Characterization of Defect Structure in Electrodeposited Nanocrystalline Ni Films

Abstract

The microstructure of electrodeposited Ni films produced without and with organic additives (formic acid and saccharin) was investigated by X-ray diffraction (XRD) line profile analysis and cross-sectional transmission electron microscopy (TEM). Whereas the general effect of these additives on the microstructure (elimination of columnar growth as well as grain refinement) was reproduced, the pronounced intention of this study was to compare the results of various seldom-used high-performance structural characterization methods on identical electrodeposited specimens in order to reveal fine details of structural changes qualitatively not very common in this field. In the film deposited without additives, a columnar structure was observed showing similarities to the T-zone of structure zone models. Both formic acid and saccharin additives resulted in equiaxed grains with reduced size, as well as increased dislocation and twin fault densities in the nanocrystalline films. Moreover, the structure became homogeneous and free of texture within the total film thickness due to the additives. Saccharin yielded smaller grain size and larger defect density than formic acid. A detailed analysis of the grain size and twin boundary spacing distributions was carried out with the complementary application of TEM and XRD, by carefully distinguishing between the TEM and XRD grain sizes.

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

“…In the case of sample TSC, the grain size raised from ∼90 to ∼377 nm due to the heat treatment up to the temperature of 750 K. Between 750 and 1000 K, the grain size further increased slightly to about 405 nm as revealed by EBSD. Our previous papers [7,8] demonstrated that in the as-deposited samples the grain sizes obtained from TEM investigations also follow a log-normal distribution, similar to the crystallite size distribution [8]. After the heat treatments, almost all samples (NOA, TSC, and SAA) preserved the log-normal characteristics of the grain size distribution.…”

“…In addition, 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 also studied. The results of these investigations have also been summarized recently in [7].…”

“…Electrodeposited nickel is a frequently investigated nanocrystalline material [3][4][5][6]. The correlation between the microstructure and the physical properties of electroplated Ni was studied in detail during the past decades; a short summary of these investigations is given in [7]. In addition, 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 also studied.…”

“…The influence of different bath additives on the microstructure and hardness of electrodeposited Ni has been studied in former papers [7,8]. It was found that even a small amount of organic additives has a significant effect on the microstructure (grain size, defect density, and texture) of nanocrystalline Ni films.…”

Microstructure and Properties of Electrodeposited nc-TiO2/Ni–Fe and Ni–Fe Coatings

“…Those discrepancies between the grain size might be connected with the local character of TEM investigations and lower volume of analysed material than in XRD. The results of grain size determination using TEM images are also sensitive to the presence of many lattice defects, such as twins, which can break the X-ray coherency [37].…”