【作者】 史晓琪；

【导师】 蒋明学；

【作者基本信息】 西安建筑科技大学 ， 材料学， 2007， 硕士

【摘要】 以微米级TiN和α-Al₂O₃粉体为原料，采用湿法球磨混合法制备了TiN-Al₂O₃复合粉体，分别在1700℃、1750℃、1800℃三个温度下，在氮气气氛常压下保温3h烧结得到TiN-Al₂O₃复合材料。研究了烧结温度、添加相TiN颗粒的含量对TiN-Al₂O₃复合材料的性能的影响，在此基础上计算复合材料的渗流阀值。研究结果表明：随着烧结温度的提高，材料断裂韧性与抗弯强度不断提高在1750℃达到最大值。在1750℃烧结3小时后，40 Vol％TiN-Al₂O₃烧结试样的抗弯强度和断裂韧性达到最大值，分别为518.1MPa、4.972MPa·m^1/2。随着试样中TiN含量的增加，复合材料的力学性能不断提高，电阻率逐渐降低，当TiN加入量为40 Vol％时电阻率为1.34×10^-3Ω·cm。TiN的加入可以大大降低材料的电阻率，复合渗流理论认为TiN-Al₂O₃复合材料属于TiN添加型导电材料，渗流作用是此材料的导电机理。当TiN颗粒的含量超过渗流阀值，材料的电阻率将急剧降低，材料由绝缘体变为导体，材料电阻率的大小随TiN颗粒的含量的增加而降低。材料的电阻率与TiN颗粒的含量关系分为三个阶段。第一阶段（0％～10％）随着TiN含量的增加，材料的电阻率在下降，但是材料仍然为绝缘材料；第二阶段（10％～20％）随着TiN含量的增加，材料开始导电；第三阶段（20％～40％）随着TiN含量的增加，电阻率下降较为缓慢。通过计算材料的渗流阀值为17.24 Vol％。试样的显微结构分析表明：当TiN在Al₂O₃基体中孤立而且被Al₂O₃包围时，材料为绝缘体；当TiN分布在Al₂O₃晶界处，分布均匀，彼此相互交织形成网络时，材料具有较小的电阻率。TiN颗粒分布在Al₂O₃晶界处抑制了Al₂O₃晶粒的长大，对材料起到了增强补韧的作用，增韧效果随着TiN含量的增加而明显增强。更多还原

【Abstract】 T1N-Al₂O₃ powders were prepared by wet ball milling with micrometer TiN, Al₂O₃ powder and alcohol as starting materials. The sintered bodies were prepared by pressureless sintering process at the sintering temperature of 1700℃、1750℃、1800℃ for 3 hours in the nitrogen atmosphere. The influences of sintering temperature and TiN content on the mechanical properties and electrical conductivity of TiN-Al₂O₃ composites were studied.Experimental results show that the mechanical properties of the composite increases with improving sintering temperature and A composite of 40Vol%TiN-Al₂O₃ with 518.1MPa bending strength and 4.972 MPa·m^1/2 fracture toughness was obtained at the sintering temperature of 1750℃ for 3 hours. The mechanical properties of the composite increases with increasing amount of TiN, while the resistivity ofcomposites decreases and reaches to a value of 1.34×10³ Ω·cm for the composite with 40Vol %TiN.The addition of an electroconductive second phase to the matrix was tolower the electrical resistivity drastically .The electric conduction mechanism of TiN-Al₂O₃ composite can be explained by using the therory perclation. The therory perclation think that TiN-Al₂O₃ compound material belongs to the increase conducting material. When the TiN pellet content surpasses the volume percolation, the material electronic resistivity suddenly will reduce, the material will become the conductor by the insulator. The material electronic resistivity reduces along with the TiN pellet content increase.The material electronic resistivity and the TiN pellet contentrelations divides into three stages. The first stage （0% ～ 10%） along with the TiN content increase, the material electronic resistivity is dropping, but material still for insulation material; The second stage（10% ～ 20%） along with the TiN content increase, the material electronic resistivity suddenly drops; The third stage （20% ～ 40%）along with the TiN content increase, the electronic resistivity dropsslowly. Through the computation material the critical percent content of TiN is 17.24%.The SEM analysis shows that the TiN are distributed uniformly among the crystal boundary of Al₂O₃ matrix and bonded together after sintered to form a net-like structure that plays a role to restrain Al₂O₃ grains to grow up and furthermore result in an enhancement of the mechanical properties of TiN-Al₂O₃ composites. The TiN grains are distributed uniformly among the crystal boundary of Al₂O₃ matrix matrix and bonded together after sintered to form a net-like structure that plays a role to restrain Al₂O₃ grains to grow up and furthermore result in an enhancement of the mechanical properties of TiN-Al₂O₃ composites. Toughening effect markedly enhanced with increasing TiN content.更多还原