THE EVOLUTION OF THE PHYSICAL PROPERTIES AND MICROSTRUCTURE OF Al_2O_3 - ZrO_2 - C SLIDE GATE AT ELEVATED TEMPERATURES

摘要

Al_2O_3-ZrO_2-C slide gate samples and its matrix mixture on the basis of the ongoing sliding gate were fired in coke bed at 1200-1600°C and their phase composition and microstructure were determined and observed by XRD, SEM and TEM linked with EDX in this paper. The results showed that the bulk density, apparent porosity and strength of all the samples were dependent of the heating temperatures, which were closely related to the phase composition and microstructure of the samples. A good deal of SiC whiskers and bean-like cristobalite balls occurred at 1200°C and 1300°C. The amount of SiC whiskers increased against temperatures. However, the morphology of SiC produced at different temperatures was remarkably diverse. In the range of 1200-1400°C, most of β-SiC whiskers were nano-sized in diameter and μm long, some of which were dumbbell shaped, and well distributed in the matrix. Up to 1500°C and 1600°C, SiC whiskers became curled, coarser and congregated. Meantime, the loose structure of the samples was produced from the escape of a great deal amount of silicon containing gaseous species out of the samples. It was logically regarded for firing of Al_2O_3-ZrO_2-C slide gate at 1300-1400°C to be adopted in manufacture process.