An amorphous Ti-Ni alloy film was prepared by RF sputtering on a water-cooled chromium substrate to investigate changes in its corrosion resistance due to annealing, and to study its possibilities of application as a coating material having a high corrosion resistance. Structural analysis of the sample was made by X-ray diffraction and Auger electron spectroscopy (AES), and its corrosion resistance was evaluated by means of an immersion test in HCl solutions. The results obtained are as follows: 1) A Ti-Ni alloy film on a chromium substrate was confirmed by X-ray diffraction analysis to be amorphous. 2) Immersion of the sample in 1 N-HCl before annealing caused the substrate to dissolve. This means that this sample does not provide sufficient protection against corrosion. 3) After annealing at 500°C, volume diffusion of the chromium substrate was not observed under AES depth analysis, but the corrosion resistance and the adhesion of the film increased markedly.
TiN films were prepared by reactive ion plating, and the influence of preparation conditions (nitrogen pressure, substrate bias voltage and ionization current) on their crystal orientation, morphology and properties was investigated. The orientation and morphology of the films were characterized by X-ray diffraction and scanning electron microscopy (SEM). The orientation of TiN films changed from (111) to (200) as the bias voltage and ionization current increased. The intensity of the (200) peak decreased as the nitrogen pressure increased. The Vickers microhardness and wear resistance of the films increased with increases in bias voltage and ionization current. TiN films that were deposited at a high bias voltage, high ionization current and low nitrogen pressure showed good corrosion resistance. The properties of those films which exhibited (200) preferred orientation were better than the (111) oriented films. The change in the film orientation was explained by the adsorption model.
Amorphous Ni-B alloy films were prepared to electroplating from a bath containing (CH3)3NBH3 (trimethyla-mineborane TMAB). The films were lustrous. Boron codeposition in the films increased as the amount of TMAB in the bath was increased and as the current density was decreased. X-ray diffraction tests showed that films with boron codeposition of approximately 5wt% (equivalent to 22at%) or more were amorphous. This study showed the existence of a zone of pH values within which high boron codeposition is obtained. The maximum boron codeposition in the film prepared in this study was 6.24wt% (equivalent to 26.37at%).
Dense and continuous Cu-Zn alloy deposits were obtained from pyrophosphate baths containing histidine. Although neither Cu and Cu-Zn alloy deposits from baths without histidine nor Cu deposits from bath containing histidine showed a smooth surface morphology at 0.5A/dm2 or above, Cu-Zn alloy deposits from baths containing histidine had a smooth surface at even higher current densities. This was because the partial current densities of Cu deposition were extremely low in the alloy baths containing histidine and did not attain the diffusion limited current at above 1.0A/dm2. Smoother alloy deposits were obtained from baths containing Zn2+ ion concentrations of 0.05M or higher. Preferred orientation to the (110) facet was observed in the deposits obtained from baths with Zn2+ ion concentrations of 0.05M or higher at current densities of 1.0A/dm2 or above. Both the smooth surface and the (110) preferred orientation of the deposits from the baths with high Zn2+ ion concentrations are attributed to high overpotentials. Both the Cu and Zn in the alloy deposits from the baths containing histidine were entirely in the metallic state, and formed an α solid solution and/or a β intermediate phase.
XPS measurements on the surface of nickel electrodeposited from Ni(CF3COO)2-H3BO3-HCONH2 solutions with thiourea revealed that nickel is in the form of Ni° and nickel oxides (NiO, Ni2O3 etc.), and the sulfur is in the form of NiS, S° and oranic sulfur compounds. Since nitrogen was not detected on the surface, it appears that no thiourea from the solution is into the electrodeposit.
Particle plating, which makes it possible to electroplate fine particles with high current efficiency and high current density, is an essential technology for the creation of new sintered composite materials. Cu-W electric contacts were prepared to research the molding and sintering characteristics of copper-electroplated tungsten particles. Sintered alloys have been produced that are denser and harder than those made by the conventional powder-mixing method. These composite powders have the following superior characteristics. (1) Components segregation by this method is less than by powder-mixing. (2) The rate of aggregation in liquid phase sintering is greater.
Composite coatings consisting of SiC particles of 1, 5 and 10μm, codeposited into an electroless nickel matrix were produced, and their physical properties were sutdied. The hardness of the coatings increased with increasing SiC content, and remained about equal for coatings of the same SiC content irrespective of particle size. The coatings were found to have excellent wear resistance, but this decreased with increased in particle size, and with heat treatment at 673K. The coatings were also found to have excellent wear resistance when applied to parts of a wire twisting machine.
The concentration of formaldehyde in electroless copper plating solution was determined by potentiometric titration with hydroxylamine hydrochloride using silver as the indicator electrode. The titration curves showed a sharp peak at the equivalent point. The reaction between formaldehyde and hydroxylamine proceeded quantitatively, and formaldehyde content could be determined accurately even at concentrations as low as 10ppm or less. Potential behaviour at the silver electrode can be explained by the mixed-potential theory, with the rest potential determined by the anodic oxidation of the reducing agent (formaldehyde before the peak and hydroxylamine after) and the cathodic reduction of dissolved oxygen. This method is more accurate and simpler than the customary sodium sulfite method.
The effets of the addition of organic acid salts and polyhydric alcohols were investigated in alkaline baths of aliphatic amines (monoethylamine, diethylamine and triethylamine), containing ammonium carbonate and ammonium fluoride. Under constant-current anodizing in the baths without additives, bath voltage increased rapidly, and burning was observed on the corners of the specimens, while in baths with organic acid salts (ammonium oxalate, ammonium tartrate and ammonium citrate) added, bath voltage decreased and uniform films were formed. The thickest (about 17μm) and most uniform film was obtained in an amine (0.1mol/L) bath containing ammonium carbonate (0.4mol/L), ammonium fluoride (0.2mol/L), ammonium citrate (0.1mol/L) and propylene glycol (0.1mol/L). It was found by SEM observation that the pore diameter in anodized films formed in monoethylamine-carbonate-fluoride baths are about 600Å, larger than those in films formed in diethylamine-carbonate-fluoride baths or triethylamine-carbonate-fluoride baths.
Al-Si casting alloys with Si contents (Csi) of 0-17wt% and ADC12 die casting alloy were anodized in 10% H2SO4 at 20°C under a constant current density (ia) to examine the anodizing characteristics and film properties of these alloys. The anode potential (Ea) and dissolution current of Al3+ (ia) during anodizing, the average film thickness (δ) and the diffuse reflectance of films were examined as functions of the abrasion thickness (X) of specimens, anodizing time (ta) and ia. The steady value of Ea, Ea*, for the casting alloys was found to increase with Csi at X=100μm, and showed a maximum at Csi=10wt% and X=1100μm. The value of Ea* for ADC12 increased steeply with ia, and was much larger than that for the casting alloys. Dissolution current efficiency, id/ia, decreased with ia, and Csi, independent of X, for both casting alloy and ADC12 specimens. Oxide films formed after anodizing for 40min showed thickness differences on both types of specimen, and the dispersion in the film thickness increased with Csi and ia. The value of δ for the casting alloys decreased appreciably with increasing Csi, independent of X, at current densities of less than 100A/m2, but increased with increasing X at 200A/m2. The value of δ for ADC12 was considerably smaller than that for the casting alloys, suggesting higher rates of side reaction such as oxygen evolution. The diffuse reflectance spectra showed that the reflectance of films decreased with increasing Csi, and with decreasing X.
A colored film was formed on SUS 430 and SUS 304 stainless steels in 5kmol m-3 H2SO4 at 353K by the potential-pulse method and some porous surface structures were observed under SEM observation. When anodic pulse potential was controlled at the transpassive potential, the film obtained showed good adhesion, but film obtained at high potentials dissolved along to the grain boundary. Active dissolution occurred when the cathodic pulse potential decreased to the active dissolution potential region. The films grown were thicker than those obtained by the sulfuricchromic immersing method or the alkaline electrolysis method. The thickness of surface films on SUS 430 and SUS 304 increased lineally with electrolytic time. Within the coloring time range, the growth rate tended to increase with increases in the anodic pulse time or decreases in the cathodic pulse time. It was found by XPS analysis that in films on SUS 304, Cr was enrichened and Fe and Ni were depleted, and that the films consisted of a complex compound of Cr and -OH at the surface layer of the film, and an oxide consisted of Cr with a little Ni and Fe at the inner layer. X-ray diffraction showed the surface film had an amorphous structure. It was also found that resistance to pitting corrosion was improved by increasing the electrolysis time.
Because of the highly corrosion resistant properties of hopeite crystals doped with manganese Zn3-xMnx(PO4)2·4H2O, EXAFS was applied to analyse the structure. Oxygen atom was found to exist at 1.62Å from manganese atom. However, since φ(K) of a Fourier transform contains a certain phase shift deviation, an inverse Fourier transform and curve fitting were carried out to determine the real bond distance, 2.15Å. There was a difference of approximately 0.5Å between the Mn-O distances obtained by the EXAFS Fourier transform and inverse Fourier transform, and this discrepancy was found to be due to the phase shift deviation. The coordination number for manganese atoms obtained from the 1st peak was 6.8. It was found that the bond distance of 2.15Å corresponds to the Mn-O bond due to the octahedral structure of MnO2(H2O)4 in the hopeite crystals. Inverse Fourier transform and curve fitting of the 2nd to 4th peaks indicated that all the peaks belonged to the Mn-P bond. The coordination number of phosphorus to manganese for the 2nd peak was 1.0. Therefore, the 2nd peak provided information about the closest phosphorus to manganese in the MnO2(H2O)4 groups.
A process of plating copper on devitrified porcelain enamel printed circuit boards has been developed, the essential feature of which is the pretreatment of the porcelain surface with fluoride solution, catalysis with an organic solution, and electroless copper plating. A fully practical pull strength of 2-3kgf/mm2 was achieved for plated copper. This makes possible the copper, plating of through holes, formation of conductors and fine patterning with line widths of about 50μm width on porcelain enamel printed circuit boards.