Study of the effective Parameters on the properties of fused silica bodies formed by cold isostatic press

Fused silica is an amorphous phase of silicon dioxide، traditionally formed by heating crystalline SiO2 above its melting point، 1730 ± 5oC، and then cooling it rapidly enough to avoid recrystallization. Its density and softening point is about 2. 2 g/cm3 and 1725oC respectively. In this research fused silica bodies was fabricated with cold isostatic press. The amount of CMC، PVA and humidity was 2%، 3% and 2% subsequently. Cold isostatic press was applied at the pressure of 2000 bar. In order to receive the maximum density and minimum crystallization، bodies were sintered at temperatures of 1250، 1300، 1350oC and at 1، 2، 3 and 4 hours. Crystallization rate and phases of the samples were analyzed by X-ray diffraction and Microstructures of them were investigated by scanning electron microscopy. The sample sintered at optimal conditions was obtained with bulk density of 1. 83 g/cm3، the open porosity of 17%، closed porosity 0. 18%، relative density 83. 18 and Thermal expansion coefficient of it in the range from room temperature to 1000oC was measured 0. 4312 × 10-6 C-1.