The operating process, versatility and the increasing research interest in optimising the process and products technology in the electroless plating method of metal coating, particularly, the electroless nickel plating of metallic substrates such as mild steel, necessitates the writing of this review. It is also aimed at providing more literature information, both of the past and the present published research in this field. In this paper, electroless nickel plating is introduced. The various nickel plating solutions and baths’ operating parameters; main types of electroless nickel plating; the mechanism involved in the plating process; application of the nickel plating process to iron powders; advantages and disadvantages and the process’s other applications are reviewed. Electroless nickel plating produces an amorphous deposit in the as-plated condition. The deposit is not dependent on current distribution and hence it is almost uniform in thickness. Electroless nickel plating is far more difficult to remove chemically than conventional nickel deposits due to its superior corrosion resistance. The deposit has a good wettability and is generally hard. However, its bath control is more complex than with electroplating. The bath also has lower efficiency and higher operating costs, even without the use of electricity.

Electroless Nickel Plating – A Review

Electrochemical and structural properties of electroless Ni-P-SiC nanocomposite coatings

In this study, a Ni–P–WC nanocomposite coating was prepared by electroless deposition methods, modifying the typical Ni–P coating through the addition of WC nano-particles. The morphology, structure, microhardness and corrosion resistance of the Ni–P–WC coating and conventional Ni–P coating were analyzed by using the optical stereoscopic microscopy (OSM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), anodic polarization curve and electrochemical impedance spectroscopy (EIS). It was observed that WC nano-particles and Ni–P deposited homogeneously on the Ni–P matrix, electroless deposited composite coatings exhibit an amorphous structure of the nickel matrix in which crystalline tungsten carbide is incorporated. The microhardness of the coating increased due to the existence of the nano-particles, and it will be improved after heat treatment. According to the results of corrosion testing in the 3.5 wt.% sodium chloride solution, the electroless Ni–P–WC coatings showed significantly improved corrosion resistance due to its special structure, compared to a conventional Ni–P electroless coating, even after 40 days immersion, it also exhibited good corrosion resistance ability.

Development of electroless Ni–P/nano-WC composite coatings and investigation on its properties

Synthesis and properties of electrodeposited Ni–B–CeO2 composite coatings

Properties of electrodeposited Ni–B–Al2O3 composite coatings

To verify the relationship between the properties of composite coatings prepared on Q235 steel and the SiC content of electroless Ni–P–SiC composite coatings, systematic experiments with varied SiC contents and surfactants have been conducted. The experimental results indicated the approximate linear relation between the SiC content and the hardness of composite coatings. With the increasing of SiC content, wear resistance increases correspondingly. In particular, the effect of SiC content on the corrosion resistance of Ni–P–SiC composite coatings immersed in different corrosive solutions (i.e. 5% H2SO4, 20% NaOH and 3.5% NaCl) is explored, followed by a comparative analysis of the corrosion resistance between Ni–P and Ni–P–SiC coatings. Corrosion test indicates that NaOH solution makes no differences in the corrosion resistance between Ni–P coatings and electroless Ni–P–SiC composite coatings, both being uncorroded. Exposed to NaCl solution, the corrosion resistance of electroless Ni–P–SiC composite coatings decreases gradually with the increasing of SiC content in coatings. In H2SO4 solution, the corrosion resistance of coatings increases initially and decreases afterwards with the sustained increasing of SiC content in coatings, and the optimized corrosion resistance is obtained at a SiC content of 9.41 wt.%. Finally, a competent electroless Ni–P–SiC composite plating process producing a high wear resistance and sound corrosion resistance of the coatings is obtained.

The effect of SiC particles added in electroless Ni–P plating solution on the properties of composite coatings

A set of experimental platforms with widths of 0.5, 1.0, 1.5, and 2.0 mm was established to explore the mechanism of flow boiling bubble dynamics in microchannels, focusing on heat transfer characteristics, pressure loss, and two-phase flow pattern identification. Bubble flow, restricted bubble flow, and dry area were observed in all four channels. The appearance of flow pattern was related to flow rate and channel width. Under the condition of the same channel width, the initial heat flux of subcooled boiling gradually increased with increase in flow rate, and this change trend was close to the linear trend. Under the same flow rate, the initial heat flux of subcooled boiling increased with decrease in channel width. This condition was due to the faster flow rate of the working medium in the narrow channel, resulting in decrease of heating time. The increase in bubble generation frequency directly led to the increase in the wall heat transfer coefficient and the decrease in the bubble separation diameter. Mathematical analysis showed that under the condition of small flow, reduction of channel size led to reduction of the total wall heat transfer coefficient. In this condition, reduction of channel size cannot enhance heat transfer. With increasing volume flow rate, the range of hydrodynamic control area increased and the index decreased. When the flow rate was large, the total heat transfer coefficient increased greatly with the decrease in channel size. The theoretical values were in good agreement with the experimental data.

https://aip.scitation.org/doi/pdf/10.1063/5.0095786

Flow boiling heat transfer characteristics of two-phase flow in microchannels

Study on hydrogen dynamic leakage and flame propagation at normal-temperature and high-pressure


 As an efficient heat and mass transfer technology, falling film evaporation attracted more and more scholars' attention. A set of experimental platforms with widths of 0.5, 1.0, 1.5, and 2.0 mm was established to explore the mechanism of flow boiling bubble dynamics in narrow channels, focusing on heat transfer characteristics, pressure loss, and two-phase flow pattern identification. Bubble flow, restricted bubble flow, and dry area were observed in all four channels. The appearance of flow pattern was related to flow rate and channel width. Under the condition of the same channel width, the initial heat flux of subcooled boiling gradually increased with the increase in flow rate, and this change trend was close to the linear trend. Under the same flow rate, the initial heat flux of subcooled boiling increased with the decrease in channel width. The increase in bubble generation frequency directly led to the increase in wall heat transfer coefficient and the decrease in bubble separation diameter. Mathematical analysis showed that under the condition of small flow, the reduction of channel size led to the reduction of total wall heat transfer coefficient. In this condition, the reduction of channel size cannot enhance the heat transfer. With the increasing volume flow rate, the range of hydrodynamic control area increased and the index decreased. When the flow rate was large, the total heat transfer coefficient increased greatly with the decrease in channel size. The theoretical values were in good agreement with the experimental data.

Mechanism Analysis of Falling Film Evaporation Two-Phase Flow in Narrow Channels

Achieving the controlled release of functional substances is indispensable in many aspects of life. Especially for the aroma molecules, their effective delivery of flavor and fragrance is challenging. Here, selected pyridines, as highly volatile odorants, were individually coordinated with copper(I) iodide (CuII) via a straightforward one-pot synthesis method, rapidly forming pure or even crystalline CuII cluster-based profragrances at room temperature. The obtained profragrances enabled the stable and high loading of volatile fragrances under ambient conditions and guaranteed their long-lasting release during heating. Furthermore, the intrinsic emission luminescence of these solid-state profragrances decayed along with the aroma release, which can serve as an additional indicator for monitoring the delivery process. This research sets a precedent for using CuII clusters as dual-purpose release agents and greatly expands their potential applications.

Shusheng Zhang

Papers

The effect of SiC particles added in electroless Ni–P plating solution on the properties of composite coatings

Flow boiling heat transfer characteristics of two-phase flow in microchannels

Study on hydrogen dynamic leakage and flame propagation at normal-temperature and high-pressure

Mechanism Analysis of Falling Film Evaporation Two-Phase Flow in Narrow Channels

Copper(I)-Iodide Clusters as Carriers for Regulating and Visualizing Release of Aroma Molecules.