Solidification of Powders in SiO<sub>2</sub>-Fe<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub>-ZrO<sub>2</sub> System by Hydrothermal Hot-Pressing

Abstract

A silicastone powder (low-quartz) containing Fe2O3 and ZrO2 up to 30wt% was kneaded with 10N NaOH solution, and then hot-pressed at 300°C and 28MPa for 3h to produce solidified bodies. During hydrothermal hot-pressing, shrinkage of starting materials was measured. Solidified bodies containing Fe2O3 consisted of low-quartz, hematite and acmite (NaFeSi2O6). The formation of acmite suppressed linkage of silica stone grains and reduced compressive strength of the solidified bodies. It also reduced the shrinkage of starting materials. Solidified bodies containing ZrO2 contained low-quartz and monoclinic ZrO2. No reaction products were detected by X-ray powder diffraction. Addition of ZrO2 up to 20wt% increased the shrinkage of starting materials and compressive strength of the solidified bodies. Mobility of silicastone grains at the early stage of hydrothermal hot-pressing was increased by addition of ZrO2. Similar phenomenon was observed by addition of graphite, a solid lubricant.