Research Of Gelcasting Of Sialon Bonded SiC

Sialon-SiC material is a kind of excellent refractory. With the increasing demands, its high quality and variety of shapes are required. However, traditional techniques and methods couldn't meet the demands. One-step-compounding method of preparing Sialon was applied in this job. Sialon bonded SiC material was produced by gelcasting which has not been reported by far.Colloidal characteristic of material and rheological behavior of their suspensions were investigated in details and proper measures were introduced to improve suspensions'rhelolgical behavior. The results showed that Si, SiO2, SiC powder were apt to be dispersed in alkali solution; bubbles were produced by the reaction among Al, Si and alkali solution; free silicon on the suiface of SiC can produce bubble in suspension. It showed that there were lots of pores in the green when pH value was high and which was caused by the reaction of Al, Si .In order to avoid these reactions washing the SiC in the alkali solution and adjusting pH value were used and they were tested effective. In addition, vacuumizing was used to diminish the bubble introduced by mixing. By using these methods, the viscosity of suspension was less than 0.32Pa.s and green strength was up to 32MPa, which made it possible to machine. Through adjusting the particle distribution the solids loading amounted to 54vol%.Some effects on the rheological behavior of slurry and green performance were investingated thoroughly and the rheological model was established. The results showed that pH value, solid loading, temperature and milling time affect the rheological behavior of slurry greatly. The stability of slurry is best when pH value is about 8.5. Al could react if milling time is too long. The slurry will agglomerate in 20 minutes when conditional temperature is above 30℃, the operational temperature should be below 25℃. Adding the activator made rheological behavior of slurry and green performance bad. The green can be obtained by using proper technics which density is up to 2.5g/cm3 and flexural strength is up to 30MPa.