【作者】 金辉；

【导师】 李维学；

【作者基本信息】 兰州理工大学 ， 凝聚态物理， 2010， 硕士

【摘要】 本文全面综述了国内外碳纳米管镁基复合材料的发展现状,研究内容包括镍包覆碳纳米管的制备方法,复合材料的界面行为、微观组织和断裂机制。主要研究内容如下：利用自制的阳极电弧设备制备出碳纳米管及其管束,其准直性好、结构缺陷少、长度和直径分布均匀。产物中含有三种形态。根据产物的组成特点制定纯化办法。纯化结果表明,棒状物中主要含有单壁碳纳米管管束,膜状物和网状物中碳纳米管的含量较高,多为单壁碳纳米管及其管束。采用化学镀的方法在碳纳米管外表面上包覆镍层,化学镀中采用的碳纳米管是依据其官能团化程度筛选出的,镀覆结果显示镀层光滑、厚度均匀,对称性好。通过热处理提高镀层的结晶化程度,使镀层由无定形态转化为结晶态。发现镀层中的镍含有两种晶体结构：面心立方结构和六角密排结构,且镀层中发生了晶格膨胀。利用自制的阳极电弧等离子体制备方法,合成了外部包覆镍金属纳米粒子的碳纳米管,并分析其制备原理。以碳纳米管和碳化硅颗粒作为增强体材料,制备镁基复合材料,其晶粒明显得到细化。加入碳纳米管之后,复合材料的位错密度增加。但过多的加入量会导致增强体在晶界处发生团聚现象,在晶界处形成大块的黑色颗粒。碳纳米管表面包覆镍层,能够改善增强体与基体之间的相容性,加强两者的结合性。碳纳米管表面的镍层与镁基体之间存在界面反应,生成界面相Mg2Ni。界面相的生成量与碳纳米管的含量有关。碳化硅颗粒与镁之间也存在界面反应,生成了中间相Mg2Si。加入碳纳米管前后,镁基复合材料的断裂方式发生明显的变化。加入碳纳米管之后,复合材料的晶界得到了加强,促使裂纹转向晶粒内部扩散,从而形成穿晶断裂。但碳纳米管难以分散,在晶界的某些区域容易发生团聚,导致这些区域有利于裂纹的产生和扩散,形成沿晶断裂。并在断口表面发现少量韧窝,这是韧性断裂的特征。证明,CNTs/Mg复合材料的断裂方式是穿晶断裂为主、沿晶断裂和韧性断裂为辅的混合断裂方式。CNTs/SiCp/Mg与其类似。将基体材料换为AZ91D型镁合金之后,CNTs/AZ91D和CNTs/SiCp/AZ91D复合材料的断裂方式为韧性断裂和脆性断裂共存的混合断裂方式。更多还原

【Abstract】 The research progress of carbon nanotubes(CNTs) modified magnesium matrix composites has been reviewed in this thesis.The interfacial behavior, microstructure, fracture properties of Mg-based composites, and the approach of the preparation of carbon nanotubes with nickel layers have been studied.The main results are listed as followings:The CNTs have outstanding properties such as quasi-straight, fewer defects and they have the similar length and diameter, which were produced by using anode arc plasma method.The product has three styles.The ways of purification are due to their characteristic. The results show that the rod-like product contains mainly single-walled carbon nanotubes bundles, the film-like and network produce contain mainly single-walled carbon nanotubes and their bundles.The CNTs with Ni coated layers were obtained by an electroless deposition process. The CNTs were chose by their degree of functional groups.The electrolessly deposited Ni layers are distributed on the individual tube homogenously.The heat-treatment caused the transformation of the amorphous Ni-P layers to the nanocrystalline Ni-P layers.The crystal structures of Ni in plating layer contain:hexagonal close-packed structure and face-centered cubic structure. The lattice has expanded.The CNTs with Ni metal nanoparticles coatings have been produced by using anode arc plasma method. The preparation principle has been analyzed.The reinforcement of CNTs and SiCp could clearly refine the primary grains of magnesium matrix composite.The increase of dislocation density is due to the adding of CNTs.But the agglomeration would take place in the case of the degree of adding is too much.The layers could improve weak interfacial bonding between CNTs and matrix.The formation of Mg2Ni is due to the reaction between Ni layers and Mg matrix.The formation of MgSi2 is due to the reaction between SiCp and Mg matrix.The adding of CNTs leads the clearly difference in the fracture way of composites. The transgranular fracture is due to the adding of CNTs, which could enhance the grain boundary. But the agglomeration would induce intercrystalline fracture.The fracture way of the CNTs/SiCp/Mg was transgranular and intercrystalline fracture, and the later was not dominated.The fracture way of AZ91D/CNTs/SiCp is a mixed fracture, which contains cleavage, intercrystalline and gliding fracture.更多还原