Toshiaki Shibata

Effect of Surface Termination on Superlow Friction of Diamond Film: A Theoretical Study

We have applied molecular dynamics simulation and density functional theory calculations to analyze the effects of H and OH terminations on the frictional properties of diamond films at the atomistic and electronic levels. Molecular dynamics simulations were carried out for H-, OH-, and non-terminated diamond surfaces against an iron surface. Results of molecular dynamics simulations show that the frictional force is clearly decreased by the H or OH termination on the diamond surfaces. Moreover, results of density functional calculations show that a covalent bond is formed between Fe and C, while H- or OH-terminated diamond surfaces interact repulsively with an iron surface owing to antibonding interactions. We concluded that this interaction change between iron and diamond surfaces is the major contributing factor for achieving a low friction in H- or OH-terminated diamond.

Development and test of a compact lidar for detection of oil spills in water

The fluorescence lidar can positively distinguish the oil from the water or biological substances. A rugged system with real- time display mounted in a small airplane and on a ship could make significant aides for pollution response sites. This paper describes a compact lidar system which is suitable for rapid identification of oil slicks with a wider field of view. Functions of the proposed system were evaluated by airborne and shipborne tests. During a flight from an altitude of 1000 ft above the water surface, spots illuminated by the laser were acquired in an image with angular view of 18.2 degrees. Fluorescence data was interpreted in terms of substances referenced with the fluorescence characteristics measured with a streak scope. A GPS instrument was used to position data precisely, to map out a flight line.

Preparation of a Single Crystalline Powder of Superconducting YBa2Cu3O7-x by the Gas Phase Solidification Method

The preparation of a single crystalline powder of superconducting YBa2Cu3O7-x was investigated for the gas phase solidification process by decomposing an evaporated solution of yttrium, barium and copper acetates. A transmission electron microscope observation of particles less than 0.3 µm in diameter showed that the as-produced particles were twinned at transformation to orthorhombic YBa2Cu3O7-x. The as-produced powder was a single phase YBa2Cu3O7-x and did not exhibit an isomer from the X-ray diffraction pattern.

Direct deposition of two nanomaterials with the same surface charge using a liquid-liquid interface.

Two negatively charged nanoparticles (SDS-coated SWCNT and polydiacetylene nanocrystals) were sequentially adsorbed onto the same water-hexane interface. The absorbed film can be transferred onto a solid substrate. Repeating the adsorption and transfer process enables assembly of the two nanoparticles in a layer-by-layer growth fashion up to three bi-layers.

In Plane Orientation of SWCNT Ultrathin Film Fabricated Using a Liquid–Liquid Interface

Non-chemically treated single-walled carbon nanotubes (SWCNTs) were assembled at a liquid–liquid interface in the shape of an ultrathin film. SWCNTs were dispersed into water phase by aid of sodium dodecyl sulfate (SDS) and were assembled at a hexane-water interface with addition of ethanol. The assembled film was transferred onto a solid substrate at various dipping speeds. Polarized absorption spectra of the transferred film indicated that the SWCNTs aligned with their long axis parallel to the dipping direction when the assembly was transferred at the dipping speed of 50 mm/min.

Evaluation of Elastic Constants of Antifouling Paint Film Using Group Delay Spectrum Method

An antifouling paint film was subjected to leaching test in artificial seawater for 89 days. An ultrasonic measurement of the film was performed before and after the test. The results were analyzed by a group delay spectrum method, and the propagation time in the film was determined. It was observed that the density and elastic constant of the film decreased after the test. This suggests that the chains of polymers are cut by water penetrating the film. When compared with plates made of the same matrix as the film, the improvements in the density and elasticity of the film were found to be mainly a result of the existence of pigments. An abnormality in the group delay spectrum of the film tested was observed, and its origin was discussed. It was also found that the paint film was a dispersive medium that absorbs sound energy considerably.

Leaching Phenomena of Antifouling Agents from Ships’ Hull Paints

The effects of pH, dissolved ion content and relative water velocity on the release rate of an antifouling agent, cuprous oxide, from ships’ hull paint have been investigated by rotating cylinder tests. Additionally, test paint panels were attached to a vessel and recovered after a certain period of voyage for the validation of the laboratory tests. In the initial period, the release rates are influenced by pH, dissolved ion content and water velocity, but once after a certain period of test, those effects become less significant. These phenomena can be explained when the paint film is fresh, the rate is controlled by chemical reaction, the surface and/or diffusion layer in the water phase governs the rate. After the antifouling substance in the paint film leached out from the near-surface region, a diffused layer (leached layer), that has little antifouling agent remained, is formed at the surface of the coating, and the diffusion in that layer can be a rate-determining process. The development of the leached layer is affected by a balance between the leaching rate of the antifouling ingredient and paint resin determined by the chemical properties and speed of the water. Thus, the leaching rates of antifouling agents are affected by the history of the paint in the water.

Computational Chemistry Study of Diamond-like Carbon: Functions and Structure Control by Frictional Force

max max 0 R R R P N − ≤ Diamond-like carbon (DLC) films attract the special interest of its applications as surface coatings in electronics devices, automotive engines, and so on. This is because they show excellent characteristics such as super-low friction, good wear resistance, hardness and air-tightness. In fact, DLC is used as coating on the silicon-based microelectromechanical system (MEMS) in which friction and stiction are major problems. DLC coating maintain low friction and improve the durability and storage stability of MEMS [1]. S.A.Smallwood et al. reported that the DLC coated devices run in vacuum showed a three hundred times increase in performance over uncoated device [2]. However, in their study the atomic-scale DLC structure which shows best property remain unrevealed. Functions of DLC films are greatly influenced by the atomic scale structure, which depends on the formation process and conditions. Also, additives in the DLC films such as H and Cr have a great influence on its function. It is therefore important to best optimize the atomic-scale structure and composition of DLC films to obtain desired functions for each application. Computational chemistry methods are effective in nano-scale materials design and extensively applied so far [3]. In this study, we used computational chemistry methods to investigate the influence of external frictional force on the structure of DLC films. To investigate the dynamics of structure change in the complex system, a method, which can deal with chemical reaction with reasonable computational time, is necessary. Therefore, we developed a novel classical molecular dynamics program with chemical reaction extension, NEW-RYUDO-CR. We have applied the developed method to study the functions and structure of DLC controlled by frictional force.