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The ultrasonic vibration-assisted polishing (UVAP) method, a recently developed advanced processing technology, is widely used in the processing of brittle materials. This study uses molecular dynamics (MD) simulations to investigate the polishing behavior of diamond grits on SiC workpieces during the UVAP process. The frequency (fz), amplitude (Az), and dimensions of the vibration are varied to investigate various aspects of the material removal process. In the low-frequency region, the UVAP processing method exacerbates taper slips and dislocations in the workpiece. In the high-frequency region, fz and Az can improve the MRR by more than 32% and reach 2–4 times higher than that of traditional scratching, respectively. The surface morphology obtained using MD simulation is consistent with the experimental results. In the ultrasonic elliptical vibration assisted polishing (UEVAP) method, fy not only causes a periodic and stable increase in temperature, which helps to transform atoms into an amorphous structure, but it also increases material removal rate (MRR) while decreasing friction factor and surface roughness. Appropriate increase of fz reduces forces and improves stress distribution. Az significantly increases MRR but results in a rough surface. In comparison to the UVAP process, the UEVAP method further improves MRR and produces smoother machined surfaces. This study uses molecular dynamics (MD) simulations to investigate the polishing behavior of diamond grits on SiC workpieces during the UVAP process. The frequency (fz), amplitude (Az), and dimensions of the vibration are varied to investigate various aspects of the material removal process. [ABSTRACT FROM AUTHOR]

This work is devoted to the computational study of the efficiency of the SIC synthesis process in an electrothermal fluidized bed at different operating temperatures of the process and different loading options in the reaction volume of the charge components. The chemical reactions volatile products entrainment effect at the silicon carbide yield is shown. It is noted that the properties of the reacting surface of carbon-containing particles mainly determine the synthesis time, but not the amount of SIC formed. Analysis of the calculation results allowed us to draw an important conclusion about the fundamental effect on the synthesis efficiency of the ratio of the number of carbon-containing particles directly involved in the SIC formation reaction to the number of carbon-containing particles associated only with evaporating SiO2 particles. The calculated yield of SiC is compared with the results of existing experiments to study the formation of SiC in an electrothermal reactor. [ABSTRACT FROM AUTHOR]

This paper reports the effect of titanium silicide active filler and the pyrolytic atmosphere (argon and nitrogen) on the ceramic conversion of polycarbosilane. Pyrolysis atmosphere and concentration of titanium silicide active filler was optimized to produce minimum shrinkage polycarbosilane derived ceramic. Detailed investigation on the phase evolution and surface morphology of the titanium silicide incorporated polycarbosilane derived ceramic under different pyrolysis atmospheres were carried out. From the results, it was concluded that 40 wt% titanium silicide loaded PCS system heat treated under nitrogen atmosphere was found to be the best precursor to obtain a minimum shrinkage ceramic phase with better properties. Therefore, this system offers the opportunity to expedite the rapid fabrication process of ceramic matrix composites, create flawless ceramic coatings, and produce bulk ceramic materials free from shrinkage. [ABSTRACT FROM AUTHOR]

It is well known that poor wettability at the interface between the Al matrix and the reinforcing phase is a technical bottleneck in the development of aluminum matrix composites. A nitrogen-induced self-forming Al composite (NISFAC) process was developed, which is a novel concept of a composite manufacturing process that does not require vacuum or external pressure. This process employs an exothermic reaction accompanying the nitridation of Al, and the heat dissipated from the reaction enables the local melting and self-sintering of the Al powder. In this study, X-ray photoelectron spectroscopy (XPS) analysis was employed to investigate the compositional changes in monolithic SiC particles and the Al/SiC mixture during heating at 700 °C for 1 h in air, argon, and nitrogen atmospheres, respectively. In addition, XPS results were used to examine the mechanism for the surface modification of Al and SiC particles during the NISFAC process and to understand why self-sintering only occurs in a nitrogen atmosphere. [ABSTRACT FROM AUTHOR]

We attempted melt-spinning and investigated the compatibility and thermal decomposition of a mixture comprising polysilsesquioxane and polycarbosilane for the purpose of manufacturing low grade silicon carbide (SiC) fibers or silicon oxycarbide fibers. The fabrication approach was selected to reinforce the strength of the as-spun fibers, as well as increase the yield of long SiC fibers. Although the addition of polysilsesquioxane increased the viscosity of the mixed polymer, the mixed polymer could be melt-spun by incorporating a softener during the fabrication process. Cross-linking between polysilsesquioxane and polycarbosilane was successfully accomplished by heating them to 600 °C. Consequently, the mixed polymer demonstrated a higher yield in comparison to pure polycarbosilane. The as-spun fibers derived from the mixed polymer had a tensile strength approximately 10 times that of the fibers derived from pure PCS using an identical approach. Thus, we were able to confirm that blending polysilsesquioxane effectively reinforced the tensile strength of the as-spun fibers to generate long SiC fibers. [ABSTRACT FROM AUTHOR]

Nanostructured silicon carbide (SiC) materials are expected to have bright prospect in application as high-performance electrode materials with excellent charge–discharge cycling stability. However, the exploration of SiC-based micro-supercapacitors (MSCs) still remains a grand challenge seriously hampered by low areal capacities and complicated multistep production process. Herein, we report that rationally designed SiC/C nanocomposite with hierarchical porous structure and improved electrical conductivity has been realized by a facile and rapid carbothermic reduction using silica sol and sucrose as silicon and carbon source. The amorphous carbon between SiC nanoparticles (NPs) contributes to enlarged surface areas and excellent conductivity, not only ensuring intimate contact between the electrolyte and the electrode but also providing an effective ion highway for electrolyte ions. As a result, MSCs based on SiC/C nanocomposite (Si/C mass ratio of 1:1.5) demonstrate an optimal specific areal capacitance of 11.8 mF cm−2 at 2 mV s−1, outstanding flexibility (104.5% retention of initial capacitance at 180° bending), and superior integration. Most notably, the capacitance remains at 97.3% of the initial value after 50000 charging/discharging cycles, superior to that of most advanced SiC-based MSCs ever reported. This work demonstrates an effective design for hierarchical porous SiC/C nanocomposite for energy storage, which gives significant inspirations on the exploration of high-performance SiC-based MSCs. [ABSTRACT FROM AUTHOR]

The epitaxial graphene layer (EG) grown on silicon carbide (SiC) is severely affected by the presence of the underlying graphene buffer layer (BL). However, little information is available on the alteration of the magnetic and electronic properties of the top layer when the BL presents structural defects. Herein, by means of first-principle density functional calculations, we investigate the electronic and magnetic properties of the SiC–BL–EG system, with a single vacancy, divacancy or a Stone–Wales defective buffer layer. Our results indicate that new highly stable magnetic states are observed in the SiC–BL–EG non-defective and defective systems, as compared to the SiC–BL models. In addition, the energy differences among the degenerate magnetic states originally found in the SiC-defective systems are further reduced upon inclusion of the EG layer. Interestingly, for the single-vacancy system, a p-type doping is noticed in the spin down channel of the M = 4 µB configuration. This is in sharp contrast with the n-type doping generally measured for EG. Moreover, charge neutrality was observed in two cases namely, the half-semimetal ferromagnetic configurations of the non-defective and the single-vacancy systems. This result may open new avenues to control the electronic doping of the epitaxial graphene layer via defect engineering. [ABSTRACT FROM AUTHOR]

In terms of aluminum alloy matrix composites, the effect of reinforcement on precipitation is worth investigating. In this work, the silicon carbide nanoparticles-reinforced 7075Al (SiCnp/7075Al) composite was fabricated through a series of powder metallurgy procedures, shift-speed ball milling, hot pressing, and hot extrusion, and the precipitation behavior of SiCnp/7075Al composite was compared with that of 7075Al alloy after T6 treatment. The results show that only a small addition (1 vol%) of SiCnp modifies the morphology and dispersion of precipitates. The uniformly dispersed small precipitates (η′ phase) and increased dislocation density have a positive influence on the mechanical properties of composites. Based on the fracture surface and element composition, a fracture mode dominated by precipitated phase-induced crack initiation was proposed. This study suggests a promising approach to design the alloy matrix composites through controlling the behavior of precipitated phases with nano-reinforcement. [ABSTRACT FROM AUTHOR]

A mullite/Si multilayer coating was deposited on a SiC substrate using atmospheric plasma spraying. Mud cracking of the protective surface mullite layer was examined using a high-temperature observation system (HTOS). In-plane surface strain distributions were also measured using the digital image correlation (DIC) method. The experimental results showed that mud cracks nucleated in the mullite layer during heating, primarily due to shrinkage of the mullite during crystallization. The cracking event was detectable by mapping the maximum principal strain distribution. We clearly demonstrated that HTOS and DIC are effective tools for investigating the degradation mechanisms of thick coatings at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, SiC with the morphologies of both particles and whiskers was grown on graphite surface by chemical vapor reaction method under different pressure conditions. According to these experimental discoveries, designed experiments with different reaction pressures and temperatures were studied in detail, and then, the influence factors were analyzed in theory. The results show that the shapes of the formed SiC are influenced mainly by the total pressure of the system. Higher total pressure is in favor of larger concentration of CO and then tends to form SiC whiskers. In addition, temperature significantly affects the size of SiC, higher temperature results in shorter length and further quantity of the SiC whiskers as well as larger diameter of the SiC particles. Based on these results, controllable synthesis of silicon carbide whiskers and particles can be realized in accordance with the requirements of application. [ABSTRACT FROM AUTHOR]

With the goal of lightweight and strong microwave absorption, polyaniline/aminopropyltriethoxysilane/silicon carbide (PANI/APTES/SiC) nano-composites with hierarchical architecture were fabricated through a facile in situ polymerization method. Herein, the SiC powders were modified with APTES in advance to achieve a more uniform envelope by PANI. The composites with different thicknesses of PANI layer and adjustable dielectric properties can be obtained by altering the PANI ratio. For the optimized sample, the minimum value of reflection loss is − 51.34 dB at 13.92 GHz with a thickness of 1.9 mm and the effective attenuation bandwidth is in a broad range from 12.19 to 17.45 GHz (bandwidth of 5.26 GHz). The outstanding absorption properties are closely related to the suitable impedance matching and the multiple loss mechanisms. [ABSTRACT FROM AUTHOR]

In this study, the thermal oxidation rate of oxygen ion (O+) implanted 4H-silicon carbide (SiC) was investigated. And the critical breakdown electric field (Ebreakdown) and capacitance-voltage (CV) curve of the grown oxide (SiO2) film were also evaluated. It is found that the thermal SiO2 growth rate on 4H-SiC (0001) face was significantly improved by O+ implantation. Ebreakdown test results showed that the unconsumed amorphous and damaged crystalline layer under the grown SiO2 contained defects leading to an inferior critical breakdown field. Thus, in order to obtain a high-quality SiO2 film, the oxidation process should be designed delicately so that the damaged layer by implantation could be fully consumed. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) and its composites are gaining interests because of their high physical and chemical stability, good oxidation and irradiation resistance, and excellent mechanical and thermal behaviors for nuclear cladding applications. In this work, ion irradiation on spark plasma-sintered SiC with and without nanostructured ferritic alloy aid (0 vol% NFA-100 vol% SiC and 2.5 vol% NFA-97.5 vol% SiC) was carried out using 5 MeV Si++ ions at 2.2 × 1018 ions cm−2 fluence and characterized based on scanning electron microscopy and Raman spectroscopy in order to understand their irradiation resistance behaviors. The surfaces of both the 0 vol% NFA-100 vol% SiC and 2.5 vol% NFA-97.5 vol% SiC samples experience a dramatic change with the creation of a well-defined dune pattern, which can be explained based on the Bradley-Harper model. The irradiation-induced damage layer has a consistent thickness and agrees with the result from SRIM simulation. Complete amorphization occurs for the SiC phase, while a crystalline structure is maintained for the Fe3Si phase. Results of the current study have great potential for developing NFA-SiC cladding materials of nuclear reactors. [ABSTRACT FROM AUTHOR]

The oxidation behavior and oxidation mechanisms of monolithic ZrB2 and particulate-ZrB2 matrix composites were reviewed. Dispersion of SiC particles into ZrB2 was found to be an effective way to prevent extensive oxidation. However, the formation of a SiC-depleted layer can become a critical problem because it can lead to spallation and delamination of the protective surface layer. The addition of ZrC in conjunction with rapid heating to temperatures higher than 2000 °C effectively reduced the porosity of the SiC-depleted layer. The formation of a dense surface layer was attributed to large volumetric expansion during the conversion from ZrC to ZrO2. The effect of the ZrC addition depended on the temperature, heating rate, and composition. This review showed that material design for specific applications is required for high-temperature applications to maximize the oxidation resistance of ZSZ composites. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) was pretreated and functionalized by using α, ω-diaminopropyl polydimethylsiloxane (PDMS) to obtain a novel inorganic filler SiC (PDMS). Then, a series of branched sulfonated polyimide/SiC (PDMS) (bSPI/SiC (PDMS)) composite membranes with different contents of SiC (PDMS) were fabricated for vanadium redox flow battery (VRFB) application. Fourier transform infrared spectra, X-ray diffraction, and field emission scanning electron microscope demonstrate the successful preparation of SiC (PDMS) and bSPI/SiC (PDMS) membranes. The thermogravimetric analysis shows that bSPI/SiC (PDMS)-1.5% membrane has better thermal stability than pure bSPI, bSPI/SiC-1.5%, and Nafion 117 membranes. The ex situ chemical stability test results show that bSPI/SiC (PDMS)-0.5-2.5% composite membranes have better chemical stabilities than pure bSPI membrane. The physicochemical properties of bSPI/SiC (PDMS) membranes, including water uptake, swelling ratio, ion exchange capacity are investigated. Thereinto, bSPI/SiC (PDMS)-1.5% membrane has the highest proton selectivity (S: 2.99 × 105 S min cm−3) and was chosen as an optimum VRFB membrane. And the VRFB assembled with bSPI/SiC (PDMS)-1.5% membrane exhibits better battery performance than that assembled with Nafion 117 membrane during 500-time cyclic charge-discharge test at 20-60 mA cm−2. Above results indicate that as-optimized bSPI/SiC (PDMS)-1.5% membrane has great potential for VRFB application. [ABSTRACT FROM AUTHOR]

This work demonstrates the functionalization of SiC with the organosilane 3-mercaptopropyltrimethoxysilane via a wet chemical process. The attachment of the covalently bound organosilane onto SiC was indicated by scanning electron microscopy, water contact angle measurements, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A Si-O-Si bridge was successfully established on the heterogeneous interface, which acts as a fluent carrier transfer channel and can effectively contribute to the quick transfer of photogenerated electrons from the SiC interior to the surface, thus increasing the number of surface active sites and prolonging the charge-carrier lifetime. The photocatalytic H2 production rate under visible light irradiation was improved to 27.5 μmol h−1 g−1, while unmodified SiC resulted in no H2 production under the same conditions. The study definitively shows that the Si-O-Si bridge modelled by organosilanes can directly lead to the observed enhanced rate and pave the way for the heterojunction construction of inorganic and organic materials. [ABSTRACT FROM AUTHOR]

Cordierite-bonded porous SiC ceramics were prepared by air sintering of cordierite sol infiltrated porous powder compacts of SiC with graphite and polymer microbeads as pore-forming agents. The effect of sintering temperature, type of pore former and its morphology on microstructure, mechanical strength, phase composition, porosity and pore size distribution pattern of porous SiC ceramics were investigated. Depending on type and size of pore former, the average pore diameter, porosities and flexural strength of the final ceramics sintered at 1400 °C varied in the range of ~ 7.6 to 10.1 μm, 34-49 vol% and 34-15 MPa, respectively. The strength-porosity relationship was explained by the minimum solid area (MSA) model. After mechanical stress was applied to the porous SiC ceramics, microstructures of fracture surface appeared without affecting dense struts of thickness ~ 2 to 10 μm showing restriction in crack propagation through interfacial zone of SiC particles. The effect of corrosion on oxide bond phases was investigated in strong acid and basic salt medium at 90 °C. The residual mechanical strength, SEM micrographs and EDX analyses were conducted on the corroded samples and explained the corrosion mechanisms. [ABSTRACT FROM AUTHOR]

Silicon carbide ceramics under shock loading is an important aspect in studying their physical and mechanical properties. Molecular dynamics simulations have been carried out using Tersoff-1989, Tersoff-1994, Tersoff-2005 and Vashishta potentials, respectively. The Hugoniot states including compression stress, shear stress, temperature and shock wave velocity are calculated, as well as shockinduced plasticity and the shock wave fronts. A comprehensive comparison among different potentials, as well as comparison to current available experiments, has been made. Tersoff-1989, Tersoff-1994 and Tersoff-2005 potentials are easily to overestimate the shock stress, shear stress and temperature, as well as shock wave velocity, while Vashishta potential shows excellent agreement with experimental data. The Hugoniot elastic limit is ~ 14.5 GPa and the maximum shear stress is ~ 6 GPa using Vashishta potential which are in good agreement with experiments, while Tersoff-like potentials yield much higher values. Due to differences in radial distribution function among these potentials, Vashishta potential is prone to produce plasticity and structural phase transformation basing on the statistics of the coordination numbers of atoms. Besides, the shock wave fronts show little difference among these potentials under elastic shock compression at low particle velocity. However, when it comes to high shock intensity resulting in plasticity or phase transition, the Tersoff-1989 and Tersoff- 1994 produce the widest shock wave fronts, followed by Tersoff-2005, while Vashishta potential has the narrowest wave front. By comprehensive comparisons, the Vashishta potential is demonstrated to be the most suitable one to describe the silicon carbides ceramics under shock loadings. Our work provides useful information to select a suitable potential to study the shock response of silicon carbides ceramics using molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

In this study, highly dense ZrB-20 vol% SiC composites with 3-10 wt% VC additives were prepared by hot-pressing at 1750 °C for 1 h under a pressure of 20 MPa in a vacuum. The densification behavior and elastic and mechanical properties of the obtained composites were examined, and the effect of the VC content on the densification and the properties is analyzed. The addition of VC promotes the activation of densification mechanism at a lower temperature and inhibits the growth of ZrB and SiC grains during the sintering. In addition, the elastic moduli, hardness and fracture toughness that measured in the obtained composites are constant and independent of the VC content, with a shear modulus of ~ 220 GPa, Young's modulus of ~ 500 GPa, hardness of ~ 20 GPa and fracture toughness of ~ 4.4 MPa m. On the other hand, the flexural strength of the composites decreased as the VC content increased from 3 to 7 wt% and then it increased with further increasing the VC content to 10 wt%, with strength values of 620-770 MPa. [ABSTRACT FROM AUTHOR]

Within the context of the design of high-temperature brazing process for C and SiC-based composites, a basic study is presented here about the wetting and interfacial reactivity of Co-Ta alloys in contact with graphite or SiC. Wetting results are presented for the first time showing that Co-Ta alloys wet C or SiC fairly or excellently depending on the relative amount of Ta. The final interfacial microchemistry and microstructures are the result of the interplay between the typical interfacial phenomena of the pure elements. Specifically, depending on the alloy composition, dissolution of the ceramic phase by Co or formation of a continuous interfacial layer of TaC that prevents dissolution prevails. The discussion about the interfacial reactivity between liquid Co-Ta alloys and graphite or SiC, as well as the interpretation of solidification phenomena and the formation of interfacial phases, is supported by making reference to new multi-component phase diagrams calculated by CALPHAD method. [ABSTRACT FROM AUTHOR]

Thermal conductivity of biomorphic SiC/Si, a silicon carbide + silicon containing two phase material, was evaluated using the laser steady-state heat flux method. These materials were processed via silicon melt infiltration of wood-derived carbon scaffolds. In this approach, heat flux was measured through the thickness when one side of the specimen was heated with a 10.6-µm CO laser. A thin mullite layer was applied to the heated surface to ensure absorption and minimize reflection losses, as well as to ensure a consistent emissivity to facilitate radiative loss corrections. The influence of the mullite layer was accounted for in the thermal conductivity calculations. The effect of microstructure and composition (inherited from the wood carbonaceous performs) on measured conductivity was evaluated. To establish a baseline for comparison, a dense, commercially available sintered SiC ceramic was also evaluated. It was observed that at a given temperature, thermal conductivity falls between that of single-crystal silicon and fine-grained polycrystalline SiC and can be rationalized in terms of the SiC volume fraction in biomorphic SiC/Si material. [ABSTRACT FROM AUTHOR]

We developed a new in situ reaction method to synthesize SiC and SiN ceramic solids from meltable precursor compositions into shaped ceramic composites with nanocrystalline grains. The process uses Si powder and 1,2,4,5-tetrakis(phenylethynyl)benzene, which readily react above 1400 °C to form the SiC and SiN crystallites in the presence of argon and nitrogen, respectively. X-ray diffraction analysis, Raman spectroscopy and density measurements indicated the formation of near stoichiometric SiC and SiN within the shaped solid. Further characterization of electrical conductivity and oxidative stability of the prepared ceramics analyzed the influence of nanoscale features on intrinsic properties of resulting composites. The hardness and elastic modulus values for the synthesized SiC determined by nanoindentation varied in the range of 25-46 GPa and 300-440 GPa. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Carbon nanotube-reinforced silicon carbide composites (CNT/SiC) produced by direct infiltration of matrix into a porous CNT arrays have been demonstrated to possess a unique microstructure and excellent micromechanical properties. However, the thickness of the array preforms is usually very small, typically less than 2 mm. Therefore, fabrication of macroscopic centimeter-scale CNT/SiC composites by chemical vapor infiltration (CVI) process requires that the nanoscale fillers could form macroscopic architectures with an open pore network. Direct infiltration of matrix into porous CNT sponges consisting of a three-dimensional nanotube scaffold may provide a possible solution to this challenge. Here, the study reports on the fabrication of CNT/SiC composites by CVI of SiC matrix into the open pore network of CNT sponges while maintaining the original CNT network. The unique microstructure, mechanical properties, electrical conductivity, and electromagnetic shielding effectiveness of the resultant composites were systematically investigated. Energy dissipation toughening mechanism at the nanoscale such as CNT pullout is observed, and the phase composition of the fabricated materials includes β-SiC and CNTs. [ABSTRACT FROM AUTHOR]

Samples of crystal modifications of porous silicon carbide were obtained by carbothermal method using carbon precursors (sucrose, carbon) and aerosil or mesoporous silicas molecular sieves SBA-3, SBA-15, KIT-6, and MCF as silicon sources. Porous β-SiC samples obtained from carbon-silica composites are characterized by high structural and sorption characteristics ( S up to 410 m/g, V up to 1.0 cm/g). High hydrogen adsorption capacity of silicon carbide samples based on KIT-6 (up to 1.24 wt% at 77 K and 1 atm.), considering low adsorption energy ( $$ \left| {\Delta \mu_{0} } \right|_{{{\text{H}}_{2} }} $$ ) up to 2.3 kJ/mol for SiC vs. ca. 5.0 kJ/mol for carbon), was determined. The highest ever reported value among the existing porous materials was observed for specific adsorption of H by SiC (specific adsorption on the pore surface, ρ up to 15 μmol/m) corresponding to almost complete filling of the surface with hydrogen in the examined conditions (77 K, 1 atm.). [ABSTRACT FROM AUTHOR]

The elastic modulus and hardness of different silicon carbide (SiC) coatings in tristructural-isotropic (TRISO) fuel particles were measured by in situ high temperature nanoindentation up to 500 °C. Three samples fabricated by different research institutions were compared. Due to varied fabrication parameters the samples exhibited different grain sizes and one contained some visible porosity. However, irrespective of the microstructural features in each case the hardness was found to be very similar in the three coatings around 35 GPa at room temperature. Compared with the significantly coarser grained bulk CVD SiC, the drop in hardness with temperature was less pronounced for TRISO particles, suggesting that the presence of grain boundaries impeded plastic deformation. The elastic modulus differed for the three TRISO coatings with room temperature values ranging from 340 to 400 GPa. With increasing measurement temperature the elastic modulus showed a continuous decrease. [ABSTRACT FROM AUTHOR]

Vitrified bonded SiC composite ceramics were prepared using a simple powder blending, forming, and sintering process. The effect of SiC particle size on the mechanical and dielectric properties of vitrified bonded SiC composite ceramics was investigated. Vitrified bonds wet and coat SiC particles during sintering and form continuous bonding networks upon cooling. The vitrified bonds render the ceramics high flexural strength and act as impedance mismatching modification layer between SiC particles and air. With varying SiC particle size, the microstructure, and properties of the vitrified bonded SiC composite ceramics change accordingly and at 7 μm, it reaches optimal microstructure, a highest flexural strength of 67.85 MPa and highest reflection loss. However, the dielectric loss of composite ceramics decreases as the SiC particle size increases. [ABSTRACT FROM AUTHOR]

Herein, we studied the structure and hydrogenation of graphene supported on hydrogen-terminated SiC, with intercalated Li atoms. Strong nonbonded interactions occur between graphene and the Si-H groups. The latter were found to be significantly augmented by the intercalation of Li atoms, which enhanced the SiH::pi interactions. Although the electronic structure of graphene did not experience significant changes when supported on hydrogen-terminated SiC, a small gap of 0.04 eV was computed at the HSEH1PBE/6-31G* level. The clustering of Li atoms over graphene was prevented by the SiC support. A significant enhancement of reactivity could be corroborated due to the presence of intercalated Li atoms, given that the C-H binding energy was increased by almost 1 eV with respect to pristine graphene. We expect that hydrogen-terminated SiC with intercalated Li atoms can be used to enhance the chemical reactivity of graphene, given that it strongly interacts with graphene but does not compete for the electrons donated by Li. [ABSTRACT FROM AUTHOR]

There have been increasing needs for high-thermal stability and high-electrical conductivity materials. In this study, we in situ synthesized silicon oxycarbide (SiOC)-TiCO composites based on the pyrolysis of polysiloxane and carbothermal reaction between TiO nanoparticles and free carbon in SiOC. The TiO to TiCO conversion is dependent on the pyrolysis temperature. Higher pyrolysis temperature leads to more TiC formation but lower thermal stability. With more homogeneous distribution of TiO, the thermal stability of the SiOC-TiCO composite increases. This family of SiOC composite also demonstrates high electrical conductivity. The highest electrical conductivity is 5.03 S cm at 400 °C measurement temperature, the highest for air atmosphere condition. The key issue for tuning the SiOC-TiCO system for both thermal stability and electrical conductivity is to avoid the destabilization of the SiOC system. [ABSTRACT FROM AUTHOR]

The presented article describes a simple technique to fabricate open/closed cell silicon carbide (SiC) foams. The SiC foams, especially pyrolyzed either at 1200 °C ( PSiC_12) or 1500 °C ( PSiC_15), offered the best thermophysical properties suitable for advance thermal management systems. Both PSiC_12 and PSiC_15 possessed almost equal concentrations of open and closed pores (~22-24 vol%). On the contrary, the 1800 °C-pyrolyzed specimen ( PSiC_18) had 40 vol% open pores and only ~9 vol% closed pores. X-ray Micro-CT observation also revealed that the PSiC_15 had significant concentration of closed pores having pore volume in the range of (2-20) × 10 mm. While PSiC_15 contained small β-SiC crystallites of ~13-nm size, PSiC_18 possessed ~55 nm crystallites of α-SiC. From room temperature to 1000 °C, thermal conductivity values of PSiC_12 and PSiC_15 varied from 0.5 to 1.6 W/m K. Both these specimens also offered outstanding oxidation resistance at 1000 and 1500 °C for up to 100 h. Extremely low thermal conductivity, the presence of closed pores that restricted inward diffusion of oxygen even at the elevated temperatures, and the formation of impervious oxide scale at the initial oxidation stage were the key factors behind obtaining such excellent oxidation resistance. On the contrary, due to the presence of much higher channel pores and relatively higher thermal conductivity (~3 W/m K), oxidation of PSiC_18 was found to be much exaggerated resulting in a few orders of magnitude higher oxidation weight gain compared to those obtained for PSiC_12 and PSiC_15. [ABSTRACT FROM AUTHOR]

Coating with silicon carbide is a preferred avenue for improving the oxidation resistance of carbon nanotubes. However, expensive and non-scalable techniques like vapor deposition are commonly used to develop such coatings. Against this backdrop, reported here is a facile, cost-effective and low temperature route, based on wet-chemical synthesis, for obtaining SiC-based coating on multi-walled carbon nanotubes (MWCNTs). The coating was achieved by dispersing surface-modified MWCNTs in silica sol (having optimized viscosity), followed by simultaneous reduction and 'carburization' of the silica (wetting MWCNTs) in the presence of Mg at 600 °C. X-ray diffraction and RAMAN spectroscopy confirmed the presence of β-SiC, while TEM observations revealed the development of uniform and thin coating (~3 nm thick) on undamaged MWCNTs. Thermo-gravimetric and differential thermal analyses up to 1500 °C in air confirmed significant improvement in oxidation resistance for the MWCNTs with SiC-based coating (just ~15 % mass loss; as against rapid mass loss of ~100 % for uncoated MWCNTs due to oxidation). Additionally, undamaged MWCNTs (with SiC-based coating) could be imaged in TEM after exposure in air at 1200 °C for longer duration. [ABSTRACT FROM AUTHOR]

In reference to the crack deflection ability of multi-layered keratin and the fibers reinforcement of the dorsal cortex in the turtle shell carapace, a bio-inspired composite of Ti-intermetallic multi-layered/SiC-reinforced Ti matrix was successfully fabricated through vacuum hot-pressing sintering using pure titanium foils, pure aluminum foils and continuous SiC ceramic fibers. Our observation reveals that Ti-intermetallic multi-layers were well bonded to each other with the formation of in situ TiAl, TiAl, TiAl and TiAl phases between Ti layers. At the same time, SiC fibers were firmly bonded to the Ti matrix through a circular joining of TiC achieved by the reaction between the deposited coating of C and the Ti matrix. Due to the strengthen effect of continuous-SiC-reinforced Ti-matrix part, the tensile and the flexural strengths of the hybrid composite along the longitudinal direction of the fibers were about 636 ± 40 and 889 ± 50 MPa (Ti-intermetallic multi-layered part stressed in tension) or 984 ± 50 MPa (continuous-SiC-reinforced Ti-matrix part stressed in tension), respectively. These values were much higher than those obtained from Ti-intermetallic multi-layered composite, corresponding to 404 ± 30 and 462 ± 30 MPa. In addition, the Ti-intermetallic multi-layered composite showed higher fracture toughness value (34.7 ± 1.2 MPa m) than that of continuous-SiC-reinforced Ti-matrix composite (24.8 ± 0.1 MPa m). In drop hammer impact test, the hybrid composite exhibited better crack resistance and higher absorb energy when the U notch was in Ti-intermetallic multi-layered side, other than U notch in continuous-SiC-reinforced Ti-matrix part. Herein, it is deduced that the hybrid composite combines the crack deflection ability of Ti-intermetallic multi-layered structure and strengthen effect of continuous SiC fibers. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotube (MWCNT)/silicon carbide (SiC) composites were fabricated by spark plasma sintering at 2000 °C under 50 MPa for 10 min in Argon. Physical properties and Williamson- Hall analyses of X-ray diffraction patterns indicated strong influence of CNT on densification, crystallite size, and lattice micro-strain of pure SiC. Structural retention of CNTs, CNT/SiC interactions, and formation of 3-4 nm thick interface in sintered composites were confirmed through electron microscopy. Meyer's exponent (1.84-1.89) of hardness data indicated almost similar indentation size effect in the studied specimens. Modified proportional specimen resistance model revealed formation of compressive surface residual stress and enhanced elastic response in CNT/SiC composites compared to pure SiC. R-curve sensitivity of present composites (toughening exponent, n ranged from 0.231 to 0.247) was found to be much improved than that obtained for pure SiC ( n = 0.155). The 0.3 wt% MWCNT/SiC composite offered the highest toughness (3.93-5.56 MPa-m) within the investigated loading range which was 17-31 % higher than those of monolithic SiC. Present composites also offered much better wear resistance up to 20 N. Wear rate of 0.1 wt% CNT/SiC composite was found to be more than 47 % lower than that obtained for pure SiC. At the highest CNT loading i.e., 1.2 wt%, composite also showed 10-12 % reduction in friction coefficient ( μ) over monolithic SiC ( μ = 0.53-0.58) due to the self-lubrication ability of CNT. [ABSTRACT FROM AUTHOR]

For cost reduction and process simplification, a homogenous liquid precursor for zirconium carbide (ZrC)-SiC ceramics was prepared by blending Zr(OCH), divinylbenzene, and polycarbosilane (PCS). The mixture was cross-linked at 150 °C, decomposed to ZrO, carbon, and SiC at 800 °C, and then ZrO and carbon reacted with each other via carbo-thermal reaction at 1500 °C to form ZrC-SiC ceramics that contained few ZrO. The ZrO content was reduced either by increasing the temperature from 1500 to 1700 °C, or by extending the holding time from 1 to 2 h. Increasing the content of PCS in the precursor not only benefited the carbo-thermal reaction but also caused the generation of free carbon in the pyrolyzed ceramic products. When the precursor contained the optimal content of PCS, the ceramics fabricated from it had a Si/Zr molar ratio of 1. C/ZrC-SiC composites were successfully fabricated via precursor infiltration and pyrolysis using the precursor. The flexural strength and fracture toughness of the composites were 212 ± 44 MPa and 13.8 ± 1.6 MPa m, respectively. [ABSTRACT FROM AUTHOR]

Intermetallic compound ZnSb is a promising thermoelectric (TE) material with the advantages of low toxicity, abundance, and low cost; however, the relatively low figure of merit ZT and the brittleness of ZnSb limit its applications in TE devices. In this study, ZnSb/SiC nanocomposites were synthesized in order to improve both the TE and mechanical properties of ZnSb. ZnSb-based nanocomposites with x vol% SiC nanoparticles ( x = 0, 0.3, 0.5, and 0.7) were prepared by mechanical alloying and spark plasma sintering. The power factor of ZnSb/SiC nanocomposite with 0.3 vol% SiC is increased. The thermal conductivity of all ZnSb/SiC nanocomposites is decreased due to the increase of interface scattering for phonons. More importantly, the fracture toughness of the nanocomposites is enhanced due to the addition of SiC. The largest ZT value and fracture toughness are found in the sample with 0.7 vol% SiC. The maximum ZT value of 0.68 is obtained at 400 °C, which is 35 % higher than that of the reference sample without SiC. The largest fracture toughness is 0.64 MPa m, which is 31 % larger than that of the reference sample. The experimental data demonstrate that ZnSb/SiC nanocomposites with simultaneous enhancement of TE and mechanical properties are favorable for practical TE applications. [ABSTRACT FROM AUTHOR]

A novel porous filter material was fabricated by element reactive synthesis method. The synthesized porous TiSiC membrane material presents a microstructure of both large substrate pores and small membrane pores, indicating large filtration flux and high filtration accuracy simultaneously. Microorganism filtration properties of the porous TiSiC membrane material were investigated by filtering the Escherichia coli suspension, which demonstrates excellent performance of the porous materials on filtration. [ABSTRACT FROM AUTHOR]

The formation of silicon by reaction between quartz and SiC has been studied in the temperature range of 1600-1900 °C in argon and hydrogen atmospheres. The reaction process was monitored by an infrared gas analyzer, and the reaction products were characterized by LECO, XRD, and SEM. Quartz-SiC reactions with SiO/SiC molar ratio of 1:1 and 1:2 were studied in a fixed bed reactor in a graphite furnace. The production of silicon from quartz and SiC was strongly affected by temperature, SiO/SiC molar ratio, and gas atmosphere. The yield of silicon in the reaction at 1900 °C in argon from samples with SiO/SiC molar ratios of 1:1 and 1:2 reached 32.7 and 44.5 %, respectively. SiO-SiC reaction at 1900 °C in hydrogen with the SiO/SiC molar ratio of 1:2 resulted in the silicon yield of 66.7 %. Higher silicon yield in hydrogen was attributed for the involvement of hydrogen in the direct reduction of silica to SiO. [ABSTRACT FROM AUTHOR]

A range of SiC-BC composites have been prepared by pressureless sintering, using different proportions of two sizes of BC; 7 and 70 μm. The interfacial area between the BC and SiC has been quantified and is shown to have a significant effect on both densification and the resultant microstructure of the composites. SiC/BC interfaces typically hinder densification. SiC/BC interfacial area is also shown to be related to grain growth and polytype distribution in the SiC. With more SiC/BC interfacial area, grain growth in the SiC is restricted and less of the SiC transforms from the starting 6H polytype to the 4H one. It is therefore suggested that it may be possible to use SiC/BC interfacial area as a means by which to engineering the microstructure. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) has excellent physical and electrical properties with potential for nuclear applications and power semiconductors. The properties of SiC, however, have not been fully determined. One property in question is the critical resolved shear stress (CRSS) for slip at room temperature. Here we evaluated the CRSS of 6H-SiC using micro-compression tests. Single-crystalline micro-pillars were fabricated on the surface of a 6H-SiC(0001) wafer. Brittle fracture occurred in all the fabricated micro-pillars. The compressive fracture strength of the material was determined to be near 24 GPa. Micro-pillars were also fabricated on a tilted specimen, to facilitate slip on the basal plane of hexagonal close-packed structure. Plastic deformation was observed in micro-pillars below 0.49 μm in diameter. Cross-sectional TEM observation of the compressed micro-pillars showed clear slip traces and dislocations on the basal {0001} planes. The CRSS of 6H-SiC was determined to be 9.8 ± 0.69 GPa from the measured stress-strain curves and the sample geometry. The CRSS evaluated here was compared with that determined from first-principle calculations reported in the literature. [ABSTRACT FROM AUTHOR]

Fatigue behavior of Sylramic-iBN/BN/CVI SiC CMC was investigated under tension-tension fatigue using a test facility which simulated simultaneously both loading and combustion conditions of hot-section components of gas turbine engines. Combustion environment was created using a high-velocity oxygen fuel gun to impinge combustion flame on one side of specimen subjected to fatigue to simulate the real situation. The flame-impinged surface of specimen was heated to average temperature of 1250, 1350, or 1480 °C. Ultimate tensile strength of CMC was about 270 MPa at 1480 °C under combustion environment. Fatigue life diagram was established at stress ratio of 0.1 and frequency of 1 Hz. The CMC survived up to 25 h at 46 and 33 % of ultimate tensile strength under combustion at 1250 and 1350 °C, respectively. However, it could not survive 25 h at 1480 °C under combustion fatigue environment even with no stress on the specimen due to degradation/erosion of the material. Microscopic analysis of fracture surface showed oxidation of BN interface, which was more on flame side than other side. Fracture surfaces showed oxide formation over matrix, fibers, and/or fiber/matrix interphase causing embrittlement and thereafter failure of CMC. [ABSTRACT FROM AUTHOR]

Silicon carbide is used for a variety of applications, however, sintering still remains a challenge due to the high temperature and pressure required as well as the need for sintering aids. The use of preceramic polymers as binder is a promising technique for pressureless low-temperature sintering of SiC without sintering aids. However, the mechanical and thermophysical properties as well as the microstructure of bodies sintered through this technique has not been extensively documented. One of the main polymers which has gained attention in the past few years as a SiC preceramic is allylhydridopolycarbosilane (AHPCS). Here, using AHPCS as binder, silicon carbide pellets were sintered at temperatures as low as 930 °C, and the microstructural, mechanical, and thermophysical property characterization is presented. Compared to conventionally sintered SiC, the material shows similar fracture toughness, lower hardness, strength, and thermal conductivity. The observed properties are explained as a result of residual porosity combined with amorphous SiC at the grain boundaries. [ABSTRACT FROM AUTHOR]

A new procedure for filamentary metal matrix composite processing is described here. It consists in running carbon-coated SiC filaments through a liquid titanium bath in levitation. The liquid metal/carbon interaction must be significant enough to enable filament wetting and sufficiently low to avoid composite embrittlement. To insure both requirements, different configurations of the initial ceramic filament can be used: (1) SiC(C) filament free of any other coating, (2) SiC(C) filament coated with a carbide obtained by reactive chemical vapour deposition (R-CVD), or (3) SiC(C) previously coated by a first metal layer. In order to choose the best conditions for developing the process, the different processing configurations were studied through modelling and numerical simulations of the filament/matrix interaction. The microstructure of the interfacial zone between filament and matrix was investigated through SEM and Auger electron spectroscopy (AES) analyses. The microstructure of the interfacial zone between filament and matrix was investigated through SEM and AES analyses. The results show that in comparison to the first processing configuration, the best way to obtain filamentary composite semi-products without excessive fibre/matrix interaction is to use the second configuration. However, the latter requires preliminary R-CVD operations, while the third configuration leads to moderate carbon embrittlement effect without requiring additional equipment. [ABSTRACT FROM AUTHOR]

Tension-tension fatigue behavior of two ceramic matrix composites (CMCs), SiC/SiC (Nicalon™/SiC) & oxide/oxide (Nextel™720/AS), and a superalloy (René 41) was characterized under combustion environment as well as under alternate salt-fog exposure for 4 h and combustion fatigue for 6 h. The run-out limit was 25 h (90,000 cycles) of fatigue. Test temperatures were 900, 1050, and 1050 °C for René 41, SiC/SiC, and oxide/oxide CMCs, respectively, and the applied maximum fatigue stress was 62 MPa. All three materials survived up to 25 h under combustion fatigue without any exposure to salt. René 41 and Nicalon™/SiC survived up to 25 h (90,000 cycles) under the alternate exposure of salt-fog and combustion fatigue. However, exposure to salt-fog exposure (5 wt%) had very detrimental effect on the combustion fatigue resistance of Nextel™720/AS. The reduction in salt concentration to 0.5 wt% had less detrimental effect. These tests were supplemented with more tests, where applied stress level, test temperature, and salt concentration were changed. Out of these three gas turbine engine materials, Nicalon™/SiC exhibited better fatigue performance in terms of applied temperature and stress level under combustion condition as well as when exposed to alternate salt-fog and combustion. [ABSTRACT FROM AUTHOR]

The complex nature of damage in ceramic matrix composites (CMCs) renders conventional methods of measuring quantitative fracture properties impractical. This paper is the first of two-part series that assesses the feasibility of using the J-integral with full-field deformation data from digital image correlation (DIC) to characterize toughness in continuous fiber SiC/SiC CMC laminates. It provides a resource for best practices when incorporating experimentally measured, full-field deformation data into J-integral evaluations of toughness. The techniques discussed are important for researchers attempting to measure fracture properties in advanced materials with damage mechanisms that have yet to be well characterized. Two methods for evaluating potential energy release rates J are presented: (1) numerical integration over a line contour and (2) Gaussian integration over an area contour. Accuracy and path independency for both methods were verified using analytically derived deformation fields for a center-cracked, infinite plate of isotropic material under equi-biaxial tension. Inherent noise in the deformation data and necessary contour truncation at the crack surfaces reduced accuracy and introduced path dependency. However, this was mitigated by careful noise filtering of the deformation data prior to the evaluation of J. Applying the line and area integrals to DIC data from tapered, double-cantilever beam, acrylic compact tension specimens resulted in the findings that (1) both integrals measured fracture toughness within a range of published values; (2) both integrals captured the constant stress intensity factor behavior that is characteristic of the tapered beam geometry; and (3) the area integral measurements were consistently larger than line integral measurements. The area integral is more accurate than the line integral as it samples more data points, reducing its sensitivity to experimental noise. Although variability in experimental data can be minimized, it cannot be eliminated. Measurement error is inevitable; thus, the line and area integrals must be used with caution when characterizing quantitative properties including fracture toughness. [ABSTRACT FROM AUTHOR]

This paper is the second of a two-part series assessing the feasibility of using the J-integral with full-field deformation data from digital image correlation (DIC) to characterize toughness in continuous fiber, SiC/SiC ceramic matrix composites (CMCs). In part I, line and area integral adaptations of the J-integral were validated with analytical and experimental deformation fields. It was found that variability in experimental data and contour truncation at the crack wake introduced error and path-dependency, but this could be mitigated through data filtering. In this paper, the line and area integral methods were evaluated for cross-ply and longitudinal CMC tensile specimens. It is demonstrated that these approaches cannot be used for quantitative characterization, but can be successfully used to examine qualitative trends. For both architectures, area integral measurements of the potential energy release rate, J, were larger (and arguably more accurate) than line integral measurements. Resistance curves were characteristic of tough materials, but the stress intensity magnitudes were larger in the longitudinal laminates than the cross-ply (for equivalent crack extension). Experimentally derived bridging laws showed that fiber bridging tractions were largest in the cross-ply laminates, which was attributed to a lower volume fraction of longitudinal fibers. Quantitative, single-value measurements of fracture toughness could not be established since (1) noise in the DIC data masked strain signals indicative of first matrix cracking, and (2) widespread matrix cracking rendered the J-integral invalid (regardless of size and position, the boundaries of the line and area contours inevitably intercepted microcracks). Rather, gross estimates of toughness and stress intensity factors were made under the assumption that the limitations in the spatial resolution of the DIC data essentially transforms regions with fine microcracking along the contour into continuous regions of elastic deformation. When evaluated with the J-integral, the smoothed deformation fields manifest as resistance curves indicative of a tough material. Thus, the J-integral was valuable for qualitative assessments of toughening mechanisms in the CMCs. [ABSTRACT FROM AUTHOR]

For thermoelectric generators, the individual thermoelectric elements are subjected to significant stresses under in-service conditions, due to thermal cycles, transients, and gradients, as well as thermal expansion mismatch and externally applied mechanical stresses. Most thermoelectric materials are brittle, possessing a low fracture toughness that is typically no more than 1.5 MPa m and is often less than 0.5 MPa m. The combination of the stresses encountered in the device application environment and the materials' low fracture toughness constitute a severe challenge to the viability of thermoelectric generators. The addition of silicon carbide nanoparticles (SiC) may provide a route to improving the fracture toughness for a wide range of thermoelectric materials. This study examines the mechanical properties, including elastic modulus, hardness, and fracture toughness for 0-4 vol% SiC incorporated into MgSi thermoelectric matrices. [ABSTRACT FROM AUTHOR]

Binary SiC-TiO ceramic composite was fabricated using reaction pressureless sintering at temperatures ranging from 1825 to 1900 °C. The raw materials for the reaction process were TiO and carbon powders, where yttria (YO) and alumina (AlO) were used as sintering aids. The SiC grain size and morphology were analyzed as a function of TiC volume fraction. The presence of TiC particles in the SiC matrix inhibited the exaggerated grain growth of the SiC grains and activated additional mass transport mechanisms. The SiC grains were found to be roughly equiaxed with very fine TiC particles preventing significant elongation. The role the TiC particles play in the densification of SiC was also discussed. [ABSTRACT FROM AUTHOR]

A silicon- and zirconium-containing polymer precursor (PSZC) for SiC-ZrC-C ceramic was successfully synthesized by chemical reaction of phenol, paraformaldehyde, tetraethoxysilane, acetylacetone, and ZrOCl·8HO. The chemical structure, pyrolysis behaviors, and pyrolysis products of PSZC were characterized by the combination of FT-IR, H-NMR, TG-DTG, XRD, Raman, SEM, and EDS. It indicates that the obtained PSZC might be Zr-O-Zr and Si-O-Si chain polymer connected by Si-O-Zr bond with hydroxymethyl phenol and acetylacetone as ligands. And the most probable reaction mechanism to form PSZC was proposed. Decomposition of PSZC is completed at 800 °C, and it gives amorphous carbon, SiO, and ZrO with a yield of 70 %. During heat treatment, SiC forms at about 1500 °C, followed by the appearance of ZrC. Defects of the carbon are cumulated to the highest at 1500 °C. Further heating at 1800 °C induces highly crystallized ZrC, SiC ceramic, and structure-ordered carbon with a structure of ZrC and SiC particles uniformly distributed in the carbon matrix. [ABSTRACT FROM AUTHOR]

High-porous SiC ceramics (density 0.50-0.58 g/cm, porosity 82-84 %, compressive stress at break 3.7-6.3 MPa) was prepared by means of polymeric technology and natural raw material (diatomite powder, 'Biosilica' grade) at the temperature of carbothermal synthesis (1400 °C). It was shown that the main phase was silicon carbide with a small (<5 %) impurity of FeSi; SiC crystallite size was found to be 23-30 nm. Using scanning electron microscopy, X-ray computerized microtomography, and dynamic light scattering in aqueous suspensions of powders obtained at ultrasonic exposure, it was shown that SiC nanoparticles in the samples were aggregated to a great extent. The degree of aggregation strongly depends on SiO-C ratio in the starting samples. [ABSTRACT FROM AUTHOR]

This article describes the strength behavior of C/SiC composites under non-stress oxidation. The oxidation kinetics model of a ceramic matrix composite contains both a reaction-controlled process and a diffusion-controlled process. The oxidation process has an effect on the fiber volume fraction, radius, and the composite interface shear stress. We obtained the residual strength of unidirectional C/SiC composites under 400-900 °C oxidation with non-stress environments by combining the mass loss rate model with the strength failure model at room temperature. This model considers the different components of the system to be subject to oxidation at different temperature ranges. Then, the influence of oxidation temperature, oxidation time, and fiber volume fraction on residual strength was studied. Experiments on C/SiC composites at 650 and 800 °C in an air environment with non-stress conditions were then performed, and the theoretical results of C/SiC composites were in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]