Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

Electrodeposition of Ni-Co Alloys and Their Mechanical Properties by Micro-Vickers Hardness Test

Nanocrystalline Ni-Co alloy deposits with grain sizes less than 30 nm were produced by electrodeposition with a direct current in a sulfamate bath. Surfaces of the Ni-Co alloy deposits showed granular morphology. The size of the granular particles and the Co content decreased when a lower current density was applied. Addition of NiBr2 and a surface brightener (NSF-E) into the bath resulted in the grain refinement effect and an increase of Co content in the deposit. The grain size reached roughly 14 nm and 60 at.% of Co content in Ni-Co alloys electrodeposited with the bath containing the two additives. Ni-Co alloys obtained in this study showed higher microhardnesses than those of pure Ni and Co deposits prepared under the same condition, which revealed the solid solution strengthening effect. With a decrease in the grain size, the microhardness further increased, and this trend followed the Hall–Petch relationship well. The maximum microhardness value of 862.2 Hv was obtained owing to both the grain boundary and solid solution strengthening effects.

The characteristics of nickel film produced by supercritical carbon dioxide electroplating with ultrasonic agitation

This study uses a novel fabrication method of thin metal coatings by Ni electroplating combining ultrasonic agitation with supercritical CO₂ (US-SC-CO₂) mixed into conventional electrolyte. Coatings were also produced by the conventional and regular SC-CO₂ electroplating methods for comparison. The characteristics obtained from the three fabrication methods such as surface morphology, hardness, roughness; crystallographic orientation, grain size; wear and corrosion resistance were all individually analyzed. Results show that plating quality achieved by US-SC-CO₂ method is superior to that of regular SC-CO₂ and conventional methods. With US-SC-CO₂ process we achieved smoother and more compact surface morphologies, smaller grain size, lower surface roughness and higher microhardness, which also suggests good wear resistance. From XRD analysis we observed changes in preferred orientation due to application of the various methods. From the results of US-SC-CO₂ electroplating and the operating mechanism of ultrasonic agitation we can confirm that this new type of ultrasonic agitation can indeed replace the role of surfactants to enhance coating aspect and properties, reducing their influence over the deposited metal coating, associated costs, and waste. In H₂SO₄ solution, the nickel coating fabricated by US-SC-CO₂ method displayed the best polarization resistance among the three processes. More detailed experimental results and in depth discussion are presented in this paper.

Interaction of nickel with carbon dioxide in [Ni(CO2)(n)](-) clusters studied by infrared spectroscopy

We present infrared photodissociation spectra of [Ni(CO2)n](-) clusters (n = 2-8) in the wavenumber region of 1000-2400 cm(-1) using the antisymmetric stretching vibrational modes of the CO2 units in the clusters as structural probes. We use density functional theory to aid in the interpretation of our experimental results. The dominant spectral signatures arise from a core ion composed of a nickel atom and two CO2 ligands bound to the Ni atom in a bidentate fashion, while the rest of the CO2 molecules in the cluster play the role of solvent. Other core structures are observed as well but as minor contributors. The results for [Ni(CO2)n](-) clusters are discussed in the context of other anionic transition- metal complexes with CO2.