Effect of heat treatment on hydrophobic silica aerogel
Effect of heat treatment on hydrophobic silica aerogel
复制标题
热处理对疏水性二氧化硅气凝胶的影响
DOI：
10.1016/j.jhazmat.2018.08.087
复制
发表时间：
2019-01-15
影响因子：
13.6
通讯作者：
Chen, Xianfeng
中科院分区：
文献类型：
--
作者：
He, Song;Huang, Yajun;Chen, Xianfeng
在各种条件下对疏水二氧化硅气凝胶进行热处理。通过物理和化学分析研究了热处理对二氧化硅气凝胶的影响。疏水二氧化硅气凝胶中的O/Si和C/Si值分别随加热温度的升高而增大和减小。在热解过程中检测到C-O、- OH和CO。SiO2气凝胶在空气中的热分解可分为3个阶段：甲基的羟基化、醇羟基的裂解和CO的氧化。当热处理温度低于350 ℃时，SiO2气凝胶的性质变化不大。随着热处理温度的进一步升高，相关参数的变化变得更加显著。二次粒子彼此聚结，并且中孔被破坏。因此，导热系数和体积密度大大提高。二氧化硅气凝胶中的碳在热处理后释放。结果表明，随着热处理温度的升高，热重分析和氧弹分析中释放的热量显著下降。
Hydrophobic silica aerogels were heat treated under various conditions. Physical and chemical analyses were conducted to study the effect of the heat treatments on the silica aerogels. The O/Si and C/Si values in the hydrophobic silica aerogels increased and decreased, respectively, with the increase in the heating temperature. C-O, - OH, and CO were detected during pyrolysis. Pyrolysis of the silica aerogels in air could be divided into 3 steps: the hydroxylation of methyl groups, the splitting of the alcoholic hydroxyl, and the oxidisation of CO. When the heat treatment temperature was lower than 350 degrees C, the properties of the silica aerogels showed little change. With further increase in the heat treatment temperature, the variation in the relevant parameters became more prominent. The secondary particles coalesced with one another, and the mesopores were destroyed. Consequently, the thermal conductivity and bulk density rose greatly. The carbon within the silica aerogels was released after heat treatment. As a result, the heat released in the thermal gravimetry and oxygen bomb analyses dropped remarkably with the increase in the heat treatment temperature.