The In-situ Synthesis Of CNTs Reinforced Titanium Matrix Composites By Chemical Vapor Deposition

Carbon naonotube (CNT) is a kind of important reinforcement in metal matrix composites because of its high module, high strength and outstanding physical performance. It is significant that exploring new manufacture technique for CNTs reinforced titanium matrix composite and investigating the effect of CNTs on the properties for developing the CNTs'application fields and improving titanium alloy capability.In the thesis, a new Ni/Ti catalyst was prepared through deposition-precipitation method. Then, the CNTs/Ti composite powder was synthesized in-situ on titanium powder with the Ni/Ti catalyst by chemical vapor deposition (CVD) process. The influence of the processing parameters, such as the content of catalyst, reduction temperature, CNT synthesis temperature, carrier gas category and the radio of methane to carrier gas, were investigated. The growth mechanism of CNTs on the new Ni/Ti catalyst during CVD was discussed. The results indicated that the processing parameters including the content of catalyst and CNT synthesis temperature have a important influence on the growth of CNTs. The CNTs with even morphology, high yield and purity can be synthesized by methane decomposition when the content of catalyst is 3wt% and the synthesis temperature is 550℃. As a result, the aim of this experiment for preparing CNTs on titanium powder using in-situ CVD process has been achieved, which points out a new method for CNTs/Ti composites manufacturing.Furthermore, The CNTs/Ti composite bulks were prepared by powder metallurgy process with the synthesized composite powder. The density and hardness of the CNTs/Ti composite bulks were tested. The Friction attrition experiment was carried out on CNTs/Ti composite bulks in a dry grinding condition. The results show that the CNTs/Ti composite has better wear resistance performance than titanium bulk. Along with increasing of friction time and load, the width of wear markers of the CNTs/Ti composite and titanium bulks were both increased, but the wearing degree of CNTs/Ti composites changed much slowly than that of titanium bulk. The Friction characteristic of the CNTs/Ti composites includes grain abrasion, oxidative abrasion and so on.