Akira Shirakura

Growth process of hydrogenated amorphous carbon films synthesized by atmospheric pressure plasma enhanced CVD using nitrogen and helium as a dilution gas

Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N2) and helium (He) at various pulse frequencies. The C2H2/N2 film showed cauliflower-like-particles that grew bigger with the increase in films thickness. At 5 kHz, the film with a thickness of 2.7 µm and smooth surface was synthesized. On the other hand, the films synthesized from C2H2/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37 µm with a smooth surface.

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

Diamond-like carbon (DLC) films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure and their hardness and gas barrier properties were measured. A decrease in size of grains and heating substrate temperature improved nano-hardness up to 3.3 GPa. The gas barrier properties of DLC-coated poly(ethylene terephthalate) (PET) sheets were obtained by 3–5 times of non-coated PET with approximately 0.5 µm in film thickness. The high-gas-barrier DLC films deposited on PET sheets are expected to wrap elevated bridge of the super express and prevent them from neutralization of concrete. We also deposited DLC films inside PET bottles by the microwave surface-wave plasma chemical vapor deposition (CVD) method at near-atmospheric pressure. Under atmospheric pressure, the films were coated uniformly inside the PET bottles, but did not show high gas barrier properties. In this paper, we summarize recent progress of DLC films synthesized at atmospheric pressure with the aimed of food packaging and concrete pillar.

Synthesis of hard hydrogenated amorphous carbon films by atmospheric pressure filamentary dielectric barrier discharge

In this study, the authors synthesized a-C:H films by filamentary dielectric barrier discharge (FDBD) to improve their mechanical properties compared to the films synthesized by glow DBD (GDBD), which is generally used for atmospheric pressure plasma enhanced chemical vapor deposition. The discharge type was transited from GDBD to FDBD by increasing the gap between the electrodes from 1 to 4 mm. The hydrogen concentration of the a-C:H films synthesized by FDBD was reduced compared to that of the films synthesized by GDBD. The hardness of the films increased from 3.7 to 11.9 GPa by using FDBD. These results show that the hard a-C:H films can be synthesized at room temperature in a large area by FDBD.

Effects of the Ar and He dilution gas mixture ratio on the hardness of a-C: H films synthesized by atmospheric pressure plasma enhanced chemical vapor deposition

Hydrogenated amorphous carbon (a-C:H) films synthesized by atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) possess a low hardness because of the large amount of incorporated hydrogen. To increase the hardness of these a-C:H films, detachment of the hydrogen is accomplished using Ar ion bombardment during the deposition process. Herein, a-C:H films were deposited by AP-PECVD and the effects of varying the dilution gas mixing ratio of Ar and He on the hardness of the a-C:H films were investigated. As the Ar ratio in the mixture gas increased from 0% to 20%, the hardness of the films increased from 0.8 to 2.7 GPa. Furthermore, as the Ar ratio increased, the metastable He atoms in the plasma decreased, the intensity of the CHx peaks related to the hydrogen decreased, and the surface roughness of the films increased. These results imply that Ar ion bombardment at the film surface occurred and was caused by the Penning effect of metastable He and Ar atoms. The hardness of the a-C:H fil...

Abrasion resistance of silica-based coatings prepared by atmospheric pressure plasma chemical vapor deposition for protection of polymeric surfaces

Silica-based films were synthesized by the dielectric barrier discharge method under atmospheric pressure from tetramethoxysilane and O2 diluted with N2. In this study, the coating area was 200 mm in diameter, which could be enlarged by altering shape of the electrodes and expanding the scanning range. Even at the low temperature of 80 °C, the hardness of the films slightly increased up to 4.3 GPa by decreasing the tetramethoxysilane flow rate. The relative ratio of Si−O−Si (cage structure) bonds to Si−O−Si (network structure) decreased, and as a result, the films became harder. Additionally, it was found that silica-based films deposited on acrylic resin-coated polycarbonate substrates had good abrasion resistance; the minimum ΔHz value after 1000 revolutions in the Taber abrasion tests was 2.5%. These results suggest that the silica-based films synthesized under atmospheric pressure have the potential to be used in mass production because the equipment enables low-cost and large-area synthesis. The authors find that there is potential in using atmospheric pressure plasma technology for the automobile industry.