Ultra water-repellent films were prepared by using rf PECVD. Relationships between the rf power and water repellency, morphological and chemical properties were investigated. Moreover, the growth process of ultra water repellent thin films was evaluated by using FESEM. The experimental results showed that surface morphology of the films strongly depends on the rf power, and that increasing the rf power made it possible to from ultra water-repellent films. At the first stage of the growth, the nano-clusters were deposited randomly on the substrate surface. These clusters were originated from a polymerization process in the gas phase and deposited on the substrate. When the film was deposited for several tens of seconds, the nano-clusters showed a tendency to form chains or islands, which means the clusters must have a spatial preference. Finally, these films have particular nano-textures with nano-scale pores of a few hundreds of nanometers in diameter among the rough web-like structure of the nano-cluster agglomerates
In order to achieve highly functional materials which show high fatigue and high tribological properties, two surface modifications, high carbon carburizing and DLC (Diamond Like Carbon) coating, were applied to low carbon steel (SCM415). However, there are some reports which raise the concern that coat materials like DLC show low fatigue strength compared with substrate only due to high heating history during the coating process. So, in this study, in order to prevent the base material from losing fatigue strength, DLC was coated by using the UBMS (Unbalanced Magnetron Sputtering) method, which can coat at low temperature. Furthermore, three types of DLC-coated specimens with different coating structures were prepared. Rotational bending fatigue tests and friction-wear tests were carried out. It was clear that the friction coefficient of each specimens coated with DLC stabilized under 0.1. And, the specimen coated a 5 μm-thick DLC film shows the highest tribological properties because the DLC coating was transcribed on the opposite material during the wear process. Furthermore, no decreases in fatigue strength were observed for any of the coated specimens. It can be concluded that it is possible to achieve highly functional materials by applying DLC hybrid surface modification as suggested in this search.
Boric acid is generally added to buffer the pH and improve the life expectancy of a nickel plating bath. The plating industry has requested alternatives to boric acid because its use will be restricted in the future. In this study, the hull cell, pH buffer correlation and cathode current efficiency tests were conducted using 21 different substitute buffering agents. From these 21 agents, acetic acid, propionic acid, nickel acetate and citric acid showed the same appearance and buffering ability as boric acid. Physical properties, such as Vickers hardness, tensile strength and internal stress test were measured on nickel samples made using these four buffering agents, as well as boric acid. When using these four organic compounds, the internal stress somewhat higher compared with a standard boric acid bath, but the other physical properties were almost all the same, except in the case of citric acid. It was found that citric acid produced samples with higher Vickers hardness. For all the buffers, as current density increased, Vickers hardness decreased and tensile strength increased. The physical properties of samples made with these buffers show the same trends vs. current density as those made with boric acid bath.