Abstract
Porous SiO₂–SiC-based ceramics were developed to achieve superior thermal insulation and mechanical performance for high-temperature applications such as thermal protection and energy conversion systems. In this study, nano-sized SiO₂, nano-sized SiC, and carbon black powders were used to fabricate porous SiO₂–SiC ceramics by sintering in air at 700–1000 °C. The effects of nano-SiC content (0–35 wt%) and sintering temperature on porosity, thermal conductivity, and compressive strength were systematically investigated. Increasing the nano-SiC content and sintering temperature led to enhanced partial densification of the struts due to silica bonding, resulting in decreased porosity from 77.1% to 69.5%. The lowest thermal conductivity of 0.043 W/m·K was achieved for samples containing 10 wt% nano-SiC sintered at 700 °C, attributed to the high interfacial thermal resistance at SiO₂–SiC interfaces. The compressive strength of porous SiO2-SiC based ceramics increased by 5.4 – 6.9 times with an increase in sintering temperature and the nano-SiC content from 0 to 35 wt% and remained significantly higher than that of previously reported porous SiC ceramics. The improved thermal insulation and mechanical strength were attributed to strong silica promoted interparticle bonding and the formation of SiO2 core/SiC shell structures. These findings demonstrate that the newly developed porous SiO₂–SiC ceramics possess a promising combination of low thermal conductivity and high strength for advanced high-temperature applications.