Characterization of alumino-silicate glass/kaolinite composite

Abstract

A novel porcelain composite of kaolin and alumino-silicate glass (ASG) as a fluxing agent was prepared. The dependence of linear shrinkage, water absorption, apparent porosity and apparent density upon glass addition and sintering temperature were investigated. X-ray diffraction study confirmed the formation of mullite at 1100 °C and existence of cristobalite phase. The glassy phase microstructure was observed using the scanning electron microscope. A self-glazed porcelain body was achieved at 25 wt% of ASG addition. The modulus of rupture (MOR) and flexural strength ( σ f ) increased with glass addition, showing maxima values at 15 wt% glass addition. Micro-hardness increased with glass addition and sintering temperature. The dielectric constant ( ε ′), dielectric loss factor ( ε ″) and dielectric loss tangent (tan δ ) are measured as a function of composition and frequency in the range (10 kHz–1 MHz). The most important property noted was an improvement of the bodies containing ASG in resistance to voltage breakdown. The results of breakdown strength exhibited a maximum value ( E br =56.60 kV/mm) for addition of 25 wt% of alumino-silicate glass sintered at 1100 °C. Owing to its lower cost it is feasible to recycle ASG waste in porcelains instead of feldspar to produce bodies having good properties.