Study On The Property Of Pressureless Sintering Silicon Carbide Ceramic

As one kind of special ceramic material, silicon carbide ceramic has many excellent performance with high intensity,high hardness,high temperature resistance,corrosion resistance,abrasion resistance,thermal-shock resistance, which used in many fields such as aerospace,power,electron,mechanical industry,petroleum and chamical industry. Because the covalent bonding of silicon carbide account for about 80%, so it is difficult to sinter compact density under the atmospheric pressure conditions, in order to make the silicon carbide sintered, we offen used the hot-pressed sintering, reaction sintering and other common sintering method, but it is still hard to get high performance conducts. Recent years, with the development of silicon cardide sintering theory, the improvement of powder performance, the diversification and deeply research of additive, so the pressureless sintering process to prepare high performance silicon carbide conduct begins to develop completely. Pressureless sintering process is simply and the cost is inexpensive, the products after sintering have rather good performance, so pressureless sintering becomes one of the developing sintering methods. This paper researched the pressureless sintering process of silicon carbide ceramic.Including:(1)The preparation process of silicon carbide ceramic: the choice of silicon carbide raw material and additives and its content, especialy researched the effect of two additive systerms to the performance of silicon carbide ceramic, and according to the experiment,comparation of several formula systerm, we choosed the best formula. Then we also disscussed the effect of some process craft such as formation pressure and sintering temperature to the performance of silicon carbide ceramic.(2)The physical performance, mechanical performance, the microstructure test and analysis of silicon carbide ceramic.(3)The sintering mechanism and crystal performance research of silicon carbide ceramic, including the chemical change,the structure,the content,the ingredient change which produces in sintering process, and the influence of atmosphere during the sintering process of the silicon carbide ceramic.According to the experiment research, we found that the best packing pressure are 140MPa and the best packing time are 90s; while the best content of the binders are acount for 3% of th whole material; the silicon carbide ceramic includes C and B4C elements as additives belongs to solid-phase sintering, the sintering process is mainly controled by proliferation mechanism and the best sintering temperature is 2150℃; the silicon carbide ceramic includes Al₂O₃,K₂O,Na₂O,MgO and other oxide elements as additives belongs to Liquid-phase sintering, the sintering process is mainly controled by interface reaction and the best sintering temperature is 1350℃. The experiment prepared silicon carbide ceramic has the maximum density of 3.16g/cm³(relative density is 98.75%), the maximum compressive strength of 550MPa. The results indicated that silicon carbide ceramic pressureless sintering process is rather simply and easy to control when we add proper content C and B4C additives, after the ceramic sintering there is about 30% volume shrinkage compared with green, we can get silicon carbide special ceramic with rather high density and good mechanical performance.