The arc ion plating (AIP) process uses a vacuum arc discharge with which almost all types of ceramic thin film can be formed. In this study, thin films of 40at% Ti-60at% Hf nitride were prepared on WC-Co substrates by AIP. The maximum microhardness obtained was Hv: 4000kgf/mm2. The crystal structure and orientation of the formed thin films were analyzed using X-ray diffraction (CuK α, 40kV-30mA). Reduced surface roughness and an increase deposition rate were studies as a function of nitrogen gas pressure. This process can be characterized by the high ionization rate of a metal vapor flux. Few studies have been made, however, on quantitatively assessing gas reactivity in a plasma process. The reaction probability of nitrogen gas in AIP was calculated from the viewpoint of metal-gas reaction kinetics, based on available data such as film deposition and nitrogen impingement rates on the substrate and compositional changes in films. The reaction probability (rN2=10-2) of nitrogen in Ti0.4Hf0.6N formation by AIP in this study was found to be equal to that in the hollow cathode discharge (HCD) process and higher than that in the activated reactive evaporation (ARE) by factors of three to ten.
The extent to which galvanized steel should be alloyed with Fe was studied in view of press formability. The buildup of delaminated coating on a die shoulder cannot be reduced by decreasing the coating thickness. Buildup can, however, be reduced by thinning the η phase. In half-alloyed coating where η and ZnFe-alloy phases exist together delamination does not occur due to biaxial stretching deformation as it does in conventional galvanized coating. It occurs from the Γ phase due to drawing deformation as it does in galvannealed coating. Half-alloyed galvanized steel can, therefore, be applied for a thicker-coated corrosion-resistant material with excellent press formability.
Sn and Pb-Sn plating steels are generally used as solderable outer-packaging materials for electrical machinery. Short-circuiting of electric machine parts due to the growth of Sn whiskers and the adverse influence of poisonous Pb on the environment arising with such materials have become increasingly serious problems. Electrogalvanized steels have been used as replacements even though their solderability is not as good as that of Sn and Pb-Sn plating steels. To improve solderability, we have studied Ni, Fe, and Sn preplating on electrogalvanized steels. In this report, we investigated solder spreadability, wettability, and peeling strength. Ni or Fe preplating under the Zn plating layer effectively improved solderability. Ni preplating showed a particularly excellent value for solder peeling strength. It was found that, while Zn gradually dissolved in solder, preplated Ni or Fe did not. This prevented the surface of the base steel from being exposed. Ni or Fe also formed Ni3Sn2, Ni3Sn, or FeSn2 with solder. These improve steel solderability.
The Corrosion behavior of sputter-deposited ceramic coatings, part of which contained various pure metals in intermediate layers, was investigated. In films coated by RF sputtering, defects such as pinholes inevitably occurred. These defects play a significant role in corrosion. In this study, various oxide films were coated on stainless steel by RF sputtering and pinhole defects in coating films were evaluated using electrochemical measurement. Electrochemical measurement was to evaluate the total defect area of the film using the value of the critical passivation current density during anodic polarization in a 0.5kmol/m3 H2SO4+0.01kmol/m3 KSCN solution, which restricts substrate steel passivation. The results obtained are summarized as follows (1) Ceramic coatings containing pure Al in intermediate layers showed better corrosion resisitance than other coatings. (2) In single- and multilayer coatings, the value of the critical passivation current density decreased in the following sequence: single-layer>double-layer>multilayer containing pure metal in the intermediate layer. (3) Coatings made in the suquence of oxide/metal/oxide had much better corrosion resistance than those in the sequence of oxide/oxide/metal.
Zn-Mn alloy electrodeposition from fluoborate baths was conducted and the deposition behavior was compared to that from citrate baths. The results obtained were as follows (1) Fluoborate baths markedly increased cathode current efficiency and the maximum current density applicable to this alloy system. The disadvantage of low productivity in citrate baths was thus largely eliminated in fluoborate baths. (2) Alloys consisting of ε and γ phases were obtained in both fluoborate and citrate baths. The morphologies of the deposited alloys considerably differed. (3) Codeposition of Mn with Zn occurred at more positive potentials in fluoborate than citrate baths. This enables the electrodeposition of a high Mn-content alloy with higher current efficiency in fluoborate baths. (4) Fluoborate baths showed a large pH buffer capacity at pH 3.5 and insoluble MnF2 formed at this pH. This indicates that Mn deposition proceeds by preceding MnF2 formation.
The effectiveness factor of Pt/Al2O3/Al plate catalyst was studied experimentally. The Pt/Al2O3 catalyst layer, prepared by anodic oxidation and hot-water treatment, had a porous structure and a narrow pore-size distribution. Catalyst porosity was about 0.5 and the mean pore radius about 2nm. The rate of cyclohexane dehydrogenation reaction increased with the thickness of Pt/Al2O3 catalyst layer to a certain peak, then the effectiveness factor decreased with thickness. This was because reactant diffusion into the catalyst layer was the controlling step. The observed reaction rate per apparent surface area is governed by the effective diffusion coefficient and the reaction rate constant. The reaction rate constant can be improved by augmenting the Pt content and Pt dispersion. The effective diffusion coefficient will be also improved with a large pore radius, which can be realized by controlling the anodized alumina layer pore structure.
The deposition mechanism in palladium electroless plating from ethylenediamine complex solutions containing trimethylamine borane (TMAB) as a reducing agent was investigated. The TMAB utilization factor was found to be 68% to 86% for palladium deposition and 25% to 32% for boron deposition. The deposition mechanism can be explained by the electrochemical mechanism, based on the following reactions. Local anodic reaction (CH3)3NBH3+2H2O→(CH3)3N+BO2-+7H+6e- Local cathodic reaction Pd2++2e-→Pd mPd2++(CH3)3NBH3+(2m-3)e-→PdmB+(CH3)3N+3H+