Sorption of Ni(II)-citrate complex from electroless nickel plating solutions onto chitosan

Spent electroless nickel plating solutions contain Ni(II)-citrate complexes which are hazardous to the environment. These complexes can be removed by using chitosan as a sorbent. Kinetic investigations indicate that Ni(II) sorption from complex solutions onto chitosan can be described by a pseudo-second order rate model. The experimental data of the adsorption under equilibrium conditions for both Ni(II) and citrate correlate well with the Freundlich isotherm equation. During the sorption of Ni(II)-citrate complex on chitosan competition between Ni(II) and citrate ions takes place. The citrate sorption prevails.

Adipate, the additive used in electroless nickel plating solutions, is not sorbed by chitosan, but its presence in solutions has an increasing effect on citrate sorption from citrate solutions without Ni(II) and the increasing effect on Ni(II) sorption from Ni(II)-citrate complex solutions. The other components of electroless nickel plating solution, i.e. hypophosphite, sulphate, phosphite have no influence on sorption.     

Monitoring of zincate pre-treatment of aluminium prior to electroless nickel plating

Zincating is used as a pre-treatment for aluminium prior to electroless nickel deposition during preparation of magnetic computer memory discs. Four immersion zincating solutions were evaluated at 22°C using single step or double zincating followed by electroless nickel deposition from a high phosphorus hypophosphite bath at 90°C. The coating process was monitored by potential vs. time curves obtained under open-circuit conditions during zincating then electroless nickel plating. The surface morphology of the aluminium, at various stages, was imaged by scanning electron microscopy and atomic force microscopy. Zero resistance ammetry was used to record galvanic currents between the aluminium and an inert platinum counter electrode during zincating. This, together with potential-time measurements, provided simple and valuable methods for following the zincating process and subsequent electroless Ni plating. Double zincating enabled a shorter induction time for electroless Ni deposition and resulted in a more complete coverage of the surface by Zn.     

Characteristics of nickel sulphide reduction in Ni2+ free background and Watts nickel plating electrolytes

Abstract

The electrochemical behaviour and composition of nickel sulphide coatings deposited on glassy carbon (GC) electrode by the successive ionic layer adsorption and reaction (SILAR) method using a nickel(II) ammonia complex and Na₂S solutions have been studied in Ni²⁺ free background, Watts nickel plating and 0·05 M H₂SO₄ electrolytes by the cyclic voltammetry and X-ray photoelectron spectroscopy (XPS) methods. Analysis of XPS data suggests that the coating is a mixture of two sulphides where NiS dominates. In the Ni²⁺ free background solution at first the electrochemical reduction of the sulphur rich nickel sulphide to NiS occurs. After that the NiS to metallic Ni is reduced in the potential range of H₂ evolution. During the cathodic reduction of the coating in Watts nickel plating electrolyte the sulphur is reduced in the potential range from 0·0 to ?0·4 V, while at the potential values <?0·5 V the sulphur rich nickel sulphide and NiS reduction in the H₂ evolution range and Ni plating occur.     

Electroless nickel deposition on silane modified bamboo fabric through silver,copper or nickel activation

Palladium-free process for the electroless nickel deposition on bamboo fabric (BF) has been developed. The process is based on 3-aminopropyltrimethoxysilane (APTMS) chemically grafted onto BF via a simple etchless method. Hence, Ni/BF composites can be obtained in three steps, namely: (i) the grafting of APTMS onto BF, (ii) the silver (Ag⁰), copper (Cu⁰) or nickel (Ni⁰) activating of the BF surface, and (iii) the nickel metallization using electroless plating bath. IR, XPS, XRD and SEM were used to characterize each step of the process. The nickel coating through silver activation has a smoother surface, higher electrical conductivity and better electromagnetic interference shielding effectiveness (EMI SE) by comparing to the other two activation samples. Magnetic property of the Ni/BF composites was measured, and composite from Ni activation has a larger saturation magnetization than the two left composites. All the nickel coatings via different metal activations are adhered firmly to the BF substrates, as determined by a standard adhesive Scotch®-tape test.     

镁合金AZ51直接化学镀镍研究

采用沉积速率计算、镀镍形貌观察和腐蚀性能测试，研究了镀镍时间对镁合金AZ51直接化学镀镍的影响。结果表明，镁合金AZ51表面可通过直接化学镀镍形成镍磷合金镀层。随着镀镍时间的增加，沉积速率先增加后降低并在镀镍时间为0．5h时取得最大值，而腐蚀速率逐渐降低，腐蚀性能逐渐增强。     

Diverse electrodeposits from modified acid sulphate (Watts nickel) baths

A diverse range of nickel-based coatings can be cathodically deposited from a classical Watts electroplating bath containing suitable additives by appropriate control over operational conditions. Modern nickel-based electrodeposits are concisely reviewed and can be seen to be longer-term developments from the publication of optimised conditions for rapid nickel plating from an acid sulphate bath by Watts 100 years ago, in 1916. Recent examples of tribological nickel electrodeposits are illustrated by examples from the authors’ laboratory: (i) low friction, hard, wear resistant surfaces (containing 2-D, layered, self-lubricating particles of Ni–P–MoS₂), (ii) superhydrophobic layers of Ni–WS₂, showing a lotus petal effect (for self-cleaning surfaces), (iii) light emitting, luminescent signal bearing surfaces of Ni–BAM (BaMgAl₁₁O₁₇:Eu²⁺) metal oxide, (providing an in-situ phosphor wear tracer) and (iv) nanocrystalline surfaces of Ni, Co, Ni–Co and Ni–Co–P (including high surface area electrocatalysts). Important trends in the deployment of the longstanding, versatile Watts nickel electroplating bath are seen to include the development of (a) surfaces having tailored structure, hence special properties, by choice of bath composition and operational conditions, (b) nanostructured composite layers containing mixed inclusions and (c) layers able to diagnose in-service wear and provide an output signal. Subject areas needing further research are suggested.     

化学镀镍作为钢酸性镀铜前处理工艺的应用研究

为了防止钢表面酸性电镀铜出现置换铜,采取在电镀铜前增加化学镀镍工序,研究了化学镀镍工艺对酸性电镀铜的影响。结果表明,化学镀镍时间超过6 min时(镍层厚度>2.5～3μm),工件在酸性镀铜液中浸泡10 min,无置换铜出现。化学镀镍层对后续的酸性镀铜层的表面形貌和附着力均无明显影响,表明化学镀镍可作为钢酸性镀铜的底层。     

WC颗粒表面超声波化学镀镍工艺

研究了利用超声波化学镀技术制备等离子熔覆用Ni包WC复合粉末的工艺方法，确定了一种优化的超声波化学镀镍工艺，并对复合粉末的形貌、性能及其等离子熔覆层的组织进行了分析与讨论。试验结果表明，经化学镀镍处理后的WC颗粒形状圆整，流动性得到改善；经等离子熔覆后，熔覆层组织均匀致密，WC烧损量减少。     

Effect of Cd as a stabilizer in the electroless nickel plating system

Bath decomposition is a major problem in the electroless nickel (EN) plating system. Although the stabilization mechanism is far from being fully understood, bath stabilizers are normally added to extend the bath life in a viable EN plating solution. In this study, the effects of Cd²⁺ as a stabilizer on the plating rate, bath stability, and phosphorus content, corrosion resistance and microstructure of the deposits were investigated. The deposited films were examined using a scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy and the X-ray photo spectroscopy (XPS). The electronic tunneling mechanism was used to elucidate the effect of the Cd²⁺ stabilizer on the plating system theoretically. The results calculated from theoretical method agreed well with the experimental data.     

Corrosion of AZ91D magnesium alloy with a chemical conversion coating and electroless nickel layer

A chemical conversion treatment and an electroless nickel plating were applied to AZ91D alloy to improve its corrosion resistance. By conversion treatment in alkaline stannate solution, the corrosion resistance of the alloy was improved to some extent as verified by immersion test and potentiodynamic polarization test in 3.5 wt.% NaCl solution at pH 7.0. X-ray diffraction patterns of the stannate treated AZ91D alloy showed the presence of MgSnO₃ · H₂O, and SEM images indicated a porous structure, which provided advantage for the adsorption during sensitisation treatment prior to electroless nickel plating. A nickel coating with high phosphorus content was successfully deposited on the chemical conversion coating pre-applied to AZ91D alloy. The presence of the conversion coating between the nickel coating and the substrate reduced the potential difference between them and enhanced the corrosion resistance of the alloy. An obvious passivation occurred for the nickel coating during anodic polarization in 3.5 wt.% NaCl solution.     

Electroless plating on the surface of kapok fibres: analysis of an effective palladium-free nickel salt activation process

A two-step, palladium-free, nickel salt activation process was tested on kapok fibres (KF). The results showed that the ratio of the concentration of hydrogen ions to the concentration of hydroxide ions ([H⁺]/[OH^?]) in the activation bath needs to be controlled within a range to achieve an optimal outcome. The final amount of deposited active Ni is not only dictated by [NiSO₄·6H₂O] but also dependent on the concentration of the reducing agent, [NaBH₄], whose proper value is complicated by its self-decomposition reaction that can be catalysed by the active Ni and H⁺ ions. The concentration of NiSO₄ employed needs to be capped to attain reasonable mass density and high electrical conductivity as required by light-weight electromagnetic interference shielding materials. An effective activation bath was formulated and experimentally confirmed to successfully initiate and sustain such an electroless plating process and a compact, uniform and amorphous Ni-P layer was formed on the KF surface.     

化学镀镍诱发过程催化活性的电化学本质

ＸＰＳ电子能谱技术的测定表明,化学镀诱发伊始,先只有镍的沉积,然后才有ＮｉＰ的共沉积出现。结合铜基试样在所设计的４种溶液体系中动电位扫描伏安曲线的结果,初步显示,对化学镀镍具有催化特性的金属,从电化学本质上来说,就是一种自身能提供到达或超过镍的析出电位的金属。通过电极电位的理论计算及混合电位的测定,说明了化学镀镍首先是镍析出,然后再发生ＮｉＰ共沉的机理     

镀镍石墨粉的电化学性质

利用化学镀方法在石墨粉表面镀覆了一层均匀、完整的金属镍,研究了镀镍石墨粉电极及镀镍石墨粉作为ＭＨ／Ｎｉ电池镍电极导电剂时的电化学性质。实验表明,石墨粉表面镀覆金属镍可增另其电化学活性;用镀镍石墨粉作为电极导电剂时,可以改善镍电极的导电性能,降低电池内阻,提高正极活性物质的利用率,且电池的循环稳定性好,以１Ｃ倍率充放电循环１２０就衰减。     

Surface behavior of pasted nickel electrodes with electrodeposited Co-Ce on substrate

1 Introduction MH/Ni batteries have supper specific energy density, better performance of charging and discharging, and are friendly to the surroundings. So, MH/Ni batteries have been applied widely in power tools[1]. The design of MH/Ni batteries is limi…     

Combinatorial performance characteristics of agitated nickel hypophosphite electroless plating baths

In this article, we present the combinatorial performance characteristics of agitated sodium hypophosphite electroless plating baths. Various performance characteristics assessed include bath conversion, plating efficiency, selective conversion, metal film thickness, average pore size, effective porosity and percent pore densification (PPD). Bath agitation was brought forward by rotating a symmetric disk shaped porous ceramic substrate with a nominal pore size of 275 nm. The plating characteristics were investigated for wide range of nickel solution concentrations (0.04-0.16 mol/L), stirrer speed (0-200 rpm) and for two different loading ratios (defined as substrate surface area per unit volume of plating solution) values (196 and 393 cm²/L). It was evaluated that stirring had a profound effect on sodium hypophosphite based electroless nickel baths, which are characterized with lower conversions (10-39%) and higher plating efficiencies (62-99%) without stirring phenomena. The stirred plating baths provided about 20-56% excess nickel plating rate when compared to the baths without stirring. This lead to a reduction in average membrane pore size by 20-42 nm and an enhancement in percent pore densification values by about 2-7%. Further, higher concentrations as high as 0.16 mol/L have been found to be detrimental to reduce the metal plating efficiency to lower values (42%). Observed data trends confirm upon the urgent need to identify suitable mass transfer enhancement techniques that target enhancement in selective conversion while providing good values of plating efficiency and PPD.     

Synthesis of novel silica-supported chelating resin containing tert-butyl 2-picolyamino-N-acetate and its properties for selective adsorption of copper from simulated nickel electrolyte

A novel silica-supported tert-butyl 2-picolyamino-N-acetate chelating resin (Si-AMPY-1) was successfully synthesized and characterized by elemental analysis, FT-IR, SEM and ¹³C CP/MAS NMR. The adsorption behaviors of the Si-AMPY-1 resin for Cu(II) and Ni(II) were studied with batch and column methods. The batch experiments indicated that the Si-AMPY-1 resin adsorbed Ni(II) mainly via physisorption, while adsorbed Cu(II) via chemisorption. The column dynamic breakthrough curves revealed that the Si-AMPY-1 resin can efficiently separate Cu(II) from the simulated nickel electrolyte before the breakthrough point. Moreover, the concentration of Cu(II) in the column effluent was decreased to be less than 3 mg/L within the first 43 BV (bed volumes), and the mass ratio of Cu/Ni was 21:1 in the saturated resin, which completely satisfied the industrial requirements of the nickel electrorefining process. Therefore, it was concluded that the Si-AMPY-1 resin can be a promising candidate for the deep removal of Cu(II) from the nickel electrolyte.     

硫酸镍铵复盐结晶法分离回收铜电解液中的镍（英文）

研究采用硫酸镍铵复盐结晶从铜电解液中分离回收镍的方法。研究发现,在相同温度的溶液中,硫酸铜的溶解度小于硫酸镍的溶解度,而硫酸铜铵的溶解度大于硫酸镍铵的溶解度。因此,加入(NH₄)₂SO₄可使铜电解液中的镍选择性结晶析出。按(NH₄)₂SO₄/NiSO₄摩尔比≤0.8加入(NH₄)₂SO₄,在-15℃冷冻结晶10 h,可使其中的镍以Ni(NH₄)₂(SO₄)₂·6H₂O的形式结晶析出。将所得结晶物热解,再将热解产物加水溶解,最后将溶解液浓缩结晶得到合格的NiSO₄·6H₂O产品。复盐结晶法是一种清洁环保、经济高效的从铜电解液中分离回收镍的方法。     

Study on a Medium Speed and Long Life-span Electroless Nickel Plating Process

A study has been made of the mechanism of hypophosphite-reduced acidic electroless nickel (EN) plating. The influences of temperature, pH value, reagents of pH, complex reagents and stabilizer etc. have been studied. Lactic acid and malic acid are selected as complexing reagents. KIO₃, HAc and ammonia are selected as stabilizer, buffer and pH regulator respectively. A new medium speed, long life-span and useful EN plating process has been developed.     

Influence of Ultrasound on the Properties of Electroless Plated Nickel

Ultrasonic agitation during electroless plating nickel affects the structure and properties of the deposits. In this work, a complete study was made of the action of ultrasound on the plating rate, micro-hardness, phosphorus content and corrosion properties of electroless plated deposits. It was found that in the presence of the ultrasound, the plating rate and micro-hardness of as-deposited were increased by about 30 and 10 percent respectively, whilst the phosphorus content was decreased from 10.49 to 8.39 at%. The changes in these parameters, in turn, affect the corrosion behaviour of the electroless deposits. The deposit formed with ultrasound exhibited active corrosion characteristics, whilst the deposit formed without ultrasound had a passive behaviour in 0.2 M H²SO⁴ solution.     

A study of chromium-free pickling process before electroless Ni-P plating on magnesium alloys

A chromium-free pickling process of magnesium alloys in H₃PO₄ + Na₂MoO₄ solution for electroless Ni-P plating was described. The dosage of Na₂MoO₄ was established by detecting adhesion and corrosion resistance of chemical nickel coatings. Electrochemical behaviors of pickling solution of H₃PO₄ + Na₂MoO₄ and NH₄HF₂ activation solution were investigated with the open circuit potential curves and the polarization curves. The results show that the Na₂MoO₄ has strong inhibition ability. Na₂MoO₄ in H₃PO₄ solution can reduce active sites of microcathodic and microanodic zones in the corrosion cells of the substrate surface of magnesium alloys and plays an inhibition role. The activation film with some oxides and fluorides can prevent the substrate magnesium from the fierce displacement and corrosion reaction of electroless plating bath. The chemical Ni-P coating with good adhesion and corrosion resistance was obtained by the pretreatment of 200 cm³ dm⁻³ 85% H₃PO₄ + 5 g dm⁻³ Na₂MoO₄ pickling bath and activation in 200 g dm⁻³ NH₄HF₂ solution. This procedure of surface pretreatment before electroless nickel plating can replace the existing acid pickling containing chromium and HF activation.