We report the study of fatigue improvement for power transmission equipment in, for example, automobiles. We coated DLC(Diamond-Like Carbon)on rollers of a rolling contact fatigue tester and carried out roller pitting tests. The results showed that the DLC coating improves the life of the rollers by more than two orders of magnitude. We observed the metal structure under the DLC coating by optical microscopy, SEM(Scanning Electron Microscopy), and TEM(Transmission Electron Microscopy), and confirmed that a major cause of fatigue damage was cracks and pitting on a surface, caused by shearing force. We also found that metal nanocrystals were formed on the surface of the sample that showed a long life in the roller pitting tests. Probably that was caused by accumulation of plastic strain from repeated stress. A small friction coefficient by the DLC coating reduced shearing force, suppressed fatigue damage, and led to the formation of metal nanocrystals.
In order to implement electrochemical processes (e.g., detection or synthesis) on a chip-based system, micromachining techniques for a glass microchip with fully integrated electrodes have been developed. Pt/Ti microelectrodes were successfully patterned on the curved surface of a glass microchannel, which was etched in a HF solution using polysilicon thin film as an etch mask, by means of a lift-off method using a positive thick photoresist. In this process, the photoresist must be exposed with a single wavelength (g line) selected from a high-pressure mercury lamp in order to obtain its microstructure with excellent edge quality and vertical sidewalls. In addition, although fusion bonding cannot be used for microchips with lead patterns in the interface between a pair of glass substrates, a glass cover plate can be bonded to a glass substrate with lead patterns embedded in the space formed on its surface by buffered HF (BHF) etching. The resulting bonded area ratio was estimated to be approximately the same as that for glass-to-glass bonding.
Highly-concentrated gaseous ozone of 15 vol% was produced from an ozone-oxygen mixture (5 vol%), generated from a pure oxygen-fed discharge ozonizer, by using silica-gel as an adsorbent. The nonwoven fabrics of stainless steel fiber were treated with 15 vol% gaseous ozone for 60 min. As a result of the ozone treatment, the total amount of metal ions dissolved from the ozone-treated stainless steel fiber during immersion in pure water decreased by 70% compared with that from non-ozone-treated stainless steel fiber. X-ray photoelectron spectroscopic analysis showed that Fe and O were enriched by 1.6-fold in the outermost surfaces of the stainless steel fiber after ozone treatment. It was suggested that the formation of a highly resistant Fe-oxide film was responsible for the improvement of corrosion resistance. Pretreatment of protein-fouled nonwoven fabrics of stainless steel fiber by 15 vol% gaseous ozone for 30 min markedly facilitated the removal of protein during subsequent rinsing and caustic alkali cleaning through the decomposition of protein molecules by O3 oxidation. In addition, fungi, Penicillium chrysogenum and Alternaria altenata, were completely sterilized by treatment with 15 vol% gaseous ozone for 1 min. The results indicated that surface modification, cleaning, and sterilization of nonwoven fabric of stainless steel fiber could be performed by its exposure to 15 vol% gaseous ozone.
Waste sludge from surface finishing industries generally contains a large amount of water. It is proposed that calcination will be a simple and convenient method for reducing the volume and weight of the sludge. However, when the sludge contains chromium, some amount of chromium in the sludge can be converted to the harmful hexavalent state during the calcining operation. In this study, the generation of hexavalent chromium in the calcination of chromium hydroxide reagent was compared with that of a sludge obtained from an actual industry. In both cases of the chromium hydroxide and the sludge, the amounts of hexavalent chromium leached from the samples became higher with an increase of heating temperature when their structures were in the amorphous state, and then the amounts of hexavalent chromium lowered after their crystallization. Calcinations of the mixtures of chromium hydroxide and one of the other hydroxides of nickel, copper, zinc, or ferric iron were attempted, but none of them could lower the hexavalent chromium at 700ºC to the level of the sludge tested in this study. However, when these hydroxides were mixed in the ratio similar to that of the sludge, the amount of hexavalent chromium leached from the sample became as low level as that of the sludge.
In order to study the relation between whisker growth and the structures of deposits with respect to matt Sn deposits plated on Cu substrates, the dimensions of the grains of the deposits and those of the whiskers and/or nodules (whiskers/nodules) were determined as a function of the thickness of the deposits. Furthermore, the extruded mass per unit area attributed to the whisker/nodule growth has been estimated from the above data and the number density of the whiskers/nodules. It has been found that (1): the matt Sn deposits are formed during electrodeposition in accordance with the mechanism known as “geometrical selection”: the average grain size is proportional to the root of the thickness of the deposits, (2): the whisker growth originates from the grains situated on the surface of the deposit ; the whiskers are considered to be the outward protrusions of the grains, and (3): the whisker growth can take place when the radius of the grain, consequently of the whisker, is larger than a critical radius, r*, and which was found to be 0.34<r*<0.43 μm. It has also been found that the extruded mass per unit area was constant regardless of the thickness when the thickness of the deposits was more than 2 μm. On the other hand, it has been shown that, in thick deposits, the grain growth, which is expected to reduce the grain-boundary free energy and the strain energy included in the deposits, can easily take place. These suggest that the nature of the excessive energy that drives the whisker/nodule growth is different from the grain-boundary free energy or the strain energy.