Effects of carbon nanotube concentration and nickel matrix crystalline on the elastic modulus of nickel-based composite coatings

Abstract

 The effects of carbon nanotube (CNT) composites on the elastic modulus of nickel-based CNT composite coating were investigated using the indentation method. The elastic moduli of the coating at CNT concentrations of 0-40 vol.% were evaluated by experimentation and numerical calculations. The elastic modulus was changed by the addition of CNTs because of changes in CNT composites and nickel crystal. The structure of the matrix changed from the columnar crystal to random crystal due to the addition of the CNTs. The elastic modulus of the coatings with low concentration of CNTs can be calculated by the rule of mixtures from the percentage of each crystal orientation and the value of elastic moduli of each crystal orientation, and were almost the same as the experimental value. The measured elastic moduli agree well with the predictions of Halpin-Tsai equations at low CNT concentrations in the matrix. The high-CNT-concentration layer, which is approximately 40 vol.%, can be prepared by periodic reverse electroplating. The coatings with a surface layer of high CNT concentration have a higher elastic modulus. Although the moduli increase with increasing CNT concentrations, the determined values are lower than the predicted values of elastic modulus derived from the Halpin-Tsai equations.