Study on the Effect of the Thiourea on Nano-Mechanical Properties and Microstructures of the Electroformed Thin Ni-P Foil

Abstract

The effect of thiourea on the nano-mechanical and chemical properties of NiP foil was studied to develop a high performance NiP deposit for automobile and machinery parts. The NiP deposit was prepared by electroforming in a modified sulphate bath with different amounts of thiourea. Chemical analysis of the electrodeposited NiP foils by energy dispersive spectroscopy showed that phosphorous in the foil was reduced with thiourea. Structural analysis by X-ray diffractometry revealed that the (111) plane of the NiP deposits grew preferentially with increasing crystallinity. Surface analysis by atomic force microscopy and fieldemission scanning electron microscopy showed that the surfaces of the NiP electrodeposited with 0 and 0.01 g/L thiourea were relatively smooth and clean showing no nodules, whereas, the cauliflower-like nodules were observed on the surfaces of the deposits prepared with 0.03, 0.05, 0.07 and 0.1 g/L thiourea. The surface roughness (R RMS) of the deposits increased by addition of 0.1 ppm of thiourea from 6 to 54 nm. Nanomechanical properties of the NiP foil such as elastic modulus, hardness and stiffness determined by tribonano-indenter were tended to increase by addition of 0.1 ppm of thiourea from 77 to 156 GPa, 6.6 to 8.9 GPa and 109.6 to 186.6 µN/nm, respectively.