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The most progress towards a practical method of fusing municipal waste incineration ash has been in the use of a plasma jet that employs arc discharge, a form of thermal plasma. However, a remaining problem is that stable plasma generation is prevented by melting of the nozzle of the plasma-jet torch by the high-temperature plasma flow. With the objective of developing high-speed fusion treatment for waste materials using an in-liquid plasma jet, basic research was conducted on plasma stability and the durability of plasma-jet torches, including electrodes and nozzles. Basic plasma jet characteristics such as the discharge voltage, current, and power value at the time of plasma jet generation were investigated experimentally. The relationship between the temperature distribution near the tip of a plasma jet torch and electrode damage was investigated by fluid-heat coupled analysis using the finite element method.

Currently, novel method to synthesize diamond film on material substrate called as in-liquid microwave plasma CVD (IL-MPCVD) has been achieved. It has been studied and improved in addition expected as new method instead of conventional gas phase microwave plasma CVD (MPCVD). The purpose of this study is to synthesize single crystal diamond using IL-MPCVD in high speed deposition. The experimental conditions, methanol was poured in to the reactor. Each of diamond particles (100) and (111) was embedded on the stainless steel substrates (SUS632J2). It was mounted to the substrate holder of in-liquid plasma equipment and installed on the top cover. The distance between the tip of the electrode and the substrate was kept to 1.5mm. A microwave of 2.45GHz was irradiated into the quartz glass tube reactor from the rectangular cavity resonator with 4 mm diameter tungsten electrode and the plasma was generated at its tip. The microwave was adjusted in appropriate power to maintain a certain substrate temperature. Diamond films were evaluated by Raman spectroscopy, Scanning Electron Microscope (SEM) and Laser Microscope (LM). As a result, the best orientation for epitaxial growth was found to be (100) which have film growth gradually and smooth surface. Whereas (111) face has polycrystalline film with irregularity growth and rough surface. The remaining H and C after CO synthesis satisfying H/C>20 is necessary to synthesized diamond using IL-MPCVD. The deposition rate was about 32 μm/h when both single crystal and polycrystalline diamond film were synthesized.

The purpose of this study is to synthesize diamond onto Si, Cu, and Fe (SUS632J2) substrates and to analyze the effect of carbon diffusion on their surfaces. Diamond was synthesized using the in-liquid microwave plasma chemical vapor deposition (IL-MPCVD) as a novel method for synthesizing diamond on various base materials. The IL-MPCVD method is superior one due to its efficiency in terms of cost, space and speed as compared to a conventional gas phase microwave plasma CVD (MPCVD). Microwaves of 2.45 GHz generated plasma in a solution which was comprised of methanol: ethanol (M:E = 97:3). Evaluation of deposited diamond films was done by a Scanning Electron Microscope (SEM) and Raman spectroscopy. Results shows that the IL-MPCVD method can form diamond films on Cu, Si and Fe substrates. The minimum time of film formation of Cu, Si and Fe are 2.5, 3.5 and 5 min, respectively. The material that forms carbide layers such as Si is a better substrate to form diamond film by the IL-MPCVD than other metal substrates such as Cu and Fe. Synthesizing diamond directly on the Fe substrate results in poor quality layers. The effect of carbon diffusion influences diamond film nucleation and diamond growth. In order to alleviate the carbon diffusion and improve the quality of the diamond film on the Fe substrate, Si has been sputtered on the Fe substrate as an interlayer. It is found that the diamond film can be formed on a Fe substrate using a Si interlayer and that heat treatment and thickening the interlayer improve its quality.