Studies on introducing phyllosilicate minerals into polymers to improve their tribological properties can provide some ideas for the development of intelligent self-healing composite materials. Polytetrafluoroethylene (PTFE) is widely used as one of engineering materials and solid lubricating materials due to its good self-lubricating ability, thermal stability, corrosion resistance and machinability. However, the molecular bond structure of PTFE exhibits unique slip characteristics during crystallization, making it prone to creep and resulting in a poor wear resistance. It is thus necessary for the modification of PTFE to improve the mechanical properties and tribological performance for engineering applications. The modification methods mainly include surface modification, blending modification, and filling modification. Recent studies indicate that the introduction of minerals such as serpentine, attapulgite, and sepiolite into PTFE can obtain PTFE-based composites with uniform mineral dispersion and excellent thermal stability, mechanical properties, and tribological properties due to the property of phyllosilicate minerals to intercalate monomer or polymer molecules. In this paper, antigorite and wollastonite minerals reinforced PTFE-based composites were prepared. The tribological properties of the composites were investigated, and the mechanism of the tribological properties improvement of PTFE caused by antigorite and wollastonite was discussed based on the worn surface analysis.

Antigorite (Atg) was extracted from natural deposited serpentine mineral in Anshan, China. Wollastonite (Wl) was provided by Dalian Global Mineral Co., Ltd., China. Polytetrafluoroethylene (PTFE) was purchased from Shandong Dongyue Co., China. The phase structure, functional groups and thermodynamic behaviors of the mixed raw powders were characterized by a model D8 Advance X-ray diffractometer (XRD), a model Nicolet 6700Fourier infrared spectrometer (FT-IR) and a model NETZSCH STA 449C simultaneous thermal analyzer (TG-DSC), respectively. The Shore hardness of the sintered composite samples was measured by a Shore hardness tester. The tribological properties of the composites were tested by a model Optimal SRV-IV ball-disc friction and wear tester. The 3D morphology, surface roughness and wear volume of the wear scars on the composites were determined by a model Olympus LEXT OLS4000 laser confocal microscope. The morphology and chemical composition of the worn composite and steel surfaces were examined by a model FEI Nova Nano SEM 450 field emission scanning electron microscope (FESEM) and an attached X-ray energy spectrometer (EDS). The chemical state of the major elements on the worn steel surface was analyzed by a model ESCALAB 250Xi X-ray photoelectron spectrometer (XPS).

Compared to pure PTFE, the peak intensity of composite materials with different components obtained by adding minerals is reduced. The possible reason is that the addition of minerals hinders the nucleation and crystallization of PTFE, leading to a decrease in the crystallinity. In addition, no chemical reaction occurs during the process of introducing serpentine and wollastonite into PTFE by a pressureless sintering technology.

The powders of antigorite and wollastonite are evenly dispersed in PTFE, with slight aggregation of antigorite. The mineral particles are tightly bound to the PTFE matrix, and there are no obvious defects such as pores and cracks in the composite. The average friction coefficient and wear volume of PTFE-based composites with simultaneous addition of 10% (in mass fraction) antigorite and 20% wollastonite are reduced by 44.2% and 71.4%, respectively, compared to pure PTFE. The composites exhibit excellent tribological properties due to the reinforcement of PTFE by minerals and the formation of a tribo-layer on the dual steel surface, which has high hardness and self-lubricating properties. Compared with the addition of a single antigorite, the addition of wollastonite minerals lowers the phase transition temperature of antigorite and promotes the formation of the tribo-layer, which has a good synergistic effect on the improvement of the tribological properties of the composites.

The mineral reinforced PTFE composite material was obtained via introducing antigorite and wollastonite minerals into PTFE and pressureless sintering, which had a dense structure, a uniform distribution of reinforcements, and an increased Shore hardness (from 11.5% to 23.7%), compared to pure PTFE.

Single addition of antigorite could improve the wear resistance of PTFE and increased the frictional stability, while the simultaneous introduction of antigorite and wollastonite could improve both the anti-wear and friction reducing properties of PTFE. The average friction coefficient and wear volume of (10Atg+20Wl)/PTFE were reduced by 44.2% and 71.4%, respectively, compared to pure PTFE.

The improvement of the tribological properties of mineral containing PTFE was attributed to the strengthening effect of minerals on the polymer and the formation of a tribo-layer with high hardness and self-lubricating properties on the dual surface. Compared with the addition of single antigorite, the simultaneous addition of wollastonite reduced the phase transformation temperature of antigorite, and promoted the formation of tribo-layer on the worn surface, thus having a good synergistic effect.

Optimizing the nanostructure of the cathode is an effective approach to enhance the performance of solid oxide fuel cells at a triple-phase boundary (TPB). The most commonly used method is an impregnation method, which can produce nano-sized particles on the cathode framework structure. However, it is not able to achieve the related large-scale application due to its laborious preparation process and unstable performance. In this paper, nano-sized and submicron-sized composite powders of La_0.6Sr_0.4CoO_3-δ-Ce_0.8Gd_0.2O_2-δ (LSC-GDC) were synthesized by flame spray pyrolysis (FSP) and spray drying (SD) methods for the preparation of cathode, respectively.

A uniform submicron-sized LSC-GDC composite powder was prepared by SD with a solution of metal nitrates as a precursor solution. Also, a uniform nano-sized LSC-GDC composite powder was directly synthesized by FSP with a solution of metal acetates as a precursor solution. The submicron-sized and nano-sized powders were blended in different mass ratios (i.e., 100∶0, 90∶10, 80∶20, 70∶30, 60∶40, 50∶50, and 40∶60) to produce cathode slurries. These slurries were then screen-printed onto the button cells of NiO-GDC|GDC|3YSZ|GDC|LSC-GDC|LSC structure with an effective electrode area of approximately 0.5 cm². The voltammetric characteristics of the cells were tested by an electrochemical workstation. The electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS) at open circuit voltage (OCV), and the impedance spectra were analyzed via distribution of relaxation time (DRT) analysis.

Nano-sized particles synthesized by FSP and submicron-sized particles synthesized by SD can be distinguished via microscopic analysis. In addition, the fine particles are evenly distributed around the coarse particles, having a porous structure that meets an expected cathode microstructure. Under the experimental conditions, the overall ohmic impedance and polarization impedance both increase and then decrease as the proportion of nano-sized particles increases. The cathode performance is optimal when a mass ratio of SD powder: flame FSP powder is 70∶30. Under SOFC mode at 850 ℃, the maximum power density of the button cell is 0.47 W/cm², with an area specific resistance of 0.62 Ω·cm². The corresponding ohmic impedance and polarization impedance values are 0.36 Ω·cm² and 0.26 Ω·cm², respectively. Combined with the results by DRT analysis, the doping of an appropriate amount of nano-sized powder significantly enhances the cathode O₂ reduction reaction (ORR) process and cathode oxygen diffusion process.

Nano-sized and submicron-sized LSC-GDC composite materials were prepared by FSP and SD as one-pot methods, respectively. The feasibility of these two approaches for the large-scale preparation of SOFC cathode powders was investigated. The results showed that incorporating an appropriate amount of nano-sized powder into the submicron-sized powder for the preparation of the cathode could effectively enhance the cell performance.

Piezoelectric ceramics for the exchange of mechanical energy and electric energy are widely used in the production of piezoelectric sensors, piezoelectric energy harvesters, piezoelectric transducers and other functional devices. Among the piezoelectric ceramics, Pb(Zr, Ti)O₃ (PZT) based perovskite piezoelectric ceramic with high piezoelectric properties is popular. However, the serious thermal depolarization behavior of PZT at a high temperature makes it difficult to meet the application requirements of high-temperature piezoelectric applications in aerospace, nuclear industry and other fields. The Curie temperature of BiScO₃-PbTiO₃ (BS-PT) perovskite piezoelectric ceramic, located at the morphotropic phase boundary (MPB), is nearly 100 ℃ higher than that of PZT-based piezoelectric ceramics when their piezoelectric coefficient (d₃₃) values are similar. Therefore, BS-PT piezoelectric system is considered as a matrix with a great potential for high-temperature piezoelectric applications. Obtaining BS-PT-based high-temperature piezoelectric ceramics with both high temperature (d₃₃) and high thermal depolarization temperature (T_d) remains a key challenge. For perovskite-type piezoelectric ceramics, the Curie temperature is like-inversely proportional to the tolerance factor, and ferroelectric active ions are usually attributed to promoting the polarization coupling. These indicate that introducing the small tolerance factor and ferroelectric active ions into BS-PT matrix could break through the bottleneck above. In this paper, Bi(Zn_2/3Nb_1/3)O₃ (BZN), with ferroelectric active Bi/Zn ions and a tolerance factor similar to BS was introduced into BS-PT matrix, and the related microstructure, electrical properties and their correlation mechanism were investigated.

For the preparation of BS-xPT-BZN (0.60≤x≤0.63) piezoelectric ceramics by a high-temperature solid-state reaction method, the raw materials were mixed and ground in a ball mill, and then sintered at 850 ℃ for 2 h. Afterwards, the sintered materials were pressed, and further sintered at 1 140 ℃ for 2 h. The BS-xPT-BZN piezoelectric ceramic with silver electrodes was placed in a silicone oil bath at 120 ℃ and loaded in a DC electric field of 50 kV/cm for 30 min for artificial polarization. The phase composition, grain morphology, ferroelectric, piezoelectric and dielectric properties of the BS-xPT-BZN ceramics were characterized by a model D8-Advance type X-ray diffractometer, a model Sigma-300 type field emission scanning electron microscope, a model ZJ-6A type quasi-static d₃₃ meter, and a model TZDM-RT-1000 high-temperature dielectric temperature spectrum test system.

All the BS-xPT-BZN ceramic samples have a dense microstructure, and the average grain sizes are 2.29-3.91 μm. Meanwhile, the BS-xPT-BZN piezoelectric ceramics sintered have a perovskite phase structure. The tetragonal phase content gradually increases and all the ceramic samples maintain the characteristics of two phases coexist as the PT content increases. As a result, the composition with a high Curie temperature and located at the morphotropic phase boundary (MPB) is obtained. Among all the compositions studied, the ceramic sample with x of 0.62 has a maximum room temperature d₃₃ value, and thus is considered as MPB composition. This is because the maximum d₃₃ value is usually obtained in the MPB composition with a flatter Gibbs free energy profile. In addition, the Curie temperature of the MPB is as high as 438 ℃, which is conducive to the acquisition of T_d and high-temperature application. Also, the in-situ variable temperature d₃₃ test results show that the depolarization temperature of MPB sample with x of 0.62 is up to 409 ℃ and accompanied by a large high temperature d₃₃ (709 pC·N^-1), which is much better than that of reported Pb-based perovskite piezoelectric ceramics. The excellent high-temperature piezoelectric performance is due to the vertical MPB phase boundary characteristics of BS-PT matrix itself, and the increase of tetragonal phase content of BS-PT matrix results from the introduction of BZN, which has a small tolerance factor and contains ferroelectric active ions. This study demonstrates that BS-xPT-BZN piezoelectric ceramics are advanced high-temperature piezoelectric materials suitable for electromechanical applications at elevated temperatures.

BS-xPT-BZN (0.60≤x≤0.63) ternary system high-temperature piezoelectric ceramics were prepared by a high-temperature solid-phase reaction method. The results showed that the ceramic samples had a good grain development and compact structure. The ceramics with x of 0.62 located at the morphotropic phase boundary had the optimal comprehensive high-temperature performance (i.e., the Curie temperature T_C of 438 ℃, thermal depolarization temperature T_d of 409 ℃, and the maximum in-situ high-temperature quasi-static piezoelectric coefficient d₃₃ of 709 pC·N^-1). The excellent high temperature piezoelectric properties could be mainly related to the MPB characteristics that maintained multi-phase coexistence in a wide temperature region. The large high-temperature piezoelectric properties and high thermal depolarization temperature indicate that BS-xPT-BZN piezoelectric ceramics could be a promising candidate for the preparation of advanced high-temperature piezoelectric devices.

Protonic ceramic fuel cells can efficiently convert chemical energy directly into electrical energy, overcoming the potential problems of fuel gas dilution and gas separation in oxygen ion conductor solid oxide fuel cells. However, the electrochemical performance of PCFCs does not exceed that of O-SOFCs, and the development and improvement of cathode materials with a high catalytic activity is the most important issue to promote the development of PCFCs at low temperatures. The future research aspects of PCFCs cathode are as follows: (a) Development and performance of high entropy perovskite oxides. High entropy perovskite oxides can exhibit the properties of many different oxides simultaneously, and achieve a good performance in PCFCs; (b) In-situ characterization and detection of reaction mechanisms. In the future, the in-depth study of in-situ characterization is expected to provide a theoretical support for further understanding of the relationship between electrode structure and performance and further optimization of cathode performance; (c) The development of low-cost cathodes. Cobalt-based perovskite materials are widely used in PCFCs. However, the thermal mismatch between cobalt-based materials and common proton-conducting electrolytes, chemical instability, and rising price of cobalt greatly limit the application of cobalt-based materials in PCFCs cathodes; (d) Optimization of nanostructures. The nanostructured electrodes and interfaces formed via atomic layer deposition or impregnation can increase the number of active sites and reduce the length of ion diffusion to active sites; and (e) Development of composite cathode. The introduction of electrolyte material in the cathode, that is, proton conduction phase, can effectively reduce the polarization resistance of the cathode, expand the length of the three-phase interface, and reduce the thermal expansion coefficient of the cathode, which can better match the electrolyte and solve the problem of delamination between the cathode and the electrolyte.

MgO-C refractories are extensively utilized as lining materials for smelting equipment (i.e., converters, ladles, and electric arc furnaces) due to their excellent resistance to slag erosion and thermal shock. Nevertheless, under high scrap ratio smelting conditions, MgO-C refractories are subjected to mechanical stress due to the introduction of scrap steel and thermal stress caused by frequent fluctuations in service temperatures, resulting in a substantial reduction in their operational lifespan. It is thus crucial to further enhance the mechanical properties and thermal shock resistance of MgO-C refractories. In recent years, effective approaches on the composition and structural design of materials are explored, which include the construction of nanostructure matrices, light-weighting and strengthening of magnesia-based aggregates, the introduction of novel additives, and the optimization of secondary carbon in binders. Among them, calcium magnesium aluminate (CMA) aggregates as a novel porous aggregate have attracted much attention. At elevated temperatures, it induces a partial liquid phase within the material matrix, effectively mitigating internal thermal stresses, repairing micro-cracks resulting from thermal shock, and facilitating the formation and growth of spinel whiskers. Consequently, a substantial enhancement in both toughness and thermal shock resistance of the material is achieved. In fact, ordinary sintered magnesia aggregates contain certain impurity phases, such as merwinite (with a melting point of 1 550 ℃) and andradite (with a melting point of 1 170 ℃). When conventional fused magnesia aggregates partially are substituted with ordinary sintered magnesia aggregates in the preparation of MgO-C refractories, localized liquid phases can be generated within the matrix at high temperatures, which may serve a similar function to CMA aggregates. Compared to CMA aggregates, ordinary sintered magnesia aggregates are more affordable, resulting in a substantial reduction in production expenses and facilitating the efficient utilization of low-grade magnesia. In this paper, ordinary sintered magnesia aggregates were selected to partially substitute conventional fused magnesia aggregates in the preparation of MgO-C materials. The microstructure evolution, mechanical properties, thermal shock resistance, and high-temperature fracture behavior of MgO-C refractories containing ordinary sintered magnesia aggregates were investigated.

MgO-C refractories were prepared via substituting 10% of ordinary sintered magnesia aggregates (w(MgO)=93.33%, w(SiO₂)=1.72%, w(CaO)=3.12%, and w(CaO)/w(SiO₂)=1.81, w is mass fraction) for conventional fused magnesia aggregates (w(MgO)=97.35%, w(SiO₂)=0.5%, w(CaO)=1.12%, and w(CaO)/w(SiO₂)=2.24) with a flake graphite as carbon source, metallic silicon powder and boron carbide as antioxidants, and thermosetting phenolic resin as a binder. After thoroughly blending the aforementioned materials, bar-shaped specimens with the sizes of 140 mm×25 mm×25 mm and standard brick specimens with the sizes of 230 mm×110 mm×70 mm were shaped at 150 MPa and then cured at 200 ℃ for 24 h. The cold modulus of rupture (CMOR) of the bar-shaped specimens, treated at different temperatures (i.e., 200, 1 000, 1 400 ℃ and 1 600 ℃) in a coke bed was measured by a model XD-117A three-point bending test machine. The microstructure and elemental composition of the specimens were determined by a model Nova Nano 400 field emission scanning electron microscope, combined with a model IE 350 PentaFET X-3 energy dispersive spectrometer. The bar-shaped specimens (140 mm×25 mm×25 mm) coked at 1 400 ℃ were selected for thermal shock test by an oil quenching method. Namely, these specimens were initially heated in a coke bed at 900 ℃ for 30 min, followed by quenching in an oil bath. After undergoing three thermal shock cycles, the residual strength index (CMOR after thermal shocks/CMOR before thermal shocks) of specimens was calculated. Subsequently, the bar-shaped specimens after thermal shock test were further heated in the coke bed at 1 600 ℃ for 3 h, and then the recovery strength index (the change of CMOR after reheating to 1 600 ℃/CMOR after thermal shocks) of MgO-C specimens was calculated. In addition, the standard brick specimens were processed into the wedge splitting specimens (100 mm×100 mm×70 mm), and heated in the coke bed at 1 000 ℃. Subsequently, high-temperature wedge splitting tests were conducted at 1 000 ℃ and 1 400 ℃ for 30 min, respectively. The specimens were surrounded in alumina crucibles filled with coke in a high-temperature furnace to establish a reducing atmosphere. Fracture parameters such as the nominal notch tensile strength (σ_NT), specific fracture energy (G_f), characteristic length (l_ch) and thermal shock resistance (R_st), were calculated to further quantitatively characterize the thermal shock resistance of specimens.

Ordinary sintered magnesia aggregates remain intact in MgO-C refractories coked at 1 000 ℃. However, the impurities within some ordinary sintered magnesia aggregates dissolve and diffuse into the surrounding matrix as the temperature increases to 1 400 ℃, disintegrating the aggregates into a porous structure. In addition, Mg₂SiO₄ particles and whiskers, as well as SiC whiskers also appear in the matrix due to the introduction of silica powder. The dissolution and diffusion of impurities increase as the temperature further increases to 1 600 ℃, generating Mg₂SiO₄ particles and SiC whiskers in the matrix. These structural changes in MgO-C refractories at high temperatures enhance the strength, even the high-temperature flexural strength, and improve the thermal shock resistance of MgO-C refractories.

The results of high-temperature wedge splitting test show that MgO-C specimens containing ordinary sintered magnesia aggregates exhibit an equivalent peak load to those of the control specimens, while their fracture displacements significantly enlarge. As evident from various fracture parameters, MgO-C specimens containing ordinary sintered magnesia aggregates exhibit higher G_f, l_ch, and R_st at 1 000 ℃ and 1 400 ℃, indicating that the introduction of ordinary sintered magnesia aggregates effectively reduces the material brittleness due to improving the thermal shock resistance of specimen Also, the specimens containing ordinary sintered magnesia aggregates exhibit a higher proportion of cracks along the aggregate-matrix interface in the crack propagation path. The enhancement of fracture toughness and thermal shock resistance of MgO-C refractories with ordinary sintered magnesia aggregates addition can be attributed to the stress relief provided by the porous structure of ordinary sintered magnesia, the promotion of sintering at 1 400 ℃ by the formation of liquid phases, and the formation of whiskers in the matrix.

The addition of ordinary sintered magnesia effectively enhanced the thermal shock resistance of MgO-C refractories due to the porous structure of ordinary sintered magnesia aggregate and its ability to form a liquid phase at high temperatures, thereby reducing the overall thermal expansion rate of the specimens. MgO-C specimens containing ordinary sintered magnesia aggregates exhibited higher G_f, l_ch, and R_st at 1 000 ℃ and 1 400 ℃ due to the higher porosity of the ordinary sintered magnesia aggregates, effectively mitigating the stress concentration. At 1 400 ℃, the impurities in the ordinary sintered magnesia aggregates dissolved and diffused into the matrix to form a liquid phase network that was conducive to absorbing stress at crack tips. The formation of this liquid phase promoted the whiskers formation and slowed down the crack propagation.

Alkaline water electrolysis is a highly mature, simple, and low-cost hydrogen production technology that is widely applied to a large-scale hydrogen production in China. In the future, the construction of new power systems will urgently need a large-scale wind power consumption capacity as well as a low-cost, green hydrogen supply in chemical and transportation industries. This requires electrolysis cells capable of adapting to fluctuating power sources, i.e., wind power. However, the existing industrial technology mainly focuses on a single-tank hydrogen production for incremental improvements. Limited progress is made to address some issues like a low current density and a poor dynamic performance. The emerging demand for green electricity to produce green hydrogen leads to higher requirements for the key materials and equipment technology of alkaline water electrolysis. The next generation of this technology can feature a high current density and a low energy consumption, operate across a wide and variable load, and have rapid start/stop capabilities to accommodate the fluctuating hydrogen production scenarios of renewable energy. The lab-research of AWE electrode catalysts should consider the needs of industrial applications. Simple organic fiber diaphragms have a poor pore structure and a high ionic resistance. Hence, thick membranes (typically >0.8 mm) are required to meet the gas barrier properties. Organic-inorganic composite diaphragms are promising for future industrial applications, although their long-term durability still requires a further verification. Moreover, there is a significant lack of research on the effect of fluctuating working conditions (i.e., variable loads and start-stop cycles) on the dissolution of electrode catalysts, detachment, and mechanical damage to the diaphragm. Beyond materials, further studies on system operation control and optimization are needed to improve dynamic performance (i.e., strategies to mitigate reverse current that limits the start-stop frequency of alkaline water electrolyzers.

Two-dimensional transition metal dichalcogenides (TMDCs) have attracted much attention due to their unique "sandwich" structure. As a typical two-dimensional layered transition metal sulfide, MoS₂ has a layered structure composed of S-Mo-S triple layers with covalent bonds. The atoms in MoS₂ layer are combined by covalent bonds, while the interaction between layers depends on the van der Waals forces. This special S—Mo—S layered structure is conductive to the rapid diffusion of lithium ions, and the intercalation of lithium ions between layers during a charging and discharging process does not affect the volume change. However, MoS₂ has some problems such as poor conductivity and easy decomposition of the structure, severely hindering the development of MoS₂ electrode materials. This paper was to composite a liquid metal (LM) with MoS₂ materials. Among them, LM has an excellent ion and electron conductivity, which can improve the conductivity of MoS₂. The moderate interlayer distance of MoS₂ can restrict LM droplets within the framework, thereby allowing LM to better exert its self-healing properties for the preparation of negative electrode materials with self-healing capabilities.

400 mg of LM was firstly added into 50 mL of N, N-Dimethylformamide (DMF), and then a certain amount of phosphomolybdic acid was added into the LM and DMF under ultrasound. Also, the required thiourea and catalyst NaBH₄ were mixed in a beaker in a molar Mo∶S ratio of 1.0∶2.6. Afterwards, the two solutions were transferred to a polytetrafluoroethylene liner and reacted at 200 ℃ for 24 h. The resulting reaction solutions were washed with deionized water, N, N-Dimethylformamide, and anhydrous ethanol, respectively. Finally, the washed materials were dried in a vacuum drying oven at 70 ℃ for 12 h to obtain the final reaction product. The prepared active material was mixed with acetylene carbon black and polyvinylidene fluoride (PVDF) in a ratio of 8∶1∶1. The material was fully ground in a ball mill in the presence of an appropriate amount of solvent N-Methyl-2-pyrrolidone (NMP) to obtain a uniformly mixed slurry. The slurry was evenly coated on a copper foil and dried in a vacuum at 70 ℃ for 12 h. The dried material was cut into 12 mm discs with a slicer as a battery negative electrode, and it was assembled into a CR2016 button battery in a glove box filled with argon. Among them, the metal lithium sheet was a counter electrode, the polypropylene porous membrane (Celgard2400) was a separator, the electrolyte solute was 1 mol·L^-1 LiPF₆, the solvent was a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a ratio of 1∶1∶1, and the foam nickel was a gasket.

The results show that the liquid metal effectively combines with MoS₂ via electrostatic adsorption and coordination bonds to form a stable composite structure. In addition, the composite material has a higher deformability and a chemical stability, promoting the repair of the crack surface of the electrode material, reducing the internal redox reaction, and improving the cycle stability of the lithium-ion battery. When a mass ratio of LM∶MoS₂ is 2∶1, the composite material shows the optimum performance. At a current density of 0.1 A·g^-1, after 100 cycles, the specific capacity of the composite material is stable at 656.1 mA·h·g^-1, the capacity retention rate reaches 74.3%, effectively improving the cycle stability of the electrode material.

A lithium-ion battery negative electrode material LM@MoS₂ with self-healing characteristics was prepared by a hydrothermal method. The cracks generated in the electrode during the charging and discharging process were repaired via utilizing the fluidity and high surface tension of liquid metal, effectively improving the cycle life of the electrode material. The optimum cycle stability of the electrode was obtained at a mass ratio of LM∶MoS₂ of 2∶1. The LM@MoS₂ prepared could reduce the internal redox reaction of the battery, thereby improving the electrochemical performance of the battery in the process of repeated insertion and extraction of lithium ions, reducing mechanical fractures, and improving the electrochemical performance of the battery.

The main feature of tubular SOFC is its relatively easy high-temperature sealing performance and low thermal stress during stack integration and operation. Each type of tubular battery structures has its own unique characteristics. In general, multi-section tubular structures are more suitable for the construction of high-power power plants, while single section tubular batteries are more suitable for small systems. At present, regardless of the structure of a single cell, there is already a relatively mature material system that can achieve a stable battery performance. The existing work mainly focus on the development and preparation of new materials, process optimization, and the development of different hydrocarbon fuel cells. Among the tubular battery supports, round tube multi-section and flat tube multi-section batteries are more suitable for single tube high-power output. The mainstream of this multi-section design battery is a single tube output of over 100 W, which is more suitable for large distributed functional systems. In addition, tubular batteries with metal or metal ceramic support structures can significantly improve the startup speed of SOFC. Tubular batteries can also be used as electrolytic cells due to the reversible structure of SOFC and SOEC. This type of battery with a fast start-up speed is more suitable for coupling with photovoltaic and wind power, achieving an efficient energy utilization. For cylindrical multi-cell batteries, one battery tube is equivalent to a stack, so the manufacturing process of tubular batteries is relatively complex, and their commercialization process lags behind that of flat panel batteries. For battery stacks, there are some issues such as battery array arrangement, heat exchange, and airflow distribution. At present, there are not many publicly reported experimental data, a further experimental research is thus needed. Although there are still some challenges for tubular SOFC, the performance, stability, and reliability of SOFC can be improved through the development of novel materials and technological innovations, thereby enhancing their application prospects in the field of sustainable energy and enabling commercial SOFC technology to be implemented.

Strontium zirconate titanate is an important dielectric material with a high dielectric constant and a low dielectric loss. Also, as a semiconductor catalytic material, it has an application potential in the fields of photocracking water and photodegradation of organic matter. However, as a semiconductor catalytic material, SrTi_xZr_(1-x)O₃ has a wide band gap and a low carrier migration rate. Element substitution is commonly performed via ion doping at the B site (i.e., Ti element site) in the lattice. The resulting lattice defects inhibit photogenerated electron-hole recombination and narrow the band gap, thereby improving the catalytic efficiency. At present, the doping of transition metal elements such as Nb, Co, Rh, Fe and Ce is beneficial to reducing the band gap and promoting its response to visible light. Little studies have been reported to explain the morphology of single crystal particles by theoretical calculations. In this paper, SrTi_xZr_(1-x)O₃ single crystal nanoparticles with different Ti/Zr molar ratios were synthesized by a hydrothermal method. The micro-morphology, crystal size and light response characteristics of SrTi_xZr_(1-x)O₃ single crystal nanoparticles were investigated. In addition, the micro-morphology of SrTi_xZr_(1-x)O₃ single crystal nanoparticles was also revealed based on the first-principles calculation.

Strontium chloride hexahydrate (SrCl₂·6H₂O) and titanium tetrachloride (TiCl₄) from Sinopharm Chemical Reagent Co., Ltd., China, were used as raw materials, respectively. Zirconium tetrachloride (ZrCl₄) and lithium hydroxide (LiOH) from Shanghai McLean Biochemical Technology Co., Ltd., China, were used as zirconium source and pH regulator. SrTi_xZr_(1-x)O₃ nano-single crystal particles with different molar ratios of titanium to zirconium were prepared by a hydrothermal method at 180 ℃ for 12 h.

The phase composition, microstructure and element distribution of the samples were determined by X-ray diffractometer and thermal field emission scanning electron microscope with energy dispersive spectrometer. The light response characteristics of the samples were characterized by UV-visible spectrophotometer. Based on the first-principles density functional theory (DFT), 3 kinds of SrTi_0.25Zr_0.75O₃, 6 kinds of SrTi_0.5Zr_0.5O₃ and 3 kinds of SrTi_0.75Zr_0.25O₃ 2×2×2 supercell configurations were designed and calculated.

SrTi_xZr_(1-x)O₃ nano-single crystal exhibits a perovskite structure. The diffraction peak becomes wider when element Zr gradually replaces elemen Ti. SrCO₃ as an impurity phase can be removed by calcining at 1 200 ℃. The hydrothermal reaction synthesized SrTiO₃ with a cubic phase shows a regular hexahedron morphology. Most of SrZrO₃ crystals with an orthorhombic phase are flat octahedron morphology. The particles basically tend to be regular hexahedron morphology when Ti∶Zr=1∶3 and 3∶1. However, the lattice distortion effect of SrTi_xZr_(1-x)O₃ crystal reaches the maximum, and some of the morphologies are star-shaped when Ti∶Zr=1∶1.

The lattice parameters of SrTi_xZr_(1-x)O₃ unit cell configuration were calculated by first-principles density functional theory. In SrTi_0.5Zr_0.5O₃ system, the configurations (iv), (viii) and (ix) are transformed into orthorhombic crystals, and the maximum lattice constant c reaches 9.5 Å. The ground state energies of configurations (iii), (v) and (xii) are 2.538, 1.530 eV and 0.949 eV, respectively. Based on the principle of energy minimization, the crystal grows preferentially according to these configurations. Thus, SrTi_xZr_(1-x)O₃ (x=0.25, 0.75) grains exhibit a uniform hexahedral morphology. The octahedral dip angle, bond lengths and angles of four configurations (iii), (v), (ix) and (vii) are selected to analyze the symmetry change and lattice distortion of the crystals. The octahedral bond angles are more than 179.9° in the three lowest ground state energy configurations, which maintain a structural symmetry. However, Ti(Zr)O₆ octahedron tilt angles of the configuration (ix) are mainly concentrated at 145°-153°. The Ti(Zr)—O bond lengths are distributed in the range of 1.711-2.926 Å. This indicates that equimolar Ti/Zr causes the lattice distortion due to the change of bond length and angle. The lattice distortion promotes the formation of star-like morphology. The light response characteristics show that the band gap of SrTi_xZr_(1-x)O₃ nano-single crystal particles decreases with the increase of Ti⁴⁺ proportion. The band gaps of SrTi_0.25Zr_0.75O₃, SrTi_0.5Zr_0.5O₃ and SrTi_0.75Zr_0.25O₃ are 3.70, 3.47 eV and 3.34 eV, respectively, which are consistent with those obtained via the first-principles calculations.

Perovskite structure SrTi_xZr_(1-x)O₃ nano-single crystal particles with different Ti/Zr molar ratios were synthesized by a hydrothermal method. SrTi_0.25Zr_0.75O₃ and SrTi_0.75Zr_0.25O₃ both were transformed into a hexahedral morphology. A special star-shaped polyhedron morphology appeared in SrTi_0.5Zr_0.5O₃ sample. The lattice parameters and energy band structure of SrTi_xZr_(1-x)O₃ were obtained via the first-principles calculations. The lattice distortion effect appeared as Ti/Zr=1. There were lattice parameters of three configurations in the supercell lattice arrangement are a=b≠c, where c can be up to 9.570 Å. The actual crystal growth process of the SrTi_0.5Zr_0.5O₃ system was partially carried out according to these arrangements. The heterogeneous nucleation mechanism was induced by different crystal configurations and the lattice distortion, which promoted the formation of star-shaped grains. The band gap change rule of the samples was verified by ultraviolet-visible spectrophotometer. The increase of element Ti ratio led to the decrease of the band gap since the energy level of Ti 3d orbital was lower than that of Zr 4d orbital.

Cement industry is one of the major carbon-emitting industries, which is characterized by a thermal efficiency below 54% and an energy consumption ranging from 3-4 GJ per ton of cement clinker. China annual average cement production reaches 2 341 million tons, contributing to approximately 14.3% of the total CO₂ emissions. In addition to the CO₂ emissions resulting from the high-temperature decomposition of limestone, which serves as a primary raw material, the cement production process significantly contributes to elevated CO₂ emissions due to its substantial energy consumption. The cement rotary kiln is a pivotal equipment in the production process, with its high energy consumption primarily attributed to subpar performance of certain refractory materials and an irrational configuration. Consequently, this leads to elevated temperatures (reaching up to 350-400 ℃) in both the transition zone and firing zone of the kiln shell, resulting in a substantial energy loss accounting for 8%-15% of the total heat input. Previous studies demonstrated that the implementation of light weight refractory materials could effectively mitigate heat loss from the kiln shell, thereby enhancing energy efficiency. The CA₆/MA composite material C₂M₂A₁₄ has the excellent high-temperature performance and chemical stability of both CA₆ and MA. It is proven to be an effective ladle lining material in the non-slag line part. Incorporating a proper quantity of Fe₂O₃ during the synthesis process of C₂M₂A₁₄ results in a denser product under identical firing conditions. In this paper, C₂M₂A₁₄ was introduced into magnesite refractories to achieve light weighting of magnesite refractories. In addition, the mechanism of achieving light weighting and the effects of addition amount and particle size on the microstructure and properties of magnesite refractories were also investigated.

Magnesium hydroxide, calcium carbonate and calcined α-alumina fine powders as raw materials were mixed. Also, 1% Fe₂O₃ was added to the mixture according to a specific mass ratio. The mixture was then pressed into cylindrical samples with a diameter of Φ36 mm×36 mm. C₂M₂A₁₄ was synthesized via firing at 1 780 ℃ for 5 h. The synthesized material was crushed and sieved to obtain fine particles with different sizes of 1-3 mm, 0.088-1.000 mm, 0.5-1.0 mm, 0.088-0.500 mm, and≤0.088 mm. Magnesia and materials such as C₂M₂A₁₄ were mixed according to the specified ratio, and then pressed into cylindrical samples with dimensions of Φ36 mm×36 mm and Φ36 mm×50 mm, as well as crucible samples with the dimensions of Φ50 mm×50 mm. These samples were fired at different temperatures (i.e., 1 600, 1 650 ℃ and 1 700 ℃) for 3 h. The bulk density, apparent porosity, true density, and cold crushing strength at room temperature of A sample with the size of Φ36 mm×36 mm were characterized according to national standards. The load softening temperature of a sample with the size of Φ36 mm×50 mm was measured. The pore size distribution of the original brick was determined by a fully automatic mercury porosimeter. Cement material in crucible was heated at 1 350 ℃ for 6 h to investigate its corrosion-resistance to cement material. The microstructure before and after corrosion of the crucible samples and original bricks was determined in a backscattered electron imaging mode by field corrosion scanning electron microscopy. The phase composition of the samples was characterized by X-ray diffraction with a software named Jade .

The results show that at 1 600 ℃, the apparent porosity of sample increases while their bulk density and cold crushing strength decrease as the amount of C₂M₂A₁₄ increases. Also, the load softening temperature decreases. The apparent porosity of samples with particle sizes ranging from 0.5-1.0 mm increases from 23.2% to 32.8% with increasing C₂M₂A₁₄ from 10% to 40%. The bulk density decreases from 2.70 g/cm³ to 2.36 g/cm³, which is lower than the one of dense refractory (which is also made of the same material) at 2.94 g/cm³, indicating a trend towards light weighting. At the same addition amount of 10%, the particle size of C₂M₂A₁₄ becomes smaller, the apparent porosity of the sample decreases, and the bulk density and cold crushing strength both increase. The load softening temperature is closer. The apparent porosity of samples with different particle sizes (i.e., 0.5-1.0 mm and 0.088-0.500 mm) gradually decreases, while the bulk density increases as the firing temperature increases. However, there is no corresponding increase in cold crushing strength. The maximum cold crushing strength is 56.6 MPa, and the particle sizes both exhibit a load softening temperature of >1 540 ℃, meeting the requirements for application in cement kiln transition zones. The presence of magnesia in the matrix during firing induces the decomposition of C₂M₂A₁₄, as evidenced by XRD and SEM analysis. In the magnesite-spinel-aluminate ternary system, a liquid phase forms at elevated temperatures, facilitating a pore formation through liquid-assisted Kirkendall effect and achieving a light weighting in the samples. Furthermore, increasing the amount of C₂M₂A₁₄ results in a higher apparent porosity, while leading to a decrease in bulk density, cold crushing strength, and load softening temperature. The corrosion resistance of group D and E samples with particle sizes of 0.5-1.0 mm and 0.088-0.500 mm was investigated at 1 350 ℃ by a static crucible method with the addition of 10% C₂M₂A₁₄. The crucibles of D series samples exhibit a visible corrosion penetration, while those of group E samples show a negligible corrosion penetration. No adhering slag appears on the side walls in either group. The microstructural analysis reveals that different sizes of C₂M₂A₁₄ particles are responsible for variations in penetration depth between the two group samples. Larger and more pores occur in group D samples, allowing cement material to penetrate through them. The introduction of C₂M₂A₁₄ particles with the sizes of 0.088-0.500 mm in group E results in smaller pores resulted from the reaction between C₂M₂A₁₄ particle and magnesia matrix, making them denser and effectively inhibiting the penetration by a low melting point cement phase.

1) Introducing Ca₂Mg₂Al₂₈O₄₆ was introduced into magnesium refractor during firing. Magnesite-spinel-aluminate ternary system formed a liquid phase at a high temperature. The pores formed with a liquid phase assisted the Kirkendall effect and resulted in magnesium refractory to achieve lightweight. The apparent porosity of samples increased, the bulk density, compressive strength and the refractoriness under load decreased with increasing the amount of Ca₂Mg₂Al₂₈O₄₆ additions. At the same amount of Ca₂Mg₂Al₂₈O₄₆ added, the performance could be improved via reducing its particle size. 2) As the firing temperature increased, the apparent porosity of specimen decreased, the bulk density increased, but their compressive strength did not increase, and the refractoriness under a load maintained at a high level (>1 540 ℃). The refractoriness under a load could reach 1 603 ℃ when 10% (in mass fraction) of Ca₂Mg₂Al₂₈O₄₆ particles with the sizes of 0.50-1.00 mm were added and fired at 1 700 ℃. 3) The static crucible experiments at 1 350 ℃ showed that the specimens with the introduction of Ca₂Mg₂Al₂₈O₄₆ particles with the sizes of less than 0.50 mm at 10% addition had the optimum corrosion resistance to cement materials when the specimens were fired at 1 650 ℃.