The Optimization of the Properties of Sodium Silicate Bonded Ceramic Sand by Nano-Oxide Particles and Ultrasonication

Abstract

In this paper, the nanoparticles (NPs) of magnesium oxide (nano-MgO) and silicon dioxide (nano-SiO2) and ultrasonication on the properties of sodium silicate bonded sand (SSBS) were studied, and the quantity of NPs and ultrasonication time in their interaction with sodium silicate binder were optimized by orthogonal experiment. This research was conducted with sodium silicate as a part of two-component (sodium silicate–silica fume) binder system to be used for heat-cured sodium silicate bonded ceramic sands. The results of experiment indicated that the addition of NPs and ultrasonication promoted the continuity and density of the bonding bridge of sand samples, the optimal quantity of nano-MgO and nano-SiO2 was 1.5% and 1.0% of sodium silicate binder, the optimal ultrasonication time was 15min, hot strength (σ0), 4-h tensile strength (σ4h) and 24-h tensile strength (σ24h) of modified sand samples increased by 11%, 25% and 27%, and the residual strength (σ800oC) decreased by 28%. The different linear expansion coefficients between nano-MgO, the new phase Na2Si3O7 and the sodium silicate system caused many cracks on the bonding bridge in the process of heating at 800°C and cooling, which resulted in the reduction of the residual strength of SSBS.