Influence of Bath Additives on the Thermal Stability of the Nanostructure and Hardness of Ni Films Processed by Electrodeposition

Tamás Kolonits,László Péter,Jeno Gubicza,Imre Bakonyi,Zsolt Czigány

doi:10.3390/coatings9100644

Abstract

The effect of bath additives on the thermal stability of the microstructure and hardness of nanocrystalline Ni foils processed by electrodeposition was studied. Three samples with a thickness of 20 μ m were prepared: one without any additive and two others with saccharin or trisodium citrate additives. Then, the specimens were heat-treated at different temperatures up to 1000 K. It was found that for the additive-free sample the recovery of the microstructure and the reduction of the hardness started only at temperatures higher than 500 K. At the same time, a decrease of the defect density and hardness was observed even at 400 K for the additive-containing films. This was explained by the higher defect density, which increased the thermodynamic driving force for recovery during annealing. At the highest applied temperature (1000 K), this larger thermodynamic driving force resulted in a recrystallization in the sulfur-containing sample, leading to a very low hardness of about 1000 MPa as compared to the additive-free sample (1300 MPa). On the other hand, the sample deposited with trisodium citrate additive showed a better thermal stability at 1000 K than the additive-free sample: the hardness remained as high as 2000 MPa even at 1000 K.

Highlights

It is well known that nanocrystalline materials usually have unique properties as compared to their coarse-grained counterparts [1,2]
An investigation was conducted to evaluate the effect of bath additives on the thermal stability of the microstructures in nanocrystalline Ni films processed by electrodeposition
The following conclusions were drawn from the results: 1. Both saccharin and trisodium citrate increased the lattice defect density, but this effect was more pronounced in the former case

Summary

Introduction

It is well known that nanocrystalline materials usually have unique properties as compared to their coarse-grained counterparts [1,2]. The effect of the deposition parameters, such as pH and temperature of the bath, the applied current density, the stirring rate, and the composition of the bath on the microstructure of the sample, was studied. The results of these investigations have been summarized recently in [7].

Objectives

Methods

Results

Discussion

Conclusion