterns revealed a phase transition from a tetragonal phase to a pseudocubic phase as the BZ content increased. The dielectric relaxation behavior of the ceramics could be described by three empirical laws (i.e., modified Curie-Weiss law, Vogel-Fulcher relation and Lorentz-type empirical law). The dielectric relaxation followed the modified Curie-Weiss law and the Vogel-Fulcher relationship. The parameters γ and E_a, which were obtained to evaluate the relaxation behavior, increased at a higher BZ content. The Lorentz-type relationship effectively described the temperature dependence of the dielectric constant on both the low- and high-temperature sides within a specific temperature range for all the ceramics.

Building a clean, low-carbon, safe, and efficient energy system and implementing renewable energy substitution actions become important issues to promote sustainable energy utilization. As a representative of clean and sustainable energy, the use of solar energy can greatly reduce carbon emissions, while meeting the growing demand for energy consumption. Since 2009, CH₃NH₃PbI₃ perovskite has been used as a light absorbing layer, achieving a photoelectric conversion efficiency of 3.8%. The organic-inorganic hybrid perovskite material has attracted much attention as a solar cell light absorbing material. However, lead halide perovskite materials are highly susceptible to various external environmental factors such as dopants, heat, light, humidity, etc., which can cause failures in the chemical or physical structure during their application, greatly restricting the commercial application of the devices. It is thus of great significance for the practical application of lead halide based perovskite devices to investigate the intrinsic relationship among the structure, properties and stability. This study employed methylammonium (CH₃NH₃⁺, MA), formamidinium (CH (NH₂)₂⁺, FA), and Cesium (Cs) as A-site ions to construct three perovskite configurations (i.e., MA_1-xFA_xPbI₃, MA_1-xCs_xPbI₃, and Cs_1-xF A_xPbI₃). The structure, stability, electronic and optical properties were investigated, and the theoretical basis for further experimental optimization and exploration of efficient and stable perovskite solar cell materials was also discussed.

The structure and optoelectronic properties of A-site modified lead halide A'_1-XA''_XPbI₃ (where A' and A'' are any of MA, FA, and Cs) perovskite configurations were investigated based on density functional theory by using CASTEP module under the Perdew Burke Ernzerhof exchange correlation functional of generalized gradient approximation via optimizing the structure and calculating the formation energy, band structure, density of states and absorption coefficient. After structural convergence testing, the energy cutoff of the plane wave was selected as 600 eV, and the Monkhorst-Pack scheme was used to mark the Brillouin zone by using a 2×3×2 k-point grid. The energy convergence standard of the system was set at 10^-5 eV/atom. The maximum force was limited to 0.03 eV/Å with the maximum stress of 0.05 GPa, and the maximum displacement of 0.01 Å.

The optimized crystal structures of MA_1-xCs_xPbI₃, MA_1-xFA_xPbI₃ and Cs_1-xFA_xPbI₃ (x=0.125, 0.250, 0.500) perovskite configurations show that the cell volume of Cs_1-xFA_xPbI₃ and MA_1-xFA_xPbI₃ increases while MA_1-xCs_xPbI₃ decreases with increasing the doping content due to the atomic distance of FA group with 3.996 A, MA group with 3.009 A and the radius of Cs⁺ only 1.88 A. Meanwhile, the doping ions at A-site can cause the distortion of Pb-I octahedron, resulting in variations on bond length, bond angle and torsion of octahedron, and MA_0.875FA_0.125PbI₃ demonstrates a slight distortion. The formation energy of MA_1-xCs_xPbI₃, MA_1-xFA_xPbI₃ and Cs_1-xFA_xPbI₃ configurations is negative. As the Cs/MA, FA/MA, and FA/Cs ratios increase, the formation energy becomes more negative, indicating the doped groups can enter the lattice spontaneously and smoothly. The formation energy of MA_1-xFA_xPbI₃ is minimum (i.e., -521.77, -1042.79 eV and -1824.49 eV correspond to x=0.125, 0.250 and 0.500), compared to that of MA_1-xCs_xPbI₃ (i.e., -492.58, -984.86 eV and -1722.95 eV) and Cs_1-xFA_xPbI₃ (-28.87, -57.79 eV and -101.61 eV), due to the large energy difference in MA and FA groups and the resulting strong force between atomic groups. This indicates that FA groups can enter MAPbI₃ lattice more easily and form a more stable structure. The energy band structure calculated shows that the conduction band minimum (CBM) and valance band maximum (VBM) of MA_1-xCs_xPbI₃, MA_1-xFA_xPbI₃ and Cs_1-xFA_xPbI₃ are located at the same high symmetric point G(0, 0, 0), thus determining direct band gap semiconductors. Furthermore, Pb 6p orbital and I 5p orbital dominate in CBM and VBM, respectively. Except that, the electron orbital of FA contributes to CBM significantly, mainly situating at 3.33 eV. The contribution of MA and Cs is primarily at -4.60 eV and 5.35 eV away from the Fermi surface, hence leading to a relatively large band gap in MA_1-xCs_xPbI₃. As for Cs_1-xFA_xPbI₃, Cs and FA orbital overlap at the conduction band (CB, 2.0-4.0 eV), and a great covalent bond can be formed between C-Cs, which facilitates the new energy orbital formed and thus more stronger orbital hybridization with Pb and I, and eventually in turn causes CB to shift upward and the band gap increases. However, compared with Cs, the interaction of MA and FA electron orbital at CB reduces, and MA_1-xFA_xPbI₃ shows a relatively small band gap. MA_0.875FA_0.125PbI₃ exhibits a decent band gap and a decreased energy band dispersion at CBM, promoting the transition of charge carriers and improving light absorption. Also, the real part of the dielectric functions ε₁(ω) peak for MA_0.875FA_0.125PbI₃ demonstrates a red shift from 533 nm to 572 nm, and ε₁(ω) is optimal with the increase of wavelength. The widened wavelength response range and high ε₁(ω) endow MA_0.875FA_0.125PbI₃ with an optimal light absorption capacity in the visible light range of 380-780 nm.

The optoelectronic properties of lead iodide-based perovskite A'_1-XA''_XPbI₃ were predicted by using first-principles via the structural optimization and the calculation of formation energy, band structure, density of states, absorption coefficient. The results indicated that MA, FA groups, and Cs ions could spontaneously enter the A-site of lead iodide A'_1-XA''_XPbI₃ perovskite to form a stable structure. Compared with MA_1-xCs_xPbI₃ and Cs_1-xFA_xPbI₃, MA_1-xFA_xPbI₃ configuration displayed a minimum distortion of Pb-I octahedral and a more stable structure. In addition to the contribution of I 5p orbitals to VBM and Pb 6p orbitals to CBM, the electronic orbitals of FA in the CBM resulted in a dramatical decrease in band dispersion, which was conducive to light absorption. The absorption peak of MA_0.875FA_0.125PbI₃ at 500nm showed a significant red shift. The widened wavelength response range and increased light absorption coefficient endowed MA_0.875FA_0.125PbI₃ with an optimal light absorption ability in the visible light range, making it a promising solar cell photovoltaic material.

The generation of biological wastes such as cow dung and aloe vera waste (AVW) causes a serious ecological pollution. The microbial electrolytic cell coupled with anaerobic digestion (MEC-AD) system can make a rational utilization of these biodegradable organic wastes, which is of vital importance for alleviating environmental deterioration and reducing resource waste. Electrode materials and accelerants are the two major factors that affect methane production in the MEC-AD system. They affect microbial attachment and electron transfer in the MEC-AD system. Bio-based carbon materials are carbon materials prepared from biomass as raw materials. They have characteristics such as a rich pore structure, good chemical stability, biocompatibility, and controllable surface properties, which can be used as accelerants and electrodes in the MEC-AD system to optimize its performance. This study was to investigate the influence of biomass-derived carbon as an electrode and accelerant on the performance of the MEC-AD system, and the mechanism for increasing the production of biogas and methane was also analyzed, thus providing a basis for the multifunctional application of biomass-derived carbon in the MEC-AD system.

A series of experimental methods were adopted to study the MEC-AD system. Two types of bio-based carbon, i.e., aloe vera waste derived spherical carbon (AVW-SC) and porous carbon (AVW-PC), were synthesized via hydrothermal carbonization. The raw AVW material was washed with water, dried, ground, and subjected to hydrothermal treatment to obtain AVW-SC. After activating AVW-SC with KOH, it was carbonized in a tube furnace to obtain AVW-PC.

In the preparation of the electrodes, bio-based carbon (AVW-SC and AVW-PC) was mixed with 5% polytetrafluoroethylene powder in ethanol and deionized water, and then ground in a ball mill for 4 h to form a slurry. The slurry was evenly sprayed on the Ti mesh, dried and sintered in N₂ atmosphere at 360 ℃ to obtain Ti-SC and Ti-PC electrodes.

Four groups of experiments were conducted to determine the optimal voltage, compare different carbon electrodes, and explore the optimal coating amount. The MEC-AD reactor adopted 500 mL wide-mouthed glass bottles with a working volume of 400 mL. Each MEC-AD system received a co-substrate mixture of cattle dung and aloe vera waste and inoculum of sewage sludge in a mass ratio of 3∶7. Afterward, they were placed at (36±1) ℃ for 35 d. The biogas was collected by a water displacement method.

The materials were analyzed by characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), and electrochemical tests were conducted on different electrodes. The composition, pH, TS, VS, TCOD and nutrient content of biogas were analyzed by standard chemical methods. Microbial community analysis was conducted using high-throughput sequencing technology. The modified Gompertz model was adopted to predict the kinetic parameters, and the coulombic efficiency and methane recovery rate were calculated according to a specific formula.

The result shows that AVW-SC is spherical and closely aggregated, while AVW-PC has a three-dimensional network structure, with average pore diameter of 9.77 nm. The electron exchange capacity (EEC) of AVW-PC (i.e., 0.75 μmol·e^-/g) is higher than that of AVW-SC (i.e., 0.15 μmol·e^-/g), indicating a better electron exchange capacity. These results indicate that AVW-PC provides more substrate and bacteria accumulation sites, and has better electron-donating and electron-accepting ability, thus improving the digestion efficiency.

In the MEC-AD system, using Ti mesh as an electrode, the effect of different voltages (i.e., 0, 0.4, 0.6, 0.8 V and 1.2 V) on the system performance is investigated, obtaining the optimum biogas production and organic matter degradation rate at 0.8 V. AVW-SC and AVW-PC are respectively coated on Ti mesh as electrodes. The results show that the MEC-AD system with AVW-PC coated Ti mesh as the electrode has a better performance. The electrochemical analysis shows that the electrode coated with AVW-PC has a larger specific capacitance and a smaller charge transfer resistance, indicating that AVW-PC can improve the electrochemical properties and electron transfer ability of MEC-AD system. The influence of coating amount (i.e., 0.025, 0.05, 0.10, 0.15, and 0.20 g) of AVW-PC on the MEC-AD system is investigated. At a coating amount of AVW-PC of 0.1 g, the cumulative biogas production and methane content of the Ti_0.8-PC_0.1 group both reach the maximum values. Different doses of AVW-PC (i.e., 0.10%, 0.15%, 0.20%, and 0.25%) are added as accelerants in Ti_0.8-PC_0.1. At the addition amount of AVW-PC of 0.20%, the Ti_0.8-PC_0.1/PC_0.2 group performs the optimum biogas production (i.e., 633.63 mL/g VS), methane content (i.e., 65.85%), and total nutrient content of biogas residue (i.e., 42.30 g/kg). In Ti_0.8-PC_0.1/PC_0.2, Bacteroidales, Pseudomonadales, Oscillospirales, Methanobacteraceae, Methanospirillaceae, Methanosarcinacea and Methanosaetaceae significantly increase. The increase in microbial diversity promotes interspecific hydrogen transfer (IHT), interspecific acetic transfer (IAT), and direct interspecific electron transfer (DIET), thereby enhancing methanogenic efficiency.

AVW-SC and AVW-PC were utilized as electrodes and accelerants to enhance methane yield in MEC-AD system. The Ti mesh electrode coated with different concentrations of AVW-PC achieved the optimal biogas production at 0.8 V. Specifically, the Ti_0.8-PC_0.1 combination could generate the maximum total amount of biogas and methane proportion. The Ti_0.8-PC_0.1/PC_0.2 combination exhibited the optimum performance (i.e., biogas yield of 633.63 mL/g VS, methane content of 65.85% and total nutritional content of 42.30 g/kg). High abundances of Bacteroidales, Pseudomonadales, Oscillospirales, Methanobacteraceae, Methanospirillaceae, Methanosarcinaceae, and Methanosaetaceae appeared in the Ti_0.8-PC_0.1/PC_0.2 group, compared to other groups. In addition, an increased microbial diversity led to an enhanced methane production through processes like DIET. This research could highlight the potential significance of AVW-PC as both electrode and accelerator for increasing methane production and provide a perspective for improving MEC-AD performance through multiple applications of biomass-derived carbon.

Sodium-ion batteries (NIBs) have attracted much attention as promising alternatives to lithium-ion batteries due to the natural abundance of sodium, low cost, and enhanced safety. Among various cathode materials, layered transition metal oxides, particularly O3-type structures, are considered highly attractive due to their high specific capacity, moderate operating voltage, and facile synthesis. High-nickel ternary oxides such as NaNi_0.6Co_0.2Mn_0.2O₂ (NNCM622) exhibit superior capacity and economic viability, making them candidates for next-generation NIBs. However, the electrochemical performance of these materials is highly sensitive to synthesis conditions, especially the heat treatment process, significantly affecting the crystallinity, morphology, and structural stability. This work was to investigate the influence of calcination temperature on the structure, morphology, and electrochemical properties of O3-type NNCM622 cathode materials synthesized via a conventional solid-state reaction.

Method In the preparation of O3-type NNCM622 cathode materials, stoichiometric amounts of Ni_0.6Co_0.2Mn_0.2(OH)₂ precursor and NaOH (with a 5% excess of sodium source) were thoroughly mixed and subsequently calcined in an oxygen atmosphere at 700, 750 ℃ and 800 ℃ for 24 hours, yielding the final products denoted as NNCM622-700, NNCM622-750, and NNCM622-800, respectively.

The X-ray diffraction(XRD) patterns show that all the samples crystallize in an O3-type layered structure (space group R-3m). The clear splitting of the (006)/(012) and (018)/(110) diffraction peaks indicates a well-developed layered structure. The Rietveld refinement reveals that the sample calcined at 750 ℃(i.e., NNCM622-750) possesses the lowest refinement discrepancy factor (R_wp = 3.374%) and optimal crystallinity. In contrast, the sample NNCM622-700 has a poorer crystallinity due to incomplete reaction at a lower temperature, while the sample NNCM622-800 likely suffers from sodium volatilization and potential structural distortions at a higher temperature. The X-ray photoelectron spectra (XPS) on the sample NNCM622-750 indicate the coexistence of Ni²⁺/Ni³⁺, Co, and Mn in the material, which is consistent with the expected valence states for this composition. The inductively coupled plasma optical emission spectra (ICP-OES) show that the elemental compositions of all the samples are close to the theoretical stoichiometry.

The images of scanning electron microscopy (SEM) reveal that all the samples consist of spherical secondary particles with the sizes of 2-10 μm formed due to the agglomeration of numerous primary particles. The sample NNCM622-700 has larger primary particles due to insufficient reaction, whereas the sample NNCM622-800 exhibits over-sintering and particle cracking. The images of transmission electron microscopy (TEM) and the mapping of energy dispersive X-ray spectroscopy(EDS) of the sample NNCM622-750 further confirm its well-crystallized layered structure with an interplanar spacing of 0.263 nm, corresponding to the (102) plane, and a homogeneous distribution of elements Na, Ni, Co, and Mn.

The electrochemical performance is evaluated in half-cells versus sodium metal. The NNCM622-750 cathode has a high initial discharge capacity of 150.5 mA·h·g^-1 at 0.1 C (1 C = 150 mA·h·g^-1) within the voltage window of 1.5-4.2 V, with a high initial Coulombic efficiency of 86.5%. This cathode also demonstrates a superior rate capability, retaining discharge capacities of 106, 95 mA·h·g^-1 and 85.9 mA·h·g^-1 at 1 C, 2 C, and 5 C, respectively. After 100 cycles at 1 C, this cathode maintains 55.3% of its initial capacity, showing a better cycling stability than the other two samples. In contrast, the NNCM622-700 and NNCM622-800 cathodes deliver lower initial capacities (i.e., 119.8 mA·h·g^-1 and 97.8 mA·h·g^-1, respectively) and suffer from more rapid capacity decay. This performance degradation is attributed to incomplete sodiation (for NNCM622-700) and sodium loss/structural defects (for NNCM622-800), increasing the electrode impedance and hindering Na⁺ diffusion.

The cyclic voltammetry (CV) curves of the NNCM622-750 cathode shows a pair of well-defined redox peaks around 2.3/2.7 V, corresponding to the Ni²⁺/N⁴⁺ redox reaction. The minimum peak potential separation (ΔV = 0.4 V) for NNCM622-750 indicates the lowest polarization and optimum reaction reversibility among the three samples. The electrochemical impedance spectra (EIS) reveal that the NNCM622-750 electrode has the minimum charge-transfer resistance (i.e., R_ct = 327.1 Ω). Furthermore, based on the Warburg coefficient derived from the EIS data, the maximum Na⁺ diffusion coefficient (D_Na⁺) for NNCM622-750 (i.e., 7.53×10^-15 cm²·s^-1) can be obtained, compared to that for NNCM622-700 (i.e., 5.12×10^-15 cm²·s^-1) and NNCM622-800 (i.e., 1.92×10^-17 cm²·s^-1). These results corroborate its superior rate performance.

The nickel-rich O3-type NNCM622 cathode materials were synthesized by a high-temperature solid-state reaction method, and their microstructures and electrochemical properties were investigated. The O3-type NNCM622 cathode material prepared under calcination at 750 ℃ for 24 h exhibited a superior crystallinity, a well-defined layered structure, and the minimum Na⁺ diffusion barrier due to its excellent structural and compositional synergy. As a result, the NNCM622-750 cathode delivered the maximum initial discharge specific capacity (i.e., 150.5 mA·h·g^-1 at 0.1 C with a coulombic efficiency of 86.5%), superior rate performance (i.e., 85.9 mA·h·g^-1 at 5 C), and relatively high cycling stability (i.e., capacity retention of 55.3% after 100 cycles at 1 C). An appropriate calcination temperature could enhance the reversibility and cycling performance of the cathode material, thereby improving the structural stability and electrochemical properties of nickel-rich O3-type NNCM622 cathodes. This work could present a simple and low-cost preparation process for synthesizing nickel-rich O3-type NNCM622 cathode materials with superior electrochemical performance, offering valuable insights for addressing the challenges associated with heat treatment in the development of next-generation layered cathode materials for sodium-ion batteries.

This study was to investigate the influence of mixed alkali effect on the structure and properties of a R₂O-CaO-Al₂O₃-SiO₂ glass system, to provide theoretical support and practical guidance for optimizing the formulation of high-level radioactive liquid waste (HLW) glass vitrification technology. The safe disposal of HLW is a critical aspect for the sustainable development of the nuclear industry. The Joule-heated melter vitrification as an internationally engineered and implemented method could immobilize radioactive waste via melting HLW with base glass frit in an electric furnace to form a stable vitrified product for long-term containment.

Glass samples with varying Z-values (i.e., Z = n(Na₂O)/(n(Na₂O) + n(Li₂O)) were prepared by a high-temperature melting method. Their structure and properties were systematically analyzed by infrared spectroscopy, Raman spectroscopy, and high-temperature resistivity analysis.

The structural characterization revealed that the silicate tetrahedral units Q² and Q³ are the primary structural units influencing glass properties. The structure exhibits regular changes as Z-value increases. At Z=0.2, the proportions of Q³ and Q⁴ reach the maximum values, while Q¹ and Q² reach the minimum values. At Z=0.6, Q¹, Q³, and Q⁴ proportions reach the maximum values, while Q² reaches the minimum value, indicating the most compact glass structure and the most significant mixed-alkali effect.

The results of performance tests demonstrate that the physical and thermal properties both are governed due to the mixed-alkali effect The density and thermal expansion coefficient both increase with increasing Z-value. The density reaches the maximum value as Z=0.6, while the thermal expansion coefficient has the minimum value. The glass transition temperature (T_g) initially decreases and then increases, reaching its minimum as Z=0.2. The high-temperature viscosity has the maximum value as Z=0.4 and the minimum value as Z=0.6.

For the electrical properties in single-alkali systems, the resistivity at the melting temperature (T₂) decreases in an order of K₂O >Na₂O > Li₂O, while it at the forming temperature (T₄) decreases in an order of K₂O > Li₂O > Na₂O. In the mixed-alkali system, the resistivity reaches the maximum value at Z of 0.6-0.8, being correlated to the "blocking effect" of alkali ions. The activation energy for electrical conduction changes nonlinearly with Z-value. In single-alkali systems, it increases in the order of Na₂O < Li₂O < K₂O.

This study clarified the mixed-alkali effect on the R₂O-CaO-Al₂O₃-SiO₂ glasses, particularly highlighting the low viscosity as Z = 0.6 and the high resistivity characteristics as Z = 0.6-0.8. These findings could provide a clear guidance for glass formulation design.

Hard optical fiber imaging components as two-dimensional array imaging materials comprised of tens of millions to billions of micro- and nano-scale optical glass fibers have extensive applications in numerous optical systems, including low-light-level image intensifiers and space target detection systems. Resolution and contrast are crucial indicators affecting the performance of these components. Elemental diffusion at the core-clad interface results in a gradient distribution of material refractive index rather than the ideal abrupt distribution, thereby degrading the resolution and contrast of the components. It is necessary for the demands for refined manufacturing processes of these components to gain a comprehensive understanding of the diffusion behavior and distribution status of elements at the core-clad interface. At present, energy dispersive spectrometry (EDS) is often employed as a characterization tool for elemental distribution status, yet it suffers from a low image resolution (20 nm) and lacks corresponding quantitative calculation methods. In this study, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was utilized to acquire high-precision images of elemental spatial distribution. Furthermore, a multi-model fusion machine learning approach was proposed to address the challenges of characterization and quantitative analysis in the study of elemental migration at the core-clad interface of hard optical fiber imaging components.

In this study, monofilaments undergoing various thermal processes were fabricated by a drawing technique. High-Angle Annular Dark-Field (HAADF) images were captured and utilized to train Tree-SVM/LDA models. These models enabled pixel-level core-clad classification and x-y two-dimensional spatial classification, thereby yielding quantitative results on elemental interface diffusion. In addition, the reliability of the models was also analyzed.

The Tree-SVM/LDA model is grounded on the following assumptions, i.e., element Si as a key component in the formation of both core and cladding glass network structures remains stable during the diffusion process. The deviation distances of other elements are benchmarked against that of Si, the average deviation (D) is defined as an arithmetic mean of the migration distances of all elements within the tested range, serving to characterize the overall diffusion behavior of elements rather than individual extreme values, elements undergo unidirectional migration, consistent with the direction of the concentration gradient, manifesting as the perpendicular direction to the interface in monofilament samples, the transition zone at the core-cladding interface is formed through the superposition of diffusion behaviors of different elements, and the algorithmic procedure of model encompasses the following steps (i.e., constructing training and prediction datasets; training the decision tree model; developing a labeled prediction dataset; and obtaining classification hyperplane parameters).

The results obtained by SVM and LDA models both indicate the thermodynamic principles at higher resolutions, with the deviation D_K∈[10, 40]nm, D_Ba∈[0, 11]nm, and D_Ti∈[0,13]nm. At lower resolutions, where the width of a single pixel in the raw data is 3 nm, the computational error of the models is amplified threefold, leading to the results that deviate from actual principles. At 810 ℃, the SVM model exhibits a poor data separability due to the low content of Ti in the cladding region, resulting in abnormal calculation results. This phenomenon underscores the superiority of the LDA model over SVM in terms of training set diversity, demonstrating a greater generalization capability. The calculation results of the SVM model and LDA model show a good consistency, while also presenting regular differences, i.e., the boundaries obtained by the LDA model tend to skew towards the cladding region relative to those of the SVM model. This regularity may be associated with differences in model characteristics and the element distribution patterns in the HAADF images of the core and cladding regions, having a further in-depth research. In general, the SVM model achieves higher accuracy than the LDA model. However, the LDA model possesses a better generalization capability.

The migration capabilities of the elements K, Ti, and Ba intensified as the wire drawing temperature increased. Specifically, the average migration distance of element K could range from 10 nm to 40 nm, while that of elements Ti and Ba could span from 0 to 13 nm. Affecting the reliability of models were since the spatial resolution of the raw data could be in atomic or sub-atomic scale, models could be sensitive to data anomalies, thus requiring repeated training, elements with great diffusion capabilities could decrease the accuracy of the model, while simultaneously enhancing its generalization capability. The SVM model demonstrated superior accuracy, compared to the LDA model, having a weaker generalization capability. The SVM model could be recommended at a high quality of the raw data, whereas the results of the LDA model could be more realistic at a low quality of the raw data.

The interfacial contact and charge conduction between the electrolyte and cathode have a direct impact on the performance and efficiency of single cells, which is a crucial area in both fundamental research and technological development of SOFCs. The following perspectives for future development are provided.

The development of novel electrolytes and electrode materials represents an effective strategy to address interfacial issues. Concurrently, the exploration of innovative interfacial structural designs can enhance the performance and stability within existing material systems. Future research endeavors should prioritize meeting the practical demands of industrial applications. Furthermore, it is essential to optimize the preparation process. The quality of the interface between the electrolyte and the cathode directly affects the overall performance of SOFCs. Therefore, optimizing the preparation process is of crucial importance. Currently, coating technologies such as pulsed laser deposition (PLD) and chemical vapor deposition (CVD) can achieve a precise preparation of specific compositions and structures. In the future, it is necessary to focus on the research and development of new high-performance, low-cost thin film preparation technologies with large-scale manufacturing capabilities to further improve interface quality. In addition, there is a focus on interdisciplinary research. Various in-situ spectroscopic characterization methods, machine learning and artificial intelligence technologies will also contribute to SOFCs research, including material performance prediction, parameter optimization design, and operating condition performance simulation. This can promote the connection between theoretical models and practical applications, driving SOFCs technology toward higher efficiency and lower costs. Finally, despite significant progress in lab-scale research, the commercialization of SOFCs still faces some challenges. In the next phase, it is necessary to further optimize the cell preparation process and operating conditions, such as electrolyte structure, composite electrode materials, and sintering processes. Reducing costs, improving cell reliability and lifespan can promote SOFCs widespread application in the energy sector.

Systematic statistical analysis reveals that distinct doping elements exert element-specific regulatory effects on the key performance metrics of layered oxide cathodes for sodium-ion batteries (i.e., capacity, rate capability, long-cycle stability, and structural integrity). Electrochemically inactive dopants enhance structural stability at the expense of reducing the number of redox-active sites due to lattice occupation, leading to capacity decay. Conversely, electrochemically active dopants improve capacity through redox reactions yet modify electron cloud distribution (i.e., exacerbating electronic disorder and altering localization/delocalization behavior), concurrently inducing lattice distortion and additional stress that compromise structural stability. Consequently, synergistic modification strategies integrating high-entropy design with doping effects emerge as a pivotal approach to transcend comprehensive performance limitations. However, this strategy confronts triple challenges, i.e., 1) synthesis requiring prolonged high-temperature annealing with precise multicomponent stoichiometric control, significantly amplifying manufacturing complexity and cost; 2) cost escalation from precious/rare-earth dopants restricting industrial scalability; and 3) insufficient mechanistic understanding of the synergistic interactions between dopant elements. A future research must prioritize developing low-cost facile synthesis techniques, advancing computational materials science-guided elemental combination optimization, and elucidating multiscale synergistic mechanisms, thereby establishing definitive composition-structure-property relationships to direct targeted fabrication of high-performance materials.