Tsuyoshi Tanimoto

Improvement of adhesion of hydrogen-free DLC film by employing an interlayer of tungsten carbide

Materials with poor adhesion present a problem for the application of diamond-like carbon (DLC) films. As a method for solving this problem, there is a technique that deposits an interlayer of metal between the DLC film and substrate. A tungsten carbide film (W-C film) is used as the interlayer. In this study, the effect of introducing the W-C interlayer on the adhesion of the DLC film was investigated. The W-C films were deposited using two types of cemented tungsten carbides (WCs) as the cathode, one containing Co (WC-Co) and the other containing Ti (WC-Ti), as a binder for forming the cathode shape. It is necessary to control the film thickness of the interlayer to introduce the interlayer to the DLC film. The film thickness control of W-C films became possible by using a discharge counter. DLC films were deposited using a bias voltage of -100u2005V. The film thicknesses of the W-C interlayer and DLC film at the time of investigating adhesion were 30u2005nm and 300u2005nm, respectively. The result of the tape-peel...

Electromagnetic wave absorption properties of carbon nanocoil composites in the millimeter waveband

Carbon nanocoil (CNC) is a carbon nanofiber with helical shape. In this study, we fabricated CNC-based composites endowed with electromagnetic wave absorption property. CNCs were synthesized by chemical vapor deposition using acetylene as a precursor and Fe and SnO2 particles as catalysts. The composites were produced by dispersing CNCs into epoxy resin or paraffin by ultrasonication, and then hardening a droplet of the solution on an aluminum substrate with ca. 2mm in specimen thickness. Paraffin was used as a solvent when producing the composites with the CNC concentration higher than or equal to 5wt.%; otherwise epoxy was used. The reflection ratio of the composites with different concentrations were measured by the free space method using lens antennas in frequency ranges of 5.6–40 and 67–110u2005GHz. The CNCs/epoxy composites of 0.1–1.0 wt.% showed poor reflection losses. The 10 wt.% CNCs/paraffin composite achieved a reflection loss of −32u2005dB at 79.2u2005GHz. Its bandwidth corresponding to the reflection lo...

Multi-spark discharge system for preparation of nutritious water

The nitrogen compound concentration in water is increased by atmospheric-pressure plasma discharge treatment. A rod-to-water electrode discharge treatment system using plasma discharge has been developed by our group to obtain water with a high concentration of nitrogen compounds, and this plasma-treated water improves the growth of chrysanthemum roots. However, it is difficult to apply the system to the agriculture because the amount of treated water obtained by using the system too small. In this study, a multi-spark discharge system (MSDS) equipped multiple spark plugs is presented to obtain a large amount of plasma-treated water. The MSDS consisted of inexpensive parts in order to reduce the system introduction cost for agriculture. To suppress the temperature increase of the spark plugs, the 9 spark plugs were divided into 3 groups, which were discharged in order. The plasma-treated water with a NO3− concentration of 50u2005mg/L was prepared using the MSDS for 90u2005min, and the treatment efficiency was about 6 times higher than that of our previous system. It was confirmed that the NO2−, O3, and H2O2 concentrations in the water were also increased by treating the water using the MSDS.The nitrogen compound concentration in water is increased by atmospheric-pressure plasma discharge treatment. A rod-to-water electrode discharge treatment system using plasma discharge has been developed by our group to obtain water with a high concentration of nitrogen compounds, and this plasma-treated water improves the growth of chrysanthemum roots. However, it is difficult to apply the system to the agriculture because the amount of treated water obtained by using the system too small. In this study, a multi-spark discharge system (MSDS) equipped multiple spark plugs is presented to obtain a large amount of plasma-treated water. The MSDS consisted of inexpensive parts in order to reduce the system introduction cost for agriculture. To suppress the temperature increase of the spark plugs, the 9 spark plugs were divided into 3 groups, which were discharged in order. The plasma-treated water with a NO3− concentration of 50u2005mg/L was prepared using the MSDS for 90u2005min, and the treatment efficiency was abo...

Preparation of multi-layer film consisting of hydrogen-free DLC and nitrogen-containing DLC for conductive hard coating

Conductive hard-coating films have potential application as protective films for contact pins used in the electrical inspection process for integrated circuit chips. In this study, multi-layer diamond-like carbon (DLC) films were prepared as conductive hard-coating films. The multi-layer DLC films consisting of DLC and nitrogen-containing DLC (N-DLC) film were prepared using a T-shape filtered arc deposition method. Periodic DLC/N-DLC four-layer and eight-layer films had the same film thickness by changing the thickness of each layer. In the ball-on-disk test, the N-DLC mono-layer film showed the highest wear resistance; however, in the spherical polishing method, the eight-layer film showed the highest polishing resistance. The wear and polishing resistance and the aggressiveness against an opponent material of the multi-layer DLC films improved by reducing the thickness of a layer. In multi-layer films, the soft N-DLC layer between hard DLC layers is believed to function as a cushion. Thus, the tribolog...