SiC fiber-bonded ceramics (FBCs), as a new thermal-structural material obtained by hot-pressing sintering of SiC fiber, has low porosity, high fiber volume fraction, high temperature resistance, oxidation resistance and high strength. It is an excellent candidate material for high temperature components such as turbine blades and rotors of aero-engine. The research progresses of FBCs were systematically reviewed in this paper. The structural characteristics and preparation methods of two types of FBCs (Tyranohex and SA Tyranohex) were introduced, the relationships among the composition, structure and performance of FBCs were discussed. It was noted that the interface carbon layer plays a crucial role in the performance of FBCs. The mechanical properties of SA-Tyranohex at room temperature and high temperature were highlighted, and the reasons for its excellent high temperature performance were analysed. The examination, verification and application development were summarized. The difficulties of FBCs in forming complex components were pointed out, and the future development trends and research directions were prospected. Finally, it was proposed that conducting research on SiC fiber-bonded ceramics is of great significance for the development of new materials for high-temperature resistant components in China.

SiC fiber is one of the common reinforcements for ceramic matrix composite (CMC) due to its superior characteristics such as low density, high tensile strength, excellent high temperature resistance and oxidation resistance. The preparation of coating on the surface of SiC fiber can not only improve the mechanical properties, high temperature resistance, oxidation resistance and electromagnetic functional properties of the fiber itself, but also effectively improve the bonding properties of the interface between the fiber and the matrix to promote the fracture toughness and mechanical properties of the composite. The preparation methods of surface coatings on SiC fiber were firstly reviewed in this paper by elaborating on the basic processes and related research progress of etching, deposition, chemical vapor infiltration, and precursor derived methods, and the advantages and disadvantages of different preparation methods were compared. Then the effects of coatings on SiC fibers and their reinforced composite materials were reviewed. Finally, the development trend of surface coating on SiC fibers was briefly summarized. The combination of experimental research and computational simulation can be used to simulate the real service environment of SiC fibers coatings, and the performance of fibers under extreme service conditions can be improved by preparing thermal barrier composite coatings.

The ZrC-SiC multiphase ceramic precursor of PZCS with abundant active cross-linking sites was prepared by a dehydrocoupling reaction between polyzrocarbonane (PZC) and polycarbosilane (PCS). The ceramization mechanism of PZCS and the composition and structure of the final ceramic were studied. The results reveal that the ceramic yield of PZCS (71.84%, mass fraction, the same below) is significantly higher than that of PZC (51.40%) or PCS (53.46%) precursor at 850 ℃, due to the promoted crosslinking of active groups during the ceramization process. Meanwhile, under the catalysis of Zr-Cp, the short-range carbon and Zr, Si elements are directly converted to carbide ceramics through the synergistic transformation of two polymers in PZCS, avoiding the adverse effects of carbon thermal reduction to the ceramics, and effectively reducing the sintering temperature. The ZrC-SiC nanocomposite ceramic with both high temperature resistance and oxidation resistance components is prepared after pyrolysis of PZCS. The generation of ZrC and SiC phases could inhibit crystallization and refine the grain size, of which the ZrC grain size is 25.4 nm. Moreover, the generation of ZrC-SiC nanocomposite structure would be beneficial for improving the comprehensive performance of ultra-high temperature ceramics.

Using carbon fiber cloth with different areal densities and tow sizes, two kinds of carbon fiber preforms with same carbon cloth laminated structure were produced through different z-direction stitching methods. Then, C/C-SiC composites were prepared by combining chemical vapor infiltration (CVI) with gas silicon infiltration (GSI). The influence of carbon fiber preform structure on the microstructure and mechanical properties of CVI-GSI C/C-SiC composites was studied. The results show that the density, phase composition, structure, and properties of the two composites prepared from preforms with the same fiber volume fraction and C/C preform density are significantly different. The smaller carbon fiber tow (1K) and carbon cloth surface density (92 g/m²), as well as the larger voids left by lock stitching, provide more sufficient channels for the infiltration of Si vapor in the GSI reaction process. Thus T1 composite finally prepared has low porosity, uniform structure, and higher performance, with bending strength, modulus, and fracture toughness of 300.97 MPa, 51.75 GPa, and 11.32 MPa·m^1/2, respectively. The comprehensive control of the initial preform structure and the C/C intermediate structure is the key to the preparation of high performance C/C-SiC composites by the CVI-GSI process.

Based on the self-made Zr_0.5Hf_0.5C precursor and commercial liquid polycarbosilane, C/Zr_0.5Hf_0.5C-SiC composite was successfully prepared by the precursor impregnation and pyrolysis(PIP) process. The influence of the thickness of pyrolytic C coating on the structure and bending properties of composite materials was studied. The results show that the self-made Zr_0.5Hf_0.5C precursor can be converted into Zr_0.5Hf_0.5C solid solution at a relatively low temperature of 1400 ℃. Because of its good permeability, the transformed Zr_0.5Hf_0.5C matrix exists in both the inter-bundle and intra-bundle regions of the C/Zr_0.5Hf_0.5C-SiC composite, which presents as a layered structure on SiC matrix. The phase composition of C/Zr_0.5Hf_0.5C-SiC composite mainly includes C, SiC and Zr_0.5Hf_0.5C. The densities of three groups of composites with different thicknesses of pyrolytic C coating (0.67, 0.84, 1.36 μm) are 2.07, 1.99, 1.98 g/cm³, respectively. SiC content in the composite decreases with the increase of the thickness of pyrolytic C coating. The three groups of composites with different thicknesses show pseudoplastic fracture mode during bending loading tests, bending strength, bending modulus and fracture toughness are above 410 MPa, 60 GPa and 15.6 MPa·m^1/2, respectively. Good interface bonding and pre-introduced SiC matrix are the keys to obtaining excellent bending properties of C/Zr_0.5Hf_0.5C-SiC composites.

The BN coating was deposited on the surface of typical domestic SiC fibers by chemical vapor permeation (CVI) process, and the fibers were oxidized at 800-1200 ℃ for 1 h. The morphology, structure and composition of BN coated SiC fibers after oxidation were characterized. The property changes of BN coated SiC fibers after oxidation were evaluated by tensile strength of monofilament. The results show that when the oxidation temperature is lower than 1000 ℃, the BN coating and its oxide can effectively prevent the erosion of the inner SiC fibers by O₂, and when the temperature continues to rise, the SiC fibers are oxidized. With the increase of oxidation temperature, the surface oxide of BN coated SiC fibers goes through the process of α-B₂O₃→SiC_xO_y→amorphous SiO₂. The tensile strength of BN coated SiC fibers decreases with the increase of oxidation temperature. Direct exposure of BN coating to oxidizing environments reduces the oxidation resistance of SiC fibers. The failure source of fiber fracture first transitions from BN coating defects to B₂O₃ oxide layer defects and finally evolves into SiO₂ oxide layer porosity defects.

Micro-arc oxidation films were prepared on the surface of SiC_p/Al matrix composites in (NaPO₃)₆, Na₂SiO₃-NaOH and NaAlO₂-NaOH electrolyte.The microstructure and phase composition of the films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).The wear resistance and corrosion resistance of the substrate and films were analyzed by friction and wear test and electrochemical workstation. The results show that the uniform micro-arc oxidation films can be prepared in all the three electrolytes. The roughness and thickness of the film prepared in NaAlO₂-NaOH is the largest. The phases of the films prepared in the three electrolytes are different. The microhardness of SiC_p/Al matrix composites is improved by micro-arc oxidation, and the hardness of the film prepared in NaAlO₂-NaOH reaches 1125HV. The friction coefficient of SiC_p/Al matrix composites is reduced by micro-arc oxidation. According to the friction coefficient and wear condition, the film prepared in NaAlO₂-NaOH has excellent wear resistance. The micro-arc oxidation film prepared in three kinds of electrolyte can improve the corrosion resistance of SiC_p/Al matrix composites. The corrosion resistance of the film prepared in Na₂SiO₃-NaOH is excellent, the corrosion potential and current density of the film prepared in Na₂SiO₃-NaOH are -0.6122 V and 2.704×10^-7 A·cm^-2, respectively.

SiC whisker was added into SiBCN ceramics obtained by pyrolysis of polyborosilazane (PSNB) by ultrasonic combined with ball milling. The effects of different mass fractions SiC whisker on the density, hardness, bending strength and microstructure of SiBCN ceramic matrix composites were studied. The results show that with the mass fraction of SiC whisker increasing from 0% to 25%, the density of the composite is first decreased and finally increased, the porosity is gradually increased, the hardness is gradually decreased, and the bending strength is first increased, then decreased and finally increased; It was found that the three-point bending strength of SiC_w/SiBCN composite with 5% SiC whisker can reach 191 MPa, which is 218% higher than that of pure SiBCN matrix without whisker (60 MPa). XRD analysis shows that the introduction of whiskers has little effect on the phase composition of sintered composites; by observing the micro morphology of the fracture surface of the materials, it was found that the existence modes of whiskers in the matrix mainly include bridging and agglomeration bridging. Bridging whiskers are conducive to strengthening the material, while agglomerated whiskers will form pores in the matrix, so as to reduce the strength of the material.

SiC ceramics were sintered with Al₂O₃-Y₂O₃-CaO as additives. The effects of sintering temperature and additives content on the relative density, polytype, microstructure and mechanical properties of SiC ceramics were investigated by Archimedes drainage method, XRD, SEM, TEM and Vickers hardness test. The results show that the relative density, hardness and fracture toughness of SiC ceramics increase firstly and then decrease from 1300 ℃ to 1800 ℃, and reach the maximum at 1700 ℃. The phase transformation from β-SiC to α-SiC occurs between 1700 ℃ and 1800 ℃. Reducing the content of additives can increase the grain boundary bonding strength, and can improve the hardness and inhibition of the grain growth. Under the condition of 1700 ℃ and 7% (mass fraction) additives content, the best sintering results are obtained, with relative density, hardness and toughness of 97.9%, 23.3 GPa and 4.1 MPa·m^1/2, respectively.

In order to further expand the application of magnesium alloy, and improve its corrosion resistance and wear resistance in an environmentally-friendly way, Ni-P-nano SiC_P deposition coating was prepared on the surface of AZ91D magnesium alloy by direct chemical deposition without chromium and fluorine. The effects of SiC_P addition on the morphology, composition, phase and properties of the deposited coating were studied by SEM, EDS, XRD, hardness tester and electrochemical workstation. The results show that with the increase of SiC_P addition, the deposition amount of particles on the surface of the deposition coating first increases and then decreases, the size of cellular structure gradually decreases and then increases, and the hardness and corrosion resistance first increase and then decrease. When the addition amount of SiC_P is 1.2 g/L the deposition amount of particles is the largest, the dispersion strengthening and fine grain strengthening effect are the best, and the deposition coating is both uniform and dense, with a thickness of about 36 μm, which has good bonding with the matrix; the hardness of the deposited coating is 682HV, which is significantly higher than that of the magnesium alloy matrix. The corrosion potential is -0.397 V, which is 75% higher than that of magnesium alloy matrix. The corrosion current density is 6.18×10^-7 A·cm^-2, which is 4 orders of magnitude lower than the matrix.

Multilayered AZ91-(SiC_P/AZ91) clad plates were fabricated at 300, 350 ℃ and 400 ℃ successfully by extrusion. The microstructure evolution, bonding interface and the mechanical properties of the AZ91-(SiC_P/AZ91) clad plates were investigated in detail. The results show that grain of both of the AZ91 layer and SiC_P/AZ91 layer are refined due to the dynamic recrystallization (DRX) during the extrusion processes and the SiC_P/AZ91 layer processes much finer grain size. The SiC_P distribution of SiC_P/AZ91 layer is improved with increasing of extrusion temperature. No obvious delamination is observed in the AZ91-(SiC_P/AZ91) clad plates fabricated at different temperatures. The metallurgical bonding of the interface between AZ91 and SiC_P/AZ91 basically occurs in the extrusion die. The room-temperature strength of the AZ91-(SiC_P/AZ91) composite lies between the AZ91 alloy and the SiC_P/AZ91, corresponding well with the rule of mixture (ROM). The inadhesion of the SiC_P in the SiC_P/AZ91 layer is the main reason for the failure of the AZ91-(SiC_P/AZ91) clad plates during tensile test.

SiC ceramics has been extensively used in heat exchangers because of their excellent mechanical properties, high thermal conductivity, and superior thermal shock, corrosion, and oxidation resistance. However, there is a wide variation in the thermal conductivity of SiC ceramics, depending on the raw materials, molding process, sintering process, and sintering additives. The thermal conductivity of SiC ceramics (≤ 270 W·m^-1·K^-1) is much lower than that of 6H-SiC single crystals (490 W·m^-1·K^-1) because of pores, grain boundaries, impurities, and defects in SiC ceramics. In this work, the important factors affecting the thermal conductivity of SiC ceramics were analyzed, including temperature, pore, crystal structure, and second phase. Further, the preparation processes of high conductivity SiC ceramics were systematically compared based on hot-pressed sintering, spark plasma sintering, pressureless sintering, recrystallization sintering, and reaction sintering. The improvement measures of thermal conductivity of SiC ceramics were summarized, including the optimization of the type and content of sintering aids, high-temperature annealing, and adding a high-thermal-conductivity second phase. Finally, the prospects and research directions of low-cost and high-thermal-conductivity SiC ceramics are proposed.

The nano-SiC/AlSi7Mg mixed powder was prepared by mechanical mixing method. The specimens of nano-SiC particle reinforced AlSi7Mg composite were fabricated by selective laser melting (SLM). The relative density, phase and microstructure were observed and analyzed, and the microhardness and tensile properties were tested. The results show that the relative densities of SLM nano-SiC/AlSi7Mg composite are increased firstly and then decreased with the increase of scanning speed and scanning space, and the maximum relative density reaches 99.75%. The microstructure of specimens is similar to that of SLM-formed Al-Si alloys, and the network-structured Si phase is uniformly embedded in the α-Al matrix. There are nano-SiC agglomerates and Mg₂Si phase in the α-Al matrix, which has a similar distribution to Si. Compared with AlSi7Mg, the microstructure of specimens is changed from columnar to equiaxed grain, and the grains are significantly refined (the average grain size is 1.36 μm). Due to the addition of SiC, grain refinement strengthening and solid solution strengthening are produced, and the hardness and strength of composite are significantly improved. The hardness, tensile strength and yield strength reach 137.3HV, 448.3 MPa and 334.7 MPa, respectively. However, the elongation is reduced to 3.9%, and the fracture mode is mainly brittle fracture.

One-staged forming of porous C/C composites as well as volume fraction control of pores were realized, based on thermophysical property analysis and proportioning design of raw materials. Short fiber reinforced C/C-SiC composites with high densification and low content of residual Si were prepared by hot-pressing-infiltration two-step method at low temperature. The structural evolution of C/C-SiC composites was analyzed in detail, the mechanical properties as well as failure behaviors were also investigated. Results show that the porous C/C composites present bipolar distribution in pore size, adding aramid fibers is an effective method to improve the connectivity of network pores, exhibiting a significant regulatory effect. Both SiC network skeleton and pinning structure with strong interface between SiC matrix and carbon fiber bundle can entrust the excellent mechanical properties of C/C-SiC composites with high carbon fiber content. In addition, the fracture toughness of C/C-SiC composites can be improved significantly with the addition of aramid fibers, resulting in the increase of crack propagation path. The isotropic distribution of carbon fiber in plane and the uniform distribution of ceramic phase between layers play a positive role in improving the bearing capacity and friction stability of C/C-SiC composites.

In order to study the influence of the service temperature load and material microstructure on the thermal fatigue crack growth behavior of SiC_p/A356 composites, and to clarify the microscopic mechanism of thermal fatigue crack growth, the thermal fatigue crack growth test of SiC_p/A356 composites was carried out. The results show that the crack growth process includes the slow growth stage caused by the deflection of SiC particles and the release of the driving force of the secondary crack growth, and the rapid growth stage where the main crack is connected with the micro-damage front end of the crack growth. When the heating temperature is low, the "step-like" feature of crack growth is obvious, the overall growth rate is slower, and the crack width is smaller, the crack propagation methods are particle fracture, light-mass matrix tearing and cracking along the interface. When the heating temperature is higher, the "oblique straight-line jump" stage is more obvious, the crack width is large and the growth rate is high, the crack growth is dominated by particle shedding and large-scale matrix tearing. Main crack always propagates forward with less resistance by choosing to follow the SiC particle group or directly pass through the α-Al matrix, when Si phase is loaded, it is easy to fracture and become the source of crack propagation. At the same time, the micro-damage at the front end of the crack propagation has a guiding effect on the crack propagation.

Laminating method is one of the key factors affecting the thermal shock resistance of SiC_f/SiC composites prepared by prepreg paving process. Based on the cohesion model, 1200 ℃ high temperature water quenching tests and finite element simulation studies were carried out on SiC_f/SiC composite square samples with different orthogonal lay-up methods, which were prepared by the precursor immersion pyrolysis(PIP) process. The results show that the surface temperature of the sample drops sharply during the water quenching process, and there is a large temperature difference between the core and the surface. The temperature difference between the corner and the core can reach up to 1077 ℃. The main failure modes are interlaminar delamination and matrix cracking, and the delamination position is related to the layering method. Moreover, significant differences in the delamination displacement can be observed, due to the difference in the orthogonal lay-up mode: tacking displacement of the main interlaminar delamination of [0/90] and [0/90/0] can reach 0.61 mm, while the [0/0/90/90] layer cracking displacement is only 0.04 mm. In addition, the cracking displacement of the main interlaminar delamination increases gradually with the increase of water quenching time, while the secondary cracks will undergo crack closure after opening.

In order to explore the ablation characteristics of C/SiC ceramic composite nozzles in the working environment of liquid rocket engines, 3D C/SiC composite nozzle was prepared by the precursor impregnation pyrolysis(PIP) process, and the ablation test of the nozzle in various working conditions was carried out. The results show that 3D C/SiC composite nozzle can meet the requirements of anti-ablation performance of the liquid rocket engine under various working conditions. The wire ablation rate of nozzle throat is about 3.92×10^-4 mm/s; after the hot test vehicle ablation test, a large amount of white matter SiO₂ remains on the inlet cylindrical section, convergent section, throat section and expansion section outer surface of the nozzle, and the ablation pit appears in the throat; the ablation mechanisms of C/SiC composites under liquid rocket engine are mainly mechanical erosion ablation and oxidation ablation.

The effects of hydrophilic and hydrophobic SiO₂ composite organic resin on the properties of FeSiCr magnetic powder cores and the effects of annealing treatment on magnetic properties were studied. After phosphating, the FeSiCr alloy powders were coated by two types of SiO₂ composite resin, which are hydrophobic and hydrophilic, respectively. The FeSiCr magnetic powder cores were prepared by compaction and curing. The results show that the coating effect of coupling modified hydrophilic SiO₂ composite organic resin is better than that of hydrophobic SiO₂ composite organic resin. With the increase of SiO₂ addition, the specific resistance and coercivity of the magnetic powder cores are increased, while the density, saturation magnetization and effective permeability are decreased. The FeSiCr magnetic powder cores coated with 0.5% hydrophobic SiO₂ composite organic resin have excellent comprehensive performance after annealing. Under the condition of 20 mT, 100 kHz, the magnetic core loss is 49.84 kW/m³, which is 16.9% lower than that of the magnetic powder cores coated with pure resin. Annealing can effectively promote magnetic properties of FeSiCr magnetic powder cores.