4. Conclusions
In this paper, the sintering and the crystallization of a glass ceramic material (composition 14.0CaO.5.5Al2O3.80.5SiO2), as obtained byGrain Glass Sintering(GGS), were studied with the aim of producing plates with an esthetic effect similar to marbles and granites for use as decorative materials. Using differential thermal analysis (DTA) and heating microscopy, thermal events were correlated with the sintering and the crystallization of coarse frits. The maximum sintering temperature increased due to the larger particle sizes in the granular frit. The granular frit underwent more significant sintering than the powder frit, including the temperature of maximum densification rate above the crystallization temperature. Above the crystallization temperature, the intragranular porosity was no longer visible in the microstructure of the material. The premature crystallization of pseudowollastonite was observed and related with the action of some component from the glass that acted as a mineralizing agent. The desired esthetic effect was obtained using coarse frits with crystallization in their boundaries that was capable of generating visual contrast with the particles in the bulk. The esthetic effects change the characteristics of the frits in the range between their crystallization and melting temperatures. A lower heating rate contributed to the visual contrast observed between the boundaries of the frits and the matrix and to the reduction of the superficial porosity. The holding time at the maximum temperature contributed to increasing crystallinity and decreasing bulk porosity in the material.