Preparation and Infrared Spectral Analysis of Nanoporous Silica Thin Film
WANG Juan，ZHANG Chang-rui，FENG Jian，YANG Da-xiang
Key Lab of Advanced Ceramic Fibers and Composites, College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073, China
Abstract：Crack-free homogeneous nanoporous silica films on silicon wafer have been synthesized via supercritical drying of wet gel films obtained by spin-coating the polymeric silica sol，which was prepared using sol-gel method with tetraethoxysilane(TEOS) as precursor.The film is amorphous and nanoporous, and three-dimensional network, cross-linked by the primary particles whose sizes distribute between 10-20 nm showed respectively by XRD and SEM micrograph.The structure of the nanoporous SiO2 thin film was studied by FTIR spectra.The SiO2 thin film was composed of Si—O—Si and Si—OR, and was hydrophobic.The film contained Si—OH and became hydrophilic after being heat-treated at 250 ℃ or above in air.The heat-treated SiO2 thin film becomes hydrophobic by reacting with trimethylchlorosilane(TMCS).The TMCS-modified SiO2 thin film remains hydrophobic and can keep its nanoporous structure at a temperature lower than 450 ℃ in nitrogen.
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