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标题:Low-density TEOS-based silica aerogels prepared at ambient pressure using isopropanol as the preparative solvent
时间:2020-03-26 12:27:40
DOI:10.1016/j.jallcom.2009.08.055
作者:Askwar Hilonga;Jong-Kil Kim;Pradip B. Sarawade
关键词:Experimental/ aerogels; catalysis; catalysts; condensation; drying; organic compounds; polymerisation; porous materials; shrinkage; silicon compounds; sol-gel processing; surface texture/ low-density TEOS-based silica aerogels; isopropanol; preparative solvent; ambient pressure drying route; hydrolysis; condensation; methanol; ethanol; butanol; oxalic acid; catalysts; shrinkage; drying; trimethylchlorosilane; one-step solvent exchange-surface modification process; textural property; physical property; chains; alkyl groups; silica polymerization; alcogels; spring-back effect; porous silica network; specific surface areas; cumulative pore volumes; sol-gel process; SiO 2/ A8270G Gels and sols A8120 Other methods of preparation of materials A8265J Heterogeneous catalysis at surfaces and other surface reactions A8235 Polymer reactions and polymerization A6140G Structure of powders and porous materials A6810 Fluid surfaces and interfaces with fluids A8115L Deposition from liquid phases (melts and solutions) A6820 S
出版源: 《Journal of Alloys & Compounds》 ,487 (1-2) :0-750
摘要:In this paper, we report experimental results on the synthesis of low-density tetraethoxysilane (TEOS)-based silica aerogels prepared with different solvents via an ambient pressure drying (APD) route. Tetraethoxysilane was hydrolyzed and condensed in different solvents (methanol, ethanol, butanol, and isopropanol) using oxalic acid and NH 4OH as the catalysts. To minimize shrinkage due to drying, the surfaces of the gels were modified using trimethylchlorosilane (TMCS) before the APD via a one-step solvent exchange/surface modification process. The effects of different solvents on the physical and textural properties of the resulting aerogels was investigated. It was observed that solvents containing longer chains of alkyl groups (-CH 2-CH 3) formed high silica polymerization in the alcogels which enhanced a distinct ldquospring-back effectrdquo during APD, and consequently preserved the highly porous silica network by preventing collapse. Silica aerogels with very low bulk densities (0.041 g/cm 3), extremely high specific surface areas (1150 m 2/g), and large cumulative pore volumes (5.2 cm 3/g) were successfully synthesized using isopropanol as a preparative solvent. [All rights reserved Elsevier].
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目录:
  • Low-density TEOS-based silica aerogels prepared at ambient pressure using isopropanol as the preparative solvent
    • Introduction
    • Materials and methods
      • Preparation of silica alcogel using a two-step sol-gel process
      • One-step solvent exchange surface modification of silica alcogels and the drying process
      • Characterization methods
    • Results and discussion
      • Mechanism of surface modification and hydrophobic properties of TEOS-based silica aerogels
      • Effects of alcohol/TMCS molar ratio and perfluorohexane/TMCS volume ratio on the physical properties of TEOS-alcohol-based silica aerogels
      • Physical properties of TEOS-based silica aerogels
      • Textural properties of the TEOS-alcohol-based silica aerogels
    • Conclusions
    • Acknowledgements
    • References

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