Effect of particle size distribution on cold sintering of amorphous silica

The effect of the particle size distribution on cold sintering was investigated using spherical amorphous silica particles with a bimodal size distribution and NaOH solutions with different concentrations. For low NaOH concentrations, the relative density of the hardened body after sintering was highly dependent on the packing properties of the raw powder. Since necking mainly occurred for fine particles, the compressive strength tended to be higher for particle size distributions with a larger proportion of fine particles. In contrast, for high NaOH solution concentrations, a higher proportion of fine particles produced hardened bodies with the highest relative density due to dissolution of these fine particles. However, an increase in NaOH concentration caused changes in the glass network and an increase in hygroscopicity, which led to a decrease in mechanical strength.