Quantitative characterization of vapour adsorption on solid surfaces and estimation of emissivity of solids using infrared thermography

Abstract

The process of adsorption of water-vapour molecules on uneven (irregular) surfaces of some solid materials at room temperature is registered by infrared camera. The pronounced "thermal flame" ("thermal fire") phenomenon developing on the samples' surfaces is exhibited and quantitatively represented. This thermal effect ranged within an order of magnitude. 3-µm-wavelength emissivities of different fabrics are obtained experimentally with the presented non-standard reflection-based method that needs for a narrow-spectral-range infrared camera. An analytical relationship between the amount of adsorbate and the measurable excess of adsorbent temperature is derived. Exclusively high sensitivity of the FPA-based infrared method as applied to the examination of initial stages of adsorption of gaseous molecules on solid surfaces is discovered. It is shown that the method makes it possible to control an incipient molecular film of 1/300-monolayer effective thickness precipitated on the exposed surface of a bulky material and of 1/600-monolayer thickness in the case of the adsorption on a thin-film adsorbent (with a double-faced surface).