The electroless deposition of nickel-iron alloy has been investigated. The bath was less stable than an electroless nickel bath due to the formation of ferrous or ferric hydroxide precipitates. Gluconate ion was one of the best complexing agents for stabilizing the bath. L-ascorbic acid is a mild reducing agent and inhibited the formation of ferric ions in the bath. The deposition rate decreased with increasing ferrous sulfate content but it was possible to increase the rate by adding glycine. Other plating parameters that affect the deposition rate and the composition of the deposits were also investigated and it was possible to obtain films containing up to 20% iron using dimethyl amine borane as the reducing agent.
As specific applications of ion implantation to surface modification, nitrogen ion implantation was applied to S45C, a steel widely used for machine structural applications, to SCM 440 thermally refined steel, and to SCM 415 carburized steel, and their friction and wear characteristics were examined. The results can be summarized as follows 1) In an effort to improve the seizure resistance of SCM 415 carburized steel, investigation centered on a certaining the friction behavior of the nitrogen-ion-implanted surface layers using a Favill Le Vally friction testing machine. It was found that under unlubricated sliding friction, the effect of carburizing treatment in the preceding step was great. Under lubricated sliding friction, however, the load vs. friction coeffient curve for SCM 415 with nitrogen ion implantation was similar to that without, the load at which seizure started was 2000kgf or more, and higher loads could be withstood if ion fluences were increased. 2) The wear volume of the steels subjected and not subjected to nitrogen ion implantation in 1) above was measured to determine their wear characteristics. Since the modified layer of the implanted steels was thinner than that of the gas-nitrocarburized steel, they tended to suffer greated wear at short friction distances. When a modified layer existed, however no great difference in wear resistance was observed between the two kinds of steel. 3) Using a pin-ring-type wear testing machine, a series of lubricated sliding wear tests were carried out on thermally refined steel and thermally refined nitrogen-ion-implanted steel under conditions under which adhesion and thermal wear occur. It was observed that the nitrogen-ion implanted steel had a lower specific wear volume than the thermally refined steel. 4) Analysis of the nitrogen-ion-implanted surface layers and observation of the friction surfaces suggest that the improvement in seizure resistance and wear resistance with nitrogen ion implantation is attributable to the formation of iron nitride ε-Fe2-3N or higher iron nitride ζ-Fe2N due to the concentration of nitrogen ions in the surface layer, and that these iron nitrides have a substantial lubricating effect.
Electro-polymerized (EP) films based on acrolein (Ac) and on 2-vinylpyridine (VPy) monomers were synthesized on various metals, and the relationship between the growth mechanism of the two types of films and the corrosion resistance of the coated metals was investigated. At all conditions of electro-polymerization, VPy films were thicker (about 10μm vs 1μm for Ac). In corrosion tests, metals coated with the VPy films had better corrosion resistance than those coated with Ac films. The growth mechanisms of the two types also differed. During electropolymorization, the Ac films acted as an insulator, but those based on VPy acted as an ion-conductor. The study showed that the metal coated with EP film is more corrosion resistant if the film that are ion-conducting during electropolymerization can i) form thicker films, and ii) make possible easier insulation after post-treatment than insulationg films.
In order to make papers with excellent EMI shielding properties, the influence on EMI shielding effect of the morphology, thickness and microstructure of electroless Ni-B films on paper has been investigated. The EMI shielding effect was found to increase with increasing film thickness and with the formation of films that penetrated uniformly into the paper. The films as deposited on the papers were amorphous, but were converted into Ni and Ni3B crystal structures by heating to 300°C or higher resulting in an improved EMI shielding effect. Electrodeposition of Cu films on to the electroless Ni-B films greatly increased the shielding effect of the plating papers, equivalent to the shielding effect of Cu foil 35μm thick.
An investigation of asymmetric alternating current plating (AACP) of Pd-Ni alloy has revealed that a marked improvement in the morphologies of Pd-Ni alloy deposits is achieved, and crack formation is inhibited. Deposits obtained by AACP at a cathode peak current density (icp) of -0.6∼-1.4A/dm2, an anode peak current density (iap) of 0.2∼0.6A/dm2, and a period (θ) of 10ms were bright, smooth and completely crack free. In a bath of 0.05mol/dm3 PdCl2, 0.12mol/dm3 NiCl2, 0.51mol/dm3 ethylenediamine having a pH of 7, current efficiency was virtually consistent with the theoretical value for the plating condition described above. The palladium content of the deposits was a content 94∼96% irrespective of icpiap and θ. However, it decreased with increases in nickle ion concentration.
In a study of the electrochemical behavior of low-cyanide silver plating baths and of the properties of the deposits obtained, it was found that the current-potential curve obtained with a solid electrode showed a two-step reduction wave, the height of the first being 1/5 that of the second. Analysis of the results of polarographic and rotating disk electrode measurmenents sugests that the rate-controlling steps were AgCN+e-_??_Ag+CN-……(1) Ag(CN)2-+e-_??_Ag+2CN-……(2) for the first and second waves respectively. The Tafel plots of the two waves showed linear relationships at their rising portions, and the reactions are accordingly concluded to be slow chargetransfer controlled. In baths to which selenocyanate ion was added, the increase in current was markedly greater for the second wave than for the first, and the wave was shifted to the positive side. Potential decay curves for the baths containing selenocyanate ion obtained by the current interrupter method showed lower differential capacities than those for baths that were free of selenocyanate ion. This indicates that the selenocyanate ions were adsorbed preferentially at the electrode, suppress the adsorption of cyanide ions and enhancing the silver deposition reaction. Deposits obtained by jet plating were matt at current densities lower than 50A/dm2, and their appearance was not affected by the addition of selenocyanate ion. At above 50A/dm2, deposits obtained from selenocyanate-free baths were burnt, but deposits obtained from baths with selenocyanate ion added were mirror-bright with a strong (200) orientation up to around 150A/dm2.
The properties of silver deposits obtained by jet plating from low-cyanide baths were investigated. Deposits obtained from baths with and without the addition of selenocyanate at current densities lower than 50A/dm2 were matte, and were composed of randomly oriented small cristallites with very weak XRD patterns. The hardness of the deposits was around Hv 100. The amount of selenium codeposition in the matte deposits obtained from baths with selenocyanate was several times higher than that in the bright deposits obtained at 80-120A/dm2, which were composed of large crystallites strongly oriented to the (200) plane. Scanning ion microscopy revealed lines inclined 45° to the substrate, which are considered to be (111) plane stacking faults or twin crystals. The hardness of the deposits was around Hv 70. The matte and semi-bright deposits obtained by full-wave plating from selenocyanate-free baths were (111) oriented, and SIM showed many lines, which are considered as (111) planes, parallel to the substrate. Regardless of appearances, the wire bonding properties of all the deposits were virtually the same, and were satisfactory for application to semiconductor leadframes.
Without surface treatment carbon steel rusts, and drastically reducing its lifetime. Springs of carbon steel are thus generally zinc-plated or painted to prevent anticorrosion and thus maintain their function. Such treatment results in considerable hydrogen absorption, however, causing hydrogen brittleness and consequent intergranular fracturing and delayed fracturing. Because the rate of hydrogen diffusion is so high, quantitative analysis is extremely difficult, so that much remains to be clarified in the relationship between hydrogen content of the steel and delayed fracturing at the various stages of zinc-plating. It was therefore decided to investigate the relationship between the amount of hydrogen absorption and the delayed fracturing of carbon steel springs, with emphasis on pickling, zinc-plating thickness and baking. Results were as follows. (1) Hydrogen content increased during pickling and zinc-plating. (2) When zinc-plating thickness was adequate, no significant decrease in the total amount was produced by baking. (3) Delayed fracturing was influenced by structure, and did not occurr in specimens subjected to Austempering. Breakage rates were reduced to 0% in the lower hardness range.