Preparation and ablation performance of silica modified phenolic/carbon fiber composite

Aimed at the problem of insufficient heat resistance and poor ablation resistance of phenolic resin (RF), and the compatibility of SiO2 particles with phenolic resin, the nano-scale SiO2/RF hybrid aerogel was prepared by the co-gel method. The interpenetrated gel network was constructed to increase the compatibility of two phases. The microstructure, chemical structure and thermophysical properties of the SiO2/RF hybrid aerogel were explored. The silica-modified phenolic/carbon fiber composite material was prepared. The ablation properties of the composite material before and after modification were compared. The results show that the hybrid aerogel possesses a bi-continuous structure of skeleton and pores. The density of the hybrid aerogel fluctuates in the range of 0.145-0.160 g/cm3. As the silica content increases, the residual carbon ratio of the hybrid aerogel increases, and the Si—O bond absorption vibration peak is more obvious, but XRD has no diffraction peak. Considering the pore size distribution and thermal physical properties, the silica-modified phenolic/carbon fiber composite material was prepared with the best performance hybrid aerogel. The mass ablation rate of the modified composite material is 0.046 g/s, and the linear ablation rate is 0.074 mm/s. Compared with the unmodified composite material, the mass ablation rate is reduced by 20.7%, the linear ablation rate is reduced by 21.3%. The oxidation resistance and the residual carbon ratio of the modified material are significantly improved

Study on Sintering Behavior of Reaction-Cured Glass Coating

High-emissivity coatings constitute an essential component of reusable thermal protection systems, determining the success or failure of hypersonic spacecraft. Reaction-cured glass coating is the basis for all current high-emissivity coatings, and the study of its sintering behavior is of great scientific significance for the development and performance enhancement of the coating. Microstructures and phase compositions of the samples before and after the sintering process were determined using SEM, XRD, and EDS. The sintering temperature, inserting temperature, and heating rate were systematically investigated. The results show that the effects of the sintering temperature, inserting temperature, and heating rate on the coating occur in decreasing order. The optimum condition for coating sintering in this study is an insertion temperature of 1100 °C, a heating rate of 10 °C/min, and a sintering temperature of 1200 °C, and a crack-free and containing SiB4 borosilicate glass coating was successfully prepared