The codeposition behavior of Zn²⁺, Ni²⁺ and SiO₂ was investigated by a galvanostatic method using colloidal SiO₂ (20nm). The SiO₂ content of the electodeposits increased with the increase of Ni²⁺ content in the bath, and the amount of Ni²⁺ adsorbed on SiO₂ particles was greater than the amount of Zn²⁺ adsorbed on SiO₂ in the bath. Ni²⁺ played an important role on the deposition of SiO₂. The relation between the amount of SiO₂ in the bath and in the electrodeposit changed in accordance with Guglielmi's theory. Adsorption of the SiO₂ on the cathode seems to occur in the first stage of the Zn-Ni-SiO₂ electrodeposition process. A part of the SiO₂ in the electrodeposit coagulated into larger particles during electrolysis because the pH on the cathode became higher than that of the electrolyte. The surface pH on the cathode during Zn-Ni-SiO₂ electrodeposition measured by micro-Sb electrode was about 5-7 at a bath pH of 2, and a current density of 10-20A/dm². This value coincided with the pH of the coagulation of SiO₂. These results indicate that the factors controlling the codeposition of SiO₂, Ni²⁺, and Zn²⁺ were: 1) adsorption of Ni²⁺ on the SiO₂ in the bath; 2) adsorption of SiO₂ on the cathode according to Guglielmi's theory; and 3) coagulation of SiO₂ by the increase of pH on the cathode during electrolysis.

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A gold plating solution was treated with sulfuric acid, hydrogen peroxide and hydrazine sulfide, removing gold as precipitates and thoroughly reducing all arsenic to arsenic (III). Atomic absorption measurement for the samples prepared by this procedure showed that total amount of arsenic could be determined at approximately c.v. 3.0%.
The amount of arsenic (III) was determined basically by direct atomic absorption measurement. The amount of arsenic (III) in the diluted gold plating solution measured directly, however, was found to contain 8.9% arsenic (V). This suggested that the amount of arsenic (III) should be calculated by
As(III)=B-0.089A/1-0.089……(1)
A: Total amount of arsenic
B: Amount of arsenic (III) measured directly
This method of determining the amount of arsenic (III) was applied to actual gold plating solutions containing various amounts of arsenic and arsenic (III)/arsenic (V) ratios. It was confirmed that the amount of arsenic (III) in gold plating solutions could be determined at approximately c.v. 5.7%.
It was also found that the amount of arsenic codeposited in gold plating films could be determined by the same procedures as for total arsenic analysis by simply adding a step in which the film was dissolved in aqua regia.

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Aluminum nitride films were grown onto a heated glass substrate at 500°C using a plasma reaction between the vaporized aluminum and the nitrogen gas at pressures reduced to the range of 10^-5 Torr. In this experiment, the distance between the hearth and the substrate was held at 370mm and a biase voltage was not applied to the substrate because it severely damaged the deposited films.
Optically semi-transparent and opaque films were grown under conditions in which the vapourized aluminum was in excess over the nitrogen gas in the atmosphere, while optically transparent films were obtained by using nitrogen gas in excess over the vapourized aluminum.
However, the correlation of the amounts of vapourized aluminum and nitrogen gas needed to obtain a transparent aluminum nitride film was greatly influenced by ionization current, which induced the plasma reaction.
Observation by SEM and X-ray diffraction showed that the semi-transparent and opaque films had a rougher surface and a higher c-axis-oriented structure than the transparent ones.
The semi-transparent and opaque films had a much lower electrical resistivity-10²-10⁸Ω·cm and a range of 10^-4Ω·cm, while the transparent films had a higher resistivity-10⁸-10¹¹Ω·cm.
This seems to be due to the presence of aluminum which mixed into the deposited films without reacting with the nitrogen gas.

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The applicability of an activation method utilizing solutions of mixed hydroxide colloids was examined for the electroless plating of copper onto ABS plastic surfaces or sintered MgO disks. The main results are as follows:
1) The activation of ABS plastic with colloid solutions of Ni(OH)₂ or Cu(OH)₂ at pH 7.8 was found to be insufficient or unattainable, whereas activation with mixed -colloid solutions of Ni(OH)₂ and Cu(OH)₂ was satisfactory.
2) The addition of neutral salts, such as MgCl₂ and NaCl, to mixed-colloid solutions of Ni(OH)₂ and Cu(OH)₂ enhanced the activation. By contrast, the addition of MgSO₄ or Na₂SO₄ had no effect on activation.
3) Copper films formed on ABS plastic, pre-activated with mixed-colloid solutions of Ni(OH)₂ and Cu(OH)₂, were sufficiently competitive to those activated by an ordinary SnCl₂-PdCl₂ method.
4) The activation method using mixed-colloid solutions requires adequate adsorption ability of colloids onto the substrate and the adequate reducibility of colloids to metallic state using a reducing agent such as KBH₄.
5) The mechanism of the process of activation of ABS plastic or sintered MgO disks can be explained by surface electrochemistry.

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A new electroless tin plating bath has been examined. The bath is unique in that it has no reducing agent, hence tin is formed not by reduction, but through a spontaneous disproportionation reaction in which stannous ions dissociate to form tin and stannate ion.
2 Sn(OH)₃^-→Sn+Sn(OH)^2-₆
(Sn(II)) (Sn(0))(Sn(IV))
The following results were obtained.
1. Stability of the bath was strongly dependent on the concentration of Sn (II) and NS ratio-the molar ratio of NaOH to Sn (II). The bath was stable with in a certain range of NS ratios, which became narrower with increases in Sn (II) concentration. At lower ratios, stannous oxide precipitate formed, while at higher ratios disproportionation occurred.
2. The deposition rate increased with increases in Sn (II) concentration and temperature, but was nearly constant independent of NS ratio when Sn(II) concentration was held constant.
3. The optimum bath composition was found to be Sn(II)0.4M, NaOH 5.2M, sodium citrate 0.9M, and deposition rates as high as 5.6μm/h were obtained at 80°C.

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The polarization behavior of aluminum in 5% hydrochloric acid was investigated by a potential sweep method and by chronopotentiometry.
The potential-current curves showed that the breakdown potential, hydrogen evolution potential and pitting current changed with changes in the cathodic reverse potential and the number of potential sweep cycles. The repassivation potential, however, remained constant at -0.95V vs. SCE. In the anodic half cycle, the chronopotentiograms for each cycle indicated an induction period and was followed by pitting at -0.79V vs. SCE. At the early stage of each cycle, the potential-time curve fluctuated greatly and the duration of the fluctuations become longer as the current density was rised and the frequency was lowered. In the cathodic half cycle, by contrast, the cathodic potential was shifted from the passivation potential to the hydrogen evolution potential region on repeated cycles.
It was recognized that the induction period occurring at each anodic half cycle was closely related to the polarization behavior at each following cathodic half cycle.

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