摘要:
在氮化硅陶瓷中α-Si3N4、β-Si3N4的相含量,对氮化硅陶瓷的性能有直接的影响。本文用X射线定量相分析的方法,测试了热压Si3N4+5%Y2O3+2%A12O3的α/β相变的相分数。研究了热压温度及时间对该成分Si3N4的α/β相变的影响。结果表明,α/β相变强烈依赖于温度。用本试验原料(β相含量11.0%),在升温速度45℃/min,压力41.1MPa的条件下,在1450℃×10min,13相达14.7%;在1650℃×10min,β相达41.9%;在1750℃×10min,β相达95.2%;从1650℃开始,α/β相变显著。热压时间对α→β相变的影响随温度的变化而不同:在1450~1550℃,热压时间延长,β相含量逐渐增加;在1550~1650℃,热压时间延长,β相含量增加显著;在1650~1750℃,随温度升高,热压时间对α/β相变的影响逐渐减小。用膨胀仪测得Si3N4陶瓷液相生成温度为1410℃。用扫描电镜观察了在1650℃时的α-β相变,由等轴状α转变为斜方β晶粒。
Abstract:
α-Si3N4, β-Si3N4 phase contents of silicon nitride ceramics directly effect the properties of silicon nitride materials. Phase fraction of α/β phase transformation of hot pressing Si3N4+5wt%Y2O3+2wt% Al2O3 have been measured by XRD quantitative phase analysis. The effect of hot pressingtemperature and time on silicon nitride α/β phase transformation was studied. The results show the stronge dependance of the α/β phase transformation on temperature. The silicon nitride powder containing 11.0% β phase have been adopted. Under the heating rate of 45℃/min, the pressure of 44.1Mpa, 1450℃×10mins, β phase is 14.7%; 1650℃×10mins, β phase 41.9%; 1750℃×10mins, β phase 95.2%. Starting at 1650℃,α/β phase transfered remarkably. The effect of time on α/β phase transformation varies with temperature. In the range of 1450~1550℃, β phase gradually increases with time. β phase remarkable increase was found at 1550~1650℃. But at 1650~1750℃, the effect of time gradually decreases on α/β phase transformation, when temperature increases Si3N4+5wt%Y2O3+2wt%Al2O3 liquide phase formation temperature (1410℃) have been measured with thermal dilatometer. The SEM observated that the equiaxed a grains transfer to prismatic β grains during the α/β phase transformation at 1650℃.
点击查看大图
下载:
