Utilizing geopolymers to stabilize silty soil and applying it in engineering construction represents a highly promising approach for resource utilization. This method enables efficient and sustainable use of silty soil and promotes large-scale consumption of industrial solid waste in China, demonstrating exceptional environmental, economic, and social benefits. Geopolymer-stabilized silty soil exhibits excellent mechanical properties, with improvements in compressive strength, shear strength, and bearing capacity, compared to conventional inorganic stabilized soil. In addition, it also shows significant advantages in key durability aspects such as water stability and freeze-thaw resistance. This performance enhancement is a macroscopic reflection of its unique microstructure and chemical bonding capabilities.

Although the existing experimental research on geopolymer-stabilized silty soil has made significant progress in macroscopic mechanical properties and microstructural characteristics, the in-depth analysis of its microscopic stabilization mechanisms and systematic studies on the influence of organic matter content on stabilization effects still require a further attention. Moreover, research on stabilized silty soil predominantly focuses on single-component geopolymer systems, while studies on binary or multicomponent geopolymer-stabilized soil remain insufficient. The application of geopolymers in soil stabilization still faces severe challenges, such as the lack of unified testing methods, performance evaluation standards, and engineering design specifications. Future research should focus on investigating the complex interfacial reactions and bonding mechanisms between geopolymers and silty soil particles, actively expanding exploration of silty soil stabilization under multicomponent geopolymer systems, and accelerating the establishment of design and construction specifications for geopolymer-stabilized soil in various engineering applications. Building a full-lifecycle standardized system can provide a technical assurance for the large-scale promotion and application of this technology.

Lightweight aggregate concrete (LWC) offers some advantages like low density, thermal insulation, heat resistance, fire resistance, and excellent seismic performance. The incorporation of hybrid fibers further enhances its toughness, durability, and crack resistance, resulting in a composite material known as hybrid fiber reinforced-lightweight aggregate concrete (HFR-LWC). In protective engineering, deformations induce a "membrane effect" at the end restraints of structures, altering their ultimate resistance and failure modes. Conventional load-bearing components are often simplified as simply supported or fixed in mechanical analyses, neglecting the influence of the membrane effect. This leads to conservative designs for ultimate bearing capacity, preventing the full utilization of component strength. Therefore, investigating the membrane effect's contribution to improving component bearing capacity is of significant importance. This paper was to design and fabricate a set of support restraint devices for horizontal stiffness and rotational stiffness to simulate the membrane effect in beam structures. Four-point bending tests were conducted on ten HFR-LWC beams under static loading. The contributions of restraint conditions, reinforcement ratios, and the presence of fibers to the ultimate bearing capacity of HFR-LWC beams were analyzed. The variation patterns of mid-span strain, crack distribution, and ultimate bearing capacity of the HFR-LWC beams were examined. In addition, the influences of horizontal stiffness and rotational stiffness on the membrane effect were also quantitatively analyzed.

Based on the Technical Specification for Lightweight Aggregate Concrete (JGJ/T 12—2019), this study developed a hybrid fiber reinforced lightweight aggregate concrete (HFR-LWC) with high strength, low density, and good workability through multiple mix proportion trials. Ten concrete beams with the dimensions of 200 mm×100 mm×1500 mm were cast, featuring a symmetrical reinforcement with A6 deformed longitudinal bars and A6@100 plain stirrups at different reinforcement ratios (i.e., ρ of 0.42% and ρ of 0.28%). After 28-d curing under identical conditions, the compressive strength and elastic modulus of concrete specimens were tested according to the standard GB/T 50081—2019 by a universal testing machine. A specialized support restraint device was designed and fabricated to account for both horizontal and rotational stiffness. The experimental program included three simply supported beams and seven boundary-restrained beams tested under four-point static bending. Five displacement transducers were evenly spaced along the beam span to measure deformation patterns under various load levels and record the deflection at ultimate load. Five strain gauges were installed at mid-span to monitor neutral axis variations and strain distribution under different support conditions and deflection levels. Additional strain gauges were placed at beam ends and mid-span to analyze strain variations caused under different restraint conditions. Through the quantitative analysis of experimental data, this research systematically investigated the influences of support constraint, reinforcement ratio and fiber incorporation on the membrane effects. The findings could elucidate the mechanisms by which these factors affected the ultimate load-bearing capacity of HFR-LWC beams, providing valuable insights for the structural design.

Based on the experimental conditions, the test beams are grouped to investigate the influences of restraint condition, reinforcement ratio and fiber incorporation on the load-bearing capacity. The analysis of test groups under different restraint conditions reveals that the presence of tie rods significantly enhances the ultimate load-bearing capacity of the beams, and variations in both the number and position of tie rods have substantial effects on this capacity. The comparative analysis of test groups at different reinforcement ratios demonstrates that for membrane effects within a certain range of reinforcement ratios, there exists an inverse relationship between reinforcement ratio and the increase in load-bearing capacity. Specifically, a lower reinforcement ratio results in more pronounced improvements in ultimate load-bearing capacity under end restraints. The examination of test groups with and without fiber incorporation shows that fiber materials effectively participate in the crack propagation process and improve the deformation performance of the members. The analysis of strain and crack development in the test beams indicates that the mechanism by which membrane effects affect a load-bearing capacity primarily involves restricting concrete cracking and crack propagation, thereby increasing ultimate capacity, while simultaneously reducing structural deformation performance. The relationship between tie rod force and deflection shows a synchronous variation with beam load-bearing capacity. In the initial deformation stage, these two parameters exhibit the similar results. However, the tie rod force surpasses the peak load-bearing capacity of the beam, with its maximum value occurring later than that of the beam's capacity as the deflection increases.

Unlike conventional calculation methods that could simplify supports, the influence of end restraints on the ultimate bearing capacity of reinforced concrete members could reflects actual engineering conditions. The membrane effect increased the ultimate bearing capacity of beams by approximately 1.5 times to 5.5 times and effectively controlled the crack propagation. Compared to the influence of horizontal stiffness on the ultimate bearing capacity, the membrane effect showed a greater sensitivity to variations in rotational stiffness. The hybrid fibers could significantly improve the cracking performance of concrete, resulting in a more uniform crack distribution, which could facilitate the development of membrane effects.

Bismuth ferrite (BiFeO₃, BFO) is a well-known ferroelectric material with excellent piezoelectric and ferroelectric properties at room and high temperatures, attributed to its high Curie temperature (1103 K). Its rich topological domain structures, such as vortex domains and skyrmions, show potential for high-density data storage due to their small size and stability. Recent studies show that ferroelectric materials near the morphotropic phase boundary (MPB) exhibit enhanced piezoelectric properties. Methods like applying strain, changing substrate orientation, and doping can create MPB structures in BFO films, improving their performance. Ferroelectric topological domains can be induced by engineering film boundaries, offering new opportunities for high-density information storage and logic devices. Pulsed Laser Deposition (PLD) was used to fabricate BFO films. By adjusting parameters, T-phase, R/T mixed-phase, and R-phase films were prepared. The effects of thickness and laser energy on crystal structure, growth mode, and domain structure were investigated. Finite element simulation and thermodynamic analysis revealed the influence of strain relaxation and deposition rate on film properties.

BFO films were fabricated on (001)-oriented LaAlO₃ (LAO) substrates using PLD with a KrF excimer laser (248 nm wavelength, 3 Hz frequency). By adjusting the number of pulses (2700, 3600, 5400) and laser energy density (0.90-1.50 J/cm²), various BFO films (T-phase, R/T mixed-phase, R-phase) were prepared. A Bi-rich B_1.1FeO₃ target was used to compensate for Bi evaporation. Growth conditions were 700 ℃ substrate temperature and 13 Pa oxygen pressure, followed by annealing at 650 ℃ in 20000 Pa oxygen for 30 min and cooling to room temperature at 5 ℃/min. The epitaxial strain on BFO from LAO was -4.5%. Characterization was performed using X-ray Diffraction (XRD) with a Rigaku Ultima IV, Atomic Force Microscopy (AFM) with a Bruker Dimension XR, and Piezoresponse Force Microscopy (PFM) with a Pt/Ir-coated Si cantilever. Finite element simulation was conducted to study strain distribution in BFO films on LAO, assuming a -4.5% strain boundary condition. The simulation, performed at 300 K with a 1 nm grid size, provided theoretical support for the experimental results.

In thin film systems, strain relaxation occurs as film thickness increases. Changing deposition cycles to increase thickness significantly impacts the crystal and domain structures of epitaxial films. With 2700 deposition cycles, the film exhibits a layer-by-layer step-flow growth mode with distinct in-plane polarization components in the T-phase BFO, forming regular stripe-like domains. Increasing cycles to 3600 results in an interwoven R/T mixed-phase stripe pattern and crescent-shaped domains, indicating a transition from T-phase to R/T mixed-phase structure. Further increasing cycles to 5400 leads to significant surface roughness, transitioning the film to R-phase BFO as the epitaxial relationship is disrupted. This suggests that excessive thickness causes strain relaxation, enhancing in-plane polarization signals in PFM images and increasing domain size.

Laser energy is another crucial factor affecting film growth. Higher laser energy increases the amount of evaporated target material and the plume size. At low energy (0.90 J/cm²), the film maintains layer-by-layer growth with impurity particles, showing in-plane polarizations in different orientations. Increasing energy to 1.35 J/cm² induces a transition to layer-island mixed growth, forming interconnected nanodots with ferroelectric characteristics. Further increasing energy to 1.50 J/cm² results in higher-density, smaller nanodots in an island growth mode, with fragmented domain structures.

Finite element simulation was used to analyze the effect of film thickness on strain relaxation in BFO/LAO films. Films with thicknesses of 10 nm and 50 nm showed minimal strain relaxation, maintaining -4.5% strain (T-phase). However, at 80 nm, strain relaxation began (-4.41%), and at 130 nm, it became more pronounced (-3.87%). This indicates that thicker films experience more significant strain relaxation, consistent with experimental observations. The concept of "evaporation depth" helps explain the impact of laser energy on growth modes. At low laser energy, fewer BFO cells are evaporated, allowing them to diffuse and form layer-by-layer structures. Conversely, high laser energy increases the number of evaporated cells and nucleation sites, promoting island growth. This study provides valuable insights into the effects of deposition cycles and laser energy on BFO film growth, offering guidance for optimizing film properties.

This study explores how epitaxial strain and growth mode affect the crystal structure and ferroelectric domains in BFO films. As film thickness increases, epitaxial strain relaxes, causing significant changes in high-strain BFO films. Films transition from T-phase to R/T mixed-phase and then R-phase BFO with increasing deposition cycles (2700 to 5400), highlighting thickness's role in strain relaxation and structure. Adjusting laser energy density (0.90 J/cm² to 1.50 J/cm²) shifts growth modes from T-phase to nanodot films, altering microstructure and domain distribution. Finite element simulations show that strain relaxation accelerates when film thickness exceeds 80 nm, with surface strain relaxing from -4.5% to -4.41%. Calculations of evaporated material per pulse reveal that low laser energy promotes layer-by-layer growth, while high energy induces island growth. These findings provide crucial insights into laser energy's role in controlling film growth and offer valuable guidance for developing high-performance piezoelectric materials and information storage devices.

Silicon photonics has emerged as a critical technology for high-performance communication and computing, with electro-optic modulators serving as essential components. Barium titanate (BaTiO₃, BTO) exhibits exceptional promise due to its outstanding electro-optic coefficient (r₄₂ ≈ 923 pm/V) and compatibility with silicon-based fabrication processes. However, achieving high-performance BTO devices requires overcoming key materials integration challenges. The primary obstacles include the formation of amorphous SiO₂ interfacial layer during high-temperature, oxygen-rich BTO growth, which prevents effective epitaxy, and the substantial lattice mismatch between BTO (a = b = 3.992 Å, c = 4.036 Å) and Si (5.431 Å), resulting in approximately 4.0% mismatch even with 45° rotational epitaxy. This mismatch induces high-density dislocations and strain relaxation, compromising film quality. Strontium titanate (SrTiO₃, STO) buffer layers (3.905 Å) can reduce lattice mismatch to 1.7%, providing stress relief and serving as an epitaxial template. The electro-optic effect in BTO strongly depends on ferroelectric domain structure and crystallographic orientation, with in-plane polarization achieving maximum coefficients. While domain structures can be controlled through strain engineering and growth conditions, current analyses rely on post-growth characterization, lacking real-time monitoring of domain evolution processes and critical transition mechanisms.

Oxide molecular beam epitaxy (MBE) combined with in situ reflection high-energy electron diffraction (RHEED) for real-time monitoring was employed to achieve controlled growth of high-quality BTO films at 2 in wafer scale. The systematic investigation focused on lattice relaxation behavior during the growth of STO buffer layers and BTO layers with varying thicknesses. Silicon substrates underwent hydrofluoric acid (HF, 10% mass fraction) treatment to remove surface SiO₂ amorphous layers, followed by rapid transfer to ultra-high vacuum chambers (background pressure ≤ 5×10^-8 Pa). STO epitaxial growth employed a two-stage process: first, 2.5 monolayers (ML) of Sr and Ti metals were deposited at a substrate temperature of 200 ℃ under ultra-high vacuum (< 5×10^-7 Pa) with precisely controlled oxygen partial pressure (< 5×10^-6 Pa). The second stage involved in situ annealing at 500 ℃ for 8 minutes under ultra-high vacuum conditions (< 1×10^-6 Pa). After three such cycles, additional STO layers were epitaxially grown using co-deposition at a thermocouple temperature of 600 ℃ under an oxygen partial pressure of 6×10^-5 Pa. BTO layers were continuously co-deposited at 700 ℃ thermocouple temperature under 6×10^-5 Pa oxygen partial pressure, ultimately obtaining 310 nm BTO/5 nm STO/Si heterostructures. Comprehensive characterization employed high-resolution four-circle X-ray diffraction (XRD) for 2θ-ω scanning and rocking curve analysis, spectroscopic ellipsometry for determining optical constants and thickness, atomic force microscopy (AFM) for surface morphology assessment, and piezoresponse force microscopy (PFM) for ferroelectric domain characterization.

Systematic RHEED diffraction pattern analysis during film growth enable quantitative analysis of lattice relaxation processes in both STO and BTO epitaxial films. STO buffer layers completed relaxation after 12.5 ML, reducing the lattice mismatch between BTO and Si from 4.0% to 2.2%. BTO films underwent progressive relaxation from the interface to a depth of 30 nm, with in-plane lattice constants evolving from 3.905 Å (STO-templated) to 4.013 Å at 30 nm, then stabilizing. During cooling from 700 ℃ to room temperature, thermal constraints from Si substrate significantly modified BTO behavior. The effective thermal expansion coefficient was ~1.5×10^-6 K^-1, much lower than that of bulk BTO (~14.6×10^-6 K^-1) but comparable to Si (2.6×10^-6 K^-1), indicating strong substrate constraint effects. The resulting 300 nm BTO films exhibited excellent quality: a rocking curve full width at half maximum (FWHM) of 0.45°, surface roughness < 0.2 nm, and critical lattice parameters a = 4.010 Å, c = 3.990 Å (c/a = 0.994< 1). This represents a 0.45% in-plane expansion and 1.2% out-of-plane contraction compared to bulk BTO, indicating a tetragonal phase reorientation with the long-axis in-plane. This anisotropic distortion creates residual tensile stress in-plane and compression stress out-of-plane, driving polarization reorientation from out-of-plane to in-plane throughout the entire film. PFM characterization confirmed this structure: lateral PFM (LPFM) signals significantly exceeded vertical PFM (VPFM) signals, demonstrating dominant in-plane polarization components. Optical characterization at 1550 nm revealed ideal performance with a refractive index n = 2.28 and an extinction coefficient k ~10^-6, indicating extremely low optical loss suitable for high-performance electro-optic modulators.

High-quality BTO epitaxial growth on 2-inch silicon wafers was achieved via molecular beam epitaxy. In situ RHEED monitoring enabled real-time observation of lattice relaxation processes during STO buffer layer and BTO film growth, revealing that STO lattice relaxation occurs within the first 12.5 ML from the interface, while BTO lattice relaxation occurs within the first 30 nm from the interface. Based on this relaxation behavior, the STO intermediate layer provides BTO with a low-mismatch template, while BTO lattice relaxation is critical for ultimately achieving in-plane polarized films. In situ RHEED data analysis demonstrated that constraints from low thermal expansion coefficient Si substrate enable BTO films to maintain larger in-plane lattice constants during cooling to room temperature, thereby stabilizing domain structures with predominantly in-plane polarization. This in situ monitoring technique provides crucial information for precise analysis of BTO film lattice relaxation processes and domain engineering, offering significant implications for developing silicon-based BTO electro-optic modulators, high-speed communication devices, and optical quantum computing chips.

Hafnium oxide-based ferroelectric memory has become a research hotspot due to its compatibility with CMOS processes, low power consumption, and inverse size effect. Memory technology has transitioned from 2D planar to 3D vertical stacking, enabling the stacking of multiple memory cells. The gate first process of 3D NAND architecture requires the ferroelectric layer to withstand high annealing temperature. Al-doped hafnium oxide films can endure annealing at 700-1000 ℃, meeting the process requirements. Florent et al. first demonstrated a 3D NAND device based on Al:HfO₂, achieving a 2P_r value of 17 μC/cm² after annealing at 850 ℃, showcasing its potential in non-volatile memory applications. As devices trend toward miniaturization and integration, reducing the thickness of the ferroelectric layer is key to achieving high-density stacking and lowering power consumption. When the thickness is scaled down to the nanoscale, interface effects become significant. Studies show that an interfacial oxide layer forms between the ferroelectric film and the metal electrode, leading to the accumulation of oxygen vacancies, the generation of a built-in electric field, and polarization asymmetry. To understand interface effects, it is essential to study them from the perspective of polarization switching. This work focuses on Hf_1-xAl_xO₂ films to investigate the influence of interfaces on polarization switching behavior. The study reveals that the interfacial layer between the ferroelectric layer and the metal electrode hinders polarization switching in the programmed state.

First, a 40 nm tungsten (W) bottom electrode was deposited on a p⁺-Si substrate at room temperature using magnetron sputtering. Subsequently, Al-doped HfO₂ (HAO) ferroelectric films with thicknesses of 6.8 nm, 15.8 nm, and 20.4 nm were prepared by atomic layer deposition (ALD) at a deposition temperature of 295 ℃. Tetrakis(ethylamido)hafnium (TEMA-Hf), trimethylaluminum (TMA-Al), and water (H₂O) were used as the hafnium source, aluminum source, and oxygen source precursors, respectively. The cycle ratio of aluminum to hafnium deposition was 1∶29. Total cycles for HAO films with thicknesses of 6.8, 15.8 nm and 20.4 nm are 90, 210 and 270, respectively. Then, a 40 nm W top electrode was deposited using magnetron sputtering, resulting in W/HAO/W capacitor structures. Finally, the two capacitor structures were subjected to rapid thermal annealing at 700 ℃ for 30 s in a nitrogen atmosphere.

The 6.8 nm, 15.8 nm, and 20.4 nm HAO films fabricated on W electrodes exhibited remanent polarization (2P_r) values of 38.8, 43.2 μC/cm² and 37.6 μC/cm² after waking up, demonstrating excellent ferroelectric properties. During the fabrication of 6.8 nm HAO films, interfacial WO_x layers with thicknesses of 0.5 nm and 1.8 nm were formed. Based on this observation, ERS and PRG polarization switching behaviors were designed to investigate interfacial effects on switching dynamics. Under an electric field of 1.8 MV/cm, the divergence in switching time between these two states amplifies with HAO film thickness scaling. Polarization switching in PRG state of 6.8 nm HAO film is hindered by the built-in electric field, exhibiting ΔP/2P_S significantly below 1, whereas ERS state achieves near-complete switching (ΔP/2P_S is about 1) with substantially faster kinetics. Comparative analysis of COD values from NLS model and KAI model fittings reveals: For ERS state, both models yield COD >0.9, indicating comparable timescales for domain nucleation and growth. In contrast, PRG state polarization switching behaviors at 1.8 MV/cm requires exclusive description by the NLS model, demonstrating nucleation-limited behavior under low fields. With increasing electric field, decreasing COD values for NLS fittings and increasing COD values for KAI fittings suggest a gradual transition from nucleation-dominated to growth-dominated switching mechanisms in ERS and PRG states.

This paper prepared HAO ferroelectric films with three thicknesses (6.8, 15.8 nm, and 20.4 nm) via ALD, and investigated the influence of interface effects on polarization switching characteristics by comparing differences in polarization switching behavior between ERS and PRG states. The results indicate that the divergence in polarization switching time between ERS and PRG states increases with HAO film thickness scaling, attributed to the thicker interfacial oxide layer at the bottom interface compared to the top interface. This asymmetry leads to higher oxygen vacancy concentration at the bottom interface, generating a built-in electric field directed from the film toward the top electrode. As HAO film thickness decreases, the proportion of interfacial oxide layers increases, amplifying the built-in electric field that hinders polarization switching in PRG state. For the 6.8 nm HAO film under ERS state, the COD values fitted by both NLS and KAI models exceed 0.9, indicating comparable timescales for domain nucleation and growth. However, in PRG state at 1.8 MV/cm, the ΔP/2P_S is significantly below 1., requiring description by the NLS model. With increasing electric field, the ΔP/2P_S progressively rises to 1 (Complete polarization reversal), accompanied by a transition from NLS to KAI model behavior. This arises because the built-in electric field impedes polarization switching in PRG state, necessitating additional energy to overcome nucleation barriers. Under high electric fields, sufficient energy is provided to surmount interfacial domain nucleation barriers, significantly enhancing PRG domain nucleation rate and accelerating polarization switching dynamics.

Porous medium combustion has high efficiency, low pollutant emissions, and effective utilization of low-calorific-value fuels, which is crucial for energy conservation and carbon reduction in high-temperature industries. As a core component of porous medium burners, the porous medium material must withstand the high temperatures generated by fuel combustion and the corrosive effects of water vapor and excess oxygen in flue gases. Among various inorganic nonmetallic materials, Alumina porous ceramics are widely used as dielectric materials in high-temperature porous medium burners due to their excellent thermal stability and resistance to wet oxidation and corrosion. However, the relatively low thermal radiation coefficient (i.e., approximately 0.3) of alumina significantly reduces the heating efficiency of the burner. Therefore, enhancing the surface infrared emissivity of alumina porous ceramics is critical to improving the radiative heat transfer performance of alumina porous ceramic burners. While enhancing material radiation primarily involves constructing infrared radiation coatings on material surfaces, these methods often overlook the combustion stability of low-calorific-value fuels in porous medium burners. This study was to address this issue by firstly preparing flower-like CeO₂ catalysts via coprecipitation and subsequently developing alumina porous ceramics coated with flower-like CeO₂. The unique flower-like structure of the CeO₂ coating could enhance both radiative heat transfer and catalytic performance, thereby improving the overall radiation capability and heating efficiency of the porous medium burner.

To address the issue of low radiation efficiency on the surface of alumina porous ceramics used in high-temperature porous media combustion, this study adopted a systematic approach. NH₄HCO₃ and Ce(NO₃)₃·6H₂O were utilized as raw materials to synthesize flower-like CeO₂ precursor via a low-temperature co-precipitation method. These precursors were subsequently transformed into flower-like CeO₂ through heat treatment at 500 ℃. Alumina porous ceramics were fabricated by an organic foam impregnation technique. Alumina porous ceramic preforms were obtained after heat- treatment at 1300 ℃. Subsequently, α-Al₂O₃ powder and deionized water were mixed to prepare an impregnating slurry, which was applied to the preforms via vacuum impregnation. After drying, these preforms underwent further heat-treatment at 1500 ℃ to finalize the alumina porous ceramics. Commercially available ordinary CeO₂, synthesized flower-like CeO₂ powder, and flower-like CeO₂ precursor powder were sprayed onto the surfaces of the alumina porous ceramic skeletons. After heat-treatment at 500 ℃, three distinct CeO₂ samples CCA, FCA, and PFCA were produced. The effect of the flower-like CeO₂ coating on the combustion characteristics, lower flammability limit, and combustion temperature of alumina porous ceramics were evaluated by a porous media combustion platform, complemented by infrared thermal imaging (Fluke TiX 1060) and flue gas analysis (Testo 350). In addition, the surface element valence, specific surface area, and microstructure of the three types of CeO₂ were also characterized to elucidate the advantages of flower-like CeO₂ over ordinary CeO₂. Furthermore, the enhancement mechanism of infrared emissivity for flower-like CeO₂ was investigated.

Flower-like CeO₂ precursor and flower-like CeO₂ are synthesized with NH₄HCO₃ and Ce(NO₃)₃·6H₂O as raw materials through a coprecipitation method and a subsequent heat-treatment at 500 ℃. Compared to conventional CeO₂, flower-like CeO₂ exhibits a significantly larger specific surface area and a higher proportion of surface reactive oxygen species. The prepared flower-like CeO₂ coating enhances infrared emissivity from 0.52 to 0.71 due to its well-developed petal and microporous structure. When applied to porous ceramic burners, this coating increases the surface temperature to 1032.6 ℃ and the heating rate from 32.38 ℃/min to 41.81 ℃/min, and reduces CO emissions to only 4.58 mg/m³. In addition, NOx emissions are lowered to as low as 0.19 mg/m³, and the lean fuel limit is extended to 3.5% (in volume fraction).

The alumina porous ceramics with flower-like CeO₂ coatings were fabricated. The interface between the coating and the alumina skeleton exhibited the superior characteristics. The unique morphology of the flower-like CeO₂ coating, characterized by well-developed inter-petal pores and micropores formed during the decomposition of CeO₂ precursor, could enhance the infrared emissivity of the coating. This improvement in emissivity led to increased surface temperature and heating efficiency of the alumina porous media burner. The flower-like CeO₂ coating had a high specific surface area and a significant proportion of reactive oxygen species, which facilitated methane combustion within the alumina porous ceramics. Consequently, this could broaden the range for stable methane combustion and substantially reduce CO emissions in the flue gas.

Making use of erasable conductive channels of atomically thin domain walls, ferroelectric domain-wall memory devices achieve exceptionally high storage densities and ultrafast write/read speeds ranging from nanoseconds to picoseconds. These devices also exhibit outstanding performance of high fatigue endurance number and long-term data retention. While demonstrations of prototypical devices have validated the fundamental operation principle of domain-wall-based memories, several critical issues must be resolved before practical application. First, many novel transport phenomena observed at conductive domain walls remain inadequately understood, demanding thorough studies of domain-wall motion kinetics and the interplay between polarization, defects, and lattice coupling. Second, the domain nucleation and domain wall motion are correlated to the device reliability; therefore, precise control over domain-wall creation, propagation, and pinning is essential for ensuring fast operations and long-term data retention. Finally, in vertically stacked three-dimensional architectures, potential cross-talks between adjacent cells must be systematically evaluated especially for stable and reliable operations of multilevel memories. These challenges are crucial for advancing ferroelectric domain-wall memories toward large-scale integration and commercialization.

To solve the problems that the porosity is difficult to accurately control and the pore structure uniformity is insufficient in the traditional process of replicating polyurethane foam with ceramic slurry, a biclinic body design method based on regular hexahedron cell structure was introduced to prepare porous ceramic parts for high-performance porous media burner. The influence of parameters (i.e., cell edge length, pore rib diameter and array layer number) on the strength and combustion characteristics of porous ceramic materials was investigated.

The model was firstly designed by a software named ANSYS Spaceclaim modeling, and then the samples were prepared by 3D printing. The compressive strength of porous ceramic structures was tested by a model TSE104B universal material testing machine at a loading rate of 0.5 mm/min. A circular loading plate with a diameter of 100 mm was used to apply pressure to the samples, and the maximum compressive strength σ_s of each sample was calculated by recording the failure load. Combustion performance testing was conducted in a porous media combustion platform, and the composition and temperature of the flue gas were monitored by a model testo 350 flue gas analyzer. The temperature changes were recorded by an infrared thermal imager.

The stress distribution and internal combustion mechanism of the porous ceramic under uniaxial compression were analyzed by numerical simulation methods. Among them, ANSYS Static Structural module was used for stress distribution analysis, and ANSYS Fluent module was used for finite element analysis of the flow field of porous media, thus evaluating the effect of porosity on gas disturbance, heat transfer behavior, fluid pressure drop, and heat exchange efficiency.

In a high porosity range (i.e., ε≥90%), extending the residence time of premixed gas and enhancing turbulence effects can effectively promote gas mixing and combustion, thereby improving the overall combustion performance. Moderately reducing porosity (i.e., from 93% to 86%) improves the compressive strength of the material (approximately 100%) although this leads to a decrease in the maximum surface temperature (about 18.4 ℃) and an increase in CO emissions (about 8.75 mg/m³). This indicates that a moderate reduction in porosity sacrifices combustion efficiency at a high porosity can enhance the strength. In contrast, the structure in a low porosity range (ε<90%) restricts the free flow of gas flow, resulting in uneven velocity distribution and reduced turbulence, hindering effective gas mixing and combustion, thereby reducing combustion efficiency. This indicates that it is difficult to simultaneously improve combustion efficiency and strength at a low porosity. It is thus possible to balance combustion efficiency and strength via finely adjusting the porosity in the high porosity range (i.e., ε≥90%), achieving a synergistic effect.

The strength of SiC porous ceramic structures could be effectively improved via reducing the cell edge length a, increasing the number of layers n, and pore reinforcement diameter d. The pore reinforcement diameter d had a more significant impact on the strength of SiC porous ceramic structures. There was a certain enhancement effect on the maximum surface temperature of SiC porous ceramic structure via increasing a and decreasing n and d. At a high porosity, a and n had a more significant impact on the maximum surface temperature of SiC porous ceramic structure. At a low porosity, d had a more significant impact on CO emissions from SiC porous ceramic structures.

Multiferroic BiFeO₃ (BFO) exhibits coupled ferroelectric, antiferromagnetic, and ferroelastic orders at room temperature, enabling unique optoelectronic properties such as switchable photovoltaic effects and polarization-driven carrier separation. The multi-valance of Fe element in BFO also implies its potential to engineer the bandgap and conductivity to enhance the photoelectric properties. Besides, the large remnant ferroelectric polarization in BFO offers the opportunity of bulk photovoltaic effect, promising to develop the optoelectronic devices based on the unique optical and multiferroic properties. While defects like oxygen vacancies are known to critically influence functional properties in oxides, especially the BFO films. The oxygen vacancies are proved to influence the electronic and magnetic properties, electromechanical response and resistive switching. Furthermore, the concentration of oxygen vacancies is clarified to be influenced by the annealed conditions, which in turn tune the photoresponse of BFO thin films. However, previous studies mainly focus on the influence of the oxygen vacancies as the point defects on properties and the atomic-resolved analyses of oxygen vacancies behavior are lacking. Here, by combining advanced STEM, UV-Vis, XRD and first-principles calculations, we systematically investigate oxygen-vacancy-engineered BFO thin films to reveal how ordered vacancy planes modulate lattice structure, create charged domain walls, reduce bandgaps and improve UV-visible absorption property, thereby demonstrating a defect-property correlation crucial for designing multifunctional devices.

BFO polycrystalline ceramic target (1% Bi-enriched), SrTiO₃ (STO) ceramic target, and commercial single-crystal substrates of NdGaO₃ (NGO) (110)_O and STO (001) were purchased from Hefei Kejing Materials Technology Co., Ltd. BFO and BFO/STO films were grown on NGO (110)_O substrates via pulsed laser deposition (PLD) using a Coherent ComPex PRO 201 F KrF excimer laser (λ = 248 nm). The substrates were preheated to 850 ℃ for 20 min and cooled to deposition temperature at 5 ℃/min. A 1% Bi-enriched BFO target was pre-sputtered for 20 min. The deposition parameters of 6 Hz repetition rate, 800 ℃ substrate temperature, 370 mJ laser energy were used to fabricate the films. Post-deposition annealing at 800 ℃ for 20 min was followed by cooling to 200 ℃ at a rate of 5 ℃/min and natural cooling to RT under 200 Torr O₂ partial pressures. Four film systems were prepared by varying O₂ partial pressures:1) BFO film: growing at 90 mTorr, annealing at 200 Torr; 2) BFO film: growing at 90 mTorr, annealing at 120 mTorr; 3) BFO/STO film: BFO layer growing at 90 mTorr, STO capping layer growing at 70 mTorr, both layers were annealed at 120 mTorr; 4) BFO/STO film: growing/annealing at 0.06 mTorr.

Cross-sectional TEM specimens were prepared using a ThermoFisher Helios 5UX FIB system with sequential steps: C/W protective layer deposition, trenching, lift-out, thinning (30 kV/90 pA → 8 kV/47 pA), and amorphous layer removal (5 kV/47 pA → 2 kV/47 pA). The atomic-resolved HAADF-STEM images were acquired on ThermoFisher Spectra 300 (300 kV, 25 mrad convergence, 71-200 mrad collection angles) with drift correction (DCFI in Velox). The strain analysis was performed using GPA via Gatan GMS3 software and the atomic positions were determined by 2D Gaussian fitting in MATLAB software. The UV-Vis measurements were performed in JASCO V-770. The RSMs were collected on Bruker D8 Advance (Cu K_α, λ = 1.5406 Å). First-principles calculations were based on the density functional theory (DFT) calculation and performed with the Vienna ab initio simulation package (VASP).

A series of BFO films were fabricated by modulating the oxygen environment to introduce the high-density oxygen vacancies. Using the Cs-STEM, the oxygen vacancy ordered plane was determined in BFO film annealed under the oxygen partial pressure of 120 mTorr, which displayed as the out-of-plane lattice expansion. Besides, the charged oxygen vacancy ordered plane would influence the surrounding polarization directions, stabilizing the tail-tail polarization distribution. By changing the annealed oxygen partial pressure and growing the capping layers, the concentration of oxygen vacancy ordered planes was evidently modulated, further extending the ultraviolet-visible absorption property of the BFO films. First-principles calculations revealed that the introduction of high-density oxygen vacancies could generate the vacancy-induced energy levels between the conduction and valance bands and thus reduce the bandgaps of BFO. The result was consistent with the UV-visible absorption measurement results.

The oxygen vacancy ordered planes were introduced in BiFeO₃ film systems by controllable growth methods. Its concentration was tunable by decreasing the annealed oxygen partial pressure and/or growing capping layers. Obvious lattice expansion was observed in BFO films by the existence of oxygen vacancy ordered planes. Besides, the polarization configuration in BFO film was modulated by the electrostatic potential of positively charged oxygen vacancy layer, accompanying the formation of tail-to-tail polarization configuration. The introduced oxygen vacancy ordered planes also had further improved the optical absorption properties of BFO films. Our results provide a further insight into the interaction between oxygen vacancy ordered planes with the ferroelectric polarization and the optical properties in multiferroic oxides and facilitate the design of nanoscale photoelectronic devices and ferroelectric solar cells.