Aminosilylated glass beads can be readily bound with palladium ion (Pd2+) in PdCl2 aq. solution. Electroless nickel deposition reactions were studied after pretreating such Pd2+ bound beads in hypophosphite (NaH2PO2) aq. solution at high temperature (Process 2). The reaction rate was found to be not dependent on the amount of loaded palladium but on the surface area of the substrate (i.e., was constant per unit area). It was also found that no anomalous increase in rate and no time lag in the initiation step were observed compared with Process 1 (the process without pretreating in NaH2PO2 aq. solution). The reasons for these results are discussed assuming that metallic palladium articles (catalytic nuclei) were formed on the substrate surface by pretreating the Pd2+-bound beads in the NaH2PO2 aq. solution. Finally, the differences of the reaction between Process 1 and Process 2 were summarized.
The possibility of electrodepositing molybdenum sulfide films using molybdenum foil as the counterelectrode was studied using combinations of various reagents and nonaqueous solvents. PC, DMF, DMA and DMSO were used as nonaqueous solvents; LiClO4, KClO4 and TEAP as supporting electrolytes; and S, KSCN, NaSCN, Na2S2O3 and (H2N)CS as sulfide reagents. The films were cathodically electrodeposited at electrode potentials of from -2.80V to -2.95V at 80°C in DMF solvent containing LiClO4 as the supporting electrolyte and KSCN as the sulfide reagent. The structures of these films were revealed by X-ray diffraction to be Mo2S3 and amorphous material. The mechanical strength was low.
In order to evaluate the utility of metal hydride films as hydrogen permeable negative electrodes in an alkaline fuel cell system, La-Ni alloy films about 2μm thick were formed on Teflon sheet substrates by RF sputtering using split-type targets composed of a nickel sheet and lanthanum chips. Sputtering conditions such as the gas pressure, RF incident power and component ratio of the target were found to influence the composition, structure and hydrogen absorption characteristics of the sputtered films. The composition of the films varied in the range of LaNi9.5∼LaNi2.2 (9.5∼31.7 at.%La-Ni). The films were either amorphous or microcrystalline in structure. The amorphous LaNi2.2 films absorbed a relatively large amount of hydrogen during electrochemical charging and eventually formed a hydride (LaNi2.2H4.1). The hydrogen absorption capacities of these sputtered films were lower than those of crystalline powder or bulk LaNi5 alloys prepared by the arc-melting method. However these amorphous metal hydrides did not result in any crack or embrittlement in the films even after a large number of hydriding-dehydriding cycles.
Electrodeposition of Ga-As alloys has been studied in alkaline solutions containig Ga2 (SO4)3 and As2O3. Pure arsenic was deposited at noble potentials, while the deposition of gallium was predominant at less noble potentials. Current-potential curves exhibited an arrest of current at potentials between -1.50∼-1.68V (SCE), where the deposition of GaAs took place. The deposition potential of GaAs was found to be more noble than that of pure gallium by 0.15V. The gallium content of the alloy increased with a negative shift in potential. The optimum current density for obtaining stoichiometric GaAs increased with decreases in the concentration ratio [Ga2 (SO4)3]/[As2O3] in the bath. X-ray diffraction analysis showed the deposits on titanium substrates had a clear GaAs diffraction line, while GaAs alloy deposited on copper substrates also had CuGa2 diffraction lines.
Silver deposits formed on copper substrates by replacement reactions show poor adhesion, and a silver film plated on such a deposit dose not adhere. Silver ion makes a highly stable complex with cyanide ion, so that in a silvercyanide solution, the activity of silver ion is very small. This is one of the reasons for the universal use of cyanide baths in the industrial silver plating. However, consideration of the difference between the values of the stability constants for the silver-iodide complex and for the copper-iodide complex suggest that the rate of replacement deposition of silver on the copper substrate in silver-potassium iodide solutions, might be comparatively low. To confirm this, the rate of replacement deposition of silver in a silver-potassium iodide solution (AgNO3 0.10mol/L, KI 2.00mol/L) and in a strike silver plating bath (AgCN 0.028mol/L, KCN 1.15mol/L) was estimated from the current density corresponding to the point of intersection of the anodic and the cathodic polarization curves. These estimated values were almost the same, and it is suggested that the silver-potassium iodide solution is not only a cyanide free silver plating bath capable of employing a copper substrate but a silver plating bath which requires no strike plating.
The structure and crystallization process resulting from electron beam irradiation of porous anodic films formed on aluminum in an Ematal bath have been investigated by high resolution electron microscopy. Ion-thinned films showed a duplex structure consisting of an anion-free inner layer with a width 1/6 that of the cell wall and an anion-incorporated outer layer. Voids, which had been produced on the metal ridges at the triplicate cell connections during anodizing, were detected. Crystal nucleation occurred preferentially in the vicinity of voids under the usual operating condition of the microscope. During the growth of initial crystals, further nucleation proceeded in the cell boundaries (inner layer) and at last in the outer layer. It is supposed that the oxide structure in the vicinity of voids is different from the typical amorphous phase of the cell walls, and that the difference is produced by the effects of a strong electric field, and by heating due to electric breakdown. The crystallization rate of the films studied here was higher than that of films formed in phosphoric acid and sulfuric acid solutions, and lower than that of films formed in chromic acid solutions. High resolution lattice images revealed that the crystallized film consisted of microcrystals in the cell walls and an amorphous layer near the pore walls. Electron diffraction patterns obtained from the films after irradiation indicated a mixed phase of γ-, η-, θ- and α- alumina.
The wettability and corrosion resistance of aluminum fins prepainted with a dual coating of cellulose on acrylic have been investigated. Formation of rust on aluminum fins in an indoor cooler was suppressed by painting with more than 0.5g/m2 thickness. Under exposure to corrosive environments, painted fins fitted to copper pipes in an outdoor cooler underwent severe galvanic corrosion. Accordingly, the corrosion resistance with acrylic painting of 1.5g/m2 was only twice as high as that of unpainted fins. The wettability of cellulose painted fins was excellent -5°-10° depending on the surfactant, and whether covering was complete or not. It was also confirmed that cellulose painting with good wettability reduced air pressure loss.
In order to obtain high productivity and quality control, synchronization of selective Ni plating with machine and assembly process was developed. It is composed of three technical parts. (1) Synchronizing system of Ni plating at same tact of spark plug manufacturing line. (2) High speed plating by rotation method. (3) Selective Ni plating without masking. This manufacturing system of spark plug has been operated by this new system.
The activity of catalytic Ag nuclei formed by current has been studied. The Ag nuclei act as a latent image in an organic ion conductor consisted of benzotriazole (BZT) and silver benzotriazole (BZT-Ag), and are amplified by heat development under the presence of reducing agents. The efficiency of latent image formation is 10-3. The amplification ratio of the latent image is 106 which is comparable to that of AgCl.