The Study Of Nickel Coated Carbon Nanotube And Reinforced Magnesium Matrix Composites

The carbon nanotubes excellent properties caused many world scientists attentionsince it was found by the Japanese electron microscope experts.People haveresearched various aspects things on the performance of carbon nanotubes because ithave huge potential application value in many fields, and has many excellent results.The carbon nanotubes surface energy is very high and the wettability with metalmagnesium is not good, there is a strong tendency of reunion that is easy to form aweak phase in carbon nanotube reinforced magnesium composite process, and theweak phase would cause the crack, pore defects easely, so the reunion is the mainreasons of reduced the physical and mechanical properties. Therefore, the mainresearch is improve the surface structure of carbon nanotubes, uniformdisperstiveness, and reinforce wettability of carbon nanotubes in matrix.Experiments with carbon nanotubes prepared with anodic arc plasma evaporationgraphite by the our task group. The self-developed product experimental device canproduce of the mesh, sheet and rod-like three kinds of carbon nanotubes. Three kindsof carbon nanotube products were purified,sensitization and activation. Thepurification inlay nickel functional groups: carbonyl (>C=O), hydroxyl group(-OH),carboxyl group (-COOH) on surface of carbon nanotube in the concentratedH2SO4and HNO3mixed acid. Nickel plating on the surface of carbon nanotubes byelectroless plating method, so that the surface of carbon nanotubes coated with a layerof about20nm thick nickel layer, thereby improving the carbon nanotube surfacestructure and performance, and enhance the compatibility of carbon nanotubes andmagnesium matrix, enhanced phase and matrix are linked closely together, that is, thereaction between the carbon nanotube coating and the magnesium matrix to generatethe interface phase of Mg2Ni.The nickel covered carbon nanotubes before and aftercoating were characterized with TEM (JEM-2010),EDS,XRD(D8) and SAED, foundthat different substances in the coating after heat treatment of different crystal spacingof the crystal face changes, you can see from the percentage of change in crystalspacing, the Ni lattice expansion existence of a face centered cubic structure is largest,which corresponds to (111) surface lattice expansion of up to1.49%; From Ni3P (bct)and Ni (Hexagonal)(112) expanding percentage,as can be seen the Ni3P (bct)expansion ratio of Ni (Hexagonal) about10times larger in the normal direction.The nickel-plated carbon nanotubes magnesium-based composite materials waspreparation by Full-liquid mixing method of casting, test the mechanical properties of the sample by the universal testing machine,When carbon nanotubes by adding1.1vol%, its tensile strength and elongation reaches its maximum, therefore, when thevolume fraction of CNTs for1.1vol%, The mechanical properties of compositematerials to achieve best. From the carbon nanotube/magnesium matrix compositeoptical microstructure photos, can be seen that the Matrix grain refinement graduallywith the amount of carbon nanotubes increase, and can prove that carbon nanotubes isplay a refine matrix grain role. When carbon nanotube content increases to1.6vol%,the figure appeared in big spots, this is a reunion of the carbon nanotubes;There areMg, C and Mg2Ni peak in the XRD patterns of the carbon nanotube/magnesiummatrix composites, This indicates that interfacial reaction occurred between thecarbon nanotube surface of the nickel layer and the magnesium matrix. Contain onlysmall amounts of carbon nanotubes and accounted for small portion of the reactionproducts between nickel and magnesium in the composite cause of Mg2Ni and C peakintensity is very weak.In this paper, CNTs/Ni/Mg, Mg/Ni/CNTs/TiO2magnesium-based carbonnanotube composites prepared by mixing casting method.The best performance of thestorage and release of Hydrogen was the best when the percent of the Ni was20wt%. The maximum hydrogen storage capacity can be reached6.94wt%when the content of nano-TiO2was2.0wt%, and the temperature of Hydrogen storage and release was also reduced obviously. After the metallic oxide TiO2and Mg were mixed by the ball grinder, the chemical dissociation of the hydrogenmolecular can be accomplished easily, and offer the new diffusion channel of the hydrogen atom,the reaction of hydrogen storage and release could catalyse the dissociation of the hydrogen molecular, and the kinetic properties of the material was improved relatively. The rate of the hydrogen storage and release of composite was increased and the formation of the hydrogenation enthalpy reduced significantly, and the composite showed good cycle steadiness, and then, the life of the material was improved greatly, the cost of the experiment was reduced. When the volume fraction ofCNTs reach1.1vol%, the mechanical properties of composites is the best, and Nickel-platedcarbon nanotubes in the composite is most uniform distribution. Carbon nanotubes can reduce theload of the substrate,hinder grain grew and refine grain by heterogeneous nucleation. This studyanalyze strengthening mechanism of carbon nanotube/magnesium matrix composites inStress transfer, dislocations and residual stress via shear lag model.From finiteelement theory, using ANSYS software establish a finite element model of carbonnanotubes reinforced magnesium matrix composites, the finite element model wasmechanical analyzed in a variety of load conditions,and study carbon nanotubes reinforcedmagnesium matrix composite stress and strain fields.