Interface Modification And Properties Of Carbon Nanotubes Reinforced Aluminum Matrix Composites

Carbon nanotubes (CNTs) have superior mechanical properties due to its special structure. Therefore, they are considered to be an ideal filler for improving the performance of metal matrix composites. CNTs are an kind of carbon materials in nanometer scale and their surface free energy is very high, thus it is difficult to make them uniform disperse in aluminum matrix. Meanwhile, the difference of density and coefficient of thermal expansion between CNTs and Al make their interfacial bonding weak. Most available CNTs in market often have some defects along their outer walls. Also, there is a significant amorphous carbon coating on their surface. These factors lead to the interface reaction between CNTs and ALFor improving the interfacial bonding between CNTs and Al, Ni coated CNTs were used as reinforcement. Firstly, CNTs need to functionalize, and then an nanoscale Ni particle were coated on their surface using electroless plating with non-palladium action procedure. The composites were fabricated by ball milling followed by hot rolling. We also use hot extrusion to prepare composites. Finally we test the mechanical properties of CNTs-Ni coated/Al composites, so we can study the benefits of Ni coated CNTs. Meanwhile, bulk samples were fabricated to examine the performance stability of composites, which have two kinds of CNTs as reinforcement and Al matrix.The results showed that CNTs treated by mixed acid and H2O2 can effectively been functionalized. The Ni coated CNTs which were produced by electroless plating have an homogeneous coating, and Ni particle is about 5 nm. The composites fabricated by hot rolling have high relative density. The XRD test of composites found that CNTs still existed in composites and there are less impurities. In 1.5 wt.% Ni-coated CNT/A1 composites, the ultimate tensile strength and hardness reach 335.53 MPa and 96.63 HB, respectively, compared to pure Al, which increased by 73.5% and 38%, respectively. Simultaneous enhancements of the ultimate tensile strength by 23.5% and the hardness by 20.4% in comparisons with that of the uncoated CNT/Al composites were achieved. We found that with the increase of tensile strength of composites, the ductility decrease at the same time. Ni coating makes the behavior of CNTs in fracture morphology changed and it helps the CNTs enter into Al particle quickly than pristine CNTs during the same ball milling time. TEM observation of Ni coated CNTs reinforced Al composites demonstrated Ni particles on CNTs surface. The interface reaction product were revealed in pristine CNTs reinforced Al composites.The tensile strength and hardness of composites fabricated by hot press and sintering indicated that the performance stability of composites is good. The tensile strength of CNT KJ-2B/5083A1 composites can reach 455 MPa, when the contents of CNTs was 1.5 wt%. The hardness of composites can reach 113 HB, when the contents of CNTs was 2.5 wt%.