Densification process of silica microspheres by multi-step sintering

Dense silica microspheres were fabricated by spray drying and multi-step sintering. The effect of sinter temperatures on densification, dispersibility and inner morphology of silica spheres was analyzed by SEM, and the densification process was deeply discussed. The results showed that single-step sintering at 1100 °C made silica spheres seriously coherent each other and spherical morphology irregular. However, a multi-step process made the sinter temperature increase to 1190 °C, while silica spheres still kept uniformly spherical and dispersed. The increased temperature resulted in that the silica particles obtained dense inner morphology, and their density reached 2.18 g · cm–3, corresponding to a relative density of 98.6% (in comparison with the density of 2.21 g · cm–3 for noncrystal silica).