3D printing is an ideal technology to prepare complex-shaped ceramic cores, however, due to the layerby-layer molding of 3D printing, the as-prepared ceramic cores exhibit significant anisotropy in microstructure and properties. Silica-based ceramic cores were prepared using digital light processing, and anisotropy in microstructure and properties was adjusted through particle grading. When the mass ratio (particle grading) of coarse powder to fine powder is 8∶ 2, the ceramic slurry exhibits good fluidity and stability, and interlayer gap of the ceramic core almost disappears, exhibiting uniform microstructure with surface roughness of 2.9 μm. The shrinkage rates in X, Y, Z three-dimensional directions are 3.15%, 3.08%, and 3.07%, indicating that the inhomogeneous shrinkage is alleviated. Interlayer strength is significantly lower than intralayer strength of ceramic cores. As particle grading changes from 6∶4 to 8∶2, the ratio of interlayer to intralayer strength increases from 0.40 to 0.62, indicating that the anisotropy of mechanical properties is alleviated. It is demonstrated that the structural and property anisotropy of 3D printed ceramic cores can be effectively controlled by particle grading, which provides a new technology to fabricating high-performance ceramic cores.

To investigate the effects of both water-based and oil-based material systems, as well as porosity gradient-enhanced (PGE) structure on the performance of 3D printed Al₂O₃ porous ceramics, various ceramic parts with different hole densities were fabricated using stereo lithography apparatus (SLA) 3D printing technology. The shrinkage rate, compressive strength, and microstructure of the printed parts in two material systems were comparatively analyzed. Additionally, the porosity, bending performance, and thermal shock resistance of the parts before and after PGE optimization were discussed in detail. The results indicated that the shrinkage and compressive strength of the parts formed by oil-based materials significantly surpassed those of water-based materials, with particles exhibiting a denser microscopic appearance. Nevertheless, the particles of parts formed by water-based materials were in spherical shape, separating from each other. Furthermore, the adoption of PGE structure effectively avoided the occurrence of regional fracture phenomenon in the parts. The PGE parts with different hole densities all achieved a 12%–14% increase in bending strength, as well as a 14%–18% improvement in thermal shock strength. In conclusion, the proper use of oil-based Al₂O₃ ceramic paste along with the rational design of PGE structures are effective approaches to improving the performance of Al₂O₃ porous ceramics, rendering its adaptation to the increasingly complex demands of industrial applications.

During aircraft flight, the buildup of supercooled water droplets on aircraft’s surface would severely compromise flight safety. De-icing technology is crucial for enhancing the safety performance of aircraft, in which, piezoelectric de-icing technology offers advantages in terms of low energy consumption and straightforward structure. This paper provides an overview of aircraft de-icing techniques based on piezoelectric ceramics and composites, categorized by their physical principles and operating frequencies. The principles and advantages/disadvantages of low-frequency piezoelectric resonance and high-frequency ultrasonic de-icing are explored, evolution of piezoelectric materials in de-icing systems is summarized, pros & cons and scope of application of traditional lead-based and lead-free piezoelectric ceramics are evaluated, and future application of flexible piezoelectric composites in aircraft de-icing are anticipated. It was deduced that the fabrication of high-power piezoelectric ceramics and high-function piezoelectric composites would be the main research area in aircraft de-icing. This paper provides ideas in improving aircraft de-icing technology.

Enhancing the wear resistance of TC11 titanium alloy is crucial for safety performance of key components of the aero-engine. In this paper, based on the surface mechanical attrition treatment, grain refinement and dispersion strengthening were achieved on the surface of TC11 titanium alloy by mixing the grinding ball and TiN powder, and a strengthening layer based on TiN particles was successfully prepared. Surface morphology and microstructure characteristics were investigated, and wear resistance was evaluated. The results indicate that surface roughness of the treated TC11 titanium alloy samples is significantly reduced, while surface hardness and wear resistance properties are significantly improved. Surface roughness of the TiN particles strengthening layer samples decreased by 43.29% and 23.14%, surface hardness increased by 9.48% and 1.8%, and width of the wear tracks decreased by 36.18% and 33.18%, respectively, when compared with the untreated and regular ground ones. This study provides a new approach to enhancing the wear resistance of TC11 and other titanium alloys, which is of reference significance in improving service performance of key components of the aero-engine.

Infrared (IR) windows and domes are the key components of opto-electronic system in aircraft. The acceleration along with various harsh, extreme working environment of aircraft puts higher demands on the optical, thermal and mechanical properties of IR transparent materials. Transparent ceramics which can be applied in IR windows and domes include oxide transparent ceramics (Al₂O₃, MgAl₂O₄, AlON, Y₂O₃, YSZ, YAG and Y₂O₃–MgO nanocomposite ceramics), fluoride and ZnS/ZnSe. Transparent wavelength range, thermal and mechanical properties of the above ceramics were compared; physical and chemical properties of these ceramics were introduced in this paper. The study mainly reviews the research progress of different ceramics from powders, ceramic forming and sintering, and compares the current research and application gaps at home and abroad. To realize the application of transparent ceramics in the fields of IR windows and domes, it is necessary to increase investment in synthesizing high-performance powders, improving ceramic density, reducing grain size, enhancing mechanical and optical properties, and preparing high-quality products with large size and complex shape. Finally, the application and development prospects of various transparent ceramics were compared mainly from the aspects of optical and mechanical properties.

In order to improve the impact resistance of thermal insulation tiles, carbon fiber reinforced phthalonitrile resin matrix composite was selected as the toughening layer, and the thermal insulation tile composite structure with protective layer was prepared by an integrated molding process. Firstly, a drop hammer impact test was carried out to compare protective effect of different toughening layers on the insulation tiles under the same energy. Then, low-velocity impact tests with different impact energies and temperatures were carried out to study impact damage characteristics of CFRP toughened thermal insulation tiles. The results show that CFRP toughened insulation tile has the best impact resistance. When the thickness of toughening layer is 1 mm, the peak load under 10 J energy impact is 2.034 kN, the impact depth is 9.904 mm, and the energy absorption rate is 96.93%. After impact, the surface toughening layer shows interface delamination and fiber cracks, crushing damage occurs inside of the insulation tile to produce powder, forming a cavity in the impact area. The surface toughening layer can withstand an impact of 20 J energy without being penetrated, and is still of impact-protection effect after treated at 450 ℃. This study provides new ideas for the impact protection research of thermal insulation tiles in future.

This study focuses on the problem of cracks generated during freeze-drying in the integrated ceramic casting mold of large-sized hollow turbine blade, and studies the stress distribution law of the casting mold. A theoretical model of stress generated by mold shrinkage obstruction was established through finite element simulation. Effects of various freeze-drying shrinkage rates, mold wall thicknesses, and curvatures on mold freeze-drying stress were analyzed. Structural optimization was carried out on trailing edge of the mold using variable wall thickness. It is found that during the freeze-drying process of integrated casting, the stress increases linearly with increase of shrinkage rate, and the stress is the highest at the position with the maximum curvature of the mold trailing edge. By increasing wall thickness at the trailing edge, bending strength of the mold during freeze-drying process is enhanced. When sample thickness increases from 4 mm to 7 mm, average strength of the base substrate increases from 8.32 MPa to 11.81 MPa. The integrated mold with structural integrity is successfully manufactured and verified by casting in this study, stress distribution law of ceramic casting mold and various wall thickness of trailing edge are obtained and proposed, which help to solve the issue of cracks generated during freeze drying for integrated ceramic casting mold.

Hafnium boride (HfB₂) ultra-high temperature ceramics have become one of the best candidate materials in the field of thermal protection due to their high melting point, high oxidation resistance and excellent corrosion resistance. The fabrication of ceramic powders with precisely controlled particle sizes is paramount for their effective application. Highpurity HfB₂ ceramic powders were prepared by crystal seed-mediated boro/carbothermal reduction method using hafnium oxide (HfO₂), boron trioxide (B₂O₃), and carbon (C) powders as raw materials. The influence of crystal seed size on the particle size of HfB₂ powders was studied, and the growth mechanism of HfB₂ powders synthesized by crystal seed-mediated method was explored. Phase and morphology of the obtained powders were analyzed and observed by X-ray diffraction and scanning electron microscope; the contents of C and O impurities in the powders were measured as well. The results show that the optimal reaction temperature for synthesizing pure HfB₂ powders by crystal seed-mediated boro/carbothermal reduction is approximately 1500 ℃ (holding for 1 h). HfB₂ ceramic powders with average particle size of 1.08–2.33 μm were obtained by controlling the initial crystal seed size. Generally, the particle size of HfB₂ increases with the increase of crystal seed size, and laser particle size measurements indicate that the addition of crystal seeds improves the dispersibility and narrows distribution of HfB₂ particle size. It is confirmed that the growth process of HfB₂ ceramic powders is divided into two stages: the cladding of HfO₂ grains on HfB₂ surface with formation of tiny HfB₂ grains, and conversion of HfO₂ to HfB₂ through mass diffusion of carbon and boron from the outside to the inside of HfO₂ particles.

Silicon carbide (SiC) material is widely used in aerospace, engineering ceramics and semiconductor fields for its excellent physical and chemical properties. At present, there are many methods for the synthesis of SiC powder, among which the carbothermal reduction is the main method for industrial production of SiC powder but during the production process, the particle size and impurity content of SiC powder would affect properties of the final product. Therefore, how to refine and purify SiC powder is becoming the issue that often needs to be explored for preparing the high-performance SiC materials. Firstly, the category, principle and characteristics of SiC powder synthesis technology are introduced; then the research progress of SiC powder refinement technology in recent years is elaborated, and the purification technology for amorphous carbon and metals & metal oxides in the SiC powder are specifically emphasized; finally, the problems that need to be solved for preparing SiC powder at present is analyzed along with an outlook for its development prospect.

The concept of multi-principal elements has opened up prospects for the development of new high-entropy ceramics (HECs) suitable for extreme application environments such as advanced turbine engines, nuclear reactors, and hypersonic flight vehicles. High-entropy metal borides (HEBs), as a new type of HECs, have high hardness, high-temperature strength, low thermal conductivity, and radiation resistance, making them suitable for use in the aerospace field. This study provides a detailed review of the preparation technologies of HEBs powders and ceramics, evaluating the advantages and disadvantages of different preparation methods. By reviewing the latest research progress in the field of super-hard ceramics and ultra-high temperature ceramics at home and abroad, the advanced position of HEBs in materials science is revealed. Future research directions of HEBs, such as advanced powder preparation technology, efficient ceramic sintering technology, machine learning, and computer simulation are discussed. This review provides scientific basis and technical support for promoting preparation, performance improvement and wide application of HEBs.

To further improve the mechanical properties of high-entropy carbides and high-entropy borides ceramic, in this study SiB₆ was introduced as a boron and silicon source into high-entropy carbide (Ti, Zr, Nb, Ta, Mo)C, and (Ti, Zr, Nb, Ta, Mo)B₂–(Ti, Zr, Nb, Ta, Mo)C based composites were synthesized via reactive spark plasma sintering at 2000 ℃. Research findings indicate that SiB₆ reacts with (Ti, Zr, Nb, Ta, Mo)C at high temperatures to form high-entropy boride (Ti, Zr, Nb, Ta, Mo)B₂, SiC and C phases. The densification of (Ti, Zr, Nb, Ta, Mo)B₂–(Ti, Zr, Nb, Ta, Mo)C based composites prepared with SiB₆ addition reaches 98.7%–99.7%. The grain size of high-entropy phases in composite ceramics with 10%–15% SiB₆ addition (volume fraction) is 0.84–0.92 μm, which is smaller than that of pure (Ti, Zr, Nb, Ta, Mo)C ceramics (~3.19 μm). Due to the fine grain strengthening, the hardness of (Ti, Zr, Nb, Ta, Mo)B₂–(Ti, Zr, Nb, Ta, Mo)C based composites (23.54–24.93 GPa) is higher than that of pure (Ti, Zr, Nb, Ta, Mo)C ceramics (~23.22 GPa). Additionally, the fracture toughness of (Ti, Zr, Nb, Ta, Mo)B₂–(Ti, Zr, Nb, Ta, Mo)C based composites increases with the addition of SiB₆, reaching up to 5.07 MPa·m^1/2, which is significantly higher than that of pure (Ti, Zr, Nb, Ta, Mo)C ceramics (3.02 MPa·m^1/2). Using (Ti, Zr, Nb, Ta, Mo)C and SiB₆ as raw materials and employing reactive spark plasma sintering, (Ti, Zr, Nb, Ta, Mo)B₂–(Ti, Zr, Nb, Ta, Mo)C based multiphase high-entropy ultra-high temperature ceramics with a fine-grained structure and excellent mechanical properties could be obtained.