Fine spots were deposited from a unstirred gold plating solution under irradiation of an argon ion laser, and the effects of laser power and electrode potential on deposition rate and fine spot size were studied. Deposition rates of 0.25μm/s were obtained at a laser power of 3W and an electrode potential of -700mV (SCE), which was 10-20 times higher than the rates of traditional gold plating. This increase was explained by convective mass transport induced by a highly localized thermal gradient and by boiling under laser irradiation. Deposition rates increased with increasing laser power and electrode potential, but the effect of laser power saturated due to boiling of the electolyte. Although the diameter of the laser beam on the substrate was about 15μm, spot diameters were several tens of micrometers due to heat conduction in the substrate and in the solution. Spot diameters increased linearly with increasing laser power and electrode potential. Defocusing of the laser beam had a remarkable effect on spot diameter.
In a study of electroless indium plating with titanium trichloride as a reducing agent, indium film was directly deposited onto Pd-catalyzed aluminum substrate at a rate of 1.56mg·cm-2·h-1, and it was possible to continue plating by renewing the bath at 30-minute intervals. The optimum bath composition was 0.08M indium trichloride, 0.32M trisodium citrate, 0.20M NTA, and 0.04M titanium trichloride. The recommended plating conditions were pH10.0 and 80°C. It was seen that further addition of EDTA to stabilize the bath greatly delayed plating. Indium alloy plating was also investigated. Binary alloy films of indium were electrolessly plated from indium baths to which various metal salts were added for alloying. Alloy films of Ni-In, Pb-In, As-In, Fe-In, and Sn-In were formed, but Co, Zn, Al, Bi, Sb and Cu were not co-deposited with indium.
Aluminized steel sheets are widely used because they combine good corrosion resistance and high-temperature oxidation resistance. Al/Ti double-coated steel sheet having a Ti interlayer, offers even better properties due to the electrochemical and metallurgical properties of titanium. Specifically, since the rest potential of Ti in neutral NaCl solution is more noble and exhibits better cathodic polarization than the steel, the steel is protected cathodically for a long period because the sacrificial dissolution of Al is prolonged, thereby preventing reversal of the electrochemical potential between the Al and the steel. Ti also exhibited a good barrier effect on the thermal diffusion of Fe, depressing the high-temperature oxidation of the steel.
The size of surface pores in anodic alumina on aluminum plates, which is considered to be fairly uniform, was analyzed by adsorption experiments using krypton and n-butylbenzene vapor. The total surface area of anodic alumina samples, including the inner surface area of the pores, was estimated by the Kr/BET method, and the external surface area of the samples, excluding the inner surface area of the pores, was estimated by the “gradient method” applied in the range of 40%∼60% of relative pressure of the adsorption isotherms of n-butylbenzene vapor. For both of the adsorbate gases the samples had a significant hysteresis loop on the adsorption isotherms due to the condensation of the adsorbates into the surface pores. The total pore volume of the surface was estimated by the condensation quantity assumed from the height of the hysteresis loop for each adsorbate gas. The mean pore diameter was estimated from the total pore volume of the surface and the inner area of the pores, which was estimated from the difference between the total surface area and the external surface area of the samples. The mean values of pore diameters (6.9nm) obtained using the two adsorbates agreed with each other, and also agreed well with the values expected from the conditions of the anodic oxidation. The vapor pressures at which adsorption increased abruptly and the capillary condensation into the pores began also agreed with the values calculated from the Kelvin equation for capillary condensation using the pore radius and the surface tensions of the adsorbates.