Study on Humidity Sensing Properties of Nano Thin Films of Silica Aerogel

• Main Authors: Chun-Lung Wu, 吳俊龍
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/40727660690715560566

碩士 === 國立雲林科技大學 === 工業化學與災害防治研究所 === 93 === In the thesis, the silica colloid solution was synthesized by sol-gel method, humidity sensors of silica aerogel thin films were obtained via supercritical drying of wet silica films of alcohol gel that coated on alumina substrate by spin and dip coating technique. The activation energy of polymerization of silica colloid solution was 17.2 kJ/mole. Microstructure analysis revealed silica aerogel thin film that was built-up by nanoparticles, particle size around 30 nm. Surface chemical structure analysis revealed silica aerogel that possesses Si-OH groups and easily bounded with water molecule or polar species. The humidity sensing characteristics of silica aerogel thin films were studied by impedance response. Silica aerogel thin films encompass better humidity sensitivity than xerogel thin films, the microstructure was directly related to the sensors performance. Silica aerogel thin films fabricated with different colloid viscosity results in different structures. Silica aerogel films S-AG15 obtained from sping coating technique showed the best humidity sensitivity, and D-AG15 showed the obvious humidity response, pore structure and films thickness were the main factors. Frequency 1 kHz of voltage was suitable to the sensors performance of humidity response. Silica aerogel thin films fabricated with lower viscosity showed the bigger hysteresis response, and on the other hand, with higher viscosity of silica aerogel films showed the wider range of hysteresis response. The response time directly related to the film thickness structure, the thinner of film layer showed the fast response time.