Long-term oxidation and ablation behavior of Cf/ZrB2–SiC composites at 1500, 2000, and 2200°C

Although C_f/ZrB₂–SiC composites prepared via direct ink writing combined with low-temperature hot-pressing were shown to exhibit high relative density, high preparation efficiency, and excellent flexural strength and fracture toughness in our previous work, their oxidation and ablation resistance at high and ultrahigh temperatures had not been investigated. In this work, the oxidation and ablation resistance of C_f/ZrB₂–SiC composites were evaluated via static oxidation at high temperature (1500°C) and oxyacetylene ablation at ultrahigh temperatures (2080 and 2270°C), respectively. The thickness of the oxide layer of the C_f/ZrB₂–SiC composites is <40 μm after oxidizing at 1500°C for 1 h. The C_f/ZrB₂–SiC composites exhibit non-ablative properties after oxyacetylene ablation at 2080 and 2270°C for >600 s, with mass ablation rates of 3.77 × 10⁻³ and 5.53 × 10⁻³ mg/(cm² s), and linear ablation rates of −4.5 × 10⁻⁴ and −5.8 × 10⁻⁴ mm/s, respectively. Upon an increase in the ablation temperature from 2080 to 2270°C, the thickness of the total oxide layer increases from 360 to 570 μm, and the carbon fibers remain intact in the unaffected region. Moreover, the oxidation and ablation process of C_f/ZrB₂–SiC at various temperatures was analyzed and discussed.     

The effects of preparation temperature on the SiCf/SiC 3D4d woven composite

Continuous silicon carbide fiber reinforced silicon carbide matrix (SiC_f/SiC) composites have promising applications in aero-engine due to their unique advantages, such as low density, high modulus and strength, outstanding high temperature resistance and oxidation resistance. As SiC fibers are main reinforcements in SiC_f/SiC composites, the crystallization rate and initial damage degree of SiC fibers are seriously influenced by preparation temperatures of SiC_f/SiC composites, namely mechanical properties of SiC fibers and SiC_f/SiC composites are influenced by preparation temperatures. In this paper, KD-II SiC fibers were woven into 3D4d preforms and SiC matrix was fabricated by PIP process at 1100 °C, 1200 °C, 1400 °C and 1600 °C. Digital image correlation (DIC) method was adopted to measure the uniaxial tensile properties of these SiC_f/SiC composites. In addition, finite element method (FEM) based on representative volume element (RVE) was adopted to predict the mechanical properties of SiC_f/SiC composites. The good agreements between numerical results and experimental results of uniaxial tensile tests verified the validity of the RVE. In last, the transverse tensile, transverse shear, uniaxial shear properties were predicted by this method. The predicted results illustrated that axial tensile, transverse tensile and axial shear properties were greatly influenced by the preparation temperatures of SiC_f/SiC composites while transverse shear properties were not significantly various. And the mechanical properties of SiC_f/SiC composites peaked at 1200 °C among these four temperatures while their values reached their lowest points at 1600 °C because of thermal damage and brittle failure of SiC_f/SiC composites.     

Additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites via paper laminating,direct slurry writing,and precursor infiltration and pyrolysis

In this study, continuous carbon reinforced C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C–SiC high entropy ceramic matrix composites were additively manufactured through paper laminating (PL), direct slurry writing (DSW), and precursor infiltration and pyrolysis (PIP). (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C high entropy ceramic (HEC) powders were synthesized by pressureless sintering and ball milling. A certain proportion of HEC powder, SiC powder, water, binder, and dispersant were mixed to prepare the HEC-SiC slurry. Meanwhile, BN coating was prepared on the 2D fiber cloth surface by the boric acid-urea method and then the cloth was cut into required shape. Additive manufacturing were conducted subsequently. Firstly, one piece of the as-treated carbon fiber cloth was auto-placed on the workbench by paper laminating (PL). Then, the HEC-SiC slurry was extruded onto the surface of the cloth by direct slurry writing (DSW). PL and DSW process were repeated, and a C_f/HEC-SiC preform was obtained after 3 cycles. At last, the preform was densified by precursor infiltration and pyrolysis (PIP) and the final C_f/HEC-SiC composite was prepared. The open porosity of the C_f/HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 7.7, 10.6, and 11.3%, respectively. And the density of the C_f/HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 2.9, 2.7 and 2.3 g/cm³, respectively. The mechanical properties of the C_f/HEC-SiC composites increased firstly and then decreased with the HEC content increase, reaching the maximum value when the HEC volume fraction was 30%. The mechanical properties of the C_f/HEC-SiC composites containing 45, 30 and 15% HEC were as follows: flexural strength (180.4 ± 14 MPa, 183.7 ± 4 MPa, and 173.9 ± 4 MPa), fracture toughness (11.9 ± 0.17 MPa m^1/2, 14.6 ± 2.89 MPa m^1/2, and 11.3 ± 1.88 MPa m^1/2), and tensile strength (71.5 ± 4.9 MPa, 98.4 ± 12.2 MPa, and 73.4 ± 8.5 MPa). From this study, the additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites was achieved, opening a new insight into the manufacturing of ceramic matrix composites.     

Evaluation of elastic constants and high temperature tensile behaviour with damage assessment of the SiC seal-coated 2.5D Cf/SiC composites having multilayered interphase and Si-B-C added matrix

Elastic constants and tensile behaviour of chemical vapour infiltration processed 2.5D C_f/SiC composites possessing multilayered (PyC/SiC)_n=4 interphase, Si-B-C containing matrix and SiC seal-coating have been evaluated with microstructural examination and damage assessment. The strength obtained as ～187 ± 2 MPa in tensile tests at 27 °C is increased by ～18% and ～22% at 1000 °C and 1250 °C, respectively due to reduced thermal stress and increased strength of load-sharing C-fibres, which are protected from oxidation till failure by a self-healing borosilicate layer. The damage evolving during tension tests has been quantified by relating it to decrease of stress-strain slope with strain. Higher (6–8 times) elastic constants measured along fibre-axes than that obtained transversely, indicate significant anisotropy. Owing to matrix cracking with fibre-debonding and pull-out, the fibre-oriented elastic constants of tensile-fractured samples are significantly lower than those of as-received composites, and the difference scales with temperature, whereas negligible change is observed perpendicular to the fibre axes.     

High-temperature flexural strength of I-CVI processed Cf/SiC composites with variable interphases

The effect of single-layer pyrocarbon (PyC) and multilayered (PyC/SiC)_n=4 interphases on the flexural strength of un-coated and SiC seal-coated stitched 2D carbon fiber reinforced silicon carbide (C_f/SiC) composites was investigated. The composites were prepared by I-CVI process. Flexural strength of the composites was measured at 1200 °C in air atmosphere. It was observed that irrespective of the type of interphase, the seal coated samples showed a higher value of flexural strength as compared to the uncoated samples. The flexural strength of 470 ± 12 MPa was observed for the seal coated C_f/SiC composite samples with multilayered interphase. The seal coated samples with single layer PyC interphase showed flexural strength of 370 ± 20 MPa. The fractured surfaces of tested samples were analyzed in detail to study the fracture phenomena. Based on microstructure-property relations, a mechanism has been proposed for the increase of flexural properties of C_f/SiC composites having multilayered interphase.     

High-temperature electromagnetic wave absorption properties of Cf/SiCNFs/Si3N4 composites

Carbon fibers reinforced Si₃N₄ composites with SiC nanofiber interphase (C_f/SiCNFs/Si₃N₄) were prepared by combining catalysis chemical vapor deposition and gel-casting process. Microstructures, mechanical properties, and electromagnetic wave absorption properties within X-band at 25°C-800°C of C_f/SiCNFs/Si₃N₄ composites were investigated. Results show that SiC nanofibers are combined well with Si₃N₄ matrix and carbon fibers, the fracture toughness is thus increased more than double from 3.51 MPa·m^1/2 of the Si₃N₄ ceramic to 7.23 MPa·m^1/2 of the as-prepared composites. As the temperature increases from 25°C to 800°C, C_f/SiCNFs/Si₃N₄ composites show a temperature-dependent complex permittivity, attenuation constant, and impedance. The relatively high attenuation capability of C_f/SiCNFs/Si₃N₄ composites at elevated temperature results in a great minimum reflection loss of −20.3 dB at 800°C with a thin thickness of 2.0 mm. The superior electromagnetic wave absorption performance mainly originates from conductive loss, multi-reflection, and strong polarization formed by the combined effects of carbon fibers and SiC nanofibers.     

Mechanical properties and microstructure evolution of 3D Cf/SiBCN composites at elevated temperatures

3D C_f/SiBCN composites were fabricated by an efficient polymer impregnation and pyrolysis (PIP) method using liquid poly(methylvinyl)borosilazanes as precursor. Mechanical properties and microstructure evolution of the prepared 3D C_f/SiBCN composites at elevated temperatures in the range of 1500‐1700°C were investigated. As temperature increased from room temperature (371 ± 31 MPa, 31 ± 2 GPa) to 1500°C (316 ± 29 MPa, 27 ± 3 GPa), strength and elastic modulus of the composite decreased slightly, which degraded seriously as temperature further increased to 1600°C (92 ± 15 MPa, 12 ± 2 GPa) and 1700°C (84 ± 12 MPa, 11 ± 2GPa). To clarify the conversion of failure mechanisms, interfacial shear strength (IFSS) and microstructure evolution of the 3D C_f/SiBCN composites at different temperatures were investigated in detail. It reveals that the declines of the strength and changes of the IFSS of the composites are strongly related to the defects and SiC nano‐crystals formed in the composites at elevated temperatures.     

Reactive brazing Cf/SiC to itself and to Mo using the NiPdPtAu-Cr filler alloy

The NiPdPtAu-Cr filler alloy was proposed for joining C_f/SiC composites. The wettability on C_f/SiC composite was studied by the sessile drop method at 1200 °C for 30 min. Under the brazing condition of 1200 °C for 10 min, the C_f/SiC-C_f/SiC joint strength was only 51.7 MPa at room temperature. However, when used a Mo layer, the C_f/SiC-Mo-C_f/SiC joint strength was remarkably increased to 133.2 MPa at room temperature and 149.5 MPa at 900 °C, respectively. At the interface between C_f/SiC and Mo, Mo participated in interfacial reactions, with the formation of Cr₃C₂/Mo₂C reaction layers at the C_f/SiC surface. The improvement in the joint strength should be mainly attributed to the formation of MoNiSi. The C_f/SiC-Mo joint strength was 86.9 MPa at room temperature and 73.7 MPa at 900 °C, respectively. After 10 cycles of thermal shock test at 900 °C the C_f/SiC-Mo joint strength of 71.6 MPa was still maintained.     

Mechanical and thermal properties of ZrC/ZTA composites prepared by spark plasma sintering

In the present work, the influence of sintering temperature and particle size of pristine ZrC particles on the microstructure, mechanical properties, and thermal properties of ZrC/ZTA ceramic composites are investigated. Specimens consolidated by spark plasma sintering at different sintering temperatures from 1500 °C to 1800 °C. XRD results revealed that α-Al₂O₃, t-ZrO₂, ZrC, and a small quantity of m-ZrO₂ phases are present in the composites. The microstructure of μm-ZrC/ZTA is found to be more compact than nm-ZrC/ZTA composites. There is an apparent increase in the average grain size with the increase in temperature. From the micrographs of fracture surfaces, step-wise transgranular fracture structures are observed. Relative densities and Vickers hardness are in proportion to sintering temperature from 1500 °C to 1700 °C. The maximum Vickers hardness of 1919 HV1 is obtained for μm-ZrC/ZTA composites. Indentation fracture toughness displays a gradual rise when the temperature rises from 1500 °C to 1700 °C, then deteriorates at 1800 °C for both nm-ZrC/ZTA and μm-ZrC/ZTA ceramic composites. The maximum fracture toughness values for nm-ZrC/ZTA and μm-ZrC/ZTA are 6.75 MPa m^1/2 and 6.83 MPa m^1/2, respectively. The thermal conductivity of the specimens decreased gradually as the temperature increases from 100 °C to 1000 °C. The obtained results indicated that the 1700 °C is the optimized sintering temperature where μm-ZrC/ZTA composites have excellent performance on microstructure, mechanical properties, and thermal properties than nm-ZrC/ZTA composites.     

Influence of pyrolysis and melt infiltration temperatures on the mechanical properties of SiCf/SiC composites

In order to improve the degree of matrix densification of SiC_f/SiC composites based on liquid silicon infiltration (LSI) process, the microstructure and mechanical properties of composites according to various pyrolysis temperatures and melt infiltration temperatures were investigated.Comparing the microstructures of SiC_f/C carbon preform by a one-step pyrolysis process at 600 °C and two-step pyrolysis process at 600 and 1600 °C, the width of the crack and microcrack formation between the fibers and matrix in the fiber bundle increased during the two-step pyrolysis process. For each pyrolysis process, the density, porosity, and flexural strength of the SiC_f/SiC composites manufactured by the LSI process at 1450–1550 °C were measured to evaluate the degree of matrix densification and mechanical properties. As a result, the SiC_f/SiC composite that was fabricated by the two-step pyrolysis process and LSI process showed an 18% increase in density, 16%p decrease in porosity, and 150% increase in flexural strength on average compared to the composite fabricated by the one-step pyrolysis process.In addition, among the SiC_f/SiC specimens fabricated by the LSI process after the same two-step pyrolysis process, the specimen that underwent the LSI process at 1500 °C showed 30% higher flexural strength on average than those at 1450 or 1550 °C. Furthermore, under the same pyrolysis temperature, the mechanical strength of SiC_f/SiC specimens in which the LSI process was performed at 1500 °C was higher than that of the 1550 °C although both porosity and density were almost similar. This is because the mechanical properties of the Tyranno-S grade SiC fibers degraded rapidly with increasing LSI process temperature.     

Microstructure and mechanical properties of hot-pressed SiC nanofiber reinforced SiC composites

This study reports on the preparation and mechanical properties of a novel SiC_nf/SiC composite. The single crystal SiC nanofiber(SiC_nf) reinforced SiC ceramic matrix composites (CMC) were successfully fabricated by hot pressing the mixture of β-SiC powders, SiC_nf and Al–B–C powder. The effects of SiC_nf mass fraction as well as the hot-pressing temperature on the microstructure and mechanical properties of SiC_nf/SiC CMC were systematically investigated. The results demonstrated that the 15 wt% SiC_nf/SiC CMC obtained by hot pressing (HP) at 1850 °C with 30 MPa for 60 min possessed the maximum flexural strength and fracture toughness of 678.2 MPa and 8.33 MPa m^1/2, respectively. The nanofibers pull out, nanofibers bridging and cracks deflection were found by scanning electron microscopy, which are believed can strengthen and toughen the SiC_nf/SiC CMC via consuming plenty of the fracture energy. Besides, although the relative density of the prepared SiC_nf/SiC CMC further increased with the sintering temperature rose to 1900 °C, the further coarsend composites grains results in the deterioration of the mechanical properties for the obtained composites compared to 1850 °C.     

Fabrication of carbon fiber reinforced ceramic matrix composites with improved oxidation resistance using boron as active filler

Boron was introduced into C_f/SiC composites as active filler to shorten the processing time of PIP process and improve the oxidation resistance of composites. When heat-treated at 1800 °C in N₂ for 1 h, the density of composites with boron (C_f/SiC-BN) increased from 1.71 to 1.78 g/cm³, while that of composites without boron (C_f/SiC) decreased from 1.92 to 1.77 g/cm³. So when boron was used, two cycles of polymer impregnation and pyrolysis (PIP) could be reduced. Meanwhile, the oxidation resistance of composites was greatly improved with the incorporation of boron-bearing species. Most carbon fiber reinforcements in C_f/SiC composite were burnt off when they were oxidized at 800 °C for 10 h. By contrast, only a small amount of carbon fibers in C_f/SiC-BN composite were burnt off. Weight losses for C_f/SiC composite and C_f/SiC-BN composite were about 36 and 16 wt%, respectively.     

Microstructure,thermophysical properties and oxidation resistance of SiCf/SiC–YSi2–Si composite fabricated through reactive melt infiltration

As an ideal component material for advanced aeroengines, SiC composite faces severe challenges of high temperatures and oxidation. Here, a high-densification SiC_f/SiC–YSi₂–Si composite was prepared through combining PIP with RMI of Si–13 at% Y alloy to achieve enhanced performance at high temperatures. Based on the analysis of the microstructure and thermophysical properties, it found that the introduction of the highly crystalline Si–Y alloy can improve the high-temperature thermal conductivity of the composite through phonon and electron conduction. In addition, Y migrates to the surface and forms yttrium silicate with increasing oxidation temperature, which facilitates the excellent long-term oxidation resistance of the composite at 1200–1300 °C. Thus, the composite retained its high strength (89.15% and 86.84%) after oxidation at 1200 °C and 1300 °C for 100 h. The experimental results clearly demonstrate that the introduction of the Si–Y alloy is an effective way of preparing high-performance SiC composites.     

Microstructure and mechanical properties of quasi-isotropic chopped fiber-reinforced PyC–SiC matrix composite prepared by novel nondamaging method

In this work, quasi-isotropic chopped carbon fiber-reinforced pyrolytic carbon and silicon carbide matrix (C_f/C–SiC) composites and chopped silicon carbide fiber-reinforced silicon carbide matrix (SiC_f/SiC) composites were prepared via novel nondamaging method, namely airlaid process combined with chemical vapor infiltration. Both composites exhibit random fiber distribution and homogeneous pore size. Young's modulus of highly textured pyrolytic carbon (PyC) matrix is 23.01 ± 1.43 GPa, and that of SiC matrix composed of columnar crystals is 305.8 ± 9.49 GPa in C_f/C–SiC composites. Tensile strength and interlaminar shear strength of C_f/C–SiC composites are 52.56 ± 4.81 and 98.16 ± 24.62 MPa, respectively, which are both higher than those of SiC_f/SiC composites because of appropriate interfacial shear strength and introduction of low-modulus and highly textured PyC matrix. Excellent mechanical properties of C_f/C–SiC composites, particularly regarding interlaminar shear strength, are due to their quasi-isotropic structure, interfacial debonding, interfacial sliding, and crack deflection. In addition to the occurrence of crack deflection at the fiber/matrix interface, crack deflection in C_f/C–SiC composites takes also place at the interface between PyC–SiC composite matrix and the interlamination of multilayered PyC matrix. Outstanding mechanical properties of as-prepared C_f/C–SiC composites render them potential candidates for application as thermal structure materials under complex stress conditions.     

Ultrafast low-temperature near-seamless joining of Cf/SiC using a sacrificial Pr3Si2C2 filler via electric current field-assisted sintering technique

A novel layered structure material, Pr₃Si₂C₂, was synthesized at a low temperature of 850 °C using a molten salt approach for the first time, and subsequently used as the joining filler for carbon fibers reinforced SiC composites (C_f/SiC). A robust near-seamless C_f/SiC joint was successfully obtained at 1509 °C (T_i) for 30 s, while an ultrafast heating rate of 6000 °C/min was applied via electric field-assisted sintering technology. The near-seamless joining process was attributed to the newly precipitated SiC grains, which were densified well with the C_f/SiC matrix by liquid-assisted sintering. The liquid phase was in-situ formed by the eutectic reaction between Pr₃Si₂C₂ and SiC. The shear strength of the near-seamless joint obtained at 1509 °C for 30 s was 17.6 ± 3.0 MPa. The failure occurred in the C_f/SiC matrix. The formation of near-seamless C_f/SiC joints dismisses the issues related to thermal mismatch between C_f/SiC matrices and traditional joining fillers.     

Preparation of SiCf/Si–O–C composites by impregnation pyrolysis of polysiloxane and its electromagnetic wave absorption properties

High-temperature structural electromagnetic wave (EMW) absorption materials are increasing in demand because they can simultaneously possess the functions of mechanical load-bearing, heatproof, and EMW absorption. Herein, SiC_f/Si–O–C composites were prepared by precursor impregnation pyrolysis using continuous SiC fibers needled felt as reinforcement and polysiloxane as a precursor, respectively. The phase composition, microstructure, complex permittivity, and EMW absorption properties of SiC_f/Si–O–C composites after annealing at various temperatures were investigated. The annealing at 1400–1500°C affects positively the EMW absorption performance of the composites, because the β-SiC microcrystals and SiC nanowires were generated by the activation of carbothermal reduction reaction in the composites, and the aspect ratio of SiC nanowires increased with the rise of temperature. The composites exhibit optimal EMW absorption performance, with the effective absorption bandwidth covering the entire X-band and the minimum reflection loss (RL_min) of −32.8 dB at 4.0 mm when the annealing temperature is raised to 1500°C. This is because that the impedance matching is improved as the rising of ε′ and decreasing of ε″ due to the conversion of free carbon in the composite into SiC nanowires.     

Combustion synthesis of SiC-based ceramics reinforced by discrete carbon fibers with in situ grown SiC nanowires

This study proposes a combustion-based ceramic matrix composite processing technique intended on single-step in situ deposition of single-crystal SiC nanowires (SiC_nw) on the surface of carbon fibers (C_f) and formation of SiC_nw–reinforced SiC matrix. This was accomplished by Ta-catalyzed combustion of poly-(C₂F₄)-containing reactive mixtures with pre-mixed chopped C_f. Depending on the combustion conditions, carbon fiber surface is subjected either to formation of diffusion layers, ceramic particle incrustation or growth of continuous arrays of carbon-coated single-crystal SiC_nw with a nearly defect-free lattice, 10–50 nm diameter and 15–20 μm length. Thermodynamics, phase and structure formation mechanisms are explored, and the optimal conditions are outlined for reproducible C_f/in situ SiC_nw dual reinforcement of SiC-based ceramics. Hot pressing at 1500 °C produced C_f/in situ SiC_nw-reinforced ceramic SiC–TaSi₂ specimens with a relative density of 97%, 19 GPa Vickers hardness, 3-point flexural strength σ = 420 ± 70 MPa and fracture toughness K_1C = 12.5 MPa m^1/2.     

Mechanical and electromagnetic shielding properties of carbon fiber reinforced silicon carbide matrix composites

Carbon fiber reinforced SiC matrix composites (C_f/SiC) were fabricated through chemical vapor infiltration. Effects of SiC content on the mechanical and electromagnetic properties of the as-prepared materials were studied systematically. The high volume fraction of SiC matrix is beneficial to the transfer of load to carbon fiber. With the increase of SiC content from 21.5 to 42.2 vol.%, the total porosity decreases from 38.5 to 17.8 vol.%, the flexural strength and fracture toughness of C_f/SiC increase from 38 ± 4 to 375 ± 10 MPa and from 6.2 ± 0.7 to 21 ± 0.3 MPa m^1/2. The electromagnetic interference shielding effectiveness of as-prepared C_f/SiC decreases from 43 ± 1.4 to 31 ± 1.1 dB over the frequency range of 8.2–12.4 GHz with the increase of SiC content. The decease of electromagnetic interference shielding effectiveness is mainly attributed to the decline of absorption loss. With the increase of SiC content, the electrical conductivity of C_f/SiC diminishes, leading to the conspicuous drop of the conductive loss, which plays the key role in lowering the absorption loss of electromagnetic waves.     

Thermal stability of CVI and MI SiC/SiC composites with Hi-Nicalon™-S fibers

The influence of high-temperature argon heat-treatment on the microstructure and room- temperature in-plane tensile properties of 2D woven CVI and 2D unidirectional MI SiC/SiC composites with Hi-Nicalon?-S SiC fibers was investigated. The 2D woven CVI SiC/SiC composites were heat-treated between 1200 and 1600 °C for 1- and 100-hr, and the 2D unidirectional MI SiC/SiC composites between 1315 and 1400 °C for up to 2000 hr. In addition, the influence of temperature on fast fracture tensile strengths of these composites was also measured in air. Both composites exhibited different degradation behaviors. In 2D woven CVI SiC/SiC composites, the CVI BN interface coating reacted with Hi-Nicalon?-S SiC fibers causing a loss in fast fracture ultimate tensile strengths between 1200 and 1600 °C as well as after 100-hr isothermal heat treatment at temperatures > 1100 °C. In contrast, 2D unidirectional MI SiC/SiC composites showed no significant loss in in-plane tensile properties after the fast fracture tensile tests at 1315 °C. However, after isothermal exposure conditions from 1315° to 1400°C, the in-plane proportional limit stress decreased, and the ultimate tensile fracture strain increased with an increase in exposure time. The mechanisms of strength degradation in both composites are discussed.     

Fabrication and properties of Cf/ZrC‐SiC‐based composites by an improved reactive melt infiltration

C_f/ZrC‐SiC composites with a density of 2.52 g/cm³ and a porosity of 1.68% were fabricated via reactive melt infiltration (RMI) of Si into nano‐porous C_f/ZrC‐C preforms. The nano‐porous C_f/ZrC‐C preforms were prepared through a colloid process, with a ZrC “protective coating” formed surrounding the carbon fibers. Consequently, highly dense C_f/ZrC‐SiC composites without evident fiber/interphase degradation were obtained. Moreover, abundant needle‐shaped ZrSi₂ grains were formed in the composites. Benefiting from this unique microstructure, flexural strength, and elastic modulus of the composites are as high as 380 MPa and 61 GPa, respectively, which are much higher than C_f/ZrC‐SiC composites prepared by conventional RMI.