Titanium oxide films, which may be of various colors due to interference, can be formed on titanium plate surfaces by CO2 laser irradiation under controlled oxygen content in the atmosphere. The irradiated surface shows some irreguralities due to rapid melting and solidification, but it is harder than and thus superior to anodic oxide coatings on titanium in terms of wear resistance. Just beneath the titanium oxide film is a hard fine-grained structure layer, which contains soluble oxygen.
Electroless deposition of Ni on the porous structure of anodic alumina formed in an oxalic acid solution was studied. Treatment by the application of Pd catalyst to the porous anodic alumina films, followed by a brief dipping in a Ni electroless plating solution, resulted in the deposition of Ni into the micropores of the anodic alumina films. The Ni deposit formed a fibrous structure which contained 5wt% P. The dependence of the depth of the deposition of Ni into tho micropores upon certain parameters, including the geometrical shape of the micropores, the concentration of the catalyzing solution and the duration of the treatment, was examined through SEM observation of the samples. Ni deposition into the inner part of the microporous structure took place at high concentrations of the catalyzing solution. It was confirmed that Ni could be deposited into micropores of 1000Å diameter to a depth of 5μm under optimum conditions. The mechanism of Ni electroless deposition into the micropores of anodic alumina was discussed based on the results obtained through SEM observation.
The leadframes for power transistors are generally of copper alloy strip plated with nickel and silver, and copper strike plating is usually applied to the nickel surface to improve the adhesion of the silver on nickel after thermal treatment. Accordingly, the mechanism by which copper strike plating increased interface adhesion was investigated by Auger electron spectroscopy. The results can be summarized as follows: (1) The poor adhesion of silver plating on nickel after thermal treatment in air was due to the penetration of oxygen into the silver layer and to the oxidation of the nickel surface. (2) The copper in the strike plated layer diffused into the silver plating after thermal treatment above a certain temperature. The diffused copper fixed the permeated oxygen at a position close to the silver surface, thereby inhibiting the oxidation of the nickel surface and improving the adhesion of the silver. (3) The copper in the strike plated layer also diffused into the nickel plating after thermal treatment, and the diffused copper is thought to act as an adhesive between the silver and nickel layers.
The effects of boric acid and plating bath pH on the average internal strain in electrically deposited nickel films were investigated by an electric resistance wire type strain gauge setup on the reverse side of a copper substrate having a preferred crystal orientation of (200), and the relation between the average internal strain and the preferred crystal orientation of the nickel film was also discussed. It was found that: (1) The internal strain in the nickel films rose rapidly with increasing bath pH near the electrode during hydrogen codeposition. (2) The addition of boric acid to the bath inhibited the hydrogen evolution reaction during nickel deposition, resulting in suppression of the rise in the internal strain in the nickel film. (3) The internal strain in nickel films deposited on the copper substrate rose in the order of (200)<(220)<(111)<disordered in terms of the preferred orientation relative to the ASTM standard for nickel powder. The brightness of the deposits also showed the same dependence on preferred orientation as did internal strain.
In the commercial production of striped, partially Sn pre-coated TFS-CT (Tin Free Steel-Chromium Type), it is very important to control the amount of metallic Cr deposited on the tin and bare Fe. On the basis of the fundamentally electrochemical behavior of Sn and Fe in a Cr plating bath, a technique for controlling the amount of metallic Cr on a continuous plating line is disclosed. The following results were obtained; 1) It was possible to achieve control of the coating amount of metallic Cr on Sn and Fe on an industrial scale using a method involving low current density at the front plating cells and high current density at the rear cells. 2) If the reductive removal of Sn-oxide film grown by aging after Sn preplating is incomplete, Cr coverage becomes insufficient and a brownish discoloration of Sn occurs. This may be avoided by applying a cathodic dichromate treatment after Sn plating, and by adjusting the Cr plating current density.
A study was conducted on epoxy urethane paint which is used as the back-side coating of steel sheet coated with polyvinylchloride (PVC) by film lamination method. The addition of melamine to the paint was effective in lowering the curing temperature, but it reduced plasticizer migration resistance and adhesion to the epoxy adhesive. Using oxime as the blocking agent for the isocyanate group and increasing the molecular weight of the epoxy urethane made it possible to lower the curing temperature to 180°C, and resulted in superior properties as back-side coating for PVC coated steel sheet.
Corrosion experiments on Au, Ag and Au-Ag alloys of various composition in 1mol/L solutions of NaHS and Na2S have been carried out at 150°C over 120 days. Ag2S was formed in NaHS solutions on Au25Ag75, Au10Ag90 and Ag100 (pure silver) and in Na2S solutions on Au50Ag50, Au25Ag75, Au10Ag90 and Ag100, but its morphology differed: The Ag2S formed in the NaHS solutions was platy, while that formed in the Na2S solutions was mostly whisker-like. It is thought that Ag2S morphology was controlled by HS- and S2- concentrations in the solutions and by the rate of sulfidation. The remarkably developed Ag2S scale seen on Ag100 was found to consist of an outer layer formed by the outward diffusion of Ag+ and an inner layer formed by the inward diffusion of S2-.
The fracture toughness KIC of cemented carbide (WC-Co) coated with TiN or TiC by PVD was measured by the Vickers hardness indentation method. It was found that the fracture toughness of the TiN-coated specimens showed a tendency to decrease with annealing at 1273K in a vacuum, whereas that of TiC-coated specimen increased.