【摘要】 研究SiC-Al2O3-Y2O3体系在无压液相烧结过程中,不同的埋粉、烧结温度和保温时间对致密化过程的影响规律以及发生的主要物理化学变化.通过对烧结体失重率、线收缩率和密度的测量和断面形貌的观察发现,以BN为惰性埋粉时,烧结助剂挥发严重,密度低;以Y2O3为埋粉时,烧结过程中Y2O3从埋粉扩散进入坯体,造成烧结体质量增加,实际上未促进烧结;Al2O3和60%(-βSiC)-25%Al2O3-15%Y2O3埋粉有利于烧结,这是由于埋粉中Al2O3的含量较试样中的Al2O3含量高,具有较高的Al2O分压,能有效抑制烧结助剂的挥发.埋粉相同时,由于烧结和挥发的竞争,密度随烧结温度的升高或保温时间的增长先增加后降低.更多还原

【Abstract】 SiC ceramics were sintered using Al₂O₃ and Y₂O₃ as sintering additives.The effects of the powder bed,sintering temperature and sintering time on the densification and microstructure were investigated.The weight loss,linear shrinkage,relative densities and chemical compositions of the sintered samples were measured.And the crystal phase compositions was characterized by X-Ray Diffraction,and the microstructures was observed by SEM.It was found that the BN powder bed could not promote the densification effectively;With Y₂O₃ as the powder bed,large amount of Y₂O₃ diffused into the sample,but the materials did not densify;With Al₂O₃ or 60%（β-SiC）-25%Al₂O₃-15%Y₂O₃ as the beds,much improved densification was obtained,the density were up to 3.07 g/cm³、3.08 g/cm³ respectively,higher than with the BN powder bed,because the weight loss of the sintering aids was suppressed or the shrinkage was improved.And it was found that β-SiC could transform into α-SiC with the holding time.The final density increased initially with sintering temperature or holding time,but dropped then due to the evaporation of the additives.更多还原