Structural Distortion and Surface Properties of II Calcium Sulfate Anhydride

Abstract

In order to study the surface ProPerties of active solid materials, the muen Ces of the structural distortion of che micany stable CaS04 on the surface ProPerties were investigated.To control the structural distortion of CaS04, nelydivided crystal grain and distorted lattice, brought about by thermald ecomPos1t1on of gy Psumand by mechanical grind in gofhighly crystalline IICaSO4, were utilized. Structural distortion was expressed by lattice strain and erystallite size measured by X-ray diffraction. The course of structural distortion was divided roughly in two steps. ln the former step, rapid change of crystallite size occurred as found at the final stage of thermal decomposition and the early stage of grinding. Whereas, in the latter step, rapid change of lattice distortion occurred as found at the early stage of thermal decompositien and the final stage of grinding.Properties relating to surface area such as adsorption, wetting and solid-acidity were influenced remarkably in the former step, whereas others relating to internal strain such as disselutien and hydration were influenced strongly in the latter step.Although lattice strain and crystallite size of both calcined and ground ff CaSO' seemed to be appaiently the same, a considerable difference between both properties was found and it was explained in terms of structural difference of both particles observed by electron microscope.