Development of a combined method of siliconising of large-sized CCCM product based on alternative liquid-phase method and process of capillary condensation of silicon vapours

Abstract

The features of the combined method of siliconising large-sized blanks of the carbon-carbon composite material (CCCM) is described. Its essence is the combination of alternative liquid-phase method, where the precursor of liquid silicon is silicon nitride, and vapor-liquid-phase method, which consists in evaporation of silicon and subsequent condensation of its vapors in the pores of the material blank. Positive results of volumetric siliconising is provided by the process of capillary condensation of silicon vapours in the 1300-1550 ºС temperature range in the presence of a temperature difference between the temperature of the silicon vapor and the temperature of the blank. Samples of carbonsilicon carbide material with a high degree of siliconising and high surface finish is obtained in two stages by the combined method of siliconising. The first stage is the process of capillary condensation of silicon vapours in heater providing a higher temperature in the crucible with silicon as compared with the temperature at siliconized bulk. The second stage is the process of impregnation of the material with liquid silicon, formed by the decomposition of silicon nitride in the heater with uniform temperature distribution along its height.