【作者】 杨明辉；

【导师】 杨海涛；

【作者基本信息】 武汉理工大学 ， 材料学， 2005， 硕士

【摘要】 本文以Al₂O₃/Si₃N₄纳米复合陶瓷为研究对象,以工业化生产的纳米氧化铝和氮化硅粉为原料,采用热压烧结致密化工艺,通过对其晶界致密化过程及晶粒长大过程的机理分析以及强化机理的研究,掌握和控制其组成、致密化工艺、显微结构和性能之间的相互关系和变化规律,制备出即致密又具有细小晶粒结构的Al₂O₃/Si₃N₄纳米复合陶瓷。 经过力学性能测试,在1600℃温度下烧结的试样是三组中最好的。其中Si₃N₄含量为3%的试样的性能最好,硬度达到了15.59GPa,断裂韧性达到了4.21Mpa.m^1/2,其值分别比纯氧化铝烧结的硬度和断裂韧性提高了近一倍和34%,增强增韧效果明显。 研究结果表明,Al₂O₃/Si₃N₄纳米复合陶瓷的致密化主要是通过液相烧结实现的,Al₂O₃和Si₃N₄反应生成β-SIALON液相,促进烧结致密化。冷却后,β-SIALON相粒子既存在于Al₂O₃基体的晶界上也存在于Al₂O₃晶粒内。随着Si₃N₄含量的不同,分别形成了“晶间”型和“晶间—晶内”混合型的纳米复合陶瓷。 在烧结中有液相生成,使得在烧结体中形成了长柱状Al₂O₃晶粒,这种常驻状的晶粒的长径比在2.5—4范围内,并且相互交错排列,起到了“自增韧”的效果;由于Al₂O₃和β-SIALON的线膨胀系数和弹性模量不同,使得Al₂O₃基体晶粒和β-SIALON相颗粒间形成的次界面上产生很大的应力,产生了晶粒的“纳米更多还原

【Abstract】 Al₂O₃/Si₃N₄ nanocomposites ceramics is studied in this paper. We used commerce-produced Al₂O₃ and Si₃N₄ powders, hot-pressing sintered method to fabricate the Al₂O₃/Si₃N₄ nanocomposites. By analysis the relationship of the sintering process and the grain grow process, we should master the principle of how to fabricate good properties Al₂O₃/Si₃N₄ nanocomposites ceramics with tight structure and small -size grains.Test show that the samples sintered under 1600℃ is the best. Sample B4, the content of Si₃N₄ is 3wt%, is the best of best .its hardness is 15.59 GPa, fracture toughness is 4.21 Mpa.m¹/2 compared with pure Al₂O₃ ceramics, the hardness and the fracture toughness is improved much.It was observed by SEM that the Al₂O₃ grains were in the shape of elongated columns with aspect ratios in the range 2.5-4. The presence of liquid phase during sintering was found to responsible for the appearance of columnar grains. β-SIALON grains formed during sintering were mainly situated at grain boundaries of the matrix material while irregular smaller particles trapped within the Al₂O₃ grains. The improvement in the mechanical properties is attributed to the change in fracture mode from intergranular fracture to transgranular fracture. The "self-reinforcement effect" arising from the elongated columnar grains of the matrix as well as the "pinning effect" due to the existence of intergranular P-SIALON particles, thedifference of the two phases’ mechanical properties lead to the Al₂O₃ grains have the trend of "nano-size" is also good to the improvement of the material.更多还原