Acoustic study of adsorption isobar of water vapor on the surface of lithium niobate

As a result of vapor adsorption on the solid hydrophilic surface of the adsorbent, an adsorption layer of water is formed. The thickness of the adsorption layer and the physical properties of the adsorbed water depend on the temperature. The effect of adsorbent temperature variations on the process dynamics of water vapor adsorption on the surface of the lithium niobate acoustic line has been studied. At temperature range of (100-60) C at the adsorbent surface there are separate groups of molecules of water localized on the active centers of adsorption. Reduce the temperature of the adsorbing surface of the acoustic line from ~ 60C to 0C leads to the formation of an adsorption layer and an increase in its thickness. Surface acoustic wave (SAW) parameters have been shown to depend on the temperature and dynamics of the adsorption process. It has been found that the SAW time delay when cooling the absorbent surface decreases, reaches a minimum value, and then increases. At the minimum point, the temperature coefficient of delay for surface acoustic waves is zero. When cooling an acoustic line in a humid gas environment, its linear dimensions, elastic properties change, and the thickness of the adsorption layer increases. The temperature dependence of the complex of the above parameters determines the nature of the change in the delay time of the SAW. A water vapor adsorption isobar was obtained from the analysis of temperature change of the SAW velocity.