THE EFFECT OF Ph ON THE PROPERTIES OF Ni-Mo NANOCRYSTALLINE ELECTRODEPOSITS

Nanocrystalline pure metals with grain size below 10nm are very difficult to prepare. Alloying enables the production of such a fine grains, even down to an amorphous state. In this work, Ni - Mo nanocrystalline coatings were electrodeposited from a citrate-ammonia base solution using a direct current (DC) technique. The grain sizes were estimated from X-ray line broadening. Mo content of the coatings was determined by energy dispersive X-ray analysis (EDS). The results showed that the grain size decreased when the Mo content of alloy was increased through reducing the bath pH. The microhardness measurements showed an increase in hardness with decreasing the pH, a maximum hardness of 820 Vickers was obtained for the coating deposited at pH9 with a 17 wt% Mo . Although, at pH values lower than 9, alloys with higher than 17wt% Mo were obtained, a softening effect was observed despite the decrease in grain size which is the result of transition from a nanocrystalline to amorphous structure.