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The hierarchical SiOC/SiCnws/CF composites (A/B/C structure) were designed via precursor infiltration and pyrolysis process. The SiOC ceramics served as the wave‐transparent characteristic materials to adjust the impedance matching. Herein, the in situ growth of SiCnws not only was used for the absorber but served as the reinforcement of SiOC matrix composites. In detail, the SiOC/SiCnws/CF‐1200°C‐2 exhibits excellent electromagnetic absorption performance with minimum reflection loss of −46 dB at 14.4 GHz with the thickness of 1.6 mm, and its effective absorption band reaches 4.3 GHz. Its compressive strength reaches 8.69 and 16.41 MPa in z and x/y directions, separately. This contribution has a guidance for the application of carbon fiber/ceramics matrix composites in harsh environment. [ABSTRACT FROM AUTHOR]

The interfacial structure between the inorganic filler and epoxy resin matrix in epoxy resin (EP) composites has a great influence on the mechanical properties, thermal conductivity, and electrical properties. In this paper, two micro@nanostructured Al2O3 fillers and their epoxy resin composites were prepared, and their morphology, interfacial bond strength, mechanical properties, thermal conductivity, and electrical properties systematically tested and analyzed. The experimental results show that modification by a nano-Al2O3 coating on the surface of micro-Al2O3 can effectively improve the infiltration of Al2O3 filler and epoxy resin, reduce the interfacial defects caused by weak bonding of Al2O3 filler and epoxy resin, and thus synergistically improve the mechanical properties, thermal conductivity, and electrical properties of epoxy resin composites. The thermal conductivity was improved by 22.5% compared with 22.65% when using micro-Al2O3/EP, the tensile and flexural strength were improved by 36.67% and 20.82%, and the alternating-current breakdown strength was improved by 12.88%. In addition, thermally stimulated current experiments were carried out to study the electron transport properties of micro@nano-Al2O3 epoxy resin composites, revealing that filler nanomodification could improve the trap depth, suppress the carrier transport, and improve the dielectric properties of the composites. [ABSTRACT FROM AUTHOR]

3D-carbon fiber felts reinforced ceramic-based composites are considered as valuable structural materials due to their excellent high-temperature mechanical performance, low density and low thermal conductivity. In order to enhance the mechanical properties of the carbon fiber reinforced silicon oxycarbide (SiOC) ceramics, in-situ growth of SiCnws on the surface of carbon fiber via a simple precursor impregnation and pyrolysis method was proposed. As a result, nanoscale SiC nanowires and microscale carbon fiber felts reinforced SiOC ceramics were successfully fabricated. The results showed that the compressive strength of the composite increased by 369% and 173% after two PIP process in x/y and z directions, respectively. The enhanced compressive strength could be ascribed to the brittle fracture of SiCnws and CFs, and crack deflection. [ABSTRACT FROM AUTHOR]

Herein, the SiC‐coated carbon fiber decorated with SiC nanowire (SiCnw/CF) composites are successfully prepared by one‐step chemical vapor infiltration (CVI) process. Microstructures, the formation mechanism of SiCnws, thermal stability performance, and electromagnetic wave (EMW) absorption performance of the composites are investigated in detail. In particularly, benefiting the dielectric loss and conductive loss, the SiCnw/CF composites obtained at 1500 °C exhibit superior EMW absorption property with the minimum reflection loss (RL) of −36.5 dB with the effective absorption band of 5.5 GHz at a thickness of 1.88 mm. This work provides a simple way to obtain and design the CF‐based materials with good microwave absorption. [ABSTRACT FROM AUTHOR]

To enhance the oxidation resistance capability of the carbon‐bonded carbon fiber composites (CBCFs), a silicide ultra‐thick coating as high as 1.6 mm with gradient structure is designed and fabricated via a multi‐step rapid sintering method. Compared with other ceramic layers on carbon fiber‐based composites, ultra‐thick anti‐oxidation layer coated‐CBCFs have the lowest thermal conductivity. Additionally, ablation behaviors of the ultra‐thick ceramics layer coated‐CBCFs under the oxyacetylene torch are also investigated. After being exposed to oxyacetylene torch, the ultra‐thick ceramics layer coated‐CBCFs possess a linear rate range from 0.6 to 1.2 μm/s, while a mass ablation rate ranges from 4.95 × 10−5 g/m2 s to 1.45 × 10−3 g/m2 s. [ABSTRACT FROM AUTHOR]

The most recent and innovative metal disilicide-based hybrid coatings are used for protecting carbon fiber-based composites in aerospace application. Here, we investigate a high emissivity coating on SiOC-modified carbon-bonded carbon fiber composites (SiOC/CBCF) for thermal protection material. Both tantalum silicide (TaSi 2 ) and molybdenum silicide (MoSi 2 )-based coatings are prepared on SiOC/CBCF composites using flash sintering method, and the emissivity value of MoSi 2 -based coating is higher than that of TaSi 2 -based coating. Significantly, improvement the density of the coating has a positive role on emissivity resulting in MoSi 2 -based coating increases about 7.2% at 400 °C and 11.5% at 1000 °C, respectively; TaSi 2 -based coating increases about 15.4% at 400 °C and 2.6% at 1000 °C. After exposure to 1500 °C for 60 min in air, the emissivity values of the coated-samples are also investigated. [ABSTRACT FROM AUTHOR]

Carbon-bonded carbon fiber (CBCF) composites are novel and important high-temperature insulation materials owing to their light weight, low thermal conductivity and high fracture tolerance. To further improve the mechanical property of CBCF composite, we propose a three-dimensional (3D) SiC nanowires structure, which is in situ grown on a CBCF matrix via directly annealing silicon oxycarbide (SiOC) ceramic precursor. The synthesized multiscale reinforcements including microscale SiOC ceramics and nanoscale SiC nanowires are mainly attributed to the initial phase separation of SiOC phase and subsequent solid-phase reaction of SiO and C phases. Compared to SiOC/CBCF composite, the resulting 3D SiC nanowires/SiOC/CBCF hybrid structure exhibited high flexural/tensile strength and fractured strain due to the pull-out and bridging behavior of SiC nanowires. This one-step process supplied a feasible way to synthesize 3D SiC nanowires to reinforce and toughen SiOC-modified CBCF composite. [ABSTRACT FROM AUTHOR]

Novel hybrid thermal protection material (TPM), consisting of TaSi 2 -based coating on carbon-bonded fiber (CBCF) composites and mullite fiber insulation tiles, is investigated using a plasma wind tunnel. Mullite fiber insulation tile is ceramically bonded to coated-CBCF composites. Results show that surface temperatures range from 400 °C°C to 1200 °C°C at low heat flux and dynamic pressure. However, at high heat flux and dynamic pressure, the surface temperature rapidly reaches 1400 °C°C, and the damage to the TaSi 2 -based coating is also observed. The cold-wall temperature of the hybrid structure remains at room temperature during ablation. In addition, TPM is invalid because of the consumption of the TaSi 2 -based coating. [ABSTRACT FROM AUTHOR]

This paper presents a double-layered coating system consisting of MoSi 2 ceramic reinforced with SiC whiskers and a MoSi 2 -TaSi 2 ceramic coating reinforced with SiC whiskers. This system improves oxidation resistance of carbon-bonded carbon fiber (CBCF) composites. Double-layer coating was about 160 µm in thickness and no interfaces or cracks between the layer and matrix were observed. Isothermal oxidation tests revealed that as-prepared coating presented excellent oxidation resistance, which could protect CBCF composites at 1500 °C for 160 min with 0.02% weight loss, whereas weight loss of single MoSi 2 ceramic coating reinforced with SiC whiskers reached 0.08%. High-temperature resistance barrier of the glassy phase and Ta 2 O 5 had a positive effect on improving the oxidation resistance of double-layer coating. [ABSTRACT FROM AUTHOR]

Silicon-carbide nanowires (SiCnws) have been considered as dielectric loss materials for application in the field of electromagnetic wave (EMW) attenuation. In this study, SiCnws/carbon fiber (CF) composites were fabricated using precursor infiltration and pyrolysis process for the in-situ growth of SiCnws. The SiCnw fraction of the SiCnws/CF composites could be adjusted using various catalysts. At a small SiCnw fraction (38 wt%), the composites exhibited excellent EMW absorption performance with the minimum reflection loss of − 18.3 dB when their thickness was only 1.2 mm and can cover the entire X and Ku bands by adjusting the material thickness. They transformed from EMW absorption performance to electromagnetic interference (EMI) shielding property with the increase in SiCnw fraction from 38 wt% to 73 wt%, reaching an EMI shielding effectiveness of 31.25 dB. In addition, the density of the SiCnws/CF composites was only 0.31–0.41 g/cm3, and their compressive strength can reach 0.61–0.99 MPa with excellent high-temperature stability. Therefore, the SiCnws/CF composite presents a promising EMW absorption and EMI shielding material that can be applied in harsh environments. [ABSTRACT FROM AUTHOR]

Herein, the SiC nanowires were successfully fabricated via chemical vapor infiltration (CVI) into carbon fiber felts (CFs) and then the SiOC/SiCnws/CFs composites were synthesized by precursor infiltration and pyrolysis (PIP) processes. Results indicated that the lightweight composites possessed enhanced mechanical performance, low thermal conductivity, and excellent electromagnetic wave absorption properties. Detailedly, the compressive strength reached to 22.0 MPa and 9.6 MPa after two PIP processes cycles in z and x/y directions, respectively. Meanwhile, the composites exhibited tailored electromagnetic wave absorption performance with the effective absorption bandwidth of 3.06 GHz, and the minimum reflection loss (RL min) was -48.2 dB with a thickness of 3.6 mm. The present work has a guidance to prepare and design multifunction properties for application in harsh environment. [ABSTRACT FROM AUTHOR]

To improve the oxidation protective ability of carbon–bonded carbon fiber (CBCF) composites. A multilayer coating containing ZrB 2 , MoSi 2 , SiCw and borosilicate glass was prepared on ZrB 2 -modified carbon–bonded carbon fiber composites (CBCFs/ZrB 2 ) by a trace oxygen sintering method and a pre-oxidation process. The microstructure, surface emissivity and ablation resistance of the multilayer coating were studied. The coating containing dense surface layer and porous inner layer was obtained. The total emissivity of the coating in the wavelength range of 6–16 μm at 300, 500 and 800 °C was 0.72, 0.73 and 0.78, respectively. The prepared multilayer coating exhibited excellent ablation resistance for 1000 s under simulated atmospheric re-entry conditions by high frequency plasma wind tunnel test with a heat flux of 131.8 W/cm 2 and stagnation pressure of 2.7 KPa. [ABSTRACT FROM AUTHOR]

Epoxy-resin-based dielectric materials play a crucial role in the fabrication of advanced power electronic devices. However, because of a high voltage stress and high heat generation density caused by device miniaturization and high-power density, epoxy composites must possess a high dielectric strength and thermal conductivity. In this study, a general strategy is developed to improve the dielectric strength of thermally conductive epoxy composites using a micron-sized diamond, by preventing an interfacial charge accumulation at the inorganic fillers–epoxy matrix interface that would reduce the interfacial electric field strength. Therefore, the dielectric strength and thermal conductivity of the epoxy composites were significantly and simultaneously improved without any additional physicochemical modification of the micron-sized diamond surface. The reported percentage increase in the dielectric strength among the highly thermal conductive epoxy composites is the highest in the last decade. In addition, the diamond/epoxy composites exhibited lower relative permittivity and excellent mechanical, thermal, and processing properties. These results suggest that the diamond/epoxy composites can be widely used for the fabrication of power electronic devices with a high voltage stress and high heat generation density. [Display omitted] [ABSTRACT FROM AUTHOR]