Application of a quartz crystal microbalance for property determination and functionality analysis of thin hydrophilic coatings on glass

Author： Wondraczek K. Johannsmann D. Wondraczek L. Deubener J.

Publisher： Society of Glass Technology

ISSN： 0017-1050

Source： Glass Technology - European Journal of Glass Science and Technology Part A, Vol.46, Iss.2, 2005-04, pp. : 179-182

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Abstract

Thin coatings are widely used to equip glass surfaces with different functionalities. Reliable quantification of the properties of these coatings and their mechanical and chemical behaviour, in particular, is a major experimental task. In the present investigation, a quartz crystal microbalance (QCM) was used to determine thickness, uptake of moisture, and moisture induced softening of different hydrophilic coatings. During a typical QCM experiment, the piezoelectric quartz crystal is coated with the layer of interest. The resonance frequency and the bandwidth shift in response to the presence of the film. Comparing the shifts of frequency and bandwidth on many harmonics, the thickness and mechanical moduli of the layer can be inferred. Exposing the coating to humidity, moisture, and other environmental factors induces a response, which is directly probed by the resonance parameters. Further analysis yields information on the degree of swelling and solvent induced softening (plasticisation). A QCM is a highly suitable tool for the ex situ characterisation of mechanical properties of thin films on glasses, including organic–inorganic hybrids, sol-gel and other soft coatings. Additionally, it enables on-line observation of swelling and de-swelling arising from coating functionalities.