【作者】 闵春燕；

【导师】 张孝彬；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2006， 硕士

【摘要】 纳米碳管增强铝基复合材料具有广泛的应用前景,通过纳米碳管增强体与铝基体的复合,使材料具有了单组元所不具备的优良性能。无压渗透是指熔融的铝合金在无外力作用下,借助浸润导致的毛细管压力渗入预制件中,无压渗透技术是一种制备金属基复合材料的新方法。与传统的固态法和液态法相比,无压渗透具有工艺简单、成本低廉、制备的复合材料致密度高等特点。本论文利用该方法制备了纳米碳管增强铝基复合材料,初步探讨了熔融的铝液向增强预制件中渗透的工艺条件,并对该铝基复合材料的摩擦磨损性能进行了相关的研究。 本文运用化学气相沉积（CVD）的方法制备了多壁纳米碳管,经超声分散处理后,用SEM、TEM以及Raman等对所制备的纳米碳管进行了表征。无压渗透法制备金属基复合材料存在的最大的困难是增强体与金属基体的浸润性问题。就本实验而言,最大的困难是CNTs/Al系统的润湿性差,导致熔融的铝液很难渗透进入增强材料中。为使渗透容易发生,本文主要采取了以下措施:1)在增强体中加入适量的Mg粉:2)加热过程中维持管式炉中有足够的氮气;3)提高渗透温度。复合材料的制备过程如下:首先将球磨好的预制粉末压制成块,然后在氮气流中将铝合金块和增强预制体加热至800℃,保温5小时,制备出CNTs增强的复合材料。用TEM、SEM、XRD和EDS测定了材料的成分和微结构,并系统地分析了无压渗透的影响因素和机理。研究结果表明,Mg能通过消耗预制块中颗粒与颗粒之间微小孔洞中的N₂、反应浸润和破坏氧化铝膜等机制改善Al液和增强体之间的浸润性。通过复合材料硬度测量和摩擦磨损实验,研究了不同纳米碳管质量分数对复合材料的硬度及摩擦磨损性能的影响。并用SEM观察复合材料断面的形貌。实验结果显示,纳米碳管均匀地分散于复合材料中,并且与铝基体结合良好;由于纳米碳管本身具有润滑作用,因此纳米碳管的加入使复合材料的摩擦系数和磨损率都随着纳米碳管含量的增加而减少。更多还原

【Abstract】 Aluminum composites reinforced with carbon nanotubes have a very good and attentive application perspective. This kind of composites fabricated by the incorporation of reinforcement CNTs and Al has very excellent properties that does not exist in the single component. The pressureless infiltration process employs a spontaneous infiltration of molten Al alloy into CNTs-Mg-Al preform though capillary press produced by the soakage of the reinforcement and the matrix. And this method is a novel way in the area of the metal matrix composites （MMC） fabrication, and is characterized by the simple process and low cost. We fabricated CNTs/Al composites using this method in this study and explored the process condition that the molten Al infiltrated into the preform. In the mean time we studied the tribological and wear properties of these composites.In this paper, CVD method was used to fabricate multi-carbon nanotubes. In order to make the CNTs become more disperse, ultrasonic machine was used before milling. In the same time the CNTs were investigated by SEM、 TEM and Raman. The biggest problem of the metal matrix composites fabrication using pressureless infiltration is the wetting between reinforcement and metal matrix. In this experiment the most difficult is the bad wetting in the CNTs/Al system. This problem led to the hard infiltration of aluminium liquid into the matrix. In order to make the infiltration become easier, the follow methods were adapted: 1) Mg was added properly in the reinforcement;2) N2 was full of the oven;3) Temperature of infiltration was enhanced. The fabrication processes of the composites are as follows: firstly, press the milled powder into block, and then put the Al block and the preform into the oven protected with N₂. After heating the oven to 800 and hold 5 hours. The composites formed and then take out of the oven. The microstructure and the component of the composites were investigated by TEM、 SEM、 XRD and EDS. And the factors affecting the pressureless infiltration and the mechanism were analysed. Theexperiment results indicated that Mg could greatly improve the wetting ability by consuming N2, reaction wetting, wetting transition, breaking up the alumina film and other mechanisms. The variation of the hardness of the composites with the content of CNTs was tested. The friction coefficent and wear rate of the composites were measured using a pin-on-disk wear tester. The fracture surface of the composite was observed using SEM and the results indicate that CNTs are well dispersed and embedded in the Al matrix. The friction coefficients and wear rates of the composites decrease with the volume fraction of CNTs. The favorable effects of CNTs on wear resistance are attributed to their excellent self-lubricating property, being well dispersed in the matrix of composites and the efficiency of the reinforcement of CNTs.更多还原