Shukai Xu

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.

Studies on the mechanism, structure and microhardness of Ni-W alloy electrodeposits

SUMMARYThe electrodeposition of Ni-W alloy has been studied on the glassy carbon electrode by the cyclic voltammetry and potentiostatic step methods. It has been found that electrodeposition of Ni-W alloy involves an intermediate valence tungsten oxide which inhibits hydrogen evolution. Ni-W alloy electrodeposition occurs by a mechanism involving progressive nucleation followed by three dimensional growth.The structures of nickel-tungsten alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD results from Ni-W alloy deposits reveal a face-centered cubic solid solution, the microstructure of the deposits exhibit (111) preferred orientation. The lattice constant and microhardness of Ni-W alloy deposit increase as the tungsten content increases, the XPS results of Ni-W alloy deposits indicate that the nickel and tungsten of the deposits exist in the metallic state, but the Ni-W alloy deposit with a tungsten content of 40.7% is an intermetallic compound. Th...

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.

Electrochemical nucleation and growth of copper on HOPG in presence of PEG and chloride ions as additives

Abstract Initial stages of copper electrodeposition on highly oriented pyrolytic graphite (HOPG) from acid sulphate solutions are studied using cyclic voltammetry and chronoamperometry. The electrolyte consisted of 0·001 mol dm−3 copper sulphate and 1·0 mol dm−3 sulphuric acid containing polyethylene glycol (PEG) and Cl−. It was found that the additives produce an initial inhibition of copper deposition, probably related to the adsorption. The initial deposition kinetics corresponded to a model including progressive nucleation and diffusion controlled growth. Addition of chloride ions and PEG did not change the initial nucleation of copper electrocrystallisation, but increased the nucleation rate and the number density of nuclei on the surface.

Studies of structure and electrocatalytic hydrogen evolution on electrodeposited Nanocrystalline Ni-Mo alloy electrodes

SUMMARY Nanocrystalline Ni-Mo alloy deposits were obtained by electrodeposition. The structures of the alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD shows that Ni-Mo alloy deposit with 15·2% molybdenum exhibits (111) preferred orientation, the lattice constant is larger than that of nickel metal. The XPS results on nanocrystalline Ni-Mo alloy deposits indicate that the nickel and molybdenum of the deposits exist in the metallic state, the binding energy of the alloyed elements increase to some extent. The nanocrystalline Ni-Mo alloy deposit electrode may offer better electrocatalytic activity than the polycrystalline nickel electrode. The electrochemical impedance spectra from the nanocrystalline Ni-Mo alloy electrode indicate that hydrogen evolution in 30% (m/m) KOH is in accordance with the Volmer-Heyrovsky mechanism.

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.

Effects of 3-thiothiol-1-propane-sulphonic acid sodium salt and sulphuric acid on the initial stages of copper electrodeposition

SUMMARY Initial stages of copper electrodeposition on a glassy carbon electrode from acid sulphate solutions are studied using cyclic voltammetry and chronoamperometry. The electrolyte consisted of 0.05 mol dm3 copper sulphate and 1.4 ∼ 1.8 mol dm 3 sulphuric acid containing 2 × 102 g dm 3 3-thiothiol-l-propane-sulphonic acid sodium salt (NaO3S (CH2)3 SSH). The results show that the additive produces an initial inhibition of copper deposition, probably related to the adsorption whereas sulphuric acid promotes copper electrodeposition. The initial deposition kinetics corresponds to a model including instantaneous nucleation and diffusion controlled growth. Addition of 3-thiothiol-l-propane-sulphonic acid sodium salt and sulphuric acid does not change the initial nucleation of copper electrocrystallisation but it increases the nucleation rate and the number density of nuclei at the surface.