Synthesis and Thermal Stability of Nanocrystalline Nickel Coatings by Direct Current Electrodeposition

The influences of current density and saccharin concentration on nanocrystalline nickel coatings synthesized by direct current electrodeposition were analyzed. Results show that in the current density range from 0.5 A/dm2 to 1.5 A/dm2, nanocrystalline nickel coatings with broad microhardness HV distribution from 4150 MPa to 6030 MPa can be synthesized by adjusting saccharin concentration. The preferred orientation in the deposits exists at 0.5 A/dm2, (111), (200) double orientation texture changes to a (200) orientation texture as saccharin concentration and (200) intensity increase. The internal stresses of the samples prepared at 0.5 A/dm2 decrease to nearly 0 MPa as saccharin concentration increases to 1.2 g/L. The results of DSC curves show that the grains start to grow until 600 °C and keep the thermal stability near to bulk nickel when grain sizes are in the range from 28 nm to 98 nm. However, when the grain size is 10 nm, the grains grow abnormally at 317 °C, and their thermal stability decrease sharply.