The interdiffusion between plated tin layer and copper zinc alloy substrate during heat treatment have been studied with special interest to the effect of the alloy composition on the diffusion behavior. Specimens were Cu-Zn alloys (5, 10, 20, 30 and 38 wt % Zn) plated with tin of 10μm in thickness. Heat treatments were made at 623, 673K for 1.8, 3.6 and 7.2ks. The diffusion layer formed was examined by optical microscope, EPMA and X-ray analysis, together with microhardness tester. Heat-treated specimens yielded η, ε or γ phases at the interface depending on temperature and alloy composition. The activation energies of γ phase formation in 5, 10 and 20wt % Zn alloys were 160, 130 and 91 KJ/mol respectively. The fact indicates that heat treatment at higher temperatures favors the formation of γ phase. The hardness of ε and γ phases were Hmv 400-420 and 480-500 respectively.

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Polarographic reduction of chromium (III) chloride hexahydrate (CrCl₃⋅6H₂O) has been investigated in aqueous and alcoholic solutions (MeOH, EtOH, and n-PrOH) containing 0.1M KCl, and 0.1M (C₂H₅)₄NCl as the supporting electrolyte. Chromium (III) chloride hexahydrate exhibited two reduction waves with wave height ratios of 1:2, and the limiting currents for these two reduction waves were diffusion controlled in the above solutions. The first wave (the reciprocal slope of logplot: ca. 120mV) corresponded to irreversible reduction of the solvation species formed in the alcoholic solutions. The second wave for the reduction of the aquochromium (III) complex species was reversible (the reciprocal slope: ca. 32-35mV). In alcoholic solutions, the cathodic reduction processes was speculated as follows: for the first step, [Cr(OH₂)₄Cl₂]⁺…Xn (Solv.)+e→[Cr(OH₂)₅Cl]⁺ +Cl^-+X_n(X_n: ROH molecules) and for the second step, [Cr(OH₂)₅Cl]⁺+2e_??_Cr(Hg)+Cl^-+5H₂O In the aqueous solution, the same as in the alcoholic solutions, [Cr(OH₂)₆]³⁺ gave a stepwise reduction to [Cr(OH₂)₆]²⁺ and then to Cr (0).

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SiC layer was uniformly deposited on the heated graphite substrate at 1100-1500°C, which was lower than the temperature used in earlier method, by means of the decomposition of Si(CH₃)₄ with glow discharge. The surface of SiC layer had a characteristic domed structrure. This layer had a relative density of 90-94%, and showed good adherence to the graphite substrate. When the substrate temperature was 1300°C, the thickness of SiC layer increased up to 300μm at relatively fast flow rate of Si(CH₃)₄ (2.0×10^-3mol/min). On the other hand, relatively slow rate of Si(CH₃)₄ (2.8×10^-4mol/min) was required for obtaining a hard SiC layer, of which maximum vickers hardness was measured to be 6000kg/mm². The hardness was not concerned with the crystallinity of SiC, but with Si/C ratio in the layer. It is considered that the formation process of the SiC layer consists of two stages; that is, (I) the radical condensation of Si(CH₃)₄ by the glow discharge, (II) the condensation and sintering on the substrate by the heat energy. In order to obtain a hard layer of SiC, it is required to supply Si(CH₃)₄ with slow rate of 2.8×10^-4 mol/min to be proceeded the reaction completely, especially at the temperature below 1300°C.

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The physical properties of the plating films originates from crystallographic structure. In this investigation, the variation of the crystallographic structure of electroplated gold film with increaseing of its thickness was studied by a transmission electron microscope. The gold film deposited on a copper single crystal grows with a certain crystallographic coherency. Since there are large crystallographic misfit and corresponding coherent stress between a copper crystal and a gold crystal, however, in the early stage of plating time, the gold film contains plenty of subgrain boundaries, twin boundaries and complicated elastic strains. And then the film consists of aggregation of very small subgrains. When the mean thickness of the film is over 0.5μm, the grain size in the gold film at the side of free surface came up comparable size with that of copper substrate. And the dencity of twin boundaries and stacking faults in the film decreased. The surface morphology of plated gold films on the (001) Cu surface revealed an aggregation of numerous pyramidlike crystals, and on the (011) Cu surface numerous rooflike crystals were exhibited. This phenomena cause the decrease of surface gloss of gold films deposited on the (001) Cu and (011) Cu surface. On the (111) Cu surface, however, this irregurarity on the gold film surface did not appear and the glossy surface was kept over 2.5μm in film thickness, because the {111} Au plane is the easy plane for growth of gold crystals.

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