Fabrication and Characterization of Aligned Carbon Nanotubes Cluster Reinforced Magnesium Composite Based On Ultrasound/Magnetic Compound Field

Carbon nanotubes (CNTs)-based materials have been the focus of intense research since their discovery because of their superior mechanical properties, good electrical conductivity and unique nano-effect of unique one dimensional nanostructures. Control and manipulation of the alignment of CNTs in the matrix can effectively affect the electrical, optical and mechanical properties of the composites. At present, there are many researches on the magnetic-field induced the alignment of CNTs in the polymer matrix, but less research on magnetic- field induced the alignment of CNTs in the metal matrix. In order to realize the alignment of CNTs in metal matrix, CNTs were firstly magnetically modified by electroless plating, and a uniform layer of cobalt nanoparticles was successfully plated on the surface of carbon nanotubes. For facilitating the macro-analysis of the different factors on the cobalt-carbon nanotubes directional effect, three kinds of matrixes (distilled water, vegetable oil and high viscosity glue) were used to simulate the magnesium alloy melt. The effects of ultrasonic, magnetic field and temperature on the Co coated CNTs dispersion and alignment in three kinds of matrix were studied by orthogonal test. It was found that the dispersion of CNTs was significantly affected by ultrasound and the alignment of CNTs affected by the magnetic field intensity. In this paper, the CNTs / Mg composites were prepared by liquid-state method and the wettability between CNTs and Mg alloy was improved by the modification of carbon nanotubes. Under the compound effect of ultrasonic and magnetic field, the alignment of the carbon nanotubes cluster in magnesium matrix composites was quantitatively characterized by Image J software. It is found that the Cobalt particles coated CNTs can respond well to magnetic field (typically 0.3-0.8T). With the increase of magnetic field strength, CNTs show higher relative frequencies along the magnetic field direction. When the magnetic field strength was 0.8T, the relative frequencies within 20-50° was 0.7. This indicated that Co-CNTs can achieve obviously alignment in AZ91D alloy under a low magnetic field. In addition, the compressive specimens were prepared according to the optimum process parameters determined by the orthogonal test. The compressive properties of the composites parallel to and perpendicular to the direction of the magnetic field were studied. The results shown that the compressive strength of the Co-CNTs/Mg composites was obviously higher than that of the magnesium matrix and exhibited anisotropy due to directional aligned carbon nanotube.