A method was investigated for the recovery of gold from solutions containing cyanide ion and for the decomposition of cyanide ion by electrolytic technique. It has become clear that the time required for the decomposition of cyanide ion was far greater than that required for the recovery of gold, and in order to accelerate the rate of the decomposition of cyanide ion, a method combining electrolysis with ultraviolet (UV) radiation was applied. This combined method proved to be much more effective in decomposing cyanide ion than electrolytic technique. Short wavelengths (184.9nm and 253.7nm) were much more effective than long ones (356∼579.1nm) in cyanide ion treatment by UV radiation. UV radiation was effective in decomposing free cyanide ion except for one coordinated to gold. Thus, it was necessary to liberate cyanide ion by electrolysis in order to treat solutions containing cyanide ion.
Electroless copper plating is an indispensable process in the manufacture of printed wiring boards, but extraneous deposition occurs during electroless plating especially if the copper plating bath is used for a long period. Baths used for five or more truns have been found to contain more that 2×106 inorganic particles (Si, Al, Na, etc.) of from 1∼5μm leading significantly to extraneous deposition. To solve this problem, precision filtration was applied, greatly reducing the numbers of particles by continuous filtration, eliminating extraneous deposition and improving the properties of the deposited film, Furthermore, electroless deposition of copper on the filter under high speed filtration was inhibited by the use of a tapered filter instead of a wound-depth type filter.
Coating of Ti-6Al-4V alloy substrates with Ti/O compositional gradient films was carried out by reactive DC sputtering to improve the toughness of the films with respect to mechanical impact, the adhesion of the films, and the biocompatibility of the alloy. Ti/O compositional gradient films were formed by continuously varying the oxygen content of the Ar-O2 sputter gas, and film characteristics were evaluated by SEM image, AES analysis, and hardness measurement. Under visual observation, the deposited films appeared to exhibit good uniformity and adhesion, but under SEM the surface was found to have fine particles dispersed on a smooth accumulated deposit. Under AES, the oxygen concentration in the films decreased gradually from the surface toward the substrate, confirming that Ti/O compositional gradient film had formed. Based on indentation-fracture tests, it was concluded that this method improved both adhesion at the film/substrate interface and film toughness.
Surface properties of ion-irradiated organic-inorganic hybrid materials have been investigated. Disk samples of a nylon-clay hybrid (NCH) material were irradiated with 2 MeV Ar+to doses of 1×1014, 1×1015 and 1×1016 ions/cm2 and its tribological properties and water wettabilty were measured and compared with those of the nylon that was ion-irradiated under the same conditions. NCH is a nanometer-order hybrid which consists of a nylon matrix and silicate layers and is superior to nylon in heat resistance and strength. Tribological properties were measured by pin-on-disk tests without lubricant using steel (SUJ2) balls as pins. Under ion irradiation to a dose of 1×1014 or 1×1015 ions/cm2, the wear resistance of the NCH decreased, becoming equivalent to that of unirradiated nylon, whereas the wear resistance of nylon was hardly changed by the same treatment. Ion irradiation to a dose of 1×1016 ions/cm2 improved wear resistance and decreased the coefficient of friction for both the NCH and nylon. In particular, in a 10-4Pa vacuum, the coefficient of friction for the NCH and nylon ion irradiated to a dose of 1×1016 ions/cm2 was extremely low (<0.1). The contact angle of the NCH with distilled water was increased from 68°to 80° by ion irradiation. Such a reduction in wettability was also observed for ion-irradiated nylon. Fourier transform infrared spectroscopy, Raman spectroscopy and spectral-reflection measurement by laser plasma soft X-ray spectroscopy revealed that the structure of the NCH was destroyed by ion irradiation and that hard amorphous carbon formed on the surface of the NCH samples that were ion-irradiated at a dose of 1×1016ions/cm2. This suggests that these structural changes produced by ion irradiation determine the tribological properties of the NCH.
The improvement of polypropylene surfaces by means of fluorine gas was investigated. It was found that polypropylene surfaces treated with fluorine gas diluted with nitrogen became hydrophilic. The optimum fluorination condition was a fluorine concentration of 0.5-1.0% and treatment times of 1-10 minutes. Hydrophilic properties were evaluated by contact angle. The polar-force component and dispersion-force component in surface free energy were calculated from contact angle using water and methylene diiodide. In particular, the lower polar-force component increased from 1.6mJ/m2 to 25.0mJ/m2. ESCA data showed that -CF-CF- and -C-CF- bondings formed on the upper surface. It has thus been demonstrated that these C-F bondings are given polarity by the fluorine which is the strongest electronegativity. The hydrophilic properties are thought to be due to this polarity. Adhesive strength was tested by cross-cut test with the hydrophilic surface coated with urethan paint. The painting exhibited good results. The high adhesion strength is thought to be the result of polar interaction. It is clear that good coating can be obtained by treating polypropylene surfaces with fluorine gas.
The initial stage of dendritic growth by zinc electrodeposits has been studied by electrochemical scanning tunneling microscopy (STM) and computer simulation. Zinc was deposited on a highly oriented pyrolytic graphite (HOPG) electrode from a 0.01mol/L ZnSO4 solution. The zinc deposits (0.018C/cm2) grew predominantly near the step line on the HOPG. Initially, the height difference (dmax) between the highest part and the lowest part of the deposit and the average roughness of the electrode surface (Ra) increased rapidly with deposition time. It is therefore suggested that the roughness of the electrode surface increases rapidly in the initial stage of electrodeposition. The simulation reproduced the morphology of the STM image (0.02C/cm2, 20nm×20nm) and the distribution of deposit heights observed by STM agreed with the result of the simulation. It was therefore confirmed that the deposition model used in the simulation is appropriate at the initial stage of zinc electrodeposition.
The mechanism of roll coating molten zinc onto steel strip was studied with horizontal and vertical roll coating apparatus, while varying the strip speed, roll speed, line tension and roll-to-strip contact arc length. Roll coating is a process in which the coating roll is wetted with molten zinc and brings it into the contact arc, where the molten zinc reacts with the steel, wetting it and resulting in the transfer of the molten zinc to the steel surface. The amount of zinc entering the contact arc is limited by the amount of zinc supplied on the coating roll, but when sufficient zinc is supplied, the amount entering the contact arc is determined by strip speed and line tension. The distribution ratio of zinc between the strip and the roll at the outlet and the amount of zinc entering the contact arc are considered related to the roughness of the roll surface.