The appearance of Ni-W-P alloy plating from Ni-tungstate-citrate bath was examined by a Hull cell test as a function of the phosphorous acid concentration of the bath. The effects of P content on the corrosion resistance of bright Ni-W-P alloy plating ware examined by CASS and SST, and then their corrosion behaviors were investigated by measuring the rest potentials in CASS and SST solutions, and by XPS analysis. The main findings obtained were as follows : (1) Mirror bright Ni-W-P alloy plating was obtained over the wide range of plating current density from the Ni-tungstate-citrate bath containing phosphorous acid of more than 0.05M. (2) In the CASS test, bright Ni-W-P alloy plating of P content higher than 7at% performed good discoloration resistance; however, the plating of P content less than 3.5at% discolored to black. On the otherhand, bright Ni-W-P plating of any P content showed interference color on the surface of the plating by the SST of 2000hr exposure, resulting in good rust-resistive property of the Ni-W-P plating layered on Ni plated steel. (3) The discoloration of Ni-W-P plating of P content less than 3.5at% from mirror bright to black by CASS test was revealed to be by conversion deposition of copper accompanied with oxidation of the W element in the Ni-W-P plating. On the other hand, good discoloration resistance achieved with the higher P content Ni-W-P plating was because of the existence of the concentrated phosphorus layer under the Ni oxide layer on top of the alloy surface.
An acrylic-urethane coating material is widely used as paint over Cr plating. Though the peeling of the coating film that occurs shortly after the painting becomes a problem, the cause of the peeling is not clear. The effects on the adhesive strength of the coating material were clarified for both the dirt in the plating process and the storage environment (temperature, humidity) of the Cr plating material before the coating was done. The adhesive strength of the coating material decreases when the plating process dirt remains on the Cr plating surface and the storage environment is at high temperature and high humidity. The ratio of Cr2O3 increases on Cr plating material in which the adhesive strength of the coating material decreases due to high temperature and high humidity. It was proven that the adhesive strength is improved by using an organic silicon compound for Cr plating material in which the adhesive strength of the coating material was lowered. The adhesive strength was slightly improved by adding an organic silicon compound to the acrylic-urethane coating material and using the pre-coating organic silicon compound for the Cr plating material. The adhesive strength of the coating film for the Cr plating material was remarkably improved by using the silicon-acrylic coating material.
The surface morphology and crystalline quality of 3C-SiC films on Si(111) substrates were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy, where tetraethylsilane (TES, Si(C2H5)4) was first used as a safety source for the growth of SiC films. While TES was expected to be the safest in various organosilane sources, it was essentially anticipated that the high C/Si ratio in TES results in deposition of carbon-rich SiC films, preventing single crystal formation. In raising the temperature after carbonization, voids appeared at the interface of SiC/Si, causing the formation of hillocks on the grown SiC films. The formation of voids and hillocks was prevented by adjusting the TES flow rate and time in the heating process to the growth temperature, leading to the growth of SiC films with a good surface morphology. As a result, it was shown that single crystal epitaxial films could be obtained in the growth of SiC films using TES, and yet a high density of stacking faults resided at the SiC/Si interface.
The base component in aluminum electrolytic capacitors gradually concentrates on the cathode terminal end, irrespective of the dc bias. If the electrolyte is a salt with a strong base component, such as quaternary alkyl ammonium, this tendency may affect the sealing. The concentration is caused by the obvious different in electrochemical characteristics between the cathode foil and the tab used for the cathode terminal end of capacitors. A cathode foil and a tab with different rest potentials together form a galvanic couple. Therefore, reversing the potential relationship between foil and tab gives the fundamental solution against this problem. For the method, we developed a new method of using a cathode foil-formed titanium nitride (TiN) coating on the surface by an arc ion plating method. The order of the rest potential, the polarization behaviors of the cathode terminal side while applying voltage in a capacitor and also the durability were investigated. The rest potential shifted from −1.20V to −0.30V due to the TiN coatings and consequently became nobler than that of the tab, −0.75V. Even while applying the rated voltage, the potential of the cathode terminal did not cross over the rest potential of the tab. In addition, the performance was maintained even after 5000h under 378K condition. Liquid leakage evaluation tests demonstrated that this method provides an excellent advantage in preventing leakage. TiN-coated foil has been already mass-produced for this purpose by NIPPON CHEMI-CON Corp.