The tribological behavior of diamond-like carbon films (DLC) is strongly dependent on the hydrogen content, sp 2 /sp 3 ratio, and sliding environment. Some hydrogenated amorphous carbon films (a-C:H) exhibit superlow friction in hydrogen conditions. However, previous works have not clarified the dominant factors of the superlow friction phenomena of DLC films. In this research, we focused on the effects of hydrogen derived from the surrounding atmosphere and the hydrogen within the DLC films on superlow friction phenomena. To investigate these effects, friction tests were conducted on three DLC films having different hydrogen contents (0, and 18, 30 at%) in the air and in low-pressure-hydrogen conditions at various hydrogen pressures. After the friction tests, the wear tracks were examined by confocal laser scanning microscopy, Raman spectroscopy, elastic recoil detection (ERDA) analysis, and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The hydrogen derived from the surrounding atmosphere and the formation of the hydrogen-rich tribofilm were key factors for the superlow friction phenomena.

Nanocube has attracted interest regarding its synthesis by the wet chemical process. Recently, nanocube with perovskite structure such as barium titanate (BaTiO3) and strontium titanate (SrTiO3) has been studied. In this study, sodium niobate (NaNbO3) was prepared by the solvothermal method and its morphology was investigated. The synthesis was carried out using niobium oxide (Nb2O5) and sodium hydroxide (NaOH) as starting materials, also using ethanol as solvent. X-ray diffraction (XRD) confirmed the presence of perovskite NaNbO3 particles and indicated that the phase is orthorhombic NaNbO3. Scanning electron microscopy (SEM) observation revealed the form of NaNbO3 to be nanocube. Reaction times and concentrations of reaction solutions are important factors for synthesis of nanoparticles. The particle size increases with the reaction times, while the particle size decreases with the concentration of the reaction solutions. The smaller crystals were synthesized in a shorter reaction time at the higher concentration of the reaction solutions.

Highly dispersed and homogeneous titanium dioxide (TiO 2) nanoparticles were synthesized by a solvothermal method with polymer gel. Polymer gel is essential for the highly dispersed and homogeneous nanoparticles. First, polyvinyl alcohol (PVA) was dissolved in water at 70°C and cooled to room temperature. Ammonium citratoperoxotitanate(IV) [(NH 4) 8 [Ti 4 (C 6 H 4 O 7) 4 (O 2) 4 ]・ 8H 2 O] was subsequently added and dissolved in the PVA solution. Next, water was evaporated from the PVA gel using a microwave. This polymer gel and ethanol as a reaction medium were placed into the Teflon reactor of a stainless-steel autoclave with an internal volume of 100 ml. Thereafter, the autoclave was sealed and kept at 230°C for 18 h. After solvothermal synthesis, the polymer gel was collected and dissolved in water at 50°C-70°C. X-ray diffraction (XRD) measurement, scanning electron microscope (SEM), and transmission electron microscope (TEM) observations were performed for the remaining unresolved polymer gel. XRD confirmed the presence of anatase TiO2. The crystallite particle size was estimated as 6.4 nm (D 101) from the XRD 101 peak using the Scherrer's equation. Highly dispersed and homogeneous TiO 2 nanoparticles were obtained from TEM observation with a particle distribution of 5.6 ± 1.2 nm.

No abstract

No abstract