The gyroscope operation relies on the electrostatic actuation and capacitance detection between the resonator and the planar electrode, with a typical gap ranging from 20-150 µm. When organic impurities adhere to planar electrode's surface, gap's capacitance changes, leading to fluctuations in the excitation detection signal and thereby affecting the accuracy and reliability of the gyroscope. TiO₂ thin film can effectively degrade organic pollutants through photocatalytic reactions. However, little research on its application on the surface of high-precision devices has been reported yet. The thickness of the TiO₂ thin film affects the generation and effective separation of photo-generated electron-hole pairs, thereby influencing the photocatalytic performance of the TiO₂ thin film. It is thus necessary to determine the thickness of the TiO₂ thin film on the surface of the planar electrode through experiments. In this paper, a TiO₂/Au composite thin film was designed to reduce the adsorption of organic substances on the surface of planar electrode and improve the thin film quality on the planar electrode surface.

TiO₂ thin films with different thicknesses were prepared on fused quartz substrates via radio frequency magnetron sputtering. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometry (UV-Vis), and photocatalytic reaction analysis. The crystalline structure, grain size, surface morphology, and optical absorption characteristics of the TiO₂ thin films were analyzed to assess their impacts on the photocatalytic performance. The optimal thickness of the TiO₂ thin film suitable for the surface of the planar electrode was determined to be 240 nm. Finally, the planar electrode with a TiO₂/Au composite thin film was fabricated. The surface film layer of the planar electrode was characterized by nanoindentation, nano-scratching, and photocatalytic reaction equipment. The exceptional performance of the TiO₂-coated planar electrode in terms of adhesion, friction resistance, and photocatalytic self-cleaning properties was validated. The final step involved assembling the prepared flat electrode with a hemispherical resonator and using a capacitance meter to validate the superior performance of the TiO₂/Au composite film structured planar electrode for reducing the impact of organic impurities on the gap capacitance between the resonator and the planar electrode.

The XRD patterns show that the crystalline integrity and grain size of the film gradually increase as the thickness of TiO₂ thin film increases. The SEM and AFM images reveal that the surface roughness increases with the enlargement of grains as the film thickness increases. Based on the analysis of the properties of the TiO₂ thin film, TiO₂ thin film with a thickness of 240 nm exhibits the smallest bandgap width and the optimal photocatalytic performance. For the mechanical properties of the surface film layer on the planar electrode, the abrasion resistance of the planar electrode coated with the TiO₂ thin film is higher than that of the electrode uncoated with the thin film. Also, the adhesion between TiO₂ thin film and Au film on the surface of the planar electrode is comparable to the adhesion between Au film on the surface of the uncoated planar electrode and the substrate. The planar electrode undergoes photocatalytic self-cleaning experiments, TiO₂/Au composite film structured flat electrode can reduce the impact of organic impurities on the capacitance uniformity between the resonator and the flat electrode, thereby contributing to the enhanceed performance of the hemispherical resonant gyroscope.

The crystallinity, grain size, and surface roughness of the TiO₂ thin film increased with increasing TiO₂ film thickness. The TiO₂ thin film with a thickness of 240 nm exhibited the smallest bandgap width and appropriate grain size, thus demonstrating the optimal photocatalytic activity. The experimental verification of mechanical, photocatalytic, and capacitive performance of planar electrodes coated with TiO₂/Au composite films revealed that the adhesion of the TiO₂ thin film on the planar electrode met practical application requirements. Leveraging the excellent hardness and elastic modulus of the TiO₂ thin film significantly enhanced the abrasion resistance of the surface film layer on the planar electrode. Also, the efficiency of photocatalytic degradation of organic impurities on the planar electrodes coated with TiO₂ thin films was 1.6 times higher than that of the electrodes uncoated with the thin film. For assembling the prepared flat electrode with a hemispherical resonator and conducting capacitance meter testing, the TiO₂/Au composite film structured flat electrode could degrade organic impurities and reduce their impact on the gap capacitance between the resonator and the flat electrode under UV light exposure. It was evident that the TiO₂/Au composite film could have a promising practical application in the fabrication of resonant gyroscope flat electrodes.

β-Ga₂O₃ as a ultra-wide bandgap semiconductor material with a great development potential has a bandgap width of 4.8 eV, and a theoretical breakdown electric field of 8 MV/cm. Its Baliga advantage value of β-Ga₂O₃ is also several times greater than that of silicon carbide (SiC) or gallium nitride (GaN). However, the low thermal conductivity of β-Ga₂O₃ seriously affected the device's heat dissipation and the application in the high-power field. Wafer bonding is an indispensable key technology in semiconductor devices, which enables the formation of new structures, efficient fabrication, device integration, and cost reduction. The silicon substrate with the advantages of low cost and high thermal conductivity is an important substrate material for heterogeneous integrations. SiO₂ layer is easily formed on the surface of silicon, and the surface structure of SiO₂ consists of a Si-O-Si three-dimensional network structure together with an unsaturated Si-O structure, and the existence of this structure is conducive to reducing the probability of bubble generation, thus improving the quality of the bonding bonding interface, so it is easier to realize the bonding of silicon and β-Ga₂O₃ by using SiO₂ as an intermediate layer. This paper was to analyze the effect of O₂ plasma activation on the wafer surface, including changes in contact angle, roughness, and surface chemical composition. In addition, the effect of annealing temperature on the strength and thermal stability of the bond structure and the structure and composition of the β-Ga₂O₃/SiO₂ bond interface was also discussed.

SiO₂/Si substrate with the thickness of 550 μm and β-Ga₂O₃ single crystals sunstrate with the thickness of 650 μm were prepared. The two wafers were cleaned with alcohol and acetone via ultrasonic cleaning , and isopropanol for 10 min, then rinsed with deionized water and blown dry with N₂. Also, β-Ga₂O₃ and SiO₂/Si substrates were processed by oxygen plasma in a reactive ion etching (RIE) equipment (PlasmaPro 100 Cobra, Oxford Instrument Co., UK) at 50 mtorr and 300 W. The two activated wafers to be bonded were initially aligned and bonded, and pressure was applied to the wafer surface with tweezers to fully expel the gas from the bonding interface and make the bonding closer. Finally, the bonded wafers were placed on a pressurized platform for pressurized resting to complete the pre-bonding process. The pre-bonded wafers were placed in the annealing furnace for low-temperature annealing to enhance the bonding strength. A testing machine was used to determine the bond strength of the bonded pairs at different annealing temperatures. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to determine the bonded interface images and elemental distribution.

The contact angle and hydroxyl density with treatment time were investigated via adjusting the treatment time of O₂ plasma. The hydrophilicity of SiO₂ and β-Ga₂O₃ wafers greatly enhances, and the hydroxyl density on the wafer surface improves as the O₂ plasma activation time increases. O-H in β-Ga₂O₃ is produced by the breakage of oxygen atoms (O_w) in water that combines with surface Ga atoms (Ga_s) to form Ga_s-O_wH_w, and H combines with surface oxygen atoms (O_s) to form O_s-H_w. The effect of annealing temperature on the surface quality and bonding strength was also investigated. The results indicate that the bonding strength increases with the increase of annealing temperature. When the annealing temperature increases to 500 ℃, the bond strength increases to 7.31 MPa. However, this process leads to the cracking of the β-Ga₂O₃ substrate. Some cracks in β-Ga₂O₃ occur due to the thermal stress resulting from the different thermal expansion coefficients between SiO₂ and β-Ga₂O₃. β-Ga₂O₃ and SiO₂ surfaces are atomically bonded with no interfacial voids or cracks. The bonding interface's elements O, Ga, and Si are fully diffused during annealing.

In this study, a high-strength bonding of β-Ga₂O₃ and SiO₂ substrates was achieved at low temperatures via O₂ plasma activation. The FTIR analysis showed an increase in the hydroxyl density of the β-Ga₂O₃ and SiO₂/Si surfaces with the increase in plasma treatment time. The XPS and FTIR analysis demonstrated the changes in the hydrophilic functional groups on the surfaces before and after the plasma treatments. The bond strength gradually increased with the annealing temperature and reached 7.31 MPa, but unbonding and cracking also occurred at the edges of the bonded regions. The SEM and TEM images of the bonding interface demonstrated the existence of tight bonding between β-Ga₂O₃ and SiO₂ with full diffusion of elements Ga, O, and Si. In addititon, a model for direct bonding of oxygen plasma-activated β-Ga₂O₃/SiO₂/Si was also proposed.

Relying on their advantages of high water reducing rate, low dosage, and strong molecular structure design ability, polycarboxylate superplasticizers (PCEs) have become the most widely used admixture in the field of concrete admixtures. Adsorption of PCEs onto the surfaces of cement particles is the prerequisite for the dispersing performance of PCE molecules. Therefore, the influences of PCE molecules with different structures on the dispersion properties of cement slurry can be understood by revealing the adsorption process of PCE and the conformation characteristics of PCE after adsorption.

It should be noted that both the adsorption process and the conformation of the adsorbed PCE involve interfacial interactions between the organic and inorganic phases, which is the dominant factor determining the overall properties of the material. Recently, molecular dynamics (MD) simulations have been applied to the PCEs to elucidate its working mechanism. However, the molecular size of these model PCEs was much smaller than those typically used for industrial applications in order to reduce computation cost. Furthermore, only pure water was used, or only Na⁺, Ca²⁺ and Cl^- were additionally added to mimic a cement pore solution. The above methods make the results unable to accurately reflect the adsorption mechanism of PCE. Therefore, to better understand and effectively control the performance of PCE, more in-depth studies at the atomic and molecular scales are needed. Our research team innovatively used MD simulations in which the molecular size of the model PCE is consistent with that of PCE commonly used for industrial applications and simulates cement pore solutions. In addition, the adsorption mechanism of sulfonation modification of PCE was studied by combining the structure, dynamics and stability of interfacial connections.

The MD simulations used the Gromacs-4.6.7 software package and a conventional oplsaa force field with RESP charges. The UFF force field was used for the substrate. The equilibrium MD simulation was conducted under the NPT ensemble for a total run time of 20 ns at a relaxed liquid configuration (25 ℃). The solution environment simulations were performed using 3000 water molecules. A relaxation system was selected and the energy was minimized by the steepest descent method with a termination gradient of 100 kJ/(mol∙nm) before the relaxation. The system temperature maintained constant through a Nosé-Hoover thermostat, and periodic boundary conditions were applied to all three dimensions. Long-range electrostatics within a relative tolerance of 1×10^-6 is calculated by the particle mesh Ewald method and a cut-off distance of 1 nm was used as the Ewald interaction and van der Waals interactions. The bond lengths of hydrogen atoms were constrained by the LINCS algorithm. A leap-frog algorithm was used with a time step of 1 fs.

Under cement solution conditions, the side chains of PAA-g-PALS molecules were not entangled with the backbone (present a network-like conformation), while a small part of the side chains of PAA-g-HPEG molecules will curl onto the backbone (most of the side chains curled into a mushroom shape). In addition, the rotation radius of PAA-g-PALS (7.8 nm) was significantly larger than PAA-g-HPEG (7.1 nm) due to the large amount of —SO₃^- with strong electrostatic repulsion.

Part of the backbone of PAA-g-HPEG was adsorbed to the particles (the side chains curl and wrap the backbone), while PAA-g-PALS was adsorbed to the substrate surface by the "flat" mode of the individual side chains (the backbone and other side chains extend into the solution). Compared with PAA-g-HPEG, the binding point of sulfation modified PCE and the substrate is relatively scattered and increases the binding surface with the substrate, which is consistent with the calculation of binding force PAA-g-PALS (174.3 kJ/mol)> PAA-g-HPEG (134.5 kJ/mol).

The vertical heights of the individual PAA-g-HPEG and PAA-g-PALS molecules on the substrate surface were 6.8 nm and 19.7 nm, respectively, and the coverage rate was 26.4% and 21.2%, respectively. When considering the polymer cross-dimensions parallel and perpendicular to the particle surface, the penetration volume formed by PAA-g-PALS on the substrate surface increased by 132.64% relative to PAA-g-HPEG.

The main conclusions of this paper are summarized as following. PAA-g-HPEG and PAA-g-PALS tend to be comb and network conformations in cement slurry environment, respectively. Sulfonated modification dispersed the distribution of binding points between PCE and the substrate, improved the binding force between PCE and the substrate, extended the polymer far away from the substrate, and significantly increase the permeability volume (by about 132.64%). The present results not only provide new insights into the action mechanism of PCE at the atomic level, but also provide a theoretical basis for promoting the development of high performance cement-based materials.

White light emitting diodes directly driven by alternating current (AC-LEDs) become increasingly popular in lighting. However, the harmful flicker occurs because the blue LED chips only work over the threshold voltage. Transparent afterglow phosphor-glass composites are thus proposed as excellent color converters to eliminate the flicker. In this paper, Gd_2.94Al₂Ga₃O₁₂:0.06Ce³⁺-SiO₂ (GdAGG:Ce-SiO₂) glass ceramics were prepared via cold isostatic pressing molding and pressureless sintering at a low temperature. The transparency, structures, microscopic morphologies and luminescence properties were investiagted. Besides, the samples were assembled on the commercial blue LED chips or blue laser diodes (LDs) to explore the potential application.

For the preparation of GdAGG:Ce phosphor, stoichiometric Gd₂O₃, Al₂O₃, Ga₂O₃ and CeF₃ (99.9%) were weighed and placed in a mortar. After fully ground for 30 min, the obtained powder was transferred into a 20 mL corundum boat and placed in a tube furnace. The gas flow of 95%N₂/5%H₂ (in volume ratio) was introduced, and the temperature was hold at 1 450 ℃ for 4 h. After cooling to room temperature, the powder was ground in a mortar.

For the preparation of GdAGG:Ce-SiO₂ glass ceramics, 0.9 g GdAGG:Ce phosphor and 9.1 g amorphous SiO₂ nanoparticles were weighed and fully ground in a mortar for 30 min. The obtained powder was sieved with a 200 mesh standard sieve. Then, 0.8 g sieved powder was poured into a stainless-steel mold with an inner diameter of 20 mm, and pressed at 40 MPa for 30 s. The obtained blocks were placed in a cold isostatic press and kept at 250 MPa for 5 min. The green compacts were sintered in a muffle furnace in air at 600-800 ℃ for 5 h. After cooling down to room temperature, the samples were double-side polished.

For the preparation of lighting devices, Gd₃Al₂Ga₃O₁₂:Ce-SiO₂ glass ceramics of different thicknesses were encapsulated on the surface of 1 W commercial 450 nm LED lamp to assemble white LED devices. Besides, 1.0 mm thick Gd₃Al₂Ga₃O₁₂:Ce-SiO₂ glass ceramic was excited by a power-adjustable 450 nm laser to simulate a reflective white LD device.

The translucent GdAGG:Ce-SiO₂ glass ceramics are yellowish green, and the color becomes lighter with increasing sintering temperature. The transmittance of glass ceramics (1.0 mm thickness) in the visible region is approximately 60% due to the mismatch of refractive index between GdAGG:Ce phosphor and SiO₂. The X-ray diffraction patterns show that the glass ceramics exhibit both bulge peak of glass phase and diffraction peaks of Gd₃Al₂Ga₃O₁₂ (JCPDS 46-0448). The scanning electron microscopy images and laser scanning confocal microscopy images indicate that GdAGG:Ce phosphor powders with the sizes of 1-10 μm are uniformly dispersed in SiO₂ glass matrix. The transmission electron microscopy image indicates that the interfacial reaction is well suppressed at a low sintering temperature.

Under 450 nm excitation, the glass ceramics show typical Ce³⁺: 5d₁→4f broadband emissions peaked at 536 nm, whose luminescence characteristics are similar to those of GdAGG:Ce phosphor. The luminescent intensity firstly increases and then decreases, reaching the maximum value at 700 ℃. After removing the excitation source, the glass ceramics show a bright yellowish green afterglow. The longest afterglow appears from GdAGG:Ce-SiO₂ glass ceramic obtained at 700 ℃. Besides, the lifetime when the afterglow intensity decays to 80% of initial one is 27 ms, which meets a requirement of AC-LED devices (no less than 0.4 ms).

The internal quantum efficiency of glass ceramics is 63%, which meets the practical application standard of white LED devices (no less than 60%). The emission intensity at 150 ℃ maintains 85.3% of that at room temperature, indicating that the glass ceramics have an excellent thermal stability.

In coupling the glass ceramic with a 450 nm blue chip, the resulting white LED device exhibits a luminous efficiency (LE) of 81.7 lm/W, a correlated color temperature (CCT) of 5 805 K and a color rendering index (CRI) of 70.8 when driven by 150 mA direct current (DC). Besides, the flicker index decreases to 68.9% when driven via alternating current (AC). Coupled with a 450 nm blue laser, the white LD device shows the LE of 132.6 lm/W, the CCT of 6 528 K and the CRI of 70.6.

Translucent GdAGG:Ce-SiO₂ glass-ceramics were prepared via cold isostatic pressing and low temperature sintering (i.e., 700 ℃/5 h). The self-made GdAGG:Ce afterglow phosphor was uniformly embedded in SiO₂ glass matrix. The glass ceramic retained the luminescent properties of GdAGG:Ce phosphor due to little interfacial reaction. The glass ceramic exhibited a broad emission band peaked at 536 nm, whose quantum efficiency was 63% after excited at 450 nm. The emission intensity at 150 ℃ was 85.3% of that at room temperature. Besides, the glass ceramic exhibited a bright yellowish green afterglow, and the lifetime was 27 ms when the intensity decayed to 80% of initial one. The glass ceramic based white LED device had the LE of 81.7 lm/W, the CCT of 5 805 K, and the CRI of 70.8 when driven by 150 mA DC, and the flicker index reduced to 68.9% when driven by AC. The white LD device showed the LE of 132.6 lm/W, the CCT of 6 528 K and the CRI of 70.6. The results indicated that GdAGG:Ce-SiO₂ glass-ceramic could have a great application potential for AC-LEDs.

As a kind of high-energy electromagnetic radiation, gamma rays can lead to radiation effect and environmental pollution. To ensure the reliability and safety utilization of gamma radiations in different areas, materials with reliable gamma shielding performances should be developed. The existing efforts are to use glasses as alternative for the conventional radiation shielding materials. As a typical window material, glass itself has attracted wide attention due to its unique chemical and physical advantages. Among them, lead-based radiation shielding materials are widely used in the field of ionizing radiation protection due to their reliable physical properties. In the nuclear industry and high energy physics laboratories, different materials can be used for temporary or permanent shielding. The lead-based glass doped with heavy metal oxide PbO is widely used in the field of radiation shielding for a long time with reliable light transmission properties, which facilitates the observation and monitoring of radiation areas. In this paper, three kinds of transparent silicate glass with different PbO contents were prepared by a high-temperature melting forming method. The gamma-rays protection abilities of the three kinds of glass were investigated through experimental and thermotical methods. The chemical and thermal stability of the glass were also analyzed. In addition, the influence mechanism of the structure and performance differences of the three kinds of glass was also discussed.

Analytical pure quartz sand (SiO₂, purity 99.5%, in mass, the same below), lead monoxide (PbO, purity 99.0%), potassium nitrate (KNO₃, purity 99.0%) and sodium nitrate (NaNO₃, purity 99.0%) were selected as raw materials for preparation of three kinds of gamma-rays shielding glass materials by a high-temperature melting method. An appropriate amount of raw materials was thoroughly mixed and added to 3 L quartz crucible and heated in air at 1 200 ℃. Then the raw materials were melted at 1 250 ℃ for 14 h. The uniform melt was quickly poured into the 150 mm×150 mm×50 mm stainless steel mold preheated at 750 ℃. Finally, the quenched glasses were annealed at 450 ℃ for 12 h and cooled naturally to room temperature.

The density of the three glass samples was tested based on the Archimedes principle. The thermal expansion coefficient of glass samples was measured by a model Netzsch DIL 402 expansion coefficient tester. The infrared spectra were measured by a model Perkinelmer Spectrum 100 FTIR Spectrometer. The Raman spectra were tested by a model HORIBA LabRAM HR800 high-resolution Raman spectrometer. The gamma ray shielding test was completed in China Academy of Engineering Physics. The chemical stability test was completed in Chengdu Guangming Glass Co., LTD. The acid stability and moisture stability of the glass samples were tested according to the national standards GB/T 7962.14-2010 and GB/T 7962.15-2010, respectively. The thermal stability of the galss was also determined.

Glass structure becomes more compact with the exchange of Pb alternatives of Si, K and Na. Increasing the density of glass is conducive to improving its shielding performance, but this leads to significant changes in the optical properties, thermal properties and chemical stability of glass due to the increase of heavy metal content. The preparation of high transmittance glass is more difficult. The coefficient of thermal expansion of glass samples gradually decreases from 103.6 × 10^-7 ℃^-1 to 89.2 ×10^-7 ℃^-1, and the values of T_g and T_f also decrease with the increase of mass fraction of PbO in glass components. The change of the thermal properties of the three glass samples is a result of the joint action of PbO, Na₂O and K₂O. The FTIR spectra show that the added PbO is transformed into [PbO₄] units with 4 coordination numbers into the network under the condition of sufficient free oxygen as PbO content in the glass increases. These [PbO₄] units participate in the formation of silicate networks. The Raman spectra indicate that the silicate network structure is de-polymerized as PbO content is increased, and the enhancement of the characteristic vibrational peaks corresponding to the Pb-Si-O indicates an increase in the degree of participation of the [PbO₄] units in the formation of silicate network. The ion packing density of the glass sample gradually increases with the increase of PbO content, which shows that the compressible free volume per unit volume of the glass sample becomes smaller. PbO with a high concentration (x = 0.50 and x = 0.66) is used as a glass-forming agent, and the [PbO₄] structural units can form a connection structure with the silicon oxide tetrahedron, which plays a role in repairing the glass network.

The permeability of the glass can be improved via strictly controlling the iron content of the introduced raw materials and making full use of the double alkali effect of the glass. The actual shielding performance of glass is not a result of simple addition of various components. This can be affected by the actual composition content of the glass, melting process and endoplasmic uniformity. The influence of glass expansion coefficient on the thermal stability is much greater than that on its chemical stability.

PbO with a high concentration (x = 0.50 and x = 0.66) was used as a glass-forming agent, and the [PbO₄] structural units could form a connection structure with the silicon oxide tetrahedron, playing a role in repairing the glass network. The measured shielding rate of ⁶⁰Co gamma-ray could be 50% and the glass with 50% PbO content (in mass fraction) exhibited a linear transmission rate of more than 85% in the range of 400-800 nm. In addition, the reliable thermal and chemical stabilities were also reflected in the glass.

The thermoelectric cooling technology has a potential in the field of refrigeration for 5G chips, infrared detector, and temperature controlling, etc.. To improve the efficiency of thermoelectric refrigeration and enhance the competitiveness of thermoelectric refrigeration technology, it is of great significance to develop high-performance thermoelectric refrigeration materials. However, the refrigeration temperature of the first-stage refrigerator is 230 K based on commercial Bi₂Te₃-based alloy, and the refrigeration temperature of the multi-stage refrigerator is as low as 150 K, while the thermoelectric performance of the commercial Bi₂Te₃-based alloy is sharply reduced at below room temperature, which is difficult to meet the needs of low-temperature refrigeration. It is thus necessary to develop high-performance low-temperature thermoelectric cooling materials to meet the low-temperature refrigeration in the future.

SiOC-based anode materials have a great potential for lithium-ion batteries, but the poor conductivity is the main problem that make it difficult to commercialize. The SiOC/C anode materials combine the high conductivity of carbon materials with some advantages of high capacity, stability, and mechanical flexibility of SiOC. Among them, SiOC/nanocarbon composite materials are developed due to their superior electrochemical performance. Although some progresses are achieved in the design of SiOC/C anode for the lithium-ion batteries, some challenges still remain in practical application. The main problems existing in SiOC/C anode materials are that the size of SiOC is larger, resulting in a lower utilization of active sites. The preliminary research conducted on nitrogen-doped carbon indicate that more active sites can be obtained via utilizing the defects. However, it is still necessary to explore the effect of other doping elements or through multi-component composites. To further enhance the feasibility of electrochemical performance, the lithium ions storage mechanism of SiOC anode materials still needs a further research. The detailed structure evolution of SiOC can be revealed during lithium ions storage process through some advanced in-situ characterization techniques. The lithium ions storage mechanisms can be further clarified, and, the electrochemical performance of SiOC-based anode materials can be improved more effectively. Improving the electrochemical performance and safety of lithium-ion batteries is a goal pursued by many researchers. Overcoming the above problems can lead to the widespread application of SiOC-based anode materials in high energy lithium-ion batteries, even in areas such as lithium sulfur batteries, sodium ion batteries, and potassium ion batteries.

The power generation of reforming CH₄ based on SOFC has great advantages in energy conversion efficiency, material flexibility and environmental protection. However, it faces some problems such as carbon accumulation and poor stability in practical application. At present, four typical anti-carbon anode materials, such as Ni-based anode doped with precious metals, CeO₂, barium oxide and Ni-free anode, can effectively improve the anti-carbon stability. Although these materials show a good carbon resistance, they have some problems such as high cost of precious metals, easy sintering of cerium oxide, poor chemical stability of barium oxide and low catalytic activity of Ni-free anode. Improving SOFC operating conditions and optimizing anode materials (i.e., modification of existing catalysts, design of anode microstructure and eforming catalysts) are the keys to achieving the efficient and stable reforming of methane. The development of anode catalysts with low cost, high chemical and mechanical stability, anti-coking and high catalytic activity is an urgent need for sustainably converting carbon-based fuels by SOFC. In addition, the internal anode elementary reactions involved in the process of SOFC reforming methane are complex and mostly exothermic reactions, accompanied by a large amount of heat generation, so it is also necessary to conduct electrochemical and thermodynamic coupling studies, combined with cogeneration technology to further improve energy conversion efficiency. In summary, it is still necessary for the commercial development of green power generation by CH₄-based SOFC to investigate the influence mechanism of CH₄-based SOFC reforming reaction, anode catalyst material optimization, and develop new research directions.

HfC and TaC are typical ultra-high temperature ceramics (UHTCs), which are important candidate materials for thermal protection components in high-speed aircraft. However, their oxidation resistance at medium and low temperatures is relatively poor. Due to the similar crystal structures of HfC and TaC, and the close atomic radii of Hf and Ta (r_Hf = 1.585 Å, r_Ta=1.457 Å, Δr < 0.15), theoretically, they can form an infinitely miscible substitutional solid solution (Hf_xTa_1-x)C (0 < x < 1). Among them, Hf_0.2Ta_0.8C has a melting point as high as 4 300 K, which is recognized as the highest melting point carbide. Compared with single-component HfC and TaC, (Hf_xTa_1-x)C exhibits higher initial oxidation temperature and lower oxidation rate, indicating significantly improved oxidation resistance. In this work, a series of processable liquid single-source precursors (SSPs) were successfully prepared by introducing HfCl₄ and TaCl₅ into allylhydridopolycarbosilane (AHPCS). Through the polymer-derived ceramic (PDC) method, SiC/(Hf_xTa_1-x)C/C nanocomposites with core-shell structured SiC@C and (Hf_xTa_1-x)C@C nanoparticles were obtained, and the evolution of phase composition and microstructure during the ceramic transformation process was investigated. Combining PDC and spark plasma sintering (SPS) technology, nearly dense SiC/(Hf_xTa_1-x)C/C bulk materials were prepared, and the mechanical properties of the resulting bulk ceramic were investigated.

Chemically stoichiometric amounts of HfCl₄ and TaCl₅ were weighed and reacted with AHPCS in CHCl₃ solvent at 60 ℃ to prepare a series of SSPs. The molecular structure of the synthesized SSPs was characterized using Fourier-transform infrared spectroscopy (FT-IR, Nicolet iS10, Thermo Fisher Scientific). Thermal behavior analysis of the SSPs was conducted using a thermogravimetric analyzer (TGA, STA 449 F5 Jupiter, NETZSCH). The SSPs were heat-treated at temperatures ranging from 900 ℃ to 1 600 ℃ to obtain SiC/(Hf_xTa_1-x)C/C nanocomposite powders. The phase composition of the ceramic powders was analyzed using X-ray diffraction (XRD, SmartLab-SE, Rigaku Corporation) with Cu Kα1 radiation (λ=1.540 6 Å). The microstructure and phase composition of the samples were analyzed using transmission electron microscopy (TEM, Talos F200S, Thermo Fisher Scientific) and selected area electron diffraction (SAED). The powders were sintered using a spark plasma sintering (SPS, CXSPS-40A, Chenxin Corporation) at 50 MPa and 2 200 ℃ to prepare SiC/(Hf_0.2Ta_0.8)C/C bulk materials, named as LAH2T8-bulk. The surface morphology of LAH2T8-bulk was observed using scanning electron microscopy (SEM, CLARA, TESCAN). The hardness and elastic modulus of the bulk materials were measured using a nano-indenter (iNano, Nanomechanics, Inc.) with a Berkovich tip under a maximum load of 20 mN. The volume density and porosity of LAH2T8-bulk were measured using the water immersion method.

During the synthesis of liquid SSPs, the main reactions are dehydrochlorination between metal chlorides and AHPCS. The crosslinking of liquid SSPs is achieved through further consumption of Si-H via dehydrochlorination reactions. The ceramic yield of the obtained SSPs at 900 ℃ exceeds 90%. By combining the PDC method with SPS, nearly dense SiC/(Hf_0.2Ta_0.8)C/C ceramic bulk with an open porosity of 4.87% were successfully prepared. In the crystalline phases, the mass fractions of β-SiC and (Hf_0.2Ta_0.8)C are 60.7% and 39.3%, respectively, with average grain sizes of both phases being less than 90 nm. The measured nanoindentation hardness is (7.72±1.36) GPa, and the elastic modulus is (76.71±7.89) GPa.

By altering the feed ratio of HfCl₄/TaCl₅ during the synthesis process of the SSPs and designing their molecular structure, the composition of the transition metal carbide solid solution products in the final SiC/(Hf_xTa_1-x)C/C nanocomposites can be effectively controlled. After heat treatment at 1 600 ℃, core-shell structured (Hf_0.2Ta_0.8)C@C and SiC@C nanoparticles were in-situ formed in the ceramic matrix. The combination of the PDC approach with SPS technology results in the bulk SiC/(Hf_0.2Ta_0.8)C/C ceramic nanocomposites with good mechanical properties.