甲基修饰二氧化硅气凝胶的红外光谱和热分析研究

Fourier Transform Infrared Spectroscopy and Thermal Analysis of Silica Aerogel Modified by Methyl Groups

采用红外光谱(FTIR)和热重-微分热重(TG-DTG)法研究了甲基修饰二氧化硅气凝胶样品在空气环境中的热分解,利用Coast-Redfern积分法和Achar微分法相结合的方法,求出了甲基修饰二氧化硅气凝胶在热分解过程中的活化能和指前因子.结果表明:Si—CH3的热稳定温度在450℃左右,至600℃时样品中的—CH3已完全分解;在空气气氛下,—CH3的热分解过程经历了4个阶段,各阶段具有不同的热动力学机理函数,其活化能分别为60.36、191.25、77.34和203.53 kJ/mol,指前因子分别为7.71×107、6.02×1018、2.49×103和2.04×1011s-1.

The thermal decomposition of silica aerogel modified by methyl groups in air is investigated by Fourier transform infrared spectroscopy （FTIR） and thermogravimetry（TG）-differential thermogravimetry（DTG）. The activation energy and frequency factor are obtained with Coast- Redfern integral method and Achar differential method. The results show that the thermal stable temperature of Si--CH3 is about 450℃ and the CH3 groups are decomposed entirely as heated to 600℃. There are four steps in the --CH3 group thermal decomposition, with different mechanism functions. The activation energy is 60.36, 191.25, 77. 34 and 203.53 kJ·mol^-1, and the frequency factor is 7.71×10^7, 6. 02×10^18, 2.49×10^3 and 2.04×10^11 s^-1 for the four steps, respectively.