To investigate the effect of cross linking time on
Fig. 2 shows GNE0877 SEM images of polyvinylsilazane microspheres prepared with different O/W mass ratios and different OP-10 concentrations with the cross-linking temperature of 180 °C. The diameter ranges of polyvinylsilazane microspheres derived from emulsions with O/W mass ratio of 1/5, 1/15, 1/20 were 0.9–1.2 μm (Fig. 2a), 0.7–1.0 μm (Fig. 2b), and 0.5–0.6 μm (Fig. 2c), respectively. This decrease of sphere size with the increasing of O/W mass ratio could be attributed to the enhanced dispersion ability of the oil phase in the aqueous. The influence of emulsifier (OP-10) concentration on the polyvinylsilazane microspheres was also investigated. As shown in Fig. 2, the diameter ranges of microspheres obtained with 0.5, 1.0 and 1.5 wt% OP-10 in aqueous solution were around 0.9–1.1 μm (Fig. 2d), 0.7–1.0 μm (Fig. 2b), and 0.5–0.7 μm (Fig. 2e), respectively. The declined trend of the microsphere size with the increasing of emulsifier concentration was attributed to the increasing of emulsion stability. In O/W emulsion, the hydrophobic alkyl chain attached to the surface of the oil droplet due to the hydrophobic interactions, and the hydrophilic ether groups stretched to the exterior, connecting to the water molecules in the form of hydrogen bonds. With increasing OP-10 concentration, close packing of emulsifiers protected the emulsion droplets from aggregation, consequently resulting in the decrease of sphere size. According to the above results, the microspheres prepared with the O/W mass ratio of 1/15 and 1.0 wt% OP-10 in aqueous solution possessed a diameter distribution of 0.7–1.0 μm and an average diameter of 0.732 μm (Fig. 2f). Considering the shrinkage (about 13%) of the microsphere during the high temperature pyrolysis process, the microspheres with the diameter distribution of 0.7–1.0 μm were most anticipated ones to fabricate ceramic microspheres with the diameter of 0.6–0.8 μm. Therefore, 1/15 of O/W mass ratio and 1.0 wt% of OP-10 concentration were chosen as the typical parameters to prepare desired microspheres.