【作者】 彭牛生；

【导师】 刘维良；

【作者基本信息】 景德镇陶瓷学院 ， 材料学， 2011， 硕士

【摘要】 Ti（C,N）金属陶瓷以其高硬度、耐磨损、耐腐蚀、耐高温等优良性能,在金属加工、高温部件等工业领域中应用前景广阔,但是脆性大制约着其广泛应用。多壁碳纳米管（MWCNTs）的强度和韧性都优于任何纤维材料。因此研究MWCNTs/Ti（C,N）金属陶瓷复合材料的制备及其性能具有重要理论意义和实用价值。本文以TiC、TiN为主要原料,以WC、Mo₂C、TaC、Cr₃C₂为硬质添加相,以Ni和Co为金属粘结相,以MWCNTs为纤维增强剂,经过改性,分散,混料,热压烧结制备了MWCNTs/Ti（C,N）金属陶瓷复合材料,研究了不同MWCNTs添加量对Ti（C,N）金属陶瓷组织结构和力学性能的影响,确定了最佳添加量和烧成制度,表征了复合材料的高温抗氧化性能,并探讨了MWCNTs对Ti（C,N）金属陶瓷增韧机理。对化学活性低的MWCNTs进行酸化,并利用钛酸四丁酯在其表面负载TiO₂,以改善MWCNTs分散性及其与Ti（C,N）金属陶瓷的相容性,结果显示:MWCNTs在浓硝酸中于80℃浸泡1h可以去除杂质,减少缠绕粘连现象,使其能较稳定、均匀地分散在乙醇溶液中;MWCNTs表面负载纳米TiO₂可增加其在乙醇中分散性能。添加酸化后的MWCNTs到Ti（C,N）金属陶瓷中制备的复合材料具有典型的芯-壳结构:黑芯-灰壳和白芯-灰壳两种,随着MWCNTs添加量的增加,白芯-灰壳结构增多,黑芯和白芯都增大,黑芯结构变得不完整,材料的相对密度先缓慢下降,当加入量达到2.5wt%后急剧下降,复合材料的抗弯强度、硬度和断裂韧性呈现先增加后降低的趋势,在MWCNTs的添加量为1wt%时,材料抗弯强度、维氏硬度和断裂韧性分别为1224.46MPa、20.96GPa和9.85MPa·m^1/2,比未添加MWCNTs的Ti（C,N）金属陶瓷的各项性能（分别为1090.87MPa、19.01GPa,8.44MPa·m1/2）分别提高了11.33%、10.26%和16.71%。通过正交试验确定负载纳米TiO2的MWCNTs在Ti（C,N）金属陶瓷中的添加量为1wt%,烧成温度为1440℃,保温时间为20min,成型压力为25MPa,可获得最佳综合力学性能复合材料S10,其抗弯强度、维氏硬度和断裂韧性分别达到1275.14MPa、22.27GPa和10.60MPa·m^1/2,比未添加MWCNTs的Ti（C,N）金属陶瓷的各项性能分别提高了16.89%、17.15%和25.59%。MWCNTs对材料的增韧机理主要有MWCNTs的桥联和拔出、裂纹偏转、残余应力以及微孔洞增韧。将S10进行高温抗氧化性试验,在SEM电镜下观察样品发现,1100℃保温2h的样品表面致密,断面氧化层厚度为56.3μm,过渡层的厚度为11.12μm,这些致密的氧化过渡层有效地阻止样品的进一步氧化,显示了较好的高温抗氧化性能。更多还原

【Abstract】 Because of the excellent properties: high hardness, abrasion resistance, corrosion resistance, high temperature resistance etc. Ti（C,N） cermet received special attention in the industry application, such as metalworking and high temperature parts, but its widely using were limited by its brittleness. The mechanical properties of Multiwalled Carbon Nano-Tubes（MWCNTs） were higher than another fiber materials. Therefore, it is an important theoretical significance and practical value to investigate the prepartion and properties of MWCNTs/Ti（C,N） cermet composites.In this investigation, MWCNTs/Ti（C, N） cermet composites were prepared by purified, dispersed and vacuum hot pressing sintering, with TiC、TiN as raw materials, WC, Mo2C, TaC, Cr₃C₂ as hard addition phases, Ni and Co as binder phases, and MWCNTs as fiber reinforcing agent, the effects of MWCNTs addition on the microstructure and mechanical properties of Ti（C, N） cermet were investigated. The optimum content of MWCNTs and sintering system were finded, the high temperature oxidation resistance was characterized and the toughening mechanisms of composites were studied.The MWCNTs with lower chemical activities were acidified and purified by concentrated nitric acid, and nano-TiO₂ were supported on its surface by reacted with tetrabutyl titanate, to improve its dispersibility and compatibility in Ti（C, N） cermet, the results showed that: the impurities in MWCNTs were rapidly and effectively removed by concentrated nitric acid at 80℃holding 1h, the issues of winding and adhesion were reduced, the dispersity of disperse liquid were improved in ethanol with MWCNTs purified and supported TiO₂.The typical core-rim microstructure existed in acidified MWCNTs/Ti（C,N） cermet composites: black core-gray rim structure and white core-gray rim structure, the volume fraction of white core structure and the size of core structure were increased as MWCNTs addition increased, but the black core were incompleted as its increased, and the densities of cermet were decreased slowly then sharply until MWCNTs addition reached 2.5wt%. The bending strength, hardness and fracture toughness of cermet were trended to increase and then decrease as MWCNTs increasing. bending strength, Vickers hardness and fracture toughness of composites was respectively reached 1224.46MPa, 20.96GPa and 9.85MPa?m1/2,when MWCNTs addition is 1wt%, and respectively 11.33%, 10.26% and 16.71% improved comparing with the mechanism properties (respectively 1090.87MPa, 19.01GPa, 8.44MPa·m^1/2) of Ti（C,N） cermet without MWCNTs contented. The best comprehensive mechanical properties of sample S10 were reached by adding 1wt% MWCNTs supported TiO2, sintering in 1440℃holding 20min and the molding pressure is 25MPa, which obtained by orthogonal test, the bending strength, Vickers hardness and fracture toughness of S10 was 1275.14MPa、22.27GPa and 10.60MPa·m^1/2, was respectively 16.89%、17.15% and 25.59% improved comparing with the properties of Ti（C,N） cermet without MWCNTs contented. Bridging and pulling out of MWCNTs, crack deflection, residual stress toughening and micro-voids toughening attributed to fracture toughness of composites.High temperature oxidation resistance of S10 were studied, in the section SEM photograph of sample,the sample which put in 1100℃holding 2h with compact surface and content oxide layer and transition layer, the thickness respectively is 56.3μm and 11.12μm, this dense layer of protection were effectly prevent further oxidation of the sample, showed the excellent oxidation resistance.更多还原