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—CH
3
is about 450 ℃ and the —CH
3
groups are decomposed entirely as heated to 600 ℃. There are four steps in the —CH
3
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 2.04×1
0
11
s
-1
for the four steps
respectively.
关键词
Keywords
references
HEGDE N D, RAO A V. Organic modification of TEOS based silica aerogels using hexadecyltrimethoxysilane as a hydrophobic reagent [J]. Applied Surface Sci, 2006, 253(3): 1566-1572.
PRAKASH S S, JEFFREY B C, HURD A J. Silica aerogel films at ambient pressure [J]. J Non-Crystalline Solids, 1995, 190(3): 264-275.
SHYLESH S, SINGH A P. Heterogenized vanadyl cations over modified silica surface: a comprehensive understanding toward the structural property and catalytic activity difference over mesoporous and amorphous silica supports [J]. J Catalysis, 2006, 244(1): 52-64.
RAO A V, KULKARNI M M. Effect of glycerol additive on physical properties of hydrophobic silica aerogels [J]. Materials Chemistry and Physics, 2002, 77(3): 819-825.
DE VOS R M, MAIER W F, VERWEIJ H. Hydrophobic silica membranes for gas separation [J]. J Membr Sci, 1999, 158(1/2): 277-288.
SˇTANDEKER S, NOVAK Z, KNEZ Zˇ. Adsorption of toxic organic compounds from water with hydrophobic silica aerogels [J]. J Coll Interf Sci, 2007, 310(2): 362-368.
WEI Qi, LI Jianlin, SONG Chunlin, et al. Preparation, characterization and hydrothermal stability of hydrophobic methyl-modified silica membranes [J]. Journal of Inorganic Material, 2004, 19(2): 417-423.
胡荣祖, 史启祯. 热分析动力学[M]. 北京: 科学出版社, 2001: 127-131.
RAO A V, HEGDE N D, SHEWALE P M. Imperviousness of the hydrophobic silica aerogels against various solvents and acids [J]. Appl Surf Sci, 2007, 253(9): 4137-4141.
BHAGAT S D, KIM Y H, AHN Y S. Room temperature synthesis of water repellent silica coatings by the dip coat technique [J]. Appl Surf Sci, 2006, 253(4): 2217-2221.
LEE S, CHA Y C, HWANG H J, et al. The effect of pH on the physicochemical properties of silica aerogels prepared by an ambient pressure drying method [J]. Mater Lett, 2007, 61(14/15): 3130-3133.