HIGH TEMPERATURE CERAMIC STRUCTURES

Effort was directed towards AlCl3 impregnating studies and radome fabricating studies. The AlC13 studies were continued to determine the impregnating method that would increase the strength and decrease the porosity of slip-cast fused silica. Four different impregnating methods were evaluated and found effective in the following order 1 simple exposure, 2 boiling, 3 vacuum-pressure, and 4 pressure. The order according to effectiveness in increasing transverse strength was 1 vacuum pressure, 2 pressure, 3 simple exposure, and 4 boiling. The effects of surface skin fine particles of fused silica developed during initial casting removal were studied in conjunction with AlCl3 studies. In general, the removal of the surface skin decreased the strength of the slip-cast fused silica impregnated by 4 impregnating methods. The bulk diffusion rate and the tendency to develop closed pores was decreased. A procedure was developed for pressure casting radomes from fused silica slips that provided a casting time of 80 minutes, or a reduction of about 9 hr over conventional slip-casting procedures to form a 38-n.-thick x 15-in.-diam x 32-in.-high radome.