气凝胶
材料科学
微观结构
热解
锆
化学工程
无定形固体
相(物质)
碳纤维
多孔性
热稳定性
热导率
四方晶系
微晶
复合材料
冶金
化学
有机化学
结晶学
复合数
工程类
作者
Yuqing Han,Youqing Wu,Sheng Huang,Hong Zhang,Zijun Liang,Xiangfeng Guan,Shiyong Wu
出处
期刊:Langmuir
[American Chemical Society]
日期:2023-11-01
卷期号:39 (45): 15950-15961
标识
DOI:10.1021/acs.langmuir.3c01887
摘要
SiZrOC aerogels were synthesized through the pyrolysis of the zirconium source-doped SiOC system using zirconyl chloride octahydrate (ZrOCl2·8H2O) at temperatures ranging from 900 to 1300 °C. This study investigates the microstructure evolution and phase separation of SiOC and SiZrOC aerogels during the pyrolysis process. Upon pyrolysis, both aerogels exhibited a Si–O–C structure with a high thermal stability. The introduction of zirconium elements significantly enhanced the pore volume (3.20 cm3/g) and porosity (96.0%) and reduced the thermal conductivity (0.023 W·m–1·K–1) of the organic–inorganic precursor aerogel. Moreover, the three-dimensional pore structure was retained even under high-temperature pyrolysis conditions. SiZrOC-1100 displayed a high specific surface area of 273.52 m2/g, a high pore volume of 1.70 cm3/g, and a low thermal conductivity of 0.033 W·m–1·K–1. At high temperatures, the SiZrOC phase transformation produces tetragonal ZrO2, which inhibits the graphitization process of free carbon and the growth of SiC grains. Furthermore, the phase separation process of the SiOxCy matrix structure generated oxygen-rich SiOxC4–x units, while carbon-rich SiOxC4–x units were negligible below a pyrolysis temperature of 1200 °C. Between 900 and 1200 °C, SiZrOC is composed of amorphous SiOC, amorphous ZrO2, microcrystalline t-ZrO2, and free carbon phase. These findings provide valuable insights into the preparation of high-performance SiOC aerogels.
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