Si₃N₄ ceramics exhibit excellent mechanical properties due to their strong covalent bonding characteristics, however, this characteristic makes them difficult to secondary process, severely limiting their widespread industrial applications. In this study, dynamic hot forging (DHF) technology was employed to process commercial Si₃N₄ ceramics, the effects of hot forging temperature on the microstructure and mechanical properties of materials were studied. The results indicate that under a dynamic pressure of (60±5) MPa and a hot forging temperature of 1 800 ℃, the Si₃N₄ ceramics exhibit optimal mechanical properties, with a hardness of 13.84 GPa, a fracture toughness of 6.88 MPa·m^1/2, and a bending strength reaching 925 MPa. All performance metrics significantly surpassing those of the original samples. This performance enhancement is primarily attributed to two key factors: firstly, the elimination of defects such as pores during the hot forging process, and secondly, the structural texturing effect induced by dynamic pressure. The DHF technology developed in this study provides an effective new method for the secondary processing and strengthening of high-performance difficult-to-machine ceramic materials.

In response to the technical challenge of high porosity in the laser cladding of high WC content non-magnetic nickel-based alloy powder on P550 non-magnetic steel surface, the response surface methodology and single factor method were used to design experiments. The influences of laser cladding process parameters on porosity were analyzed and the main effect factor was researched. Taking the laser power, scanning speed, powder feed rate, and overlap ratio as inputs and the porosity as the response target, a multivariate regression prediction model was established to optimize the process parameters. The results show that the coating porosity can be reduced to 0.22% when laser power is 1 015 W, scanning speed is 5.1 mm/s, powder feed rate is 0.6 r/min, and overlap ratio is 40%, meeting the requirement of engineering application. The microstructure of the coating is uniform, which is mainly composed of cellular crystal, dendritic crystal, and secondary dendritic crystal. The microhardness of the coating is about 1.6 times than that of the matrix, and the wear rate is reduced to 1.5% of the substrate. The research results can provide a process solution for laser cladding low porosity and high wear-resistance coating for the surface strengthening of non-magnetic drilling tools, and promote the engineering application of this technology in the field of petroleum drilling.

GH3536 alloy exhibits stable performance at elevated temperatures and is extensively utilized in high-temperature resistant components, including eddy current devices and engine blades. In this research, GH3536 alloy blocks were fabricated using laser powder bed fusion with partitioned block rotating scanning. The surface microstructure of the alloy was analyzed through scanning electron microscope and electron backscatter diffraction. Additionally, the mechanical properties and microhardness of the printed alloy were evaluated at room temperature. The results indicate that GH3536 alloy exhibits a limited number of pores and microcracks. Furthermore, a distinct microstructural difference is observed between the horizontal surface (XOY plane) and the constructed surface (XOZ plane). The XOY plane displays parallel scanning tracks, whereas the XOZ plane reveals melt pools, and the grains are fine and the dislocation density is relatively high at the melt pool boundaries. The room temperature tensile strengths of the alloy parallel to the XOY direction and the XOZ direction are 878 MPa and 762 MPa, respectively, and the elongation rates are 32% and 42%, respectively. There are a large number of small dimples at the tensile fracture. The microhardness (HV_0.2) for the XOY and XOZ planes are 308 and 299, respectively.

As a key material for turbine disks, powder metallurgy (PM) superalloys are developing in the direction of higher performance. However, there are still some urgent key problems in the preparation process of the alloys, which restrict the further development and application. This paper outlines the progress of PM superalloys from three aspects: the development history, the composition, and the preparation process, analyzes the causes and corresponding solutions to the problems of difficult removal of inclusions, easy to crack, and high cost in the alloys, summarizes the current status of the research on PM superalloys, and looks forward to the future development trend of the alloys.

In this study, thin-layered C/C composites with a spread-stitching architecture were prepared by chemical vapor deposition. The effects of high-temperature heat treatment on the microstructure, mechanical and thermal expansion properties of the C/C composites were systematically investigated. The results indicate that high-temperature heat treatment leads to a reduction of shear strength at interface between the carbon fiber and pyrolytic carbon, while simultaneously enhancing the degree of graphitization in both materials. After high-temperature heat treatment, the tensile strength of the C/C composites increases from 112.3 MPa to 195.3 MPa, which is primarily attributed to the weakened interfacial shear strength. In contrast, the compressive strength decreases from 300.0 MPa to 121.6 MPa, mainly due to the degradation of interlaminar bonding strength, with interlayer delamination identified as the dominant failure mode. Furthermore, the enhanced graphitization degree of the C/C composites after high-temperature heat treatment is demonstrated to be the primary factor governing the increase in modulus and the reduction in the coefficient of thermal expansion of the composites.

FeMnCoCrC high-entropy alloys were fabricated using laser powder bed fusion (LPBF) from pre-alloyed (Fe₄₅Mn₃₅Co₁₀Cr₁₀)₉₉C₁ gas-atomized powder. The effects of LPBF process parameters on the microstructure and mechanical properties of the alloy were investigated by scanning electron microscope, transmission electron microscope, X-ray diffractometer, and room-temperature tensile test, with the aim of elucidating the underlying deformation mechanisms. The results indicate that the FeMnCoCrC high-entropy alloy exhibits a stable single-phase FCC structure, with randomly oriented grains and no significant texture. Furthermore, rich dislocation cell structures formed during the LPBF process, while no carbide precipitation is observed. The alloy fabricated under the optimal parameters (laser power of 120 W and scanning speed of 400 mm/s) demonstrates a enhanced yield strength while maintaining good elongation, achieving a yield strength of 603 MPa, a tensile strength of 850 MPa, and an elongation of 44.0%. The plastic deformation mechanism of the FeMnCoCrC high-entropy alloy is primarily governed by dislocation slip and twinning-induced plasticity, which collectively contribute to a sustained work-hardening capacity. In contrast, the martensite-induced plasticity mechanism is completely suppressed during deformation.

As an economically viable material with extensive applications, morphology regulation of CeO₂ has remained a critical challenge. This study developed a flux method for spheroidizing blocky CeO₂, with systematic investigation into the regulatory mechanisms of Na₂CO₃, NaCl, and their composite fluxes on CeO₂ morphology. The results reveal flux type and concentration can significantly affect the spheroidization process of CeO₂. Na₂CO₃ facilitates micro-scale (~5 μm) quasi-spherical particle evolution above 900 ℃ through chemically activated mechanisms combining Na⁺ lattice intercalation and oxygen vacancy compensation. Optimized spherical CeO₂ with sphericity index 0.80 is achieved at 1 000 ℃ when mass ratio of Na₂CO₃ and raw materials is 1.8∶10. Comparatively, NaCl-dominated systems generate nano-sized particles (500-800 nm) via physical fluxing effects but exhibit pronounced agglomeration. The composite flux system demonstrate antagonistic interactions between components, leading to degraded sphericity relative to single-component counterparts. This work confirms that process regulation can overcome intrinsic limitations of conventional solid-phase method morphology control. The Na₂CO₃-dominated system features operational simplicity, cost-effectiveness, and superior particle dispersibility, offering a scalable pathway for industrial synthesis of spherical CeO₂ with precisely tunable diameters (1-10 μm).

Lattice structures are increasingly utilized in aerospace, automotive manufacturing, and biomedical fields due to their advantages of lightweight construction, excellent sound insulation, high specific strength, high specific stiffness, and superior vibration absorption properties. To investigate the relationship between gradient strategies and the mechanical response of gradient lattice structures, this study designed gradient lattice structures with different gradient strategies and fabricated corresponding specimens using selective laser melting technology. The compressive properties of these structures were systematically investigated through a combined approach of simulation and experimental validation. The results indicate that during compression, the nodes of the lattice cells serve as primary stress concentration locations. Uniform structures, unidirectional gradient structures, and bidirectional gradient structures exhibit distinct deformation behaviors. Gradient lattice structures exhibit higher elastic modulus, yield strength, compressive strength, and plateau stress compared to uniform structures. Furthermore, bidirectional gradient structures demonstrate superior mechanical properties over unidirectional gradient structures and superior energy absorption performance compared to both uniform and unidirectional gradient structures. This study provides technical support for predicting the compressive response of diverse gradient lattice structures.

This study systematically investigated the thermodynamic, mechanical, and electronic structure properties of B₁₂Sc and B₁₂Y under pressures ranging from 0 GPa to 50 GPa via first-principles calculations. The results indicate that the calculated lattice constants and formation enthalpies are all consistent with existing literature data. The calculated elastic constants of B₁₂Sc and B₁₂Y satisfy the mechanical stability criteria for cubic crystals. With increasing pressure, the elastic constants C₁₁, C₁₂, and C₄₄ increase with different rates, C₁₂ exhibits the largest increase, followed by C₁₁, and then C₄₄. Meanwhile, the bulk modulus shows the most significant increase with increasing pressure, followed by elastic modulus, then by shear modulus. The Vickers hardness of B₁₂Sc and B₁₂Y at ambient pressure are 32.45 and 36.34, respectively, suggesting their potential as strengthening phases in Mg alloys. The sound velocities, Debye temperatures, and lattice thermal conductivities increase with rising pressure, the Debye temperatures of B₁₂Sc and B₁₂Y are 1 336.6 K and 1 233.2 K at 0 GPa, respectively, indicating high melting points and strong interatomic interactions in these compounds. Both B₁₂Sc and B₁₂Y exhibit metallic behavior, with covalent bonds formed between B and B atoms, providing strong interatomic interactions that contribute to their high Debye temperatures and hardness.

Although traditional pressure-assisted sintering techniques at high temperature and the use of sintering aids can improve the formability of ZrB₂ ceramics, they often cause an increase in the thermal conductivity or a decrease in high-temperature strength, hindering synergistic optimization of mechanical properties and thermal insulation performance. Here, pure-phase porous ZrB₂ ceramics were fabricated via loose-pack sintering using ZrB₂ raw powders with different particle size ratios. The effects of the raw powder size ratio on the microstructure, compressive performance, and thermal conductivity were investigated using X-ray diffractometer, scanning electron microscope, and computed tomography. The sintering forming, strengthening, and thermal insulation mechanisms of ceramics were elucidated. Results indicate that the porosity of loose-pack sintered ZrB₂ ceramics ranges from 43.42% to 46.68% across different particle size ratios. At a fine-to-coarse powder mass ratio of 1:9, the ceramic develops a robust ZrB₂ skeleton and a uniform dual-scale pore network at the micrometer level, achieving a high compressive strength of 364.70 MPa and a low thermal conductivity of only 32.79 W/(m·K). During sintering, moderate fine powders effectively reinforce the skeleton formed by coarse powders, facilitating a uniform microstructure evolution. The connected and isolated pores establish a gradient energy dissipation and defense mechanism, which synergize with the robust ZrB₂ skeleton to ensure excellent compressive performance. Meanwhile, effective thermal insulation results from blocked solid conduction, prolonged gaseous heat transfer paths, induced Knudsen effect via pore structure, and enhanced phonon scattering at high-density large-angle grain boundaries.

To overcome the bottleneck of synergistic enhancement in strength, wear resistance, and corrosion resistance of traditional coatings, this study employed pulse electrodeposition to prepare Ni-P/Ni-W-NbC nanocomposite coatings. The effects of NbC nanoparticle mass concentration on the microstructure and properties of the coatings were systematically investigated using scanning electron microscope, energy dispersive spectroscope, and X-ray diffractometer. The results indicate that NbC significantly refines the grains of the Ni-W coating through heterogeneous nucleation, achieving optimal dispersive distribution at a mass concentration threshold of 1 g/L. At this mass concentration, the coating exhibits optimal comprehensive performance with a peak microhardness (HV) of 1 123.2, the lowest friction factor of 0.16, and a significantly reduced wear rate. When the NbC nanoparticle mass concentration is 1 g/L, the coating possesses the finest grain size and the densest structure. NbC synergistically optimizes the microstructure of the coating through solid solution strengthening, grain boundary pinning, and reduced porosity. An appropriate amount of NbC (1 g/L) significantly enhances the corrosion resistance of the coating in a NaCl solution with a mass fraction of 3.5%, manifested by an increased charge transfer resistance and a decreased corrosion current density. However, excessive NbC leads to particle agglomeration, inducing microcracks and structural defects, which degrade the mechanical properties and corrosion resistance of the coating. This study elucidates the interfacial synergistic strengthening mechanism between NbC and the γ-Ni-W coating during pulse electrodeposition, providing a theoretical basis and technical pathway for developing gradient functional coatings with high hardness, low friction, and excellent corrosion resistance.

TiO₂ hollow microspheres, as a new type of inorganic functional material with both the intrinsic excellent properties of TiO₂ and the features of hollow structures, demonstrate broad application prospects in the fields of photocatalysis, environmental governance, energy storage, and biomedicine. This paper systematically reviews six mainstream preparation methods (hard template method, Stöber method, microemulsion method, solvothermal reaction method, layer-by-layer self-assembly method, and spray reaction method) for TiO₂ hollow microspheres, and provides a detailed comparative analysis of their mechanisms, advantages, and limitations. It examines the application progress in photocatalysis, including reaction mechanism, pollutant removal, and biomedical applications. It further analyzes key factors of limiting photocatalytic performance and summarizes optimization strategies such as microstructure regulation, elemental doping, and heterostructure construction. Although large-scale production and practical application of TiO₂ hollow microspheres still face numerous challenges, future integration of computational simulation and artificial intelligence technologies is expected to achieve efficient, controllable, and green synthesis, advancing their transition from laboratory research to industrial application.

Constructing a 3D skeleton inside lithium metal anodes can suppress anode volume change, reduce local current density, and retard lithium dendrite growth. In this study, Li ingots, amorphous B powder, and ZnF₂ powder were used as raw materials to prepare a Li-B-Zn alloy with internal 3D skeleton via a melting method. X-ray diffractometer, scanning electron microscope, and energy dispersive spectrometer were employed to characterize the phase composition and internal skeleton structure of the alloy, while the electrochemical performance of the Li-B-Zn alloy anode was evaluated. Results show that nano-sized LiZn particles are uniformly distributed on the LiB fiber skeleton, forming a composite skeleton with abundant lithiophilic sites and excellent structural stability. In symmetric cells, the Li-B-Zn anode achieves a long cycle life of 1 500 h at a high capacity of 5 mAh/cm². The Li-B-Zn|LFP (LiFePO₄) full cell exhibits outstanding electrochemical performance, with a capacity retention rate of up to 90.15% after 370 cycles at 1 C. Li-B-Zn alloy anode has significant performance advantages in practical applications, and constructing an internal composite 3D skeleton is an efficient approach to address current challenges of lithium metal anodes.

Thermal barrier coatings (TBCs) are extensively utilized in the metal hot-end components of aircraft engines. The primary cause of delamination failure of TBCs ceramic layers is deep-seated stresses in the ceramic layer. The present study focuses on the La₂Zr₂O₇/YSZ double-ceramic thermal barrier coating system, which operates at higher temperatures. In the YSZ layer, a Y₂O₃:Eu³⁺ fluorescent stress-responsive units were identified, and sintering experiments at 1 300 ℃ were conducted on TBCs. The deep-seated residual stress of TBCs was calculated by combining the Eu³⁺ fluorescence-stress response equation, and the fluorescence migration mechanism was explained through density functional theory calculations. The results indicate that the detection depth of the stress-responsive unit can reach 100 μm, and the deep layers of TBCs undergo a transition between compressive and tensile stresses. Stress can to induce lattice distortion in the Y₂O₃:Eu³⁺ fluorescent stress-responsive unit, leading to changes in its electronic cloud structure, and ultimately resulting in regular changes in optical properties.

In this study, ultrafast high-temperature sintering was employed to fabricate diamond composites using CuCoCrNi multi-principal element alloy as the bonding phase. The effects of sintering parameters on the degree of diamond graphitization and densification behavior were investigated with X-ray diffractometer, scanning electron microscope, Raman spectroscope, and friction experiments. The results demonstrate that ultrafast high-temperature sintering can produce CuCoCrNi/diamond composites with low graphitization (I_G/I_D=0.201 4), low friction factor (μ=0.06), and relative density of 91.22% in a short time by adopting suitable process parameters. Joule heating generated by high current density and localized thermal focusing significantly enhance the sintering driving force, promoting the bonding of Cr in the matrix with the diamond surface to form an interface layer is conducive to the densification of the composites. However, too high energy input can cause diamond particle agglomeration and severe diamond graphitization (I_G/I_D>1.0), reduce the affinity and the interfacial bonding strength between Cr element and diamond particle surface, leading to the decrease of density and friction properties (μ>0.1) of diamond composites.

This study prepared Cu-Graphite-CNTs composites with varying composition ratios (CNTs mass fraction is 0.1%-1%, Graphite mass fraction is 10%-20%), and current-carrying friction tests were conducted at 0, 1, 3, and 5 A. The friction and wear behavior of the composites was characterized using scanning electron microscope, energy dispersive spectrometer, and Raman spectrometer. And the effects of composition ratios and current on the current-carrying friction performance were investigated. Results indicate that current indirectly affects friction performance by influencing the continuity and integrity of the lubricating film. At 0 A, a fragmented film induces adhesive-abrasive wear, resulting in a high and fluctuating friction factor. Between 1-3 A, moderate Joule heating promotes lubricating film formation, effectively isolating interfaces and suppressing wear. At 5 A, excessive Joule heating causes cracks and film detachment, exacerbating thermal fatigue-adhesive wear. The lubricating film exhibits maximum stability when 0.5% CNTs+10% Graphite (mass fraction) synergize with a 3 A current. This study provides theoretical support for designing high-performance mechanical-electrical composites for wind power slip rings.

The tungsten layer on the surface of diamond was prepared using WO₃, Mg, and diamond powders as the reaction system and NaCl as the diluent by the self-propagating high-temperature synthesis technology. The adiabatic temperature change was achieved by regulating the NaCl content, and its effects on the coverage radio and thickness of the tungsten layer on the diamond surface were systematically studied. The results show that the coverage radio and thickness of the tungsten layer on the diamond surface increase with the increasing adiabatic temperature. Under the condition that the mass ratio of WO₃, diamond, Mg, NaCl is 1:0.53:0.34:0.13, when the adiabatic temperature reaches 3 569 K, a tungsten layer with a coverage radio of approximately 82%, a thickness of approximately 340 nm and uniform distribution can be obtained. Moreover, the unique instantaneous high-temperature-rapid cooling characteristic of self-propagating high-temperature synthesis effectively improves the stability of diamond, and therefore no obvious graphitization is observed.

NiTi alloys, known for their shape memory effect, superelasticity, and excellent biocompatibility, are widely used in aerospace and biomedical fields. In this study, Ni_50.95Ti alloys were fabricated via laser powder bed fusion to systematically investigate the effects of laser power and scanning speed on metallurgical defects and microhardness. The microstructural features of the scan and build surfaces under optimal processing conditions were characterized, and the regulation effect of electrolytic polishing on the surface morphology of lattice nodes was evaluated. Results show that low scanning speeds (450, 550 mm/s) tend to induce cracks, while higher scanning speeds (650~850 mm/s) significantly improve densification, however, energy densities above 110 J/mm³ promote pore formation. Under optimal parameters (135 W, 650 mm/s), the alloys consisted of B2 austenite and B19′ martensite exhibit〈100〉//BD and〈110〉//BD textures, and are crack-free. Electrolytic polishing for 3 min effectively remove unmelted powders, produce a smooth and pit-free surface, providing process support for the application of lattice-structured NiTi alloys in biomedical field.

To meet the increasing performance requirements of next-generation hypersonic vehicles, this study employs the solid solution ceramic Ta_0.2Zr_0.8C to matrix-modify C/C composites used in their hot-end components, thereby further enhancing their ablation resistance. C/C-Ta_0.2Zr_0.8C-SiC and C/C-TaC-ZrC-SiC composites were fabricated through a high-solid-loading slurry impregnation method combined with a precursor infiltration and pyrolysis process. The microstructures and ablation properties under an oxyacetylene flame of the two composites were investigated using X-ray diffractometer, scanning electron microscope, and transmission electron microscope. The results indicate that after 120 s of ablation, the C/C-TaC-ZrC-SiC composite exhibits mass and linear ablation rates of 6.67 mg/s and 22.76 μm/s, respectively, whereas the C/C-Ta_0.2Zr_0.8C-SiC composite shows significantly lower values of 0.67 mg/s and 0.18 μm/s, demonstrating superior ablation resistance. During ablation, within the Ta-Zr-O oxide layer on the surface of the C/C-Ta_0.2Zr_0.8C-SiC composite, a Zr-rich oxide skeleton phase provides a pinning effect, while a Ta-rich oxide binder phase provides a connective and filling effect. The synergistic effect between the two phases effectively suppresses the spallation and splashing of oxides, increases the compactness of the oxide layer, and ultimately improves the ablation resistance of the composites.

The resource utilization of agricultural wastes has always been a concern for humans. As a renewable resource, biomass rice husk is rich in Si and C elements, and it is a cheap, readily available, and sustainable use waste resource. Researchers have conducted numerous studies to finding low-cost, large-scale, and green sustainable processes for the development and utilization of rice husk. In this paper, the composition and structure of rice husk are first briefly introduced. The reaction mechanisms and characteristics of SiC and Si₃N₄/SiC nanopowders synthesized by traditional methods and new processes are reviewed in detail. Finally, the existing problems of SiC and Si₃N₄/SiC nanopowders synthesized from rice husk are summarized, so as to further promote the development of high quality rice husk-based silicides.