Rapid in-situ solidification of SiO2 suspension by direct coagulation casting via controlled release of high valence counter ions from calcium iodate and pH shift

Rapid in-situ solidification of SiO 2 suspension under the joint action of releasing calcium ions and shifting pH has been proposed. When the suspension was heated up to 60   ℃, decomposition of calcium iodate which released calcium ions , as well as hydrolysis of diacetate (GDA) which shifted the pH toward the isoelectric point, both contributed to the solidification of suspension. The controlled coagulation of SiO 2 suspension could be realized via controlled release of high valence counter ions and pH shift at 60   ℃ within 30   min, which could considerably shorten the coagulation time compared with present reported results (1–3   h). Green body prepared by heating the SiO 2 suspension with 6.5   g   L −1 calcium iodate and 2.0   vol% GDA at 60   ℃ for 30   min shows uniform microstructure with compressive strength of close to 0.3   MPa. SiO 2 ceramics sintered at 1275   ℃ for 3   h possess homogeneous microstructure with bulk density of 2.06   g   cm −3 and flexural strength of 40.3   MPa.