Mainly with regard to the barrier films on Al and partly on Ta, the influence of pretreatments, forming electrolyte, anodizing conditions and heating in air, water or electrolyte solutions on the leakage current, tan δ, durability for water and acid, transient behaviour and breakdown voltage were reviewed along with the characterization of the film. In conclusion, it is emphasized that the characteristic of the film is not inherent but is so variable as to be markedly influenced by those factors listed above, especially by anion species in the forming electrolyte.
A study was conducted the effects and mechanisms of three chelating reagents, 8-hydroxyquinolin [HQ], 8-mercaptoquinolin [MQ] and anthranilic acid [AA], in inhibiting zinc corrosion in 3%NaCl solution (25°C, pH=5.0, 7.0 and 9.0). The chelating reagents were expected to protect the zinc surface by polarization and weight loss, while inhibiting mechanisms were investigated by analysis of infrared spectra and infrared-attenuated total reflection spectra. Experiments on polarization and weight loss showed that HQ and MQ had good inhibiting effects at all values of pH studied, but AA had a high inhibiting effect only at pH=5.0. Analysis of the infrared spectra and infrared-attenuated total reflection spectra showed that HQ and MQ formed insoluble metal chelate complexes on the zinc surface at all values of pH studied, but in case of AA, no complexes were formed at 7.0 and 9.0. Reagents, HQ and MQ, which formed metal chelate complexes with zinc, acted as effective inhibitor at all values of pH studied, but AA form no complexes at pH 7.0 and 9.0 showing poor inhibiting effect.
Diamond film was deposited by microwave plasma CVD from a CH4-H2 reactant gas at a subatmospheric pressure of 3.0kPa, in order to investigate the effects of such parameters as gas composition and flow rate on the growth rate and properties of the film. The silicon substrate, when polished with 5μm diamond paste, was observed to have a favorable affect on film deposition. Growth rate reached a maximum of approx. 1μm/hr at 3% CH4, at<3% CH4 the growth rate was essentially dependent on the flow rate, while at>3% CH4, the rate decreased with an increasing flow rate. The films exhibited an agglomerate structure of idiomorphic grains when deposited at low CH4 levels, and consisted of agglomerates of increasingly round fine crystals when deposited at higher levels. The deposition rate was essentially constant over the whole reaction time. The highest film deposition rate was obtained at a microwave power of 220W, whereby the substrate was, estimated to reach a temperature of 1173K.
A new type of electroless tin plating bath has been applied in a disproportionation reaction of Sn (II) ion involving 2Sn(OH)3-→Sn+Sn(OH)62- (Sn(II) Sn(0) Sn(IV)) In a previous paper, a Sn (II)-NaOH system bath (called a Na bath) was proposed. To develop a bath having higher plating rate, alkali hydroxide was replaced by KOH (a K bath) or LiOH (a Li bath). Plating rates and the morphologies of deposits from the K and Li baths were compared with those from the Na bath. The following results were obtained. 1. In terms of the width of the transparent stable region, the baths were in the order NaOH>KOH>LiOH, the same order as the solubility of the alkali hydroxides. 2. The K bath had the highest plating rate under the same conditions (Sn (II) 0.4M, KOH 5.2M, K3-citrate 0.5M, 80°C; 11.5μm/h). 3. Semibright compact deposits were obtained by simply lowering the temperature of the bath from 80°C to 60-75°C. 4. The plating and spontaneous decomposition reactions proceeded through disproportionation.
Aluminum specimens of 99.99% purity were rolled and annealed under various conditions. Occupation ratios of (100) planes were measured as a function of rolling reduction, annealing temperature and time. The specimens were etched at 100mA/cm2 in 5% HCl solution at 80°C and anodized at 240V. Capacitance measurements and SEM observations of pits morphology were made. It was found that high occupation ratios (more than about 80%) were obtained under a rolling/annealing sequence involving primary cold rolling of more than 90% reduction, intermediate annealing at 250°C for 5h to 350°C for 3min, secondary cold rolling of 20% to 35% reduction, and final annealing at above 300°C for 1h. Capacitance increased with the increase in the occupation ratio of the (100) planes caused by intermediate annealing, and with cube texture formation during final annealing.
A technique of microscopic ellipsometry that measures a thickness of thin film on microareas of about 10μm∅ diameter has been developed. Application of this technique to analyze the thickness distribution of hydrated chromium oxide film on various kinds of Tin Free Steel (TFS) has shown that there are extensive differences in the uniformity of the film. It was also found that there is a good correspondence between the thickness distribution and the bond durability of side-seam cans made of TFS in retort treatment. Bond durability of TFS is already known to be affected by chromium oxide composition, including sulphate impurity and the degree of hydration. This study has revealed that the uniformity of oxide film layer is an another important factor of the bond durability of TFS.
Lead (II) impurity in zinc or zinc-alloy plating baths has an adverse effect on the finish. To remove this lead (II) we attempted the separation of lead (II) and zinc (II) coexisting in aqueous solutions using silica-titania gel, which is known to be porous and stable at high temperatures. It was first found that in a solution containing 10mg dm-3 of both lead (II) and zinc (II) equimolar silica-titania gel solely adsorbed lead (II) at pH 2.4 and it was therefore realized that the separation of both metals dissolved in solutions was possible at this pH range by means of gel adsorption. At the zinc concentrations up to 104mg dm-3, lead removal efficiency was high. The relationship between the equilibrium concentration in solution and the amount of metal adsorbed obeyed the Freundrich adsorption isotherm. The optimum composition of silica-titania gel here was 3:1. The silica-titania gel may be reused repeatedly with elution of the adsorbed lead (II) using 1M nitric acid, followed by surface treatment with 1M sodium nitrate solution.