Toshifumi Yuji

Experimental Study of Temperatures of Atmospheric-Pressure Nonequilibrium Ar/N2 Plasma Jets and Poly(ethylene terephtalate)-Surface Processing

To understand the mechanism of surface processing using atmospheric-pressure nonequilibrium plasma jets, we measured the vibrational and rotational temperatures in the plasmas by optical emission spectroscopy. Plasma was excited using a high-frequency pulsed power supply, using a gas mixture of Ar (20 L/min) and N2 (0.1 to 0.5 L/min) as the plasma gas, and changing the flow rate of N2 gas at an input power of 100 W and plasma frequencies of 5 and 10 kHz. The measured vibrational and rotational temperatures in plasma were approximately 0.18 to 0.26 eV and 0.21 to 0.28 eV, respectively. We also carried out a plasma surface processing of polyethylene terephtalate film to measure the changes in water contact angle before and after the processing. We found a monotonic decrease in the contact angle of the processed poly(ethylene terephtalate) (PET) film as plasma rotational temperature increased. It is concluded that the hydrophilicity of the PET surface increases with plasma rotational temperature.

Optical Emission Characteristics of Atmospheric-Pressure Nonequilibrium Microwave Discharge and High-Frequency DC Pulse Discharge Plasma Jets

With an aim to understand the mechanism of surface processing by atmospheric-pressure nonequilibrium discharge plasma jets, we measured the vibrational and rotational temperatures in the plasmas by means of optical emission spectroscopy (OES) measurement method. This paper focuses on the OES measurement method using a torch-shaped atmospheric-pressure nonequilibrium discharge plasma jet power supply consisting of a microwave (2.45-GHz) generator and a high-frequency (5.0-10-kHz) dc pulse power supply, using a gas mixture of Ar (8.0 L/min) and N2 (0.1-0.5 L/min) as the discharge plasma gas, and changing the flow rate of N2 gas at the input power of 100-150 W. Upon comparing vibrational and rotational temperatures (0.18-0.27 eV) determined from the OES measurement method using two types of atmospheric-pressure nonequilibrium discharge plasma jets, results indicate that the microwave discharge plasma jet has considerably low vibrational and rotational temperatures.

Surface Modification of Si Wafer by Low-Pressure High-Frequency Plasma Chemical Vapor Deposition Method

In recent years, a flexible type of solar cell that can maintain various shape changes and that is applicable to virtually all products has attracted global attention. In the present research, we describe equipment for the production of thin-film material for flexible type solar cells that uses a high-frequency plasma chemical vapor deposition (CVD) method. This equipment is now at the development stage, and in order to clarify the cardinal trait of the plasma, we performed a plasma treatment on the surface of a Si wafer. Using X-ray photoelectron spectroscopy and contact angle meter measurements, we identified one index that clarifies the simple cardinal trait of plasma CVD.

An Analysis of ZnS:Cu Phosphor Layer Thickness Influence on Electroluminescence Device Performances

Electroluminescence (EL) device is a new technology; its thickness is within micrometer range which can bend more easily and emit light. However, the thickness of ZnS:Cu phosphor layer may affect the light intensity, so we have analyzed the thickness of ZnS:Cu phosphor layer on EL device. The EL devices consist of ITO:PET/ZnS:Cu phosphor/insulator (BaTiO3)/Ag electrode. The EL devices were fabricated in changing thickness 10 μm, 30 μm, and 50 μm. At 100 V 400 Hz, the luminance of EL devices was 51.22 cd/m2 for thickness 30 μm more than that of 45.78 cd/m2 (thickness: 10 μm) and 42.58 cd/m2 (thickness: 50 μm). However, the peak light intensity was achieved at wavelength of 507 nm which was not influenced by the thickness of the ZnS:Cu phosphor. The use of the ZnS:Cu phosphor layer at thickness 30 μm in the EL device significantly improves the luminescence performance.

Ceramic waste glass fiber-reinforced plastic-containing filtering materials for turbid water treatment

To utilize waste glass fiber-reinforced plastic (GFRP) and to reduce environmental pollution in rivers and lakes, we developed a filtering material that can clean contaminated water. The high strength and porous nature of glass fiber-reinforced ceramic made by mixing clay and crushed waste GFRP before firing was exploited to do so. Various specimens with different pore size distributions were made by changing the mixing ratio of clay and crushed GFRP, the GFRP particle size, and the mixture firing temperature. Bending strength and permeability tests indicated that several types of ceramics with good permeabilities and adequate bending strengths could be produced, which enables their use as filtration materials for turbid water. Filtration tests on simulated turbid water clarified the relationship between the pore size distribution and the filtering ability of the ceramic for turbid water. Filtration tests on river water verified their practical suitability as ceramic filtration materials. It is proposed that ceramics made from clay and GFRP could be used as filtering materials for turbid water.

The Development of Polyethylene Naphthalate Films by Low-pressure High-frequency Plasma Chemical Vapor Deposition System with Advance Oxidations Process

Abstract The low-pressure high-frequency plasma chemical vapor deposition (CVD) system was developed with non-thermal plasma process to study the Polyethylene naphthalate (PEN) surface characteristics. Plasma surface treatment by oxygen can improve the adhesive properties. A mixture of Ar and O2 gas was used in the plasma treatment. The oxygen gas flow rate was between 0.1 L/min and 0.5 L/min, whereas the Ar gas flow rate was set at 10 L/min. The surface was investigated by contact angle meter and X-ray photoelectron spectroscopy (XPS) to determine the differences between untreated and treated surfaces. The results indicated that the low-pressure high-frequency plasma chemical vapor deposition system could be used for surface modification.

An Analysis of Low-Pressure High-Frequency Plasma Chemical Vapor Deposition System for Flexible Solar Cell Characteristics

The flexible dye-sensitized solar cells have a need to improve adhesive property in each layer in order to increase efficiency of this solar cell. Flexible surface with Polyethylene naphthalate (PEN) were modified by using surface treatment from developed the low-pressure high-frequency Plasma Chemical Vapor Deposition system in order to improve adhesive characteristic. The oxygen plasma treatment can improve adhesive property of Polyethylene naphthalate (PEN) films and also cleaning surface. We were using the mixture of Ar and O2 gas for plasma treatment with oxygen gas flow rate from 0.1 L/min. to 0.5 L/min. while Ar gas flow rate was set at 10 L/min. and 5 minute for treatment time. The results indicate that using low-pressure high-frequency Plasma Chemical Vapor Deposition system can be possible improvement adhesive characteristic of PEN films with radical increased on films.

Low-Temperature Naturatron Sputtering System for Deposition of Indium Tin Oxide Film

In this paper, we have newly developed a metal thin film-forming sputtering system using the Naturatron Sputtering method that can prevent the plastic film from suffering damage caused by the high-energy particles in plasma and carry out the low-temperature high-density metal deposition with a sputtering chamber and a film deposition chamber separated from each other. This system has made it possible to deposit the indium tin oxide (ITO) thin film on the poly(ethylene naphthalate) film as a substrate. As a result of energy-dispersive X-ray spectroscopy analysis or scanning electron microscope analysis performed for the ITO thin film, it has been proven that the uniform-surface ITO thin film can be deposited on a plastic film.

PEN Film Surface Development Using High-Frequency - Low Pressure Plasma Chemical Vapor Deposition System

Solar cell converts sunlight into electricity with no moving parts and environmental friendly. Although silicon based solar cell is currently more efficient, the dye-sensitized solar cell is considerably cheaper to manufacture because of its low cost materials and simplicity process of fabrication. In this paper, the development of plasma formed equipment for thin film material on flexible solar cell using low-pressure high frequency Plasma Chemical Vapor Deposition method on the surface of Polyethylene naphthalate (PEN) with the mixture of Ar gas and N2 gas is presented. The results indicate that using this method can be possible for surface modification.

Study on the scale thickness measurement technique in the steel pipe for Geothermal power station

Until now, authors thought it required extending the life of steel tubes for piping in order to use the geothermal power station in the good state over a long period of time. It has dealt with development of the deterioration-diagnosis technology of the geothermal power station steel tubes for the piping by the simple nondestructive inspection technique using an impact (shock) sensor for the purpose of this preventive maintenance. As a result, it succeeded in catching change of the stream in the steel pipe by change of the thickness of the mineral-rich sediment (the following, scale) adhering to the piping inner wall in steel tubes for piping by an impact sensor. So, in this paper, it measured about stream change using the ultrasonic sensor considered to be suitable for the metal deterioration diagnosis of steel tubes for piping rather than the impact sensor. As a result, since the increase in an ultrasonic wave signal with scale thickness and correlativity was checked, it reports.