Sm Zhou

Electrochemical study on electroless copper plating using sodium hypophosphite as reductant

Abstract The process of electroless copper plating, using sodium hypophosphite as the reductant and sodium citrate as the chelating agent, was studied using liner sweep voltammetry. The effects of temperature, pH, and concentration of nickel ion on the anodic oxidation of hypophosphite and the cathodic reduction of copper ion were tested. The results indicated that the higher bath temperature accelerated both the anodic and the cathodic processes. The increasing pH value promoted hypophosphite oxidation, whereas it blocked the reduction of the copper ion. The nickel ion not only intensively catalyzed the hypophosphite oxidation but also codeposited with the copper ion to form the Cu-Ni alloy. With regard to its catalytic activity, this alloy enabled the continuation of the electroless copper plating reaction.

Study of the structures of pulse plating Zn-Fe deposits

Abstract Pulse plating Zn-Fe (6.0 wt%–7.4 wt%) deposits have been studied by means of X-ray diffraction. The results showed that pulse current parameters affected not only the textures of the deposits but also their phase constitutions. Under the condition of average current density of 6 A/dm 2 in pulse plating, when pulse frequency was larger than or equal to 100 Hz, the Zn-Fe deposits were identified as h.c.p. η-phase; if pulse frequency was less than or equal to 1 Hz, the Zn-Fe deposits were of η- and monoclinic ζ-phases. At constant average current density and pulse frequency, an increase of the duty cycle results in an increase of the (101) texture coefficient of the Zn-Fe deposits, while the decrease of the duty cycle favoured the formation of a deposit with (112) texture. A Zn-Fe deposit with (112) highly preferred orientation was obtained.

Electrocrystallisation of cobalt during preparation of Co/Cu multilayers

Abstract The electrocrystallisation of cobalt onto a glassy carbon electrode from cobalt sulphate electrolytes either with or without the addition of a small amount of copper ions was investigated through the electrochemical techniques of cyclic voltammetry and chronoamperometry. Voltammetric results showed that the cobalt deposits obtained were impure and the overpotential for cobalt nucleation was low for electrolyte with a small amount of copper ions. Analysis of the current–time transients by chronoamperometry indicated that the nucleation mechanism of cobalt in cobalt sulphate solution occurred by a combination of two different kinds of parallel nucleation processes, instantaneous or progressive nucleation with two-dimensional or three-dimensional growth, which depended on the overpotential applied. However, in the presence of copper ions, the nucleation mechanism was in accordance with 3D growth under diffusion control. Progressive nucleation occurred at a lower overpotential and instantaneous nucleation at a higher overpotential. The deviation of the experimental data from the theoretical model was explained.

Influence of chloride and PEG on electrochemical nucleation of copper

SUMMARY The influence of chloride ions and polyethylene glycol (PEG) on the nucleation of copper on glassy carbon from acid sulphate solutions was studied by measuring potentiostatic current transients (the chronoamperometry method). It was found that instantaneous nucleation occurred at the surface for solutions without additives. The initial stage of copper nucleation did not change on addition of chloride ions, but gradually changed from progressive nucleation to instantaneous nucleation at increasing potentials in the presence of PEG. Chloride ions and PEG increase the nucleation rate and the nuclear number density of nuclei at the surface.

A Study on the Effect of Bath Composition on the Internal Stress of a Palladium Electrodeposit

SummaryThe effects of bath composition on the internal stress of palladium electrodeposits are studied in neutral media with Pd(NH3)2Cl2, K3C6H5O7, (NH4)2C2O4 and the additives of the mixture of the synthesized products of nicotinic acid and nicotiamide (NANA), pyridine-3-sulfonic acid(PSA), α-furane formic acid(FF) and cetyl trimethyl ammonium bromide(CTMAB). The results show that the internal stress of electrodeposits is quite changeable at the beginning of electrodeposition later becoming stable gradually. Deposits obtained from pulse electrodeposition have lower stress than that from direct current. After electrodeposition, all the deposits keep in tensile stress which increases with time.

Study on some properties of the electrolyte solution in the electrodeposition of palladium

Some properties of Pd electroplating solution were studied. The results showed that current efficiency and velocity of palladium deposition were decreased and increased respectively by raising the current density, which indicated that the stirring of plating solution was an effective route to raise current efficiency. The choice of concentrations of potassium citrate and ammonium oxalate in solution was mainly determined by the complexing ability of potassium citrate for the palladium ion and the solubility of ammonium oxalate. The electrolyte was shown to have a good throwing power and excellent covering power Hull cell tests showed that an adherent, smooth, bright and white Pd electrodeposit could be obtained.

非晶态Ni-W/ZrO 2 复合镀层的制备、热处理及腐蚀行为

A Ni-W/ZrO2 composite coating was prepared by electrodeposition from a Ni-W bath containing zirconia solid particles suspended in an electrolyte solution by stirring. Results showed that the presence of zirconia particles influenced the electrodeposition, surface morphology, crystallographic structure, thermal treatment and corrosion resistance of the obtained composite coating. By comparison to Ni-W alloy electrodeposition both W content in the Ni-W matrix and deposition current efficiency for the composite coating decreased. After heat treatment at 400 ℃ for 1 h some embedded zirconia particles were removed from the Ni-W matrix and W was enriched at the top surface of the deposit. Scanning electron microscopy (SEM) results revealed that the composite coating had a granular morphology and was crack-free. A differential scanning calorimetry (DSC) experiment combined with X-ray diffractometry (XRD) indicated that the Ni-W/ZrO2 composite coating was amorphous. The microhardness of the composite coating was higher than that of the nanocrystalline Ni-W alloy. After heat treatment of the composite coating its microhardness and corrosion resistance in 3% NaCl solution were greatly enhanced.A Ni-W/ZrO2 composite coating was prepared by electrodeposition from a Ni-W bath containing zirconia solid particles suspended in an electrolyte solution by stirring. Results showed that the presence of zirconia particles influenced the electrodeposition, surface morphology, crystallographic structure, thermal treatment and corrosion resistance of the obtained composite coating. By comparison to Ni-W alloy electrodeposition both W content in the Ni-W matrix and deposition current efficiency for the composite coating decreased. After heat treatment at 400 ℃ for 1 h some embedded zirconia particles were removed from the Ni-W matrix and W was enriched at the top surface of the deposit. Scanning electron microscopy (SEM) results revealed that the composite coating had a granular morphology and was crack-free. A differential scanning calorimetry (DSC) experiment combined with X-ray diffractometry (XRD) indicated that the Ni-W/ZrO2 composite coating was amorphous. The microhardness of the composite coating was higher than that of the nanocrystalline Ni-W alloy. After heat treatment of the composite coating its microhardness and corrosion resistance in 3% NaCl solution were greatly enhanced.