Platinum nanoparticle-supported activated carbon (Ketjenblack) was prepared in supercritical carbon dioxide solutions through hydrogen reduction reactions of bis-hexafluoroacetylacetonate-platinum (II). The dependence of temperature and reaction time on the particle size distribution was investigated, especially for particles smaller than 5 nm. Marked agglomeration of platinum was observed when the deposition temperature was high. Platinum nucleation took place mainly from 30 min to 60 min of the reaction time. Agglomeration and coarsening occurred mainly from 60 min to 90 min of the reaction time. The total volume of the platinum particles increased with increasing deposition temperature and reaction time.
This study investigated the behavior of isocyanide additives, which have π acidity, as stabilizers in an Electroless Nickel (EN) Plating bath. Stabilization using five isocyanide additives (1-isocyanobutane, tert-butyl isocyanide, 2-isocyano-2,4,4-trimethyl pentane, isocyanocyclohexane and isocyanomethyl benzene) was investigated. All these additives suppressed decomposition in an EN plating bath. Concentrations of 1–100 μmol/L kept deposition proceeding and suppressed decomposition, demonstrating that isocyanide additives can function as stabilizers in an EN plating bath. Polarization curves were produced to show EN plating bath stabilization characteristics attributable to tert-butyl isocyanide. It suppressed both anodic and cathodic reactions, which suggests that the stabilization of an EN plating bath using isocyanide additives is characterized by the suppression of both anodic and cathodic reactions. The suppressive effect of isocyanide additives was also examined in comparison to those of nitrile additives, which are isomers with a CN bond instead of the NC bond of isocyanide. Nitrile additives showed no suppressive effect on decomposition. Analysis of the polarization curve reveals that although these additives suppress the cathodic reaction somewhat, they do not suppress the anodic reaction at all, which indicates that the stabilization effect of isocyanide additives on an EN plating bath is generated by the NC bond in the additives.
Flowing-type micro-droplet cells (f-MDC) were applied to the anodic polarization of titanium surface in sodium-chloride-containing ethylene glycol solution. Anodic current attributable to removal of the surface oxide and the dissolving substrate flowed locally at the area limited with f-MDC, forming a hole on the surface. The hole shape and morphology were dependent on the applied voltage, polarization time, flowing volume rate, and the capillary employed for the f-MDC. Suitable conditions for polarization to obtain an ordered hole with f-MDC were discussed.
Deposition of micropored PVD hard coatings can be achieved using Cu microparticles fabricated on Ni-plated SKD11 substrate using square-wave pulse current electrolysis method. In this new process, reducing pin-holes in the Ni layer is crucial for stable generation of Cu particles because excessive deposition of Cu occurs to offset the current of dissolution of steel substrate at pin-holes in the Ni layer. Multilayered Ni plating reduced the number of pin-holes of Ni film of the SKD11 substrate. Moreover, no change was found in adhesion of CrN coating with the substrate. Increasing the thickness of the Ni film slightly decreased the adhesion of the CrN coating; a critical load higher than 50 N was maintained with the film thickness less than 1 μm. Pin-on-disk testing of the CrN coating with micropores with applied MoS2 as lubricant showed that the micropores brought about a low friction coefficient. Cupping test results demonstrated that maximum drawing force was lower when Cu microparticles remained on the CrN films. We concluded that friction properties of the coatings by this new process were equivalent to or superior to those obtained using previously reported processes using polymer microparticles.