【作者】 罗芳；

【导师】 贾德昌；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 硕士

【摘要】 本文采用热压烧结工艺制备了不同粒径的α-Al₂O₃基体、不同助烧剂SiO₂含量和纳米TiNp含量的Al₂O₃-TiN基复合陶瓷材料。利用XRD、SEM、TEM分析了复合材料的微观组织结构;采用维氏压痕法、三点弯曲法和单边缺口梁法评定了复合材料的力学性能;通过电学性能试验系统地研究了TiN含量和α-Al₂O₃粒径对复合陶瓷电阻率、耐高压性能的影响,并探讨了导电机理。研究发现,以SiO₂为助烧剂的Al₂O₃-TiN基复合陶瓷材料的致密度都达到了98%以上,说明添助烧SiO₂能有效地促进材料的致密化,同时控制其加入量,可使材料具有优异的力学性能,例如维氏硬度最高达到22.3GPa,断裂韧性在4⁵MPa·m^1/2之间,三点弯曲强度最高达到561MPa。基体α-Al₂O₃采用7.5μm和20nm两种粒径,复合陶瓷的力学性能试验表明,微米基体复合陶瓷的维氏硬度在20GPa以上,最大达到25.5GPa;断裂韧性在4⁶MPa·m^1/2之间,三点弯曲强度最高达到578MPa。纳米基体复合陶瓷的维氏硬度在10GPa以上,最大值为16.0GPa,断裂韧性在4⁶MPa·m^1/2之间,三点弯曲强度最高达到566MPa。与Micro-Al₂O₃基复合陶瓷材料相比,Nano-Al₂O₃基复合陶瓷材料的硬度小,强度和断裂韧性相近,而两种复合陶瓷的力学性能都是由于纳米颗粒TiN的加入而增强。Al₂O₃-TiN基复合陶瓷材料具有高强度和高断裂韧性的主要原因在于,高熔点和高硬度的TiNp均匀分散在基体中,可以对基体的位错运动产生钉扎作用,同时TiN与Al₂O₃基体膨胀系数存在差别而造成热膨胀失配导致残余应力增韧。断裂类型主要是沿晶断裂。电学性能试验发现,Micro/Nano-Al₂O₃基复合陶瓷的电阻率随TiNp含量的增加而降低,在TiNp含量为10vol.%时,电阻率都满足设计的要求。与Nano-Al₂O₃基复合陶瓷的电学性能相比,Micro-Al₂O₃基复合陶瓷的电阻率要高,而且耐压可达7000V/cm,耐高压性能较强,电压稳定性较好。从TEM显微组织观察分析得知,Nano-Al₂O₃基复合陶瓷材料中,导电相TiN分布在基体Al₂O₃边界较多;其次由于微米体系的基体比纳米体系的基体大,从而造成Micro-Al₂O₃基复合陶瓷材料的导电网络更难形成。更多还原

【Abstract】 In this thesis, Al₂O₃-TiN composites with different content of SiO₂ or TiN and different particle size of Al₂O₃ were prepared by hot-pressing （HP） technique. Microrostructure was studied by XRD, SEM and TEM; mechanical properties were measured through Vickers indentation, three-point bending and single-edge-notch beam （SENB） bending tests; effects of TiN content and particle size of Al₂O₃ on the electrical conductibility behavior of the ceramics was investigated and the conductibility mechanism was discussed.Results show that Al₂O₃-TiN ceramics stabilized by SiO₂, whose relative density reach above 98%, nearly full density was obtained in the composites with of SiO₂ as sintering aids, which show excellent mechanical properties: Vickers hardness attains about 22.3GPa, fracture toughness is 4.42MPa·m^1/2, while flexural strength reaches 560.7MPa.Average particle sizes of startinglα-Al₂O₃ powers are 7.5μm and 20nm, respectively. The Micro-Al₂O₃-TiN ceramics manifest more excellent mechanical properties: Vickers hardness attains to 20GPa, and the highest is 25.5GPa, fracture toughness is between 4 and 6MPa·m^1/2, while flexural strength reaches 578.2MPa. While the mechanical properties of nano-Al₂O₃-TiN ceraMicros: Vickers hardness attains to 10GPa, whose the highest is 16.0GPa, fracture toughness is between 4 and 6MPa·m^1/2, while flexural strength reaches 565.8MPa. In general, with the increase of TiNp content and the particle size of Al₂O₃, the mechanical properties of the ceraMicros are improved.High flexural strength and fracture toughness of Al₂O₃-TiNp composite ceramics has been achieved by introduction of evenly distributed TiN particles with excellent mechanical, which in matrix materialα-Al₂O₃, as well as the difference coefficient of thermal expansion will involve the mismatch flexibilizer. The mode of fracture is primarily intergranular cracking.Electrical conductibility tests indicate that the electrical resistivity of Micro/nano-Al₂O₃-TiN ceraMicros both are descending with the increasing content of TiNp, according to the STAR barrel TOF standard, the Micro/nano-Al₂O₃-TiN ceramics will be added 10vol.% TiNp. Electrical conductibility tests also show higher electrical resistivity than that of nano-Al₂O₃-TiN ceramics, and the high- voltage properties, the maximizing voltage is 7000V/cm. Microstructure study under TEM shows that the distribution of TiNp in nano-Al₂O₃-TiN ceramics concentrated on grain boundary of matrix materialα-Al₂O₃. The smaller size of theα-Al₂O₃ matrix particles, the more difficult the conductibility network of Micro-Al₂O₃-TiN ceramics is formed.更多还原