Calorimetry Applied to Evaluate Surface Properties of Solids

3 Calorimetry Applied to Evaluate Surface Properties of Solids 

In practice, the experimental procedure is quite long and fastidious referring to the successive determinations of the Gibbs energy of adhesion Aadh G ibetween a given solid and an apolar or polar liquid, which requires, in accordance with Eq. 6.17, measurement of the surface tension ylg, contact angle , and vapour adsorption isotherm (to calculate for each solid-liquid couple. To make matters worse, the very precise measurement of is possible only for atomically smooth surfaces. Finally, the additive approximation expressed by Eqs.6.9a, 6.9b and 6.12 is better suited to calculation of the enthalpy term than to that of the free energy, since the interactions may have both mechanical and entropic contributions [41]. 

The determination of the related surface enthalpy terms //Jq and H[q from direct calorimetry measurements provides an alternative way to evaluate the hydrophobic-hydrophilic character of a solid surface [38, 42-44], since the following deconvolution procedures may be proposed for the surface enthalpy in analogy with those holding for the Gibbs energy (Eqs. 6.8-6.13a, 6.13b)  

Solid-Liquid interfacial enthalpy (Berthelot principle)  

It should be always remembered that the global treatment of surface hydrophobi-city-hydrophilicity based on surface and interfacial enthalpies does not include the entropy effects. 

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