Haixia Yang,Chunming Li,Xiandong Yue,Jianchun Huo,Feng Ye,Jingxiao Liu,Fei Shi,Jie Ma
Although pure silicon oxycarbide (SiOC) aerogels have unique properties of low density and high temperature resistance, they are still difficult to apply at a large scale due to brittleness. To overcome this drawback, a strong boron nitride/silicon oxycarbide (BN/SiOC) aerogel composite with high-temperature resistance and thermal insulation was prepared by the sol-gel method and pyrolysis of the precursor aerogel. The microstructural, mechanical and thermal insulation properties of the composites were investigated, and the effect of the BN content on the microstructure and properties was also clarified. The results indicate that the obtained mesoporous composites exhibit low thermal conductivity (0.04–0.20 Wm −1 K −1 ) and high-temperature resistance (∼1300 °C). As the BN content increased from 0 to 15 vol %, the compressive strength of the composites increased from 2.2 to 20.3 MPa. The obtained composites exhibit considerable promise in high-temperature thermal insulation applications.
Jianhao Zhang,Quan Li,Yi Jia,Li Sun,Yang Wang,Sheng Cui,Jian Yang
Developing radar-infrared-compatible stealth materials is challenging because the material performance requirements between infrared and radar stealth are contradictory. At present, ceramic aerogel is one of the candidate materials that may solve this problem. Here, polymer derived SiC/SiOC aerogels were prepared and their microstructures were tailored by annealing temperature. It is found that the synergistic effects of the pore size distribution, the formation of nano-turbostratic carbons (NTCs) network and the content of SiC nanoparticles contribute to the excellent electromagnetic wave absorption and improved infrared stealth performance of SiC/SiOC aerogel. When the thickness of SiC/SiOC aerogel is 1.78 mm, the minimum reflection loss is -53.5 dB and the maximum effective absorption bandwidth is 6 GHz. In addition, SiC/SiOC aerogel exhibits excellent thermal insulation properties and improved low infrared emissivity. This study provides insights for the development of materials with radar-infrared-compatible stealth properties.
Zongwei Tong,Bixin Yan,Baojie Zhang,Hui Xu,Xiaolei Li,Huiming Ji
Generally, SiOC aerogels are prepared utilizing the high-temperature pyrolysis of polyorganosiloxanes or polycarboorganosilanes in an inert gas atmosphere. However, the crosslinking and drying of the precursor rely on the catalysts of noble metal, the equipment of autoclave, and the technology of supercritical drying, which limit the batch production of SiOC aerogel. In this work, the SiOC aerogels were prepared via pyrolysis of methyltrimethoxysilane/triethoxyvinylsilane (MTMS/VTES) organosilane aerogel precursor (O-SAP), which was synthesized using sol-gel method and ambient pressure drying technology. Under the temperature of 1500 °C, the SiOC aerogel exhibited excellent properties with high porosity (80%), high compressive strength (11.52 MPa), and low thermal conductivity (0.08 W m K −1 ), which overweighed most state-of-the-art SiOC aerogels. More significantly, a new concept of “gases truing” was firstly proposed to explain the microstructure evolution of O-SAP during pyrolysis. This paper is expected to provide insights for the preparation of high-performance SiOC aerogels, with promising applications in heat insulation and anode material of Li-ion battery.
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