An abrasion wear tester was used to ascertain the difference between the wear resistances of Cu/Ni multilayer films that were prepared electrochemically using single or dual baths. The formation of oxide layers on the deposited layers and the containment of phosphorus in the Ni layers improved the films' wear resistance. For conditions in which phosphorus was contained and surface oxide layers were formed, the film prepared using a dual bath exhibited slightly higher wear resistance than the film prepared using a single bath. The difference in the wear resistances was regarded as caused by the difference in the degree of the film surfaces' exposure to air because the film was exposed directly to air during transfer between the two baths in the dual-bath method. Therefore, for the single-bath method, the exposure of Ni layers to air after electrodeposition of each layer produced higher wear resistance of the film. Detailed analysis of the oxidation state of the metal and the surface morphology of the films using an X-ray photoelectron spectroscope, a scanning electron microscope, and an atomic force microscope revealed that the smooth Ni oxide layer formed on the Ni layers contributes to improved wear resistance of the films.
Bulk nanocrystalline Ni (nc-Ni) was electrodeposited using a sulfamate bath with different gloss agents. Saccharin sodium, 2-butyne-1,4-diol and sodium allylsulfonate, which were popular gloss agents for Ni plating, were chosen as gloss agents. Mechanical properties were evaluated to investigate the influence of gloss agent types on tensile properties in electrodeposited bulk nc-Ni. Results showed that gloss agent types strongly affect grain size, microhardness, and tensile properties of bulk nc-Ni. All bulk nc-Ni prepared using the sulfamate bath with gloss agents had a more refined grain size and higher microhardness than that prepared using a sulfamate bath without gloss agents. Particularly, bulk nc-Ni exhibited microhardness of greater than 700 Hv, when 2-butyne-1,4-diol was added to the bath. The tensile properties of bulk nc-Ni show different trends according to gloss agent types. When 2-butyne-1,4-diol was added to the bath, bulk nc-Ni exhibited no plastic deformation. Bulk nc-Ni obtained from sulfamate bath with saccharin sodium showed superior tensile ductility of greater than 10%. Bulk nc-Ni obtained from the sulfamate bath with sodium allylsulfonate exhibited high tensile strength of 1.8 GPa. These results suggest that bulk nc-Ni with different tensile properties can be prepared by choosing gloss agents.
In electroless copper plating using a nanodispersion of polypyrrole, adhesion and the deposition mechanism were studied. Using this electroless plating method, copper plating with high adhesive ability was produced on resins while maintaining a smooth surface. Results of XPS and SEM measurements suggest that the palladium ions in catalyst solutions are reduced by electron-donating dedoped polypyrrole to give zero-valent palladium, which acts as a catalyst of electroless copper plating. The reduction effects of polypyrrole on the palladium ions operate in the direction of polypyrrole thickness. Consequently, not only the polypyrrole surface but also the polypyrrole inner layer can supply electrons for palladium ions. Regulation of the polypyrrole thickness is necessary to obtain plating with high adhesive ability. This method is applicable to various resins because high adhesion between the polypyrrole layer and resins can be accomplished by choosing suitable binders for respective resins. In addition, direct pattern plating is obtainable by the pattern printing of polypyrrole using this method because palladium catalysts are only adsorbed onto sites with polypyrrole. In summary, this method is expected to be effective as a technology for use in etching-free plating on resins.
Pickling, zincate, chemical conversion, and electroplating processes were examined and optimized to obtain highly corrosion-protective coatings on AZ91D and AZ31 Mg alloys based on aspects of corrosion control in respective processes. The Pickling process bath composition was adjusted to suppress pitting corrosion and galvanic coupling corrosion between the α-phase and the β-phase to produce a flat dissolution surface. Potentiostatic anodic polarization was applied in the stannate chemical conversion process to an alloy specimen immersed in the conversion bath, thereby supplying sufficient Mg2+ ions to induce formation of a dense and uniform conversion coating. With the zincate process, Cu pretreatment in the precursory activation process enabled dense and uniform Zn deposition suitable for the plating process. Using these methods and conditions, better corrosion-protective coatings with dense, uniform, low-defective and high-adhesive properties were obtained on Mg alloys.
Thermal expansion properties of Invar (Fe-36 mass%Ni) alloy electrodeposits were investigated. The Fe-36 mass%Ni alloy electrodeposits from sulfate/chloride electrolytes using additives, saccharin sodium, and malonic acid. The electrodeposits, of about 150 μm thickness, had no crack. The thermal expansion curve showed that contraction of the electrodeposits occurred in the 270-420 °C range during first heating. During the first cooling and second heating, it showed the same behavior as that of melted Invar alloy. The coefficient of thermal expansion α (CTE) exhibited approximately α = 10×10−6/°C for the as-deposited electrodeposits and approximately α = 1×10−6/°C for electrodeposits annealed above 500°C. The CTEs of the electrodeposits annealed above 500 °C showed excellent agreement with that of the melted Invar alloy. The decrease in the CTE resulted from the increase of the fcc phase in the electrodeposits caused by heat treatment. Invar alloy electrodeposits are anticipated for application to high-definition electroformed products with low CTEs.
In the present paper, we describe direct copper electrodeposition on high resistivity substrates such as TiN and ITO from ethylenediamine complex bath. The copper electrodeposition was carried out at 1 A/dm2 and 50 °C. Smooth surface was obtained by adding thiodiglycolic acid. Good adhesion of deposited copper film on TiN was achieved from tape peeling test. Internal stress of deposited copper film from ethylenediamine complex bath was decreased by adding 5 mg/L NiSO4·6H2O in the bath. This bath could be used for the formation of copper wiring on high resistivity substrates as an alternative to conventional acidic copper sulfate bath.
A new recycling electroless nickel plating system has been developed using nickel hypophosphite as the source of metallic ions and as a reducing agent. In the system, phosphite ions, which are deleterious for the plating process, are fixed as the precipitate of calcium phosphite. Then they are removed from the solution. During repetitive plating operations, we maintained the plating solution composition and pH as almost constant values. The quantitative change of the reaction products provides theoretical confirmation that the system can be characterized as a ‘zero-emission-type recycling model’.
This study examined Ni-P electroplating with saccharin sodium salt. Hardness of the deposited films increased concomitantly with increasing concentration of the saccharin sodium salt in the plating bath. It reached Hvm = 822 at the concentration of 8.3 mol m−3. Crystallites in the films were too small to account for film hardening by the Hall-Petch mechanism.