Nano-Composite Coating of Ni+RuO2 by Co-Electrodeposition Part II: Morphology, RuO2 paricle size distribution and substrate pretreatment

Surface morphology and structure of a nano-composite coating of Ni+RuO₂ on Ni substrate were characterized by SEM, SEM-EDX, X-Ray Map. The Morphology observations by SEM revealed that the co-electrodeposited coating of Ni+RuO₂ has a rough surface covered by cauliflower-like particles which distributed homogeneously on the Ni substrate. The bare Ni; however, has a partly smooth and porous surface. The presence of 3.62 %w RuO₂ on the coating surface which diffuse less into the coating was confirmed by SEM-EDX. Study of the RuO₂ particle size distribution in colloidal suspension by light scattering (LS) showed a homogeneous Gaussian distribution with no sign of agglomeration. The X-ray Map followed by image analyzing demonstrated a non-uniform nano particle size distribution below 100 nm on the coating surface. Additionally, the average RuO₂ particle size of 527nm in the suspension and 42nm on the coating surface were measured. The coating activity was also enhamced with mechanical polishing compared with chemical etching according to linear sweep voltametry results. In the former the cathode surface was rough but uniform while in the lather a smooth surface was observed by SEM.