Effect of different crystal phase of microsilica on bending strength for sodium silicate bonded sand cores

The inorganic sand cores involving sodium silicate binder and microsilica have the environmental advantages. Nevertheless, the bending strength of sodium silicate bonded sand (SSBS) needs to be further improved. In this research, the effect of distinct crystal phase of microsilica on the bending strength of sand cores was studied. The experimental results revealed that the microsilica powder contains amorphous and crystalline silicon dioxide can be adopted as an optimal modifier to enhance the bending strength of SSBS. According to the SEM and spectroscopy techniques, the dense bonding bridges and the complex Si-O-Si network containing more Q₃ type silicon atoms contributes to the excellent bending strength, with a 43.7 % increase in cold strength (24 h) than the commercial powder modified sand cores.