【作者】 赵鲁；

【导师】 刘英才；

【作者基本信息】 中国海洋大学 ， 材料物理与化学， 2007， 硕士

【摘要】 氧化铝基陶瓷材料具有高硬度、耐高温、耐腐蚀和磨损等金属材料难以比拟的优点,其原材料广泛、价格低廉又是其它陶瓷材料所无法相比的。但陶瓷材料本身所固有的本质脆性始终是其广泛应用的瓶颈。本文以纳米SiC颗粒及微米Al₂O₃为主要原料,成功制备了Al₂O₃/SiC陶瓷基纳米复合材料。研究了纳米粉体的分散技术。探讨适合Al₂O₃/SiC系统的分散方法及具体工艺,得出复合粉体均匀分散的最佳工艺参数并制备出性能优良的粉体。利用Al₂O₃在烧结时易各向异性长大的特点,通过控制烧结工艺,调整SiC的加入量实现了对Al₂O₃/SiC微观结构的剪裁,以获得最佳的力学性能。分析了Al₂O₃/SiC纳米复合材料烧结热力学与动力学过程,将复合材料的烧结过程划分为三个阶段。烧结过程中“晶内型”结构的形成取决于界面驱动力,基体晶界及第二相纳米颗粒的迁移速率等因素。界面能高及界面两侧相邻晶粒的差别大,有利于晶界的迁移,从而有利于形成“晶内型”结构。对Al₂O₃/SiC的制备工艺进行了优化,得到了SiC均分散于Al₂O₃基体中的烧结体。部分纳米SiC位于Al₂O₃晶粒内部,部分位于晶界上,成功制备出了“晶内型”结构的纳米复合材料。Al₂O₃/SiC纳米复合材料有良好的力学性能,其抗弯强度和断裂韧性的最大值分别为668.02Mpa和4.9MPa·m1/2,与单相Al₂O₃陶瓷相比具有显著的提高。纳米SiC的加入改变了Al₂O₃的晶界结合状态,使晶界强化,晶内“纳米化”,促使Al₂O₃陶瓷由沿晶断裂模式向穿晶断裂模式的转化。晶内SiC的纳米强韧化,裂纹的偏转和基体晶粒的细化是复合材料力学性能提高的重要原因,Al₂O₃/SiC纳米复合材料在抗弯强度及断裂韧性方面都有显著提高。具有多种途径的协同增韧机制是Al₂O₃/SiC纳米复合材料的特点。更多还原

【Abstract】 Alumina （Al₂O₃） was a widely used ceramic due to its refractoriness, wear resistance and chemical stability. However, the brittleness of Al₂O₃ limited its potential applications. In this paper, nano-SiC particle toughened Al₂O₃ ceramics were studied. The nano-composites possess higher mechanical properties than monolith alumina.The dispersing of nano-particle was researched. We studied the suitable dispersing method and processing for the Al₂O₃/SiC system. Obtained best parameters and prepared the powders those have excellent properties.The abnormal grain growth of Al₂O₃ often occurs during sintering of commercial purity Al₂O₃. By means of controlling sintering process and contents of SiC to produce tailored microstructure, the optimum properties were obtained.The sintering mechanism of Al₂O₃/SiC ceramic nanocomposite was researched. We divided the sintering process into three parts. The priority of densification occurred in aggregated nano-particles. Dispersion of mixed original powders and the SiC content in composites was important.The formation of intragranular microstructure depended on driving force of interface and movement velocity of inclusion and matrix grain bounding. Higher grain surface energy and lower curvature radius of dispersoids contribute to more intragranular particles.In Al₂O₃/SiC nano-composites, the SiC particles were uniformly dispersed in Al₂O₃ matrix. Part of nano-SiC, is embedded in Al₂O₃ grains, and another nano-SiC particles is existed at Al₂O₃ grain boundaries. Nano-composites with intragranular microstructure was successfully prepared. Al₂O₃/SiC nano-composites possessed favorable mechanical properties. The maximum strength and toughness are 668.02Mpa and 4.9MPa·m^1/2, were significantly improved compared to monolith alumina.The grain boundaries of Al₂O₃ were strengthened by SiC. Intragranular nano- SiC changed the fracture mode of Al₂O₃ from intergranular fracture to intragranular fracture. Various strengthen and toughen mechanism acted on Al₂O₃/SiC nano-composites. That was the intragranular SiC makes the Al₂O₃ grains into nano size、refined microstructural strengthen mechanism of SiC and deflection of crack.更多还原