The Syntheses Of SiC Ceramic Precursor Powders And Study On Their Sintering

Silicon carbide (SiC) has been recognized as an important structural ceramic with high hardness, high strength, high-temperature resistance, chemical and high thermal conduction and low thermal expansion etc, which is widely applied in various industry fields. The sintering, structure and properties of silicon carbide ceramic are closely related to raw materials synthesis, molding methods, sintering processes and additions and so on. At present, in order to obtain good performance of silicon carbide ceramics, the addition of sintering aids are absolutely necessary, and the different ways to draw sintering additives into the silicon carbide base have great influence on the sintering properties of silicon carbide powder.On the basis of reviewing the present status of SiC powder preparation and ceramic sintering, silicon carbide ceramic precursor powders were prepared and Al₂O₃-Y₂O₃ sintering additives were added into silicon carbide powder with different methods: ultrasonic dispersion, high-energy ball milling and sol-gel. Through the sintering experiment, it was confirmed that different sintering conditions affected on the shrinkage rate, weight loss, volume density and so on. This paper summarized the sintering properties of the precursor powders obtained by these three methods, it offered the reference for the production of non-pressurized sintering silicon carbide ceramic and had a certain application prospect.Silicon carbide ceramics precursor powders were prepared by introducing Al₂O₃ and Y₂O₃ with ultrasonic agitation. The precursor powders preparation method was simple, the obtained powders was molded and sintered. The maximum volume density and relative density of sintering bodies sintered under 2000℃for 30min is 2.810g/cm-3 and 84.3% respectively. The weight loss rate of sintering bodies is increasing with the increasing of alumina content. It is good when the content of sintering additives is 8-10%. The optimal molar ratio of aluminum and yttrium is 2.Silicon carbide ceramics precursor powders were prepared with ball-milling method and characterized by TG-DTA, FTIR and XRD. It was showed that sintering additives Al₂O₃ and Y₂O₃ formed YAG at about 960℃. The maximum volume density and relative density of sintering bodies is 3.158g/cm-3 and 96.0% respectively. By SEM analysis, it's founded that grains on surface and section are clear, the crystal boundaries are obvious, compact degree on section is higher than that on surface.Silicon carbide ceramics precursor powders were prepared by sol-gel method and their sintering additives Al₂O₃ and Y₂O₃ were evenly distributed.The precursor powders were characterized by TG-DTA,FTIR and XRD. Compared with TG and XRD of YAG prepared by sol-gel, it's determined that sintering additives of composite powders formed YAG at 910℃. The maximum volume density and relative density of sintering bodies is 3.219 g/cm-3 and 97.8% respectively. It was showed by EDS, SEM analysis that compact degree on section was higher than that on surface, grains connected tightly generally and crystal boundaries were clear.