Interfacial mechanics of carbonaceous reinforcements in electrophoretically deposited nickel coatings

Electrophoretically deposited nickel and its composite coatings are extensively used in aerospace and automotive industry for steel plating, super mirror, multilayer monochromator due to superior corrosion resistance and mechanical properties. The present article proposes a systematic approach of comparing the elastic modulus of electrophoretically deposited Ni with diamond, carbon nanotubes (CNT) and graphene reinforcements. Dynamic modulus mapping of electrophoretically deposited coatings exhibited an increased elastic modulus on the addition of diamond, CNT and graphene (259.8 GPa, 217.6 GPa and 210.7 GPa, respectively) than that of pure Ni (167.7 GPa). This conflicting effect on the elastic modulus arises due to the difference in reinforcement's morphology, which is further examined using the rule of mixture (ROM), combined Voigt-Reuss model (V-R) and Hashin-Shtrikman model (H-S). Closer prediction of elastic modulus via V-R model indicates that volume fraction plays the more dominant role than the aspect ratio of the reinforcements. In ROM and H-S model, the values of elastic modulus of CNT and graphene reinforcements are closer to the lower bound, while with diamond reinforcement, elastic modulus value approaches in between the upper and lower bound, ascertaining strong interfacial anchoring of diamond with matrix than CNT and graphene. Reinforcement factor (Rf) has also confirmed this strong mechanical interlocking of diamond with the matrix which was ~ 1.7 and ~ 3.0 times higher than CNT and graphene, respectively.