【摘要】 研究了以Al2O3、Y2O3、Al2O3-Y2O3、SiO2-YAG为烧结助剂时,SiC液相烧结行为以及烧结过程中发生的主要物理化学变化.与传统固相烧结相比,液相烧结使SiC陶瓷性能显著提高.通过对烧结体失重率、线收缩率及密度的测量和断面形貌的观察发现:Al2O3对坯体致密化的促进效果较差;Y2O3为助剂烧结时,由于高温下剧烈挥发,不能有效促进致密化;不同配比的Al2O3-Y2O3助剂能有效促进坯体致密,当配比满足形成YAG的化学计量比要求时,最有利于SiC的烧结.同时对SiC的液相烧结机理也进行了探索.更多还原

【Abstract】 Silicon carbide ceramics have been widely used in petroleum chemical,automotive,mechanical and aerospace industries because of their excellent resistance to thermal shock,high temperatures,oxidation and chemical corrosion.In this paper liquid phase sintered silicon carbide ceramics were prepared with A₂O₃、Y₂O₃、A₂O₃-Y₂O₃ and SiO₂-YAG as sintering additives respectively.Compared with solid state sintered silicon carbide ceramics,the liquid phase sintered one exhibits superior performance.The effects of different additives on the densification and microstructure were also investigated by the measurement of weight loss,linear shrinkage and relative density as well as X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis.It is found that A₂O₃ was not effective sintering additive due to its high evaporation rate at the sintering temperature.With Y₂O₃ as the sintering additive,large amount of Y₂O₃ from the powder bed diffused into the sample,but the materials did not densify,so Y₂O₃ could not improved the densification of silicon carbide effectively.However,different ratios of A₂O₃-Y₂O₃ significantly promote the sintering,and much improved densification were obtained.With the best result for A₂O₃-Y₂O₃ ratio right for the formation of YAG,the final density was 3.03 g/cm³,and SEM showed the densification of this sample was highest.The liquid-phase sintering mechanisms of SiC were also studied.更多还原