Li2O-Al2O3-SiO2 glass-ceramic coating on a porous silica ceramic substrate

Li2O-Al2O3-SiO2 based glass powder was used to prepare glass-ceramic coating on a porous silica ceramic substrate. The precursor glass powder became to crystallize slightly above the glass transformation point. To obtain the glass-ceramic coating, the glass powder was painted on the top of the substrate followed by sintering at a temperature above the crystallization peak temperatures. During the sintering, the coating passed by the crystallization peak temperatures region quickly and had partially crystallized leaving some glass phase behind. At the higher soaking temperature, the viscosity of the residual glass phase was reduced and a relative compact coating could be obtained. β-Spodumene-silica solid solution (LiAlSi3O8) was formed in the coating sintered at 1150 °C. The surface coating layer partially penetrated into the open pores of the substrate, forming a well interconnected interface. The prepared coating exhibits high thermal shock resistance due to its smaller coefficient of thermal expansion than the substrate. The glass-ceramic coated silica block shows excellent waterproofing performance.