In a previous paper the authors reported a novel wet preparation method for electro-conductive white powders homogeneously coated with In2O3-Sn film. Further experiments were performed to obtain insight into aging treatment of the suspension after hydrolysis reaction of the ITO compound, and into coupling agent treatment to stabilize the electro-conductivity of the resulting powders. The electro-conductivity of the final product was greatly improved by aging a suspension of fine powders coated with mixed ITO composition hydroxides for 60 minutes at pH 6.5±0.5 and 343K. Generally, the electro-conductivity of ITO-coated powders deteriorates owing to the influence of atmospheric oxygen. Coupling agent treatment of ITO-coated powders was found to be very effective in averting this effect. The applicability of various coupling agents, both silane type and titanate type, were examined. A coupling agent is an insulator by nature, so the use of excess amounts must be avoided. However, a suitable amount of coupling agent treatment exhibited remarkable effectiveness in improving the electro-conductivity of ITO-coated powders. A silane type coupling agent with a mercapto group was particularly effective. The decay of electro-conductivity over time caused by oxygen can be almost completely averted by use of coupling agent.
Diamond particles and films can be synthesized from the vapor phase using CVD, but thus far this has been subject to restrictions on substrate materials, substrate temperature, and synthesis conditions. It is especially difficult to synthesize diamond on Fe and Ni substrates because of the diffusion of carbon and other factors. In this study, we investigated diamond synthesis on Fe-P and Ni-P alloy plated substrates from a methane-hydrogen reaction gas system using microwave plasma CVD. Deposits were characterized by SEM, XRD and Raman spectroscopy. High quality diamond deposits were recognized on the Fe-P substrates. On the Ni-P substrates, it was found that both deposition rate and nucliation density increased in comparison to Si substrate. Diamond synthesis was possible using plating substrates such as Fe-P and Ni-P alloy, which are thought to suppress the diffusion of carbon into the substrate.
In a continuous reel-to-reel strip electroplating apparatus, electrical current is fed to a moving cathode strip through a conductor-roll in contact with the strip. Dent defects are occasionally induced on the strip surface from a irregular surface texture on the conductor-roll generated by non-uniform metal deposition onto the conductor-roll in the vicinity of the up-stream contact line area. We attempted numerical simulation of metal electrodeposition onto a conductor-roll in a thin drag-out electrolyte close to the contact line. The overall approach of the model was to treat the system as a problem of secondary current distribution, using measured electrochemical kinetics as the boundary conditions in binary alloy electrodeposition, under the assumption that the mass-transport effect is of minor importance. The potential posed on the domain thus obeys Laplace's equation, and the boundary conditions apply as non-linear functions determined by the anodic and/or cathodic polarization curves. An electrogalvanized steel sheet was used as the anode and a hastelloy sheet as the cathode. Using contact resistance between strip and couductor-roll, electrolyte resistance, strip ohmic resistance, difference in equilibrium potential, and activation overpotential, as the process variables pertaining to metal deposition on the conductor-roll, the electrodeposition rate onto a couductor-roll surface was numerically simulated for a zinc-nickel alloy electrodeposition system.
Self-lubricant Ni-CF (S) (Nickel-Graphite fluoride (S)) composite has been coated by electroplating from CF (S) particles suspended in nickel-watt electrolytes. We studied fine CF (S) particle dispersion in the electrolyte and factors controlling the amount of deposited CF (S) in the composite coating. CF (S) particles were dispersed in the electrolyte by adsorbing fluorocarbon cationic surfactants on to particles. Maximum amount of about 4.3wt% CF (S) was deposited in the Ni-CF (S) composite coating at a dispersion concentration of 70g/L. The amount of CF (S) and overpotential decreased linearly with increased nickel ion concentration in that electrolyte and increased temperature. The amount of CF (S) thus appears related to overpotential.
The co-deposition mechanism of TiO2 and Ni was studied. The amount of TiO2 particles in composite coating films increased linearly with the electrodeposition time and amount of Nickel deposited. Therefore, it was surmised that TiO2 particles close to the cathode are entrapped by the reduction of Ni2+ ion to Ni. TiO2 particles that adsorb cationic surfactants have a positive charge. Therefore, this adsorption affects the concentrarion of TiO2 particles close to the cathode and then the amount of co-deposited TiO2.
In anodization of alminum, electrolyte anions are incorporated into the oxide film from the liquid electrolyte. The anion distribution is related to physical and chemical properties and the mode of film formation. Prompt Gamma-ray Analysis (PGA) has higt sensitivity (2000cps·mg-1) and a low detection limit (0.002μg) for boron, so it is applicable to the determination of boron in aluminum oxide films. It was found that the average boron content was 0.25wt% with electrolysis at 25°C in a 0.5mol·dm-3 H3BO3-0.05mol·dm-3 Na2B4O7 solution. Differences of the electrolytes and in formation voltages, i.e. in the thickness of the barrier films, had little effect on this value, but it varied in proportion to the boron concentration in the electrolyte and decreased at higher temperatures. Boron was distributed to a distance of half the depth from the surface, and was not detected near the oxide/metal interface. This result can be explained on the basis of the transport number (0.45-0.6) of Al(III) ion and by the absorption of borate ions into hydrous aluminum oxides.