Effect of firing temperature on humidity self-regulation functionality in a ceramic tile composition

The effect of sintering temperature on the humidity regulating capacity of a ceramic composition based on the mineral gibbsite has been studied. The humidity self-regulation functionality is due to the presence of mesopores in the material.In this work, it has been found that the adsorption-desorption capacity decreases drastically with sintering temperature, preserving a certain regulating activity up to temperatures as high as 1200 C-o. The variation of the regulating capacity with temperature is consistent with the transformation of gibbsite from transition alumina to alpha alumina, which leads to a sharp decrease of the mesopore volume which can be determined from mercury porosimetry and especially nitrogen gas adsorption. The adsorption-desorption curves fit well to a pseudo-second order kinetic model and it is found that the equilibrium moisture is proportional to the specific surface area while the sorption rate constant depends on permeability for water diffusion through the porous structure.