SILICA-BASED CERAMIC MATERIALS FOR INVESTMENT CASTING: THE EFFECT OF ALUMINA NANOPARTICLES

Abstract

Silica-based ceramic cores containing various contents of alumina nanoparticles were prepared by ceramic injection moulding with zircon as a sintering aid. The alumina nanoparticles were introduced into the mixture in the form of a colloidal sol. The phase evolution and morphology of the sintered ceramic specimens were analysed by X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive spectrometry (SEM/EDS), respectively. Three-point bending tests were carried out on all of the prepared ceramic specimens. The results showed that the addition of alumina nanoparticles not only promoted the crystallisation of the fused silica, but also increased the formation of a liquid phase in the silica-based ceramic specimens during the sintering. The increased formation of a liquid phase was mainly attributed to the presence of Al, Na and K elements in the alumina nanoparticles, which diffused as a liquid phase into the pores between the silica particles and improved the densification. The flexural strength of the sintered ceramic specimens was improved by adding a proper amount of alumina nanoparticles, which could be attributed to the reinforcement of the sintering necks between the particles and the strengthening of the silica particles.

Keywords

• alumina nanoparticles
• silica-based ceramic core
• cristobalite crystallisation
• flexural strength
• open porosities