Effect of particle size of raw materials on densification and bending strength of porcelain

Abstract

Effect of particle size of quartz and feldspar on the densification and bending strength of porcelain bodies in the quartz-feldspar-kaolin system was investigated. Measurements of bulk density, 3-point bending strength and X-ray diffraction, and the observation of microstructures were performed. Quartz powders of an average particle size in the range of 1.2-8 μm and feldspar of 1.2-4μm were prepared using a dry pulverizing machine attaching an air classifier. Raw materials of quartz, feldspar and kaolin were mixed in a mass ratio of 30 : 31 : 39 and the slip-cast specimens were fired at temperatures from 1100 to 1350°C. Densification temperature lowered with decreasing the particle size of quartz and feldspar powders. When quartz and feldspar powders of 1.2 μm in particle size were used, porcelain bodies fully sintered at about 1175°C. Bending strength of the bodies increased with decreasing the particle size of quartz and feldspar powders. The maximum bending strength of 176 MPa was obtained when 1.2 μm powder of both quartz and feldspar were used. The particle size of quartz powder has a larger effect on the bending strength than that of feldspar powder.