Ozone treatment of polypropylene films of homopolymer, random copolymer and block copolymer (with ethylene) was investigated as a means of modifying their surface properties. The chemical and physical characteristics of the surfaces of the treated films were then studied by contact angle measurement, ATR IR spectrometry, and SEM observation. Ozone treatment was shown to be effective in improving the wettablity of polypropylene surfaces at water-contact angle of up to 67°C. Furthermore, ultrasonic cleaning with organic solvents was shown to be effective in removing from the surface the degraded fragments formed by ozone treatment.
Nonelectrolytic plating of nickel onto three types of polypropylene-homopolymer, random copolymer and block copolymer (with ethylene)-were investigated. The substrate plates were pretreated with ozone, and adhesion strength of the plated samples was tested and evaluated by the cross cut and thermal cycle methods The effects of ozone pretreatment on the properties of the plated samples were then discussed in terms of the chemical and morphological changes found in the polypropylene surfaces after treatment. Ozone treatment is shown to provide sufficient surface modification for plating, and sufficient adhesion strength is thougth to be obtained by the cooperation of polar interaction and the anchor effect between metal and substrate caused by the ozone etching It was also found that solvent washing after ozone treatment is important in obtaining better metal abhesion.
Laser transformation hardening was carried out on two types of steel that differed in hardenability, using a 1kW CO2 laser under various conditions, and the effects of processing parameters-such as scan rate and the defocussing of the laser beam-on the hardened case depth and width, microstructure, hardness distribution and wear properties were investigated. The results obtained were as follows: 1) The maximum depth and width of hardened case decreased with increasing scan rate. 2) A two-step change in hardness was observed, in which the second step corresponded to an incompletely hardened layer between the maximum hardness layer at the surface and the matrix. 3) In the hardened surface layer, X-ray diffraction analysis revealed the existence of retained austenite. 4) Hardening occurs independently of hardenability in the steels tested, due to the fact that the cooling rate in laser hardening is much faster than the critical cooling rate of the steels. 5) The wear resistance of the laser-hardened steels was much better than that of the normalized steels. The improvement produced by laser hardening was particularly marked in sliding rates of 0.8m/s or less. This was attributed to the fact that the hardened area on the sliding surface increased with decreasing scan rate.
Ni (II)-Citrate complexing equilibrium and the correlation with electrolysis in nickel-citrate plating baths were studied. From absorption spectra, pH buffer capacity, and calculated simulation studies, it has been revealed that various complexes, NiHCit0, NiCit-, NiCit24-, Ni (H-1Cit)2- etc., were formed in nickel citrate solutions, and the concentration distributions of these complexes were varied by the changes in the compositions and/or pH of the solutions. Above pH 4, the formation of 1:1 complex (NiCit-) was recognized. In the pH range of 5 to 8, the proportion of NiCit- decreased and that of NiCit24-, which has lower molar absorptivity, increased with an increase in the Cit/Ni ratio in the solution. Above pH8, nickel-tetraionized citrate complex Ni (H-1Cit)2-, which has large molar absorptivity, was formed, and the pH value of formation of this complex became higher with an increase in the Cit/Ni ratio in the solution. Electrolysis studies have revealed that, in neutral or alkali solutions, nickel-citrate equilibrium affected nickel deposition from nickel citrate solutions, and NiCit24- and Ni (H-1Cit)2- were more electrochemically innert than NiCit-. In acidic solutions, the addition of citrate accelerated the evolution of hydrogen, and decreased the current efficiency of nickel deposition.
The effects of surface conditions of galvannealed steel sheet on corrosion resistance in a single-coat acrylic-resin painting system that does not include the process of activation by TiO2 were investigated by measuring the width of delamination after an immersion test of scribed panels in a 3%NaCl aqueous solution. In analyzing the test results, electrochemical measurements were carried out in the phosphating bath to evaluate the phosphatability of the material. As a result, measuring the polarization of the coating in the phosphating bath clarified that measuring τ (time-lag for self-passivation of the coating in the phosphating solution) is a suitable way to evaluate phosphatability of the coating. From a multiple regression analysis, it was shown that phosphatability, surface roughnes sand coating weight mainly effect the delaminated width of paint film. It was also clarified that the deterioration of phosphatability results from the enrichment of Al-oxide at the surface of galvannealed the coating.
An attempt was made to electroplate a uniform and defect-free Ni-Al dispersion coating which is rich in Al particle content. Since bare Al particles without surface treatment quickly dissolved into a Watts Ni bath and yielded cracked deposits, the particles were surface-treated with one of silane coupling with γ-aminopropyltrietoxy silane (γ-APS), boiling in distilled water for 20min., or electroless plating with a Ni-B alloy. Although these treatments strongly suppressed the dissolution of Al into the bath, baths containing the silane-coupled Al particles still yielded a cracked deposit. Deposits that were crack-free and uniform in Al particle distribution were obtained from baths containing the boiled Al particles or the Ni-B plated Al particles, the surfaces of which were composed of Al (OH)3 or Ni (OH)2, respectively. Among many plating variables, diluting the watts Ni bath and decreasing the stroke of the pumping plate were found to be quite effective in increasing the Al particle content of the coating.
The properties of codeposited Ni-Se and Ni-Te cathodes were investigated in order to develop cathodes with low hydrogen overvoltage for chlorine electrolytic cells. The surface morphorogy, by SEM, EPMA, ESCA, BET, and electrochemical techniques analysis, chemical composition and electrochemical properties of the cathodes were examined. Hydrogen overvoltage decreased with increasing amounts of Se or Te. The over voltage potential of an Ni-Se codeposited electrode (Se 12.8%) was 200mV lower than that of Ni at a current density of 1A dm-2 in 2.5N NaOH solution at 25°C. These results suggest that the codeposited Se or Te catalyzes the hydrogen evolution electrochemically and reduces the overpotential.
A high temperature bath of pH8 to 9, continuously supplied with ammonia water, has long been believed optimum for tungsten alloy plating. However, since ammonia is volatile and harmful to both working personnel and peripheral devices, we have formulated a citric acid-ammonia Ni-W alloy plating bath of pH6, which is free of ammonia smell even on boiling. On the basis of the data on alloy composition and current efficiency, we selected a bath temperature of 70°C as optimum. Baths of high nickel concentrations of pH6, 70°C yielded alloys of high tungsten content with relatively high current efficiencies, eg.44wt%W alloy at 49%CCE. The highest tungsten content obtained was 61wt%, which corresponds to Ni2W stoichiometry. The tungsten content of the deposits did not show any abrupt change on variation of nickel concentration in the bath, and remained almost constant at current densities exceeding 8A/dm2. The room temperature hardness of 44 and 51wt%W alloys was about Hv 1350 after heating at 650°C for 1h. Dilation measurements showed that the alloys were more densely deposited than those plated at high temperature/pH conditions. On the basis of these encouraging findings, studies on metal ion replenishment were also conducted. The methods recommended are the addition of ammonium para-tungstate solution for tungsten, and the use of a soluble nickel anode for nickel.
In the process of etching aluminum electrolytic capacitors, high purity (99.99%) aluminum was galvanostatically electrolyzed at a current of-800mA/cm2 for 20s in a 1.0%NaCl solution containing HCl and alumina powders, and pitting sites were produced at a density of 1.4×1012/m2on the surface.
The influence of metallic additives on the electrodeposition of gold has been studied by the impedance method. The electrodeposition rate of gold was influenced when additives were included in the electrolyte, but the rate-determining step in the processes of gold deposition was scarcely influenced. The gold deposition was controlled by the chargetransfer reaction.