Diamond-like carbon (DLC) films have been widely applied to machine components of many types. DLC has excellent tribological properties, but it must be improved to reduce friction further. Deposition with a different element-doped DLC on both sides of a sliding surface is expected to produce a superior friction coefficient. Therefore, we investigated the tribological properties of different element-doped DLC/DLC sliding to achieve sliding with lower friction. For our study, we used Plasma-Based Ion Implantation and Deposition (PBIID) to prepare three DLC films of pure-DLC, Si-DLC, and Ti-DLC. Each DLC film bond structure was analyzed using Raman spectroscopy. Hardness and roughness were measured by nano-indentation and atomic force microscopy. Regarding their tribological properties, friction coefficients were measured using ball-on-disk friction tests. Subsequently the chemical elements in wear tracks were analyzed using energy dispersive x-ray spectroscopy. Results obtained through the study revealed the following. (1) Different kinds of DLC/DLC sliding achieved a much lower friction coefficient than a single kind of DLC/DLC sliding. (2) Occurrence of mild wear particles functioned as a solid lubricant. The particles effectively reduced the friction coefficient. (3) Adhesion of wear particles was observed in wear tracks after Si-DLC/Ti-DLC sliding. (4) Friction coefficients of the Si-DLC/Ti-DLC sliding were the lowest, about 0.021, by appropriate adhesion of the wear particles.
The correlation between wear resistance and the chemical state of the elements of nitrogenated diamond-like carbon films (NDLC) is characterized and discussed in this paper. NDLC have been deposited on tungsten-carbide, silicon and glass substrates by rf plasma chemical vapor deposition from C6H6-N2 mixtures. The nitrogen content in the films measured by electron microprobe analysis was found to be proportional to the N2 flow rate. X-ray diffraction pattern indicated that the diamond-like carbon (DLC) and NDLC were an amorphous structure. X-ray photoelectron spectroscopy measurement (XPS), which probed the chemical state of elements of the films, indicated that the sp3/sp2 ratio went down as nitrogen content increased. Raman spectra of the films showed that the intensity ratio (ID/IG) of D band to G band increased with increasing nitrogen content. Electric resistivity of NDLC drastically reduced compared with that of DLC. The friction coefficients of the films, which were determined by the ball-on-disk test, increased with increasing nitrogen content, whereas the friction coefficient dependence on load was not observed in each film. The wear rate of NDLC was bigger than that of DLC. The wear mode of DLC showed adhesive wear. However, that of NDLC was abrasive wear. The film hardness measured by Berkovich stylus, which decreased with increasing nitrogen content, was found to be dependent on the sp3/sp2 ratio.
For the field of nickel electroforming, where thickness of about 100-500 μm is obtained at the current density of 20-50 A/dm2, increase in the current density is demanded for higher plating speed. Regarding the environmental impact, a plating bath without boric acid is also in demand. Results obtained from studying various organic acids to replace boric acid show that acetic acid facilitates high-speed plating without burning at a current density of up to 200 A/dm2. The effect of acetic acid was attributed to its excellent buffering capability.
Surface patterning is an important technology for improving product design. This paper describes the fabrication of three-dimensional microstructures on aluminum plates using photolithography, anodization, and chemical etching. Photoresist patterns were prepared on an aluminum plate using a standard photolithography technique. The aluminum plate was anodized in sulfuric acid at a controlled concentration and bath voltage. During anodization, an anodic oxide film was formed on the photoresist/aluminum plate interface and in an open region. The oxide film formation was sensitive to both sulfuric acid concentration and bath voltage. The aluminum plate was expanded by anodization. The volume expansion factor (calculated as the ratio of the oxide film thickness to the thickness of the consumed aluminum) was 1.44-1.69. The oxide film was removed by chemical etching in phosphoric acid. Thereby, the aluminum surface was exposed, and convex shapes were formed. The surface roughness of the plate after chemical etching was comparable to its value before fabrication. The mean roughness Ra was <20 nm. Quadrangular pyramids, cones, and hexagonal pyramids were fabricated successfully on the aluminum plate by changing the photoresist mask pattern. Anodization and chemical etching conditions were controlled for accurate shape control of the three-dimensional metallic microstructures.
DLC films deposited from C2H2 and SF6 mixtures were used to study the correlation between the surface properties and the tribological performance of sulfur-incorporated DLCfilms prepared by PBII process. The elemental content of the films was analyzed by Auger electron spectroscopy, and the surface properties of the films were measured by contact angle measurement. The hardness and elastic modulus of the films were measured by nano-indentation hardness testing. The average surface roughness was measured by atomic force microscope. The tribological performances of the films were evaluated using a ball-on-disk friction tester. The results of the study do not show any direct correlation between the surface contact angle, the surface energy, the polar force, the wettability, and the tribological performance of S-DLC films. Sulfur incorporation did not lead to significant changes in the surface roughness, but it did lead to changes in the surface contact angle, the surface energy and the polar force. With 2.9 %–4.3 % sulfur, the surface exhibited low wetting and sticking tendencies, and the surface contact angle increased, while the surface energy and the polar force decreased. The best tribological performance was observed at a bias voltage of −5 kV with 4.3 % sulfur, which nearly had the poorest wettability. At the same time, the S-DLC films with the highest polar force and the best wettability performance did not exhibit the lowest friction coefficient because of the transfer of the film and the high hardness and elastic modulus. Moreover, the surface energy and the surface contact angle measurements were performed on the molecular level, while the tribological tests were run at the macro-level and the shear forces were in the kN range.