Yang Haixia, Ye Feng
School of Textile and Materials Engineering, Dalian Polytechnic University Dalian 116034 P. R. China
School of Materials Science and Engineering, Harbin Institute of Technology Harbin 150001 P. R. China.
RSC Adv. 2022 Apr 22;12(19):12226-12234. doi: 10.1039/d2ra01336c. eCollection 2022 Apr 13.
Insights into the micro-texture, micro-morphology, and pore structure of SiN/SiO aerogel composites at high temperatures are presented. At high heat treatment temperatures, the silica aerogel inside the composite material gradually crystallised, and the fusion of micropores caused the decrease of pores and the increase of pore size. Compared with the pure SiO aerogel, SiN particles embedded in the nano-network structure provided effective support and hindered the aerogel crystallisation at high temperatures. To reduce the radiative thermal conductivity, SiN/silica aerogel composites were doped with the opacifier TiO. At higher TiO content, the thermal diffusivity and thermal conductivity of the composites decreased more slowly below 800 °C, and substantially above 1000 °C. For TiO 20 wt%, the measured dielectric constant was 2.85, and the thermal conductivity of the composite decreased by approximately 35% (at 1300 °C). The results show that an appropriate TiO content improved the thermal insulation performance of the composite, but damaged the wave permeability, whereas high contents were unfavourable. This study provides theoretical and technical support for the preparation and application of high temperature wave permeable insulation materials.
本文介绍了对SiN/SiO气凝胶复合材料在高温下的微观纹理、微观形态和孔隙结构的见解。在高温热处理温度下，复合材料内部的二氧化硅气凝胶逐渐结晶，微孔的融合导致孔隙减少和孔径增大。与纯SiO气凝胶相比，嵌入纳米网络结构中的SiN颗粒提供了有效的支撑，并在高温下阻碍了气凝胶的结晶。为了降低辐射热导率，SiN/二氧化硅气凝胶复合材料掺杂了遮光剂TiO。在较高的TiO含量下，复合材料的热扩散率和热导率在800℃以下下降得更慢，在1000℃以上则大幅下降。对于TiO含量为20 wt%的情况，测得的介电常数为2.85，复合材料的热导率下降了约35%（在1300℃时）。结果表明，适当的TiO含量提高了复合材料的隔热性能，但损害了波透性，而高含量则不利。本研究为高温波透性隔热材料的制备和应用提供了理论和技术支持。
