Ceramic composites with improved thermo-mechanical properties

The ceramic composites from the quaternary Al2O3-SiO2-MgO-ZrO2 system, with the major compounds: mullyte, cordyerite, zircone silicate and silica have important applications for the dental technics, because of their interesting thermo-mechanical properties. There can be obtained materials of high purity, good homogeneity, fine precision and also very good thermo-mechanical properties (the thermal expansion coefficient alpha from 20 to 920 degrees C between 2.5 and 4 x 10(-6) K-1), extremely good chemical stability, without risc related to toxic inclusions in dental materials. Several thermal treatement programs are proposed for the obtaining of the samples from ceramic composite materials of four different compositions and there is determined the influences of thermal history on the properties of the studied samples. The chemical composition influence on the thermo-mechanical properties is also studied, especially for the systems with different proportions of cordyerite. The samples are investigated through the determinations of the physical and chemical properties comprising: density, porosity, water absorbtion, mechanical strenght, thermal expansion coefficient, thermal schock resistance, chemical resistance, X-ray diffraction, Raman and FTIR Spectroscopy, Scanning Electronic Microscopy-SEM.