Copper substrate with a double-layer silver/nickel film having copper strike plating between the layers was analyzed by Auger electron spectroscopy after thermal treatment in a nitrogen atmosphere, and the thermal diffusion behavior of several elements, including oxygen, was measured. These profiles were compared with those obtained after thermal treatment in air. The results can be summarized as follows (1) The thermal diffusion of the copper in the copper strike plating was considerably influenced by the oxygen concentration during thermal treatment. (2) Some of the copper of the intermediate layer diffused onto the silver surface after thermal treatment in nitrogen. Diffused copper formed an oxide film with a slight amount of oxygen, and the surface discolored. (3) Since inner oxidation of the plating layers did not occur with thermal treatment in nitrogen, the adhesion of the plating was good.
It was experimentally shown that when nickel oxide films were formed on nickel films electrodeposited by controlled potential technique, solderability declined with increasing quantity of electricity in anodic oxidation. Nickel films 1∼7μm in thickness were electrodeposited from a Watts bath. The real thickness of nickel oxide films was represented by the quantity of electricity in anodic oxidation because measurement by ellipsometry had a large error. Soldering to electrodeposited nickel films was virtually impossible in anodic oxidation at quantities over 15.5×10-3C cm-2. Solderability was not affected at quantities below 3.0×10-3C cm-2. After nickel electrodeposition, the nickel oxide films were dissolved by hydrogen forming by cathodic reduction at -1.40V vs. Ag/AgCl and solderability was raised.
Up to now, an extremely high density of atomic hydrogen was supposed to be necessary for the gas phase growth of diamond, so that hydrogen was usually used as the plasma base gas. Therefore, we have investigated the chemical vapor deposition of diamond in Ar/H2-CH4-O2 plasma, especially the effect of the plasma gases (Ar or H2). Only diamond phase could be successfully grown even in the Ar-based plasma, revealing that the sufficient amount of hydrogen atoms was supplied by the cracking of methane molecules in the plasma. The comparison of the deposits in Ar-based and H2-based plasmas showed that both the morphology and the growth rate were similarly dependent on substrate temperature. Although the gas-phase composition in Ar-based plasma might be different from that in H2-based plasma, the composition in the vicinity of growth interface would be virtually identical in both cases.
Because diamond films are synthesized from vapor phase CVD, studies are being conducted on applications of their properties as industrial materials. Epitaxial growth is necessary, however to obtain properties like those of natural diamond, and reports exist of epitaxial growth on diamond or cBN substrates, and of local epitaxial growth on Ni substrates. To obtain basic data for diamond epitaxial growth, diamond synthesis was carried out by microwave plasma CVD from a methane-hydrogen reaction gas system on substrates of poly and single-crystal Ni, having nearly the same lattice distance as diamond. On poly-crystal Ni substrates, it was found that although the range of conditions suitable for diamond growth were narrow, high-quality diamond having a diamond peak of narrow FWHM on the Raman spectrum could be obtained if suitable conditions were chosen. On single-crystal Ni substrates, on the other hand, hetero epitaxial growth was not observed, and the quality of the diamonds grown was degraded be the presence of DLC. This phenomenon is attributed to the crystalline stability of Ni substrates in the diamond synthesis atomosphere, and the instability of the crystalline orientation of Ni substrates during fluctuations in substrate temperature.
Nickel was plated on steel and tin plated on top of that. The alloy films formed at the Sn-Ni interface were then analyzed by glow discharge emission spectrometry (GDS) and the effects of heat-treatment on X-ray diffraction patterns and anodic polarization curves were investigated. The GDS results showed that interdiffusion between tin and nickel layers proceeded and a diffusion layer was formed by heat-treatment at 200°C for 4-24 hours, the thickness of which increased with increasing thickness of the tin layer and the heat-treatment time. X-ray diffraction measurements confirmed the formation of intermetallic tin-nickel compounds. The rest potential for tin/nickel double plating films in 0.1N HCl solution shifted to a more noble potential and current values on anodic polarization curves were suppressed by heat-treatment at 200°C, while current values decreased with increasing heat-treatment time, indicating that corrosion resistance of tin/nickel double plating films was improved by heat-treatment at 200°C.
Electroplated films obtained from chromic acid plating baths containing NaNO3 were investigated using XPS analysis and X-ray diffraction. When the concentration of NaNO3 in the plating bath was raised to 4mM, the amount of nitrogen involved in the films increased to 4.2at%. Binding energy of N 1s and Cr 2p3/2 observed on XPS spectra for films indicated the existence of a kind of Cr-N compound. X-ray diffraction patterns showed that as-deposited film had hcp crystal structure and did not contain chromium nitrides (Cr2N or CrN). With heat treatment at 600°C for 4 hours the crystal structure changed from an hcp deposit to bcc chromium including chromium nitride.
The thermal stability of the electrical resistance properties of electroless NiReP alloy films with three levels of Re content was evaluated, using a pulse heating method that provided a very high heating rate (up to 105Kmin-1) and very short heating time (200ms). The temperature coefficient of resistance (TCR) of the three films had a range of only -100∼250ppmK-1, and the amorphous structure in the as-deposited condition was maintained for all three films even by pulse heating, although, the specific resistance changed slightly. After annealing at 500°C, the specific resistance (340μΩcm) and TCR (18ppmK-1) of the film with the greatest Re content (Ni51Re44P5) was not changed by pulse heating. It was found that the electroless NiReP alloy films were much more stable under pulse heating, than were the electroless NiWP and NiMoP alloy films with good thermal stability.
The boric/sulfuric acid anodizing process has been developed in the U. S. as a replacement for chromic acid anodizing to meet stricter environmental regulations. A comparative study has been conducted on the microstructures of boric/sulfuric acid films and sulfuric acid films. The sulfur and boron contents of the oxide films were determined by prompt gamma ray analysis. The type of V-t and I-t curves, and the morphology of pores were not appreciably influenced by the presence of boric acid in the anodizing bath, but the rate of formation of the boric/sulfuric acid films increased slightly and the rate of their disolution in phosphoric acid solution decreased slightly. The concentration of boric acid did not influence the amount of surfur incorporated into the oxide films. After the pores were sealed, surfur content decreased significantly due to the dissolution of sulfur compounds to the sealing solution. The boron content of porous type films was negligible, in the order of ppm. This is in remarkable contrast to the barrier type films formed in borate solutions, where boron contents of the order of several per cent have been reported. The boron content increased with increasing concentration of boric acid in the electrolytes.
The effect of surface treatment on corrosion behavior of AZ91D diecast magnesium alloy coated with epoxy resin has been investigated by salt spraying test. The corrosion test results revealed that corrosion under the epoxy coating was inhibited in all samples subjected to surface treatment, and corrosion was observed to develop from cross-cuts. The maximum corrosion width increased in the following order of surface treatments; stannating, chromating and phosphating. The corrosion resistance of uncoated magnesium alloy correlated well with the maximum corrosion width. The corrosion behavior of magnesium alloy coated with epoxy resin is discussed in terms of a galvanic model in the same way as for uncoated magnesium alloy.