Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST ENERGY  

A lignin solution in methanol was treated with in-liquid plasma at 27.12 MHz radio frequency to produce H-2 and aromatic monomers. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses were performed to characterize the produced gases and degradation products contained in the solution. GC analysis identified H-2, CO, CH4, C2H2, CO2, and C2H4 in the sample. GC-MS analysis identified several products, including benzene. toluene, and phenol The quantity of each of these products was determined. These results indicated that the bonds around the benzene ring were broken in the plasma and reacted with OH radicals and CH3 radicals from methanol.

DOI： 10.3775/jie.97.171

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST ENERGY  

High-voltage pulse discharges were generated between underwater two metallic Tin (Sn) wires in order to synthesize nanoparticles. Nanoparticles were synthesized in pure water or aqueous gelatin solution. In pure water, Sn and SnO2 particles of approximately 5 nm in diameter were synthesized. However, synthetic particles in pure water had a problem of aggregation. The influence of gelatin solution on the particle size and dispersibility of the synthetic particles was investigated. In 10 mg/L gelatin aqueous solution. metallic Sn particles of approximately 40 to 400 nm in diameter were synthesized and were dispersing separately. From the peak width of X-ray diffraction (XRD) spectrum, the particle size was estimated using the Schemer's equation. As a result. the minimum size was approximately 20 nm at 2 mg/L of aqueous gelatin solution.

DOI： 10.3775/jie.97.186

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.7567/jjap.57.07le05

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

To enhance hydrogen production efficiency by in-liquid plasma, the method inserting catalytic metal into in-liquid plasma reaction field was considered. To retain a bubble at the tip of in-liquid plasma electrode, a plate is fixed over the electrode. That plate and electrode are composed of a catalytic metal. Methanol is decomposed by in-liquid plasma, and the gas generation rate and composition rate are measured. The gas is composed of 67% H2, 30% CO, and 3% other. This rate is independent of the material of the electrode or plate. The plate enhances the hydrogen production rate. When the plate and electrode are composed of Ni (0.37 Nm3/kWh), the maximum hydrogen production rate is obtained.

DOI： 10.1016/j.ijhydene.2018.01.060

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Begell House Inc.  

In this study, decomposition of methane hydrate using an argon plasma jet was investigated in the pressure range of 0.1MPa to 2.0MPa. The plasma was successfully generated under high-pressure conditions, which is difficult to achieve when using the conventional radio frequency plasma in-liquid method. From the emission spectrometer analysis, excitation temperature of the argon plasma jet was found to decreases as the pressure increases, while conversely, the rotational temperature of OH increases. During the plasma irradiation process, the required basic reactions for methane hydrate decomposition, that is, methane hydrate dissociation, steam methane reforming, and methane cracking reaction were not fully satisfied due to an insignificant amount of methane that did not react. The gas chromatography analysis confirmed that only the methane cracking reaction has occurred to generate hydrogen and carbon, due to the absence of acetylene and ethylene as byproducts. In comparison with the other basic reactions of methane hydrate decomposition, the steam methane reforming reaction became dominant in converting methane into hydrogen.

DOI： 10.1615/ihtc16.nee.023225

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CENTRE ADVANCED RESEARCH ENERGY-CARE  

Hydrogen shows great promise for being such a solution for providing sustainable energy while at the same time protecting the environment from greenhouse gases (GHGs). A 27.12 MHz RF plasma in liquid was used to decompose biomass-derived cellulose suspension for hydrogen production. At 1.0 M of sodium hydroxide, the result showed the highest hydrogen yield and the lowest greenhouse gases yield. An increase in molar concentration resulted in an increase of hydrogen production rate. On the other hand, it is noted that regardless of molar concentration, the hydrogen production rate significantly dropped with residence time.

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Language：English   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.38.0_2p4-7

CiNii Research

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Energy  

There is an imperative need to explore new technologies for hydrogen energy production without sacrificing life and environment. A 27.12 MHz radio-frequency plasma in liquid was used to decompose cellulose suspension for hydrogen production. The experiment was conducted to investigate the effects of sodium hydroxide and ultrasonic irradiation pretreatment. Molar concentration of sodium hydroxide was varied to 0.001 M, 0.01 M and 0.1 M and ultrasonic irradiation time was varied between 15 and 60 minutes in order to observe the hydrogen production rate and hydrogen yield. Hydrogen production had no significant enhancement at lower than 0.01 M sodium hydroxide. On the other hand, the hydrogen production rate increased dramatically to 23.0 μmol/s at 0.1 M sodium hydroxide. Typical optical emission spectrum of 0.001 M sodium hydroxide solution showed t hat radical species including OH (281.1 nm), Hβ (486 nm), Hα (656.3 nm) and O (777 and 845 nm) were generated which are very beneficial in attacking and decomposing organic molecules for hydrogen production. The highest production rate was obtained at 30 minutes of pretreatment. A longer than 3 0 minutes pretreatment with ultrasonic irradiation reduced the hydrogen production rate. Thus, ultrasonic irradiation pretreatment between 15 and 30 minutes was the potential condition for hydrogen production without sacrificing greenhouse gases effect.

DOI： 10.3775/jie.96.451

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

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. (C) 2017 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.precisioneng.2017.04.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Energy  

The aim of this study was to investigate the effect of gas flow rate on the gas production rate from n-dodecane using steam reforming in-liquid plasma. A steam reforming of n-dodecane was carried out within the reactor vessel which was connected to a waveguide, an aluminum rectangular tubes that guides the propagation of electromagnetic waves with minimum loss of energy. The liquid medium used for plasma generation was n-dodecane (commercial reagent). The tip of a single electrode was positioned in the bottom center of the reactor vessel for plasma formation. The produced gas flowed through an aspirator and was trapped and collected in a water filled container. The gas production rate was measured and its compositions were analyzed using a gas chromatograph. The gas production rate by plasma with steam feeding was 1.4 times greater than that by plasma without steam feeding. The hydrogen content of the gas produced ranged from 73% to 82%. The maximum energy efficiency, as indicated by the ratio of the enthalpy difference of the chemical reactions to the input energy, was approximately 12%. The maximum hydrogen generation efficiency obtained from experiments was up to 59% higher than the efficiency of hydrogen production from electrolysis of alkaline solutions as reported in literatures. The energy payback ratio of hydrogen (EPRH2)was also calculated in order to obtain the hydrogen production efficiency.

DOI： 10.3775/jie.96.86

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Language：English   Publishing type：Research paper (scientific journal)  

In this study, decomposition of methane hydrate using argon plasma jet investigated in the pressure range of 0.1MPa to 2.0MPa. The plasma generated under the high-pressure condition, which is difficult to achieve when using radio frequency (RF) plasma in the liquid method. By using emission spectrometer analysis, the excitation temperature is found to increase as the gas pressure increases, whereas, it decreases as the argon flow rate increases. During the process of plasma irradiation, the required essential reactions for methane hydrate decomposition, such as methane hydrate dissociation (MHD), steam methane reforming (SMR), and methane cracking reaction (MCR) were not completely satisfied due to an insignificant amount of methane. The gas chromatography analysis confirmed that the methane cracking reaction (MCR) was only occurred to generate hydrogen and the C(s), due to the absence of C2H2 and C2H4 as the byproducts. In comparison with the other primary reactions of methane hydrate decomposition, steam methane reforming reaction became dominant in converting methane into hydrogen. Although the hydrogen production efficiency is less than that of radio frequency plasma in liquid, the reduction of CO2 by the thermal decomposition of Teflon from CO making it possible is considered as an advanced promising technique in the future.

DOI： 10.18517/ijaseit.7.6.2638

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Language：English   Publishing type：Research paper (scientific journal)  

J-GLOBAL

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© 2017 Trans Tech Publications, Switzerland. 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 32m/h when both single crystal and polycrystalline diamond film were synthesized.

DOI： 10.4028/www.scientific.net/KEM.749.211

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Energy  

Metal air battery attracts attention as an automobile battery, because of its high energy density. In order to reuse the battery, it is necessary to undertake reduction of metal oxide which is generated at the cathode without large environment load. We conducted the reduction of ZnO powder by radio-frequency dielectric heating. The ZnO powder and a reducing agent of organic liquid is put into a reaction vessel, and the tip of the electrode inserted from the top of the vessel is in contact with the surface of the powder. By measuring the spectrum of the blackbody radiation, the temperature was found to be approximately 2000 K. The reduction amount of ZnO increased remarkably when 0.7 to 1.4 mL of methanol was added as a reduction agent to 2.0 g ZnO powder, with a maximum of 27.6 mg at 1.1 mL reached. The reduction amount was smaller when ethanol, acetone, furfural, cyclohexane or dodecane were added as a reduction agent. The maximum energy efficiency is 3.3% without taking the reaction energy of the reduction agent into consideration, whereas it becomes 1.0% when taking it into consideration.

DOI： 10.3775/jie.96.357

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmecs.2017.55.K0704

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The use of ultrasonic welding in water to decompose cellulose placed in water was examined experimentally. Filter paper was used as the decomposition material with a horn-type transducer 19.5 kHz adopted as the ultrasonic welding power source. The frictional heat at the point where the surface of the tip of the ultrasonic horn contacts the filter paper decomposes the cellulose in the filter paper into 5-hydroxymethylfurfural (5-HMF), furfural, and oligosaccharide through hydrolysis and thermolysis that occurs in the welding process. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.07KE02

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmecs.2016.54._417-1_

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>The decomposition of cellulose suspension for hydrogen production by using a 27.12MHz in-liquid plasma is carried out at atmospheric pressure. Various types of electrolyte, such as 1 mol/dm³ H₂SO₄, 1 mol/dm³ NaOH and 0.333 mol/dm³ Na₂SO₄, are used and the gas production rate are compared. An employing 1 mol/dm³ NaOH for decomposition process indicated that the gas production rate was 7 times higher than that of decomposition of cellulose in pure water. When cellulose content is 20 wt%, the hydrogen ratio in the produced gas is approximately 60%. EPR (energy payback ratio) in which measured for economical production of hydrogen is the highest When 1 mol/dm³ NaOH is used as an electrolyte for decomposition process.</p>

DOI： 10.1299/jsmeted.2016.G122

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, the synthesis of single-wall carbon nanotubes (SWCNT) using in-liquid CVD method is attempted. Si substrate on which Co micro particles are deposited as the catalyst is used. Electrical resistance heating method is used for glowing carbon nanotubes in pure ethanol. The synthesized materials are analyzed by scanning electron microscope, transmission electron microscope and Raman spectroscopy. As a result, the synthesis of SWCNT was successful on a wide area of the substrate surface. By investigating the synthesized carbon nanotubes changing experimental conditions such as pressure, substrate surface roughness and others, it is cleared that surface roughness of the substrate and the bubble behavior are related to the synthetic mechanism of carbon nanotubes.</p>

DOI： 10.1299/jsmeted.2016.G114

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Energy  

Hydrogen energy is the most promising source of sustainable energy under development. The decomposition of cellulose suspension for hydrogen production by using a 27.12 MHz in-liquid plasma was carried out at atmospheric pressure. Various types of reagents, such as 1 mol/dm3 H2SO4, 1 mol/dm3 NaOH and 0.333 mol/dm3 Na2SO4, were used and compared as to the rate of gas production. Cellulose dispersed in acid liquids is decomposed indirectly by active radicals by the plasma. The highest hydrogen production rate was obtained by employing 1 mol/dm3 NaOH. The gasification rate of cellulose suspension was determined from the increase of C atoms in the product gas. When 1 mol/dm3 NaOH was used, the rate was 7 times greater than that for pure water. It was found that carbon atoms in the product gas is indicative of the decomposition rate of the cellulose suspension.

DOI： 10.3775/jie.95.1105

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>This research investigates the direct phenol production from toluene by dielectric-barrier discharge (DBD) plasma in a mixture gas of argon and water vapor. Two kinds of experiment were conducted. The first experiment was by irradiating the surface of liquid toluene with DBD plasma jet, and the second one was by generating DBD plasma in a bottle of toluene into which the mixture gas was flowing. The maximum phenol yields at the first and second experiment were 0.8×10^-3% and 3.2×10^-3%, respectively. The phenol yield at the first experiment increased with decrease of input power for the DBD. The phenol yield at the second experiment took the maximum when the water for making the mixture gas by bubbling was the room temperature.</p>

DOI： 10.1299/jsmeted.2016.G123

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

This research involves two in-liquid plasma methods of methane hydrate decomposition, one using radio frequency wave (RF) irradiation and the other microwave radiation (MW). The ultimate goal of this research is to develop a practical process for decomposition of methane hydrate directly at the subsea site for fuel gas production. The mechanism for methane hydrate decomposition begins with the dissociation process of methane hydrate formed by CH4 and water. The process continues with the simultaneously occurring steam methane reforming process and methane cracking reaction, during which the methane hydrate is decomposed releasing CH4 into H-2, CO and other by-products. It was found that methane hydrate can be decomposed with a faster rate of CH4 release using microwave irradiation over that using radio frequency irradiation. However, the radio frequency plasma method produces hydrogen with a purity of 63.1% and a CH conversion ratio of 99.1%, which is higher than using microwave plasma method which produces hydrogen with a purity of 42.1% and CH4 conversion ratio of 85.5%. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.applthermaleng.2015.06.074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Hydrogen is a very attractive source of highly efficient and environmentally friendly energy. Investigation into hydrogen production from glucose decomposition by 27.12 MHz radio-frequency in-liquid plasma with and without ultrasonic vibrations was carried out utilizing 29 kHz and 1.6 MHz ultrasonic transducers to determine the effects of agitation and acoustic streaming. In-liquid plasma is generated inside a bubble, resulting in a high temperature chemical reaction field within the liquid which is then irradiated by ultrasonic vibration. The dependence of hydrogen production rate, hydrogen yield, hydrogen purity and hydrogen production efficiency on the types of ultrasonic vibration applied was investigated. Higher intensities of active C atoms species were observed in the emission spectrum of RF in-liquid plasma when irradiated with ultrasonic vibration and it is believed that these species function as precursors or intermediaries for other components in the gas product. Hydrogen production rate was enhanced by 30% when RF in-liquid plasma was irradiated by the 1.6 MHz piezoelectric transducer. The highest hydrogen yield was 72% for RF in-liquid plasma with the 29 kHz ultrasonic transducer at an initial concentration 1.0%. The hydrogen purity was enhanced by 5% for the highest initial concentration when applying the 29 kHz ultrasonic transducer to the RF in-liquid plasma. Thus the acoustic streaming effect by 1.6 MHz piezoelectric vibration enhanced the hydrogen production rate, while on the other hand, the agitation effect by 29 kHz ultrasonic vibration enhanced hydrogen yield and hydrogen purity. Though the hydrogen production efficiency of RF in-liquid plasma with ultrasonic vibration applied was lower overall when compared to that without ultrasonic vibration except for decomposition of glucose 20 wt% by RF in-liquid plasma with 1.6 MHz ultrasonic transducer which was 7% higher than that without ultrasonic vibrations, this remains a process that could be considered as a promising future technique for hydrogen production. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2015.04.152

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Metal air-batteries with high-energy density are expected to be increasingly applied in electric vehicles. This will require a method of recycling air batteries, and reduction of metal oxide by generating plasma in liquid has been proposed as a possible method. Microwave-induced plasma is generated in ethanol as a reducing agent in which zinc oxide is dispersed. Analysis by energy-dispersive x-ray spectrometry (EDS) and x-ray diffraction (XRD) reveals the reduction of zinc oxide. According to images by transmission electron microscopy (TEM), cubic and hexagonal metallic zinc particles are formed in sizes of 30 to 200 nm. Additionally, spherical fiber flocculates approximately 180 nm in diameter are present.

DOI： 10.1088/2053-1591/2/2/025004

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmecs.2015.53._1114-1_

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmecs.2015.53._1113-1_

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The objective of this research is to investigate the possibility of producing phenol directly from a mixture of toluene and water by in-liquid plasma and to understand the process of converting toluene into phenol. Radio frequency (RF) in-liquid plasma was used to synthesize phenol from toluene. In addition, GAUSSIAN was used to predict the process of conversion and other products. In the proposed method of phenol production, OH radicals produced from water molecules by in-liquid plasma play a major role during the process of direct chemical reaction with toluene. The experimental results showed that phenol can be directly produced from toluene, and benzyl alcohol and formaldehyde were synthesized in the process.

DOI： 10.1299/jsmeted.2015._C233-1_

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Language：English   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.36.0__2P4-13-1_

CiNii Books

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© Springer International Publishing Switzerland 2014. Clathrate hydrates, which were formed from methane and cyclopentane, were decomposed by plasma at atmospheric pressure. Methane hydrate was synthesized by injecting methane into shaved ice in the reactor at a pressure of 7 MPa and a temperature of 0 °C. In addition, cyclopentane hydrate was formed by adding surfactant into cyclopentane-water emulsion at 0.1 MPa and a temperature of 0 °C. The process of plasma decomposition of clathrate hydrates has been carried out by irradiating high frequency plasma at the tip of the electrode in clathrate hydrates. 2.45 GHz MW oven and 27.12 MHz RF irradiation were used. This study results gas production that its content identified by gas chromatograph. High purity of hydrogen would be extracted from clathrate hydrate using the in-liquid plasma method.

DOI： 10.1007/978-3-319-07896-0_30

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Energy  

The purpose of this study is to efficiently produce hydrogen gas from saccharide using 27.12 MHz radiofrequency (RF) in-liquid plasma with and without ultrasonic irradiation. The experiments were conducted adopting two different ultrasonic frequencies, one from a 29 kHz horn-type ultrasonic transducer and the other from a 1.6 MHz piezoelectric transducer. The glucose solution and cellulose suspension concentrations were varied from 0.5 wt% to 50 wt% and 0.5 wt% to 20 wt% respectively. Hydrogen gas was then produced by the decomposition of the glucose solution and cellulose suspension by RF in-liquid plasma with and without ultrasonic irradiation. The hydrogen production rate from glucose solution with ultrasonic irradiation applied was greater than that without ultrasonic irradiation. However, no hydrogen production rate enhancement was observed from decomposition of cellulose suspension with ultrasonic irradiation applied. Ultrasonic atomization and agitation enhanced the chemical reaction of nonvolatile glucose in in-liquid plasma. The increase of the gas production rate was caused by the direct decomposition of the glucose by the plasma due to the atomized glucose molecules being fed into the plasma in a bubble. In addition, by using a high-speed camera, it was clarified that acoustic streaming occurred when a 1.6 MHz piezoelectric transducer was used in the experiment.

DOI： 10.3775/jie.93.1207

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Hydrogen is more attractive as an efficient and environmental friendly source of energy. In order to study the effect of ultrasonic vibration on enhancing the production of hydrogen, 27.12 MHz radio-frequency (RF) in-liquid plasma was observed with and without ultrasonic vibration applied. Two types of ultrasonic transducers were used, a 29 kHz horn-type ultrasonic transducer and a 1.6 MHz piezoelectric transducer. In-liquid plasma is generated inside a bubble generated by evaporation of a liquid heated by plasma resulting in a high temperature chemical reaction field within the liquid to which ultrasonic vibrations were then applied to enhance the chemical reaction process. 120 ml of glucose solution was used as a biomass model. The solution varied from 0.5wt% to 20wt% of glucose in order to observe the hydrogen production rate, hydrogen yield and selectivity. The results indicated that the application of 1.6 MHz ultrasonic vibration to RF in-liquid plasma enhanced the hydrogen production rate by approximately 34% due to acoustic streaming. On the other hand, enhancements of 13% of hydrogen yield and 4.6% of hydrogen selectivity were indicated by the application of 29 kHz ultrasonic vibration to RF in-liquid plasma with. The reason is believed to be due to a mechanochemical effect. Hence, ultrasonic vibration synergized the production of hydrogen from glucose solution.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A process for synthesis of nanoparticles using plasma in water generated by a radio frequency of 27.12 MHz is proposed. Tungsten oxide, silver, and gold nanoparticles were produced at 20 kPa through erosion of a metallic electrode exposed to plasma. Characterization of the produced nanoparticles was carried out by XRD, absorption spectrum, and TEM. The nanoparticle sizes were compared with those produced by a similar technique using plasma in liquid. (c) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2013.05.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The electrical breakdown of microwave plasma in water was investigated between 1 and 30 kPa. The dependency of the ignition power for generating plasma on the size of coaxial electrode was measured. The ignition power decreases with a decrease of the diameter of the inner electrode. The behavior of microwave plasma in water was observed using a high-speed camera. The plasma ignites in a bubble generated by microwave heating. The model for calculating the electric field was created on the basis of the captured images of the bubble just before plasma ignition. The method presented can be used to visualize the electrical field distribution in the bubble. The electric field breakdown was calculated using the measured ignition power. The electric field breakdown of plasma in water is of the same order as gas phase plasma. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cap.2013.02.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Tungsten trioxide nanoparticles were synthesized from a tungsten wire by plasma generated in water by 2.45 GHz microwaves. The effect of synthesis pressure, power and wire diameter on the formation of nanoparticles and the production rate was investigated. The character of the produced nanoparticles was determined by XRD, absorption spectrum, TEM and particle size distribution. The method proposed in this paper allows control of the nanoparticle size and shape and the optical properties through pressure alone without any additives. In one specific experiment, spherical nanoparticles with a peak diameter of 7 nm were synthesized from a tungsten wire with a diameter of 1 mm by 200 W at 20 kPa at a high production rate of 4 mg/s. Whereas, rhombic cylindrical nanoparticles together with spherical nanoparticles were synthesized with a peak diameter of 13 nm at 101 kPa. In addition, plasma and bubble behavior was observed by high-speed camera. Use of a plate to control the updraft of the bubbles caused the gap between the plate and the coaxial electrode to remain consistently filled with bubbles, and plasma generation continued without pause. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2013.01.137

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Methane hydrate, formed by injecting methane into 100 g of shaved ice at a pressure of 7 MPa and reactor temperature of 0 degrees C, was decomposed by applying 27.12 MHz radio frequency plasma in order to produce hydrogen. The process involved the stimulation of plasma in the methane hydrate with a variable input power at atmospheric pressure. It was observed that production of CH4 is optimal at a slow rate of CH4 release from the methane hydrate, as analyzed by in light of the steam methane reforming (SMR) and the methane cracking reaction (MCR) processes in accordance with the content of gas production. In comparison with the steam methane reforming (SMR), it was found that methane-cracking reaction (MCR) was dominant in conversion of CH4 into hydrogen. An H-2 content of 55% in gas production was obtained from conversion of 40% of CH4 at an input power of 150 W. The results clearly show that hydrogen can be directly produced from methane hydrate by the in-liquid plasma method. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2012.07.099

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Experimental investigations were carried out on RF plasma within a ceramic tube placed on an insulating plate in dense NaCl solution (1.7-24.5 Sm-1). RF power was applied between two electrodes, and the insulating plate was placed between them. Upon performing spectroscopic measurements, we observed H and OH lines as well as strong Na lines in the emission spectra of RF plasma. Colored solution containing methylene blue was exposed to the plasma. The absorbance spectra of the colored solution before and after exposure to RF plasma clearly show that obvious degradation of methylene blue was realized. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.108005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The erosion of a conventional bare metallic electrode for generation of microwave plasma in liquid was investigated. The spectra of plasma, the surface temperature of the electrode and the erosion rate were measured by a spectroscope, a radiation thermometer and an analytical balance, respectively. The intensity of the spectral lines indicating the erosion of the metallic electrode and erosion rate depends upon the microwave power. To avoid metallic contamination, a coaxial electrode for generating microwave plasma on a dielectric material was developed. The metallic electrode is encased in an alumina closed tube. The side of the alumina closed tube is further covered with an open Teflon tube. It has been confirmed that the electric field is strongest at the point where the alumina closed tube, Teflon opened tube and liquid intersect as determined by the two-dimensional Finite-Difference Time-Domain (2D-FDTD) method. Synthesis of amorphous-carbon deposition in ethanol was conducted. The developed electrode enables synthesis with a smooth deposition. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2011.09.045

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Nanoparticles are continuously synthesized from submerged magnesium, zinc, and silver rods 1-2 mm in diameter by microwave plasma in pure water at 20 kPa. Magnesium-hydroxide nanoplates shaped as triangles, truncated triangles or hexagons with 25-125 nm in size are synthesized with a production rate of 60 g h(-1). Zinc-oxide nanoparticles formed as sharp sticks with diameters of 50 nm and lengths of 150-200 nm are synthesized with a production rate of 14 g h(-1). Silver nanoparticles with a diameter of approximately 6 nm are synthesized with a production rate of 0.8 g h(-1). The excitation temperature is estimated by applying the Boltzmann plot method in assumption of local thermodynamic equilibrium. The excitation temperatures obtained from hydrogen, magnesium, and zinc lines are 3300 100 K, 4000 +/- 500K, and 3200 +/- 500 K, respectively. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2011.09.068

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Language：English   Publisher：JAPAN SOC APPLIED PHYSICS  

DOI： 10.1143/APEX.4.099201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The purpose of this study is to clarify the mechanism of diamond synthesis using an in-liquid plasma chemical vapor deposition (CVD) method. We investigated the chemical reactions from a liquid mixture of methanol and ethanol (in-liquid plasma CVD) and a gas mixture of methane and hydrogen (gas-phase CVD). Carbon monoxide (CO) is firstly synthesized and then a chemical reaction using the remaining carbon (C) and hydrogen (H) is induced to synthesize a carbon substance. Residual H radicals act as an etchant removing the incompletely binding carbon atom that hinders diamond crystal growth. From spectroscopic measurements, CO peaks were clearly observed when the oxygen component is contained in the raw materials. From the experimental results of carbon deposits using various liquid and gas mixtures as the raw materials, we found that the region of the remaining H and C after CO synthesis satisfying H/C &gt;20 is necessary to synthesize diamonds using in-liquid plasma CVD method. The region of H/C &gt;20 in the Bachmann C-H-O diagram nearly agrees with the experimental results of synthesizing diamonds. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2011.07.010

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A radio frequency plasma was generated and maintained in water over a wide range of water conductivities (0.2-7000 mS m-1). The conductivity of water was changed by adding NaCl to it. The size of the plasma increased with conductivity. Although the intensity of the OH(A-X) line monotonically decreased with increasing conductivity, the generation of hydrogen peroxide and the degradation of methylene blue suggested that the number of generated OH radicals decreased with increasing conductivity in the range 0.2-80 mS m-1 and increased in the range 80-7000 mS m-1. Ultraviolet irradiation was found to enhance the degradation of methylene blue not only in pure water but also in high-conductivity water (≃5000 mS m-1). © 2011 IOP Publishing Ltd.

DOI： 10.1088/0963-0252/20/3/034016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The purpose of this research is to develop a process to use the plasma decomposition of clathrate hydrates to produce fuel gas. An ordinary microwave (MW) oven is used as the source of 2.45 GHz MW radiation under atmospheric-pressure. The plasma decomposition of the hydrates could pave the way for a new utilization of atmospheric pressure plasma. Cyclopentane (CP) hydrate formed at atmospheric pressure was decomposed by plasma in a MW oven generating gas with a content of 65% hydrogen, 12% CO, and 8% CO(2). About 7% of the MW input power was consumed to decompose the hydrates. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/APEX.4.066201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The excitation temperature, electron density, temperature of OH, and behavior of bubbles generated by a 27.12 MHz in-liquid plasma are investigated in water under pressures ranging from 0.1 to 0.4 MPa. The excitation temperature decreases as the pressure increases and, conversely, the temperature of OH and the electron density increase. Since the plasma can be generated stably even under high-pressure conditions and the liquid provides a cooling effect, the electrode is not damaged by the heat. The bubbles generated from the tip of the electrode have a fixed relationship between their diameter and departure frequency. The in-liquid plasma can be stably generated even under high pressures and it maintains a high superheated state of a few thousand K. A boiling phenomenon in the in-liquid plasma uses the plasma itself as a heat source.

DOI： 10.1088/0963-0252/20/3/034012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We analyzed the gas generated by a radio-frequency plasma in water and found that the ratio of oxygen to hydrogen in it was approximately 0.7-11%. Numerical simulations of the chemical reactions occurring inside and outside the bubble with increasing energy supply in the concentric volume in it were carried out. Thermal conduction and diffusion occurring inside and outside the bubble, and evaporation (condensation) and solution of gases at the surface were taken into consideration. After terminating the energy supply, we found that nearly all the oxygen within the bubble was consumed but that hydrogen remained, and that oxygen in the water produced from dissolved chemical species diffused into the bubble. Good agreement with experiment results was obtained for reducing the production rate of hydrogen and the oxygen-hydrogen ratio that occurred with a pressure increase. We found that in comparison with experimental results the hydrogen production rate was underestimated by approximately 35%.

DOI： 10.1088/0963-0252/20/3/034020

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A radio frequency plasma was generated and maintained in water over a wide range of water conductivities (0.2-7000 mS m(-1)). The conductivity of water was changed by adding NaCl to it. The size of the plasma increased with conductivity. Although the intensity of the OH (A-X) line monotonically decreased with increasing conductivity, the generation of hydrogen peroxide and the degradation of methylene blue suggested that the number of generated OH radicals decreased with increasing conductivity in the range 0.2-80 mS m(-1) and increased in the range 80-7000 mS m(-1). Ultraviolet irradiation was found to enhance the degradation of methylene blue not only in pure water but also in high-conductivity water (similar or equal to 5000 mS m(-1)).

DOI： 10.1088/0963-0252/20/3/034016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Nanoparticles are synthesized efficiently from zinc electrode by microwave plasma in liquid. The nanoparticles synthesized from alcohol resulted in pure zinc particles in the shape of spheres or hexagonal cylinders with a production rate of 3.3 g/h, and energy consumption of 267 J/mg for 1 mg. Whereas the nanoparticles synthesized in pure water are composed of Zn and ZnO. The Zn reacts with water through heat or the passage of time to become ZnO, releasing hydrogen gas. An upper disk placed 1 mm away from the electrode along with the bubbles generated simultaneously with the plasma ignition plays a key role in the synthesis of nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2010.09.068

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Language：English   Publisher：The Japan Society of Sonochemistry  

Strong emission in liquid is observed by radio frequency irradiation using a submerged electrode. Plasma is generated in liquid, and because the liquid around the plasma is evaporated instantly, the plasma seems as if to be generated in a bubble. We measured the spectrum of the plasma emission, analyzed the produced gas by plasma in water and also measured the production rate of hydrogen gas. The mole ratio of hydrogen to the produced gas is 90 to 99% and the rate of hydrogen gas is 1.2 to 2.3 larnol/s at 150 W. The rate of the hydrogen gas decreases with increase of the pressure from 60 to 100 kPa. To clarify the gas production mechanism, we carried out numerical simulations of the chemical reactions inside and outside the bubble. As a result, the mole ratio of the produced gas is .approximately agreeable to the experimental result.

DOI： 10.20577/pamjss.20.0_97

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

The purpose of this research is to develop a process to use plasma decomposition of hydrocarbon liquids or clathrate hydrates in a microwave oven to produce fuel gas while simultaneously solidifying the carbon and synthesizing it into useful carbonized materials, such as CNTs or activated charcoal. Hydrogen gas with a purity of 60% to 80% can be extracted using a conventional microwave oven. This means that the energy efficiency of hydrogen production using this method is estimated to be approximately 50% of that by electrolysis of alkaline water and approximately 1% of that by the natural gas steam reforming method However, this process has the added benefit of producing solid carbon at the same time. This method can be applied to a wide variety of waste liquids, or hydrate. Surplus electrical energy could be used to process waste liquids from homes and factories, and the resulting hydrogen energy could be stored and used.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Plasma was generated in water by irradiation at high frequency of 13.56 MHz, and the behavior of bubbles including the plasma was observed by a high-speed camera. The generation pattern of the bubbles was classified into four types according to liquid temperature and supplied power. Conducting the simulation, the maximum temperature in the bubble was found to be from 3500 K to 4300 K. and the decomposition of water molecule occurred. The gas in the bubble was found to become high ratio of hydrogen. The phenomenon can be regarded as a film boiling of exceptionally high heat flux. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijheatmasstransfer.2010.03.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The characteristics of diamond synthesis by 2.45 GHz microwave plasma chemical vapor deposition (CVD) under pressures greater than atmospheric pressure were investigated. The deposits on Si substrates were identified by scanning electron microscopy and Raman spectroscopy. The growth rate of diamond was found to be 250 mu m/h at 300 kPa, which is ten times greater than that of the conventional low-pressure CVD method. In order to make high-speed deposition of diamond effective, the diamond growth rates for gas-phase microwave plasma CVD were compared to those from the in-liquid plasma CVD method. The growth rate was found to increase as system pressure increased, displaying the same tendency of that in-liquid plasma CVD. The amounts of input microwave energy per unit volume of diamond in the gas-phase and in-liquid plasma CVD methods were also compared. The amount of input microwave energy per unit volume of diamond was found to be 0.6 to 1 kWh/mm(3). (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2009.12.018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The effect of the shape of the electrode to generate 2.45 GHz microwave plasma in pure water is examined. Three variations of a common coaxial electrode are proposed, and compared according to the power required for plasma ignition and the position of plasma ignition in pure water at 6 kPa using a high-speed camera. These coaxial electrodes are calculated using three-dimensional finite-difference time-domain method calculations. The superior shape of coaxial electrode is found to be one with a flat plane on the tip of the inner electrode and dielectric substance located below the tip of the outer electrode. The position of the plasma ignition is related to the shape of the coaxial electrode. By solving the heat-conduction equation of water around the coaxial electrode taking into account the absorption of the microwave energy, the position of the plasma ignition is found to be not where electric field is the largest, but rather where temperature is maximized.

DOI： 10.1063/1.3319616

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The degradation of methylene blue by radio frequency (RF) plasmas in water under ultraviolet (UV) irradiation was studied experimentally. When the methylene blue solution was exposed to RF plasma, UV irradiation from a mercury vapor lamp enhanced degradation significantly. A lamp without power supply also enhanced degradation since weak UV light was emitted weakly from the lamp due to the excitation of mercury vapor by stray RF power. Such an enhancement is explained by the fact that after hydrogen peroxide is produced via the recombination process of OH radicals around the plasma, OH radicals reproduced from hydrogen peroxide via the photolysis process degrade methylene blue. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhazmat.2009.09.076

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Distributions of emission intensity from radicals, electron temperature, and rotational temperature at a radio frequency of 27.12 MHz plasma in water are clarified by detailed spectroscopy measurement. Through this investigation, the following were observed. The points of maximum emission intensity of H alpha, H beta, O (777 nm), and O (845 nm) are almost the same, while that of OH shifts upward. The electron temperature decreases, while the rotational temperature increases with pressure. The distribution of the electron temperature changes at a threshold pressure, which is concerned with a change in the electron discharge mechanism. The self-bias of the electrode changes from a negative to positive at a threshold pressure. The point of the maximum rotational temperature of OH radicals shifts to approximately 1 mm above that for the maximum intensity of OH emission.

DOI： 10.1063/1.3264671

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Hydrogen is produced by generating in-liquid plasma in a conventional microwave oven. A receiving antenna unit consisting of seven copper rods is placed at the bottom of the reactor furnace in the microwave oven. 2.45 GHz microwave in-liquid plasma can be generated at the tips of the electrodes in the microwave oven. When the n-dodecane is decomposed by plasma, 74% pure hydrogen gas can be achieved with this device. The hydrogen generation efficiency for a 750 W magnetron output is estimated to be approximately 56% of that of the electrolysis of water. Also, in this process up to 4 mg/s of solid carbon can be produced at the same time. The present process enables simultaneous production of hydrogen gas and the carbide in the hydrocarbon liquid. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3236575]

DOI： 10.1063/1.3236575

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In order to make high-speed deposition of diamond effective, diamond growth rates for gas-phase microwave plasma chemical vapor deposition and in-liquid microwave plasma chemical vapor deposition are compared. A mixed gas of methane and hydrogen is used as the source gas for the gas-phase deposition, and a methanol solution of ethanol is used as the source liquid for the in-liquid deposition. The experimental system pressure is in the range of 60-150 kPa. While the growth rate of diamond increases as the pressure increases, the amount of input microwave energy per unit volume of diamond is 1 kW h/mm(3) regardless of the method used. Since the in-liquid deposition method provides a superior cooling effect through the evaporation of the liquid itself, a higher electric input power can be applied to the electrodes under higher pressure environments. The growth rate of in-liquid microwave plasma chemical vapor deposition process is found to be greater than conventional gas-phase microwave plasma chemical vapor deposition process under the same pressure conditions. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3117198]

DOI： 10.1063/1.3117198

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Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO2 conditions (8-20 MPa). Temperature evaluated from C-2 Swan bands (d (3)Pi(g)-&gt; a (3)Pi(u)) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p (5) P-3,P-2,P-1 -&gt; 3s (5) S-2(0)) of hf plasma under sc CO2 conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.

DOI： 10.1063/1.3091927

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOCIETY APPLIED PHYSICS  

The synthesis of diamond using in-liquid plasma chemical vapor deposition (CVD) is investigated in this study. Plasma in methanol solution is generated by applying microwave radiation of 2.45 GHz. The composition of the solution and the pressure in the container were varied as experimental parameters. No substrate cooling equipment was required in this process owing to the cooling effect of the liquid itself. The deposits on Si substrates were identified by scanning electron microscopy (SEM) and Raman spectroscopy. A diamond film containing impurities, which was confirmed to have a growth rate of 192 mu m/h, was obtained. The deposit had sufficient hardness within the 15 to 80 GPa range, which is suitable for industrial hard coating. Deposition rate increased as system pressure increased, displaying the same tendency of conventional microwave CVD. Optical emission spectroscopy was used to characterize the in-liquid plasma for chemical reaction. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.031601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A new high-rate crystal diamond synthesis method using plasma submerged in liquid alcohol was developed. The diamonds are grown by contact with the in-liquid plasma created by applying microwaves to a liquid methanol solution. The chemical reaction rate in the plasma is much higher than in the conventional gas phase plasma because the plasma is stably generated in a bubble in the liquid solution. Therefore, a very high diamond deposition rate (100 mu m/h) becomes possible even under low pressure. The success of this method will be the foundation for the high-volume supply of low-cost diamond substrate. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.diamond.2008.04.010

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Language：Japanese   Publisher：The Heat Transfer Society of Japan  

&ldquo;In-liquid plasma&rdquo; is generated inside the bubbles on the tip of an electrode by applying microwave radiation from the electrode. The in-liquid plasma on the tip of an electrode consists of a plasma generation region, vapor phase, bubble interface, and liquid phase. The growth of the bubble, including the plasma, in n-dodecane was observed using a high-speed camera. This was done because the pressure and the temperature surrounding the plasma needed to be clarified for utilizing it in such processes as chemical vapor deposition. The dependence of the bubble growth on the vessel pressure and on the microwave power was clarified, and the internal pressure of the bubbles was calculated by substituting the approximation curve of the observed bubble diameter in the Rayleigh-Plesset equation. The bubbles grow not continuously but intermittently as the plasma region expands and contracts. The growth of the bubbles increases with increase in the microwave power or decrease in the vessel pressure. The value of the internal pressure of the bubbles peaks between 200 and 600 hPa, it increases as the microwave power increases, and the effect of the vessel pressure on it is small. In addition, we measured the temperature surrounding the plasma using a thermocouple. The temperature can be measured vertically from the vapor phase to the liquid phase by moving the thermocouple in that direction. The point where the temperature measurable by the thermocouple reaches a maximum moves away from the tip of the electrode as the microwave power increases. The maximum temperature reaches the approximate saturation temperature of the liquid.

DOI： 10.11368/tse.16.131

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Radio frequency (RF) plasma in water was used for the degradation of methylene blue. The fraction of decomposition of methylene blue and the intensity of the spectral line from OH radical increased with RF power. RF plasma in water also produced hydrogen peroxide. The density of hydrogen peroxide increased with RF power and exposure time. When pure water (300 mL) is exposed to plasma at 310 W for 15 min, density of hydrogen peroxide reaches to 120 mg/L. Methylene blue after exposed to plasma degraded gradually for three weeks. This degradation may be due to chemical processes via hydrogen peroxide and tungsten. The comparison between the experimental and calculated spectral lines of OH radical (A-X) shows that the temperature of the radical is around 3,500 K. Electron density is evaluated to be similar or equal to 3.5 x 10(20) m(-3) from the stark broadening of the H(beta) line.

DOI： 10.1007/s11090-008-9142-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The plasma in water is generated by applying high-frequency (HF) irradiation of 27.12 MHz or microwave (MW) radiation of 2.45 GHz from an electrode. The electrode is heated by joule heating by the HF or MW irradiation, and vapor bubbles are generated simultaneously. The plasma is then ignited inside the bubbles on the electrode. The glow discharge plasma can be maintained in spite of atmospheric pressure due to the cooling effect of the liquid itself. The electron temperature of the plasma generated by the 27.12 MHz radiation is higher than that generated by the 2.45 GHz radiation. (C) 2008 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.1.046002

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A supercritical carbon dioxide (CO2) plasma process for fabricating one-dimensional tungsten oxide nanowires coated with amorphous carbon is presented. High-frequency plasma was generated in supercritical carbon dioxide at 20 MPa by using tungsten electrodes mounted in a supercritical cell, and subsequently an organic solvent was introduced with supercritical carbon dioxide into the plasma. Electron microscopy and Raman spectroscopy investigations of the deposited materials showed the production of tungsten oxide nanowires with or without an outer layer. The nanowires with an outer layer exhibited a coaxial structure with an outer concentric layer of amorphous carbon and an inner layer of tungsten oxide with a thickness and diameter of 20-30 and 10-20 nm, respectively.

DOI： 10.1088/0957-4484/18/49/495603

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A supercritical carbon dioxide (CO2) plasma process for fabricating one-dimensional tungsten oxide nanowires coated with amorphous carbon is presented. High-frequency plasma was generated in supercritical carbon dioxide at 20 MPa by using tungsten electrodes mounted in a supercritical cell, and subsequently an organic solvent was introduced with supercritical carbon dioxide into the plasma. Electron microscopy and Raman spectroscopy investigations of the deposited materials showed the production of tungsten oxide nanowires with or without an outer layer. The nanowires with an outer layer exhibited a coaxial structure with an outer concentric layer of amorphous carbon and an inner layer of tungsten oxide with a thickness and diameter of 20-30 and 10-20 nm, respectively.

DOI： 10.1088/0957-4484/18/49/495603

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

The behavior of 2.45 GHz microwave in-liquid plasma n-dodecane was observed using a high-speed camera. The system pressure before plasma generation was 1 or 100 hPa. The plasma was generated at the tip of a sharpened electrode, after which the plasma was found in a bubble in the liquid on the electrode. The plasma did not continuously emit light. The profile of light intensity varied between 1 and 100hPa when the plasma faded. The behavior of the bubble by heat generation in the bubble was numerically simulated. To match experimental results, the heat generation was continued for 0.9 ms at 1hPa and throughout the simulation at 100hPa. The internal temperature ranged from 2,000 to 4,000K, and the ratio of vapor n-dodecane to hydrogen produced by chemical reaction was at almost the same order at 1 hPa and approximately 1% at 100 hPa.

DOI： 10.1143/JJAP.46.6015

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An experiment was conducted for generating high-frequency plasma in supercritical carbon dioxide; it is expected to have the potential for applications in various types of practical processes. It was successfully generated at 6-20 MPa using electrodes mounted in a supercritical cell with a gap of 1 mm. Emission spectra were then measured to investigate the physical properties of supercritical carbon dioxide plasma. The results indicated that while the emission spectra for carbon dioxide and carbon monoxide could be mainly obtained at a low pressure, the emission spectra for atomic oxygen could be obtained in the supercritical state, which increased with the pressure. The temperature of the plasma in supercritical state was estimated to be approximately 6000-7000 K on the assumption of local thermodynamic equilibrium and the calculation results of thermal equilibrium composition in this state showed the increase of atomic oxygen by the decomposition of CO2. (C) 2007 American Institute of Physics.

DOI： 10.1063/1.2724240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The purpose of this study is to elevate the temperature and induce necrosis tumor cells that include ferrite powder to 50-60 degrees C by applying an alternating magnetic field. The achieved temperature is higher when compared to the conventional hyperthermia methods. We performed an experiment in which a high-water content agar phantom that was used as a quasi-tissue had 50 nm-10 mu m magnesium ferrite (MgFe2O4) dispersed in it and was then heated to a level of 190-700 kHz. The results show that the temperature of the phantom is higher for higher frequencies, larger particle sizes, and higher quantities of dispersed ferrite powder. Also, taking into account heat generation due to the magnetic powder, heat generation due to tissue metabolism, and the cooling effect of the blood flow, we solved the thermal equation related to local thermal therapy. Small differences in the distribution of ferrite powder affect the temperature increase of the tissue and the area where cell necrosis is induced.

DOI： 10.1080/01457630701483711

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Publisher：Acoustical Society of America (ASA)  

<jats:p>In-liquid plasma is a useful invention because its chemical reaction rate is several thousand times higher than those of conventional plasma techniques. However, in-liquid plasma is not so familiar now because its fundamental characteristics remain unclear. We investigated characteristics of in-liquid plasma in a continuous liquid flow to facilitate its application as a chemical decomposition or synthesis device. N-dodecane is supplied by the pump and a stable liquid flow is set in the rectangular vessel. Because the flow velocity is insufficient, a nozzle is set 2 mm distant from the microwave electrode tip. The average flow velocity of n-dodecane at the nozzle top is 0–19 m/s and the Reynolds number is as high as 1.2×104. A 2.45-GHz microwave is introduced by a monopole antenna electrode inserted into a rectangular cavity resonator. In-liquid plasma is generated and observed in the flowing cavitation bubbles generated from the ultrasonic horn tip. The vessel’s inner pressure is adjusted to 65–450 hPa. The temperature in the plasma reached 3600±300 K; it was almost independent of the flow velocity because the physical properties of the plasma are influenced only slightly by the acoustic cavitation stream.</jats:p>

DOI： 10.1121/1.4788092

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Publisher：Acoustical Society of America (ASA)  

<jats:p>Behavior of a single bubble under an ultrasound resonant state in a hydrocarbon liquid such as n-dodecane or benzene was observed using a stroboscope and a charge-coupled device (CCD) camera. Although sonoluminescence was not confirmed because of bubble stability limitations, bubble deformation was observed at a situation of stability limitation. Deformation occurred when the bubble contracted to its minimum size. Numerical analyses of deformation growth by Rayleigh-Taylor instability of an oscillated bubble were carried out at the surface. The distortion amplitude of all degrees continued oscillating as the bubble expanded or contracted, and the oscillation frequency increased with the degree. The distortion amplitudes are amplified through the afterbounce by the resonance effect if the oscillation frequency of the distortion amplitude of some degree is approximately equal to the frequency of the afterbounce. The distortion amplitude of all degrees, except for amplified degrees, was dampened by the viscosity effect, and if the distortion amplitudes of all degrees were dampened, the bubble was considered to form a sphere and become stable. A phase diagram of stability of an oscillated bubble showed a function of an ambient bubble radius and the amplitude of forcing pressure.</jats:p>

DOI： 10.1121/1.4788090

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We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

DOI： 10.1143/JJAP.45.8864

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The purpose of this study is to investigate the thermal characteristics of Mg1-XCaXFe2O4 ferrite powder by applying AC magnetic field and to predict the effect of thermal coagulation in vivo. We found that heating characteristics of the ferrite powder became greater as the frequency through the 400 kHz to 700 kHz range. The highest heat generation was attained using 7-15 nm ferrite powder. We also carried out a heat transfer simulation in which we were able to demonstrate that this material has sufficient heat generating characteristics to thermally coagulate a tumor cell and that it is possible to predict the range of the coagulation from the present simulation. (c) 2006 Springer Science + Business Media, Inc.

DOI： 10.1007/s10853-006-6749-7

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The generation of microwave plasma in liquid with vapor bubbles has been achieved and will soon be applied to high-speed chemical vapor deposition. Vapor bubbles are induced from an electrode by heating. The deposition rate of diamondlike carbon films depends on the pressure and the power of the microwave supply. Polycrystalline silicon carbide is synthesized on a silicon substrate in a mixture of n-dodecane and silicone oil. The dispersion of water droplets in liquid creates many pores on the silicon carbide films. The synthesis of carbon nanotubes can be achieved in liquid benzene. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2208167

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The behavior of cavitation bubbles is important in sonoplasma, which is generated by simultaneous microwave and ultrasound irradiation. Sonoplasma is expected to be applied in great many fields, such as high-speed chemical vapor deposition. In this study, the behavior of a single bubble in n-dodecane with ultrasonic irradiation was first observed using a charge-coupled-device camera and a stroboscope. In the observation, though sonoluminescence was not confirmed, the bubble was expanded and contracted synchronously with the ultrasonic frequency and was deformed when it contracted to its minimum size. The mechanism of the deformation of the bubble was clarified by numerical analysis. The stability of the bubble can be determined according to initial radius and the amplitude of the sound pressure.

DOI： 10.1143/JJAP.45.4165

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Heat transfer enhancement using a horn-type transducer was carried out in the natural convection region while a flat plate was used as a wall-like obstacle in front of the heating surface. Three types of plate were used as obstacles: acrylic, aluminum, and Styrofoam. A horn tip of 6 mm diameter and 60.7 kHz was used as the ultrasonic transducer. The acoustic cavitation jet induced by the ultrasonic vibration exhibited the same tendency as the axisymmetric freejet. The acoustic jet from the horn tip was shut out by the flat plate; however, the ultrasound passed through the flat plate and transferred the flow effect and agitation effect to the area behind the plate. By applying ultrasonic vibration, the heat transfer coefficient of the heating surface behind the flat plate was increased by up to threefold. The heat transfer coefficient decreased as the thickness of the flat plate increased. The heat transfer coefficient was the highest for the acrylic plate, then the aluminum plate, and lowest for the Styrofoam plate.

DOI： 10.1143/JJAP.44.4674

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The mechanism of cavitation bubble streaming by ultrasonic vibration in a water tank was experimentally investigated. A standard ultrasonic cleaner unit with a resonant frequency of 40 kHz was used as an ultrasonic generator. The behavior of the streaming was visualized by the schlicren method and sonochemical luminescence, and the velocity of the streaming was measured by laser Doppler velocity measurement equipment (LDV). The cavitation bubble streaming has two structures. A cavitation cloud, which consists of many cavitation bubbles, is shaped like a facing pair of bowls with a diameter of approximately 1/3 the wavelength of the standing wave, and moves inside the standing-wave field with a velocity of 30 to 60 mm/s. The cavitation bubbles move intensely in the cloud with a velocity of 5 m/s at an ultrasonic output power of 75 W. The streaming is completely different from conventional acoustic streaming. Also the cavitation bubble is generated neither at the pressure node nor at the antinode.

DOI： 10.1143/JJAP.44.3161

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Stable plasma can be generated in a liquid hydrocarbon such as n-dodecane or benzene by simultaneous microwave and ultrasonic irradiation. The authors refer to this plasma as "sonoplasma" and distinguish it from "sonoluminescence" on the basis of the continuity of emission. The temperature in the plasma was obtained by measuring two specified emission intensities from the plasma which reached approximately 5000 K. To analytically estimate the temperature, numerical simulations of the behavior of a single bubble in sound field, taking into account the absorption of microwave energy, were carried out. The temperature inside the bubble in n-dodecane reached approximately 8000 K. In benzene, the temperature inside the bubble, which continued expanding through absorption of microwave energy, exceeded 2000 K.

DOI： 10.1143/JJAP.43.2833

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The purpose of this report is to investigate the heating effect of agar phantom containing ferrite powder by applying external AC magnetic field. Mg ferrite is most applicable for local hyperthermia. When using AC magnetic field with a frequency of 190 to 700kHz, the higher the frequency can increase the temperature of agarphantom containing 3.0 and 5.0% Mg ferrite powder. Even to the same weight of ferrite powder, the lager heat generation is obtained at the larger powder size. Moreover, a slight difference of distribution of ferrite powder has marked effects on the maximum temperature in vivo.

DOI： 10.1299/jsmemecjo.2003.7.0_57

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TAYLOR & FRANCIS LTD  

Boiling inception experiments were conducted in water and in ethanol with an electrically heated platinum wire. For water, the platinum wire is red-heated for one minute, and thereafter a series of runs is done. Boiling tends to initiate harder as the platinum wire experiences more red-heats. However the effect is gradually saturated. The boiling inception condition depends on presuppression. On the contrary, it does not for ethanol except for very weak presuppressions, and the vapor nuclei at boiling inception are extremely small.
The above results are discussed from the viewpoint of wetting to lead to the conclusions that boiling inception in ethanol will generally be due to the growth of spontaneously created vapor nuclei except for very weak presuppressions, and that smaller vapor nuclei will tend to collapse easier.

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In the present study, two methods for methane hydrate decomposition were conducted, one was using 27.12 MHz radio-frequency plasma jet and another was radio-frequency plasma using a monopole antenna. The objective of this research is to investigate a method to enhance production of hydrogen gas by the plasma from methane hydrate. When the RF plasma irradiated to methane hydrate, the hydrogen production ratio was 42.6% and the hydrogen generation efficiency was 1.9 ml/kJ. On the other hand, the ratio of hydrogen in exhaust gas by the decomposition using plasma jet was decreased with increase of the flow rate from 0 to 150 mL/min. However, when the flow rate was 200 mL/min, the ratio of hydrogen had most greatly 15.6%. The hydrogen generation efficiency tended to be a similar analysis result.

DOI： 10.1299/jsmeted.2014._E143-1_

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In the present study, two methane hydrate decomposition methods, one using radio frequency wave (RF) and the other microwave (MW) plasma in-liquid, are conducted to investigate in the production of hydrogen the relationship between gas production rate and CH4 conversion ratio. The objective of this research is also to develop a process to use methane hydrate plasma decomposition to produce fuel gas. Thermal decomposition is the dominant method for methane conversion into hydrogen. Using this method, the methane hydrate is broken down and collected as hydrogen gas, with the carbon content left solidified on the ocean floor. For practical application, since electrical power is necessary to generate the plasma, the key is to determine which renewable energy should be incorporated into this system.

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Language：Japanese   Publisher：化学工業社  

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DOI： 10.1299/jsmecs.2013.51._309-1_

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DOI： 10.1299/jsmecs.2013.51._310-1_

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The purpose of this study is to produce hydrogen gas from saccharide efficiently using 27.12 MHz radio-frequency (RF) in-liquid plasma. In order to enhance the production rate of hydrogen gas, ultrasonic irradiation was added to the plasma. The experiments were conducted adopting two different ultrasonic frequencies, 29 kHz using a horn-type transducer and 1.6 MHz using a piezoelectric transducer. When 29 kHz ultrasonic irradiation was added to the RF plasma in 0 to 10wt% glucose solution, the hydrogen production rate increased 4-17% from that without ultrasonic irradiation. When 1.6 MHz ultrasonic irradiation was applied to the RF plasma in 5wt% glucose solution, the gas production rate increased 90-150% from that without ultrasonic irradiation. The effects of ultrasonic atomization and agitation in the solution of nonvolatile glucose enhance a chemical reaction of the in-liquid plasma.

DOI： 10.1299/jsmeted.2013.59

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DOI： 10.1299/jsmecs.2013.51._1317-1_

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The purpose of this experiment is conversion of cellulose dispersed in water as fuel using in-liquid plasma. 27.12 MHz high-frequency plasma was generated in aqueous suspension of cellulose powder or aqueous solution of glucose which is monosaccharide. The gas production rate was measured and the components of the gas production were analyzed. When the concentration of cellulose was 40wt% or higher, the production rate became remarkably high because the ball-like aggregation of hydrous cellulose fell into the plasma and the cellulose was decomposed directly by plasma. On the other hand, the glucose and cellulose with 27wt% or lower was decomposed indirectly by plasma, because the emission spectrum from the species which comprises carbon atom was not detected by spectroscopic analysis.

DOI： 10.1299/jsmeted.2012.449

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DOI： 10.1299/jsmecs.2012.50.30201

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DOI： 10.1299/jsmecs.2012.50.30101

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DOI： 10.1299/jsmecs.2012.50.131401

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DOI： 10.1299/jsmecs.2012.50.131601

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DOI： 10.1299/jsmecs.2012.50.131501

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The purpose of this research is the industrialization of hydrogen production using a commercial microwave oven by generating plasma in waste oil. N-dodecane, engine oil and cooking oil were used as a liquid. N-dodecane can be circulated in the experimental device to assume continuous production of hydrogen. The gas production rate was measured, the content of the produced gas was analyzed. The energy efficiency which was expressed as the ratio of the consumed power for the chemical reaction to the microwave power was calculated. The energy efficiency increased with decrease of the microwave power, and reached 14% at the maximum. To improve the energy efficiency the reaction vessel was decompressed. The gas production rate became approximately 2 times larger and the ratio of hydrogen in the produced gas.

DOI： 10.1299/jsmeted.2012.441

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DOI： 10.1299/jsmecs.2012.50.131701

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DOI： 10.1299/jsmecs.2011.49.425

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DOI： 10.1299/jsmecs.2011.49.437

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DOI： 10.1299/jsmecs.2011.49.423

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Language：Japanese   Publisher：The Heat Transfer Society of Japan  

液中プラズマ化学蒸着法におけるダイヤモンドの生成には，基板の材質や基板の表面処理方法が重要である．本研究では基板の材質や表面処理方法を変化させ，液中プラズマ化学蒸着法における適切な基板の材質と表面処理方法の実験を行った．適切な基板の材質と表面処理方法はSiにダイヤモンドパウダーを用いて研磨を行った基板が良好な結果が得られた．また，実験に用いた基板の温度における線膨張係数を比較し，ダイヤが成膜できた基板ではダイヤモンドの線膨張係数の曲線に近いことが分かった．またSiがダイヤモンドの線膨張係数の曲線に最も近似しており最適だと考えられる．

DOI： 10.11368/nhts.2011.0.238.0

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高速度カメラを用いて高周波水中プラズマの励起温度分布の測定を行った．プラズマの発光の様子をダイクロックミラーで波長の違いにより２つの像に分解し，２つの像からバンドパスフィルターによりHαとHβの発光のみを取り出し，並べられた２つの発光の様子を高速度カメラで撮影した．励起温度は２つの発光強度の関係から求められた．励起温度の時間変化はプラズマの周囲の水の蒸発によってできる気泡の生成・成長・離脱の周期と同期した．気泡の離脱直前に励起温度は最大となり温度分布は細長く伸びることが明らかとなった．

DOI： 10.11368/nhts.2011.0.237.0

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本研究では減圧状態から4気圧の圧力範囲で液中プラズマを水中で発生させ，その分光測定から，励起温度，電子密度，ガス温度を求めた．OHの回転温度から得られる液中プラズマの気泡内のガス温度は，圧力の増加につれて高くなり，大気圧下で約3500K，4気圧では約5000Kに達する．液中プラズマはプラズマ自身が熱源となって沸騰する現象である．伝熱面からの沸騰現象では実現が難しい数千Kオーダーの過熱度を持った沸騰現象を液中に容易に発生させることができる．

DOI： 10.11368/nhts.2011.0.284.0

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DOI： 10.1299/jsmecs.2011.49.187

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液体中で亜鉛の電極を利用しマイクロ波プラズマを発生させて電極を原料としたナノ粒子の合成を行った。エタノール中でプラズマを発生させると10-200nmの六角柱または球体の亜鉛ナノ粒子が合成され、純水中で発生させると亜鉛ナノ粒子と酸化亜鉛ナノ粒子が凝集した約200nmの花びら型をした粒子が合成された。また、電極上部に設置された金属プレートの直径と位置を変え、ナノ粒子の合成に及ぼす影響を調べた。ナノ粒子の合成速度は金属プレートの直径が大きいほど、位置が電極先端に近いほど大きくなった。投入電力が230Wの場合、合成速度は5g/hourとなった。さらに、銅の電極を利用し放電開始電力を調べた。放電開始電力は金属プレートの位置が近いほど小さくなった。

DOI： 10.11368/nhts.2011.0.55.0

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DOI： 10.1299/jsmecs.2011.49.441

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The purpose of this research is to develop a process to use the plasma decomposition of clathrate hydrates to produce fuel gas. An ordinary microwave (MW) oven is used as the source of 2.45 GHz MW radiation under atmospheric-pressure. The plasma decomposition of the hydrates could pave the way for a new utilization of atmospheric pressure plasma. Cyclopentane (CP) hydrate formed at atmospheric pressure was decomposed by plasma in a MW oven generating gas with a content of 65% hydrogen, 12% CO, and 8% CO_2. About 32% of the MW input power was consumed to decompose the hydrate.

DOI： 10.1299/jsmeted.2011.239

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液体中での高周波やマイクロ波の照射によって発生するプラズマは，周囲の液体を蒸発させることにより，あたかも気泡の中で発生しているように見える．今後，この液中プラズマによる反応場としての利用が期待されている．本研究では，これまで測定されてきた温度分布や電子密度分布，ならびに反応による生成割合等について紹介するとともに，気泡の成長と減衰に関する数値シミュレーションを行い比較する．特に，水素の生成割合が非常に高くなるという実験結果に対して，気泡内の水分解反応と気泡の挙動との関係から明らかにする．

DOI： 10.11368/nhts.2010.0.160.0

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DOI： 10.1299/jsmecs.2010.48.331

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純水中に発生するマイクロ波液中プラズマの点火位置を高速度カメラで観察した。また、3D-FDTD法を用いて電極表面の電界を計算し、マイクロ波によって加熱される液体が吸収する熱量を計算した。この熱量を使って電極周辺の液体の温度計算した結果、プラズマが発生する電極表面の電界強度の最も高い位置と、最も温度が高い位置は必ずしも一致しないことが明らかになった。また、実験から測定したプラズマの点火位置と数値計算によって求めた最も温度の高い地点が一致した。

DOI： 10.11368/nhts.2010.0.31.0

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Since in-liquid plasma can be used in a liquid as a chemical reactor, it has an advantage in a treatment technology of a waste liquid and fuel gas production. The purpose of this research is to examine the basic characteristic of in-liquid plasma. In this research, a spectroscope is used for measuring the emission spectra of the in-liquid plasma. In-liquid plasma is generated by applying high-frequency (HF) irradiation of 27.12MHz into a pure water. As for the distribution of the emission intensities, of the emission intensities H and 0 are high in the vicinity of the plasma, where that of OH becomes high in the upper area of the plasma. Electron temperature has a distribution, and becomes the highest at the center of the plasma at 10kPa. The change of the electron temperature in the vertical direction is bigger than that in the horizontal direction. The electron temperature decreases with pressure increases.

DOI： 10.1299/jsmemecjo.2009.3.0_51

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In-liquid plasma has been expected as an advanced technology of generating plasma in a liquid by a high frequency(HF) or a microwave(MW) irradiation. In this study, 27.12MHz HF plasma is generated in pure water as well as in air. The phase difference of voltage and current waveforms before and after plasma ignition, and the self-bias voltage are investigated by using an oscilloscope. The electrical property of plasma as an equivalent circuit can be explained from the difference of the phase difference qualitatively. The self-bias voltage became positive with pressure increase when the electrode made of a tungsten rod is used. As pressure increases, the electron supply into the plasma changes from a secondary electron discharge to thermionic emission.

DOI： 10.1299/jsmemecjo.2009.3.0_49

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The purpose of this study is to clear the synthesizing mechanism of the compound materials using plasma CVD method. The determination method of the chemical reaction using the values of electronegativity and ionization energy is presented. The chemical reaction between the atom that has the highest electronegativity and the atom that has the lowest ionization energy occurs with first priority. The calculated results using the method have good agreement with the experimental results of synthesizing materials such as carbon and silicon carbide. Consequently, the method is useful to synthesizing compound semiconductors using plasma CVD method.

DOI： 10.1299/jsmeted.2009.95

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Distributions of emission intensity from radicals, electron temperature and rotational temperature at a radio frequency of 27.12MHz plasma in water are clarified by detailed spectroscopy measurement. Through this investigation, the following were observed. The points of maximum emission intensity of Hα, Hβ, O(777 nm) and O (845 nm) are almost the same, while that of OH shifts upward. The electron temperature decreases, while the rotational temperature increases with pressure. The distribution of the electron temperature changes at a threshold pressure, which is concerned with a change in the electron discharge mechanism. The point of the maximum rotational temperature of OH radicals shifts to approximately 1 mm above that for the maximum intensity of OH emission.

DOI： 10.1299/jsmeted.2009.99

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Language：English   Publisher：AMER SOC MECHANICAL ENGINEERS  

The plasma in liquid is generated by applying High-Frequency (HF) irradiation of 27.12 MHz or Microwave (MW) irradiation of 2.45 GHz from an electrode, namely, a monopole-antenna electrode inserted into a reactor vessel. n-dodecane, methanol, and water are used as test liquids. The glow discharge plasma can be kept in spite of atmospheric pressure due to the cooling effect of liquid itself The light emission from the plasma changes substantially according to the behavior of the bubble. The present Chemical Vapor Deposition (CVD) process also enabled simultaneous production of hydrogen gas and the synthesis of the Carbon Nano-Tubes (CNTs) in hydrocarbon liquids. The actual production of hydrogen per unit energy by this process corresponds to approximately 1% of that by conventional steam reforming method and about 32% of that by the alkaline water electrolysis. Moreover, this process can make the solid carbon of about 14 g/h at the same time.

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純水中に高周波を照射する電極を設置し，電極先端でプラズマを発生させる．高速度カメラでプラズマを内包する気泡の挙動を観察する．気泡の生成様式は，水温と供給電力により4つに分類され，加熱沸騰の場合との比較を行った．供給電力に対して，水温の上昇に消費される熱は約90%，蒸発として消費される熱は約10%，気泡表面から水中へと伝導される熱は約30%，さらに，化学反応により消費される熱は1%以下となることがわかった．

DOI： 10.11368/nhts.2009.0.30.0

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DOI： 10.1299/jsmecs.2009.47.101

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Language：Japanese   Publisher：公益社団法人 化学工学会  

DOI： 10.11491/scej.2009.0.414.0

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DOI： 10.1299/jsmecs.2009.47.99

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DOI： 10.1299/jsmecs.2009.47.121

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DOI： 10.1299/jsmecs.2009.47.103

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本研究の目的は，液中プラズマを市販の電子レンジを用いて発生させ，水素を製造すると同時に，炭素を固定化して，カーボンナノチューブや活性炭などの有用炭化物を生成する方法を開発することである．反応溶液にn-ドデカンを使用しプラズマを発生させと，最大で約純度80％の水素と，メタン，エチレン，アセチレンなどの低級炭化水素が発生する．また，ナノサイズのカーボン粒子，カーボンナノチューブが水素と同時に製造できることを明らかにする．

DOI： 10.11368/nhts.2008.0.218.0

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液中プラズマは気相プラズマとは異なる特徴をもち，応用研究は活発に行われている．一方，基礎的な発生メカニズムや物性に関する研究報告は少ない．本研究では，プラズマ発生と同時に，プラズマを内包しながら発生し成長する泡の挙動を高速度ビデオカメラで撮影し，画像から気泡内部の圧力を求め，熱電対を用いてプラズマ周辺の温度を測定する．液中プラズマの気泡は系圧力が小さいほど大きく成長し，気泡が膨張，収縮する周期が長くなる．周辺温度はプラズマが消費するエネルギー量が大きく，系圧力が大きいほど上昇する．

DOI： 10.11368/nhts.2008.0.99.0

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DOI： 10.11316/jpsgaiyo.62.2.2.0_213_1

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DOI： 10.1299/jsmecs.2007.45.219

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Stable plasma can be generated in a liquid hydrocarbon such as n-dodecane or benzene by simultaneous microwave and ultrasonic irradiation. The authors refer to this plasma as "sonoplasma" and distinguish it from "sonoluminescence" on the basis of the continuity of emission. The temperature in the plasma was obtained by measuring two specified emission intensities from the plasma, which reached approximately 5000 K. To analytically estimate the temperature, numerical simulations of the behavior of a single bubble in sound field, taking into account the absorption of microwave energy, were carried out. The temperature inside the bubble in n-dodecane reached approximately 8000 K. In benzene, the temperature inside the bubble, which continued expanding through absorption of microwave energy, exceeded 2000 K.

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Other Link： http://iyokan.lib.ehime-u.ac.jp/dspace/handle/iyokan/1452

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.1.2.0_217_3

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Language：Japanese   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.25.0_431

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Language：Japanese   Publisher：The Visualization Society of Japan  

A stable plasma within cavitation bubble created in a liquid can be achieved by applying microwave and ultrasonic irradiation simultaneously. We refer to the latter plasma using ultrasonic vibration as sono-plasma. We propose that plasma in a liquid be applied as a new technique to replace the gas-phase. To control the plasma for practical application, it is important to clarify the behavior of bubbles in liquid. The behavior of a single air bubble in water, n-dodecane and benzene with ultrasound was visualized by use of stroboscope, and calculated by numerical simulation. Single bubble sonoluminescence was observed in the case of using water. However the luminescence phenomenon was not observed in liquid hydrocarbon. When the bubble size is minimum, the deformation of the spherical bubble occured in liquid hydrocarbon. Ultrasonic wave had to be irradiated with much lower amplitude of sound pressure than that in water to hold the bubble, which moved and became unstable with increased of sound pressure. The numerical analysis results are compared with that of the observation data to check the reliability of the analysis.

DOI： 10.3154/jvs.24.Supplement2_111

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Language：Japanese   Publisher：Institute for Ultrasonic Elecronics  

DOI： 10.24492/use.24.0_237

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

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Event date： 2023.5

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2023.3

Presentation type：Poster presentation  

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Event date： 2022.9

Language：Japanese   Presentation type：Poster presentation  

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Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2021.10

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Event date： 2021.3

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Event date： 2021.3

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Event date： 2021.3

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Event date： 2020.3

Language：Japanese   Presentation type：Poster presentation  

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本研究では減圧状態から4気圧の圧力範囲で液中プラズマを水中で発生させ，その分光測定から，励起温度，電子密度，ガス温度を求めた．OHの回転温度から得られる液中プラズマの気泡内のガス温度は，圧力の増加につれて高くなり，大気圧下で約3500K，4気圧では約5000Kに達する．液中プラズマはプラズマ自身が熱源となって沸騰する現象である．伝熱面からの沸騰現象では実現が難しい数千Kオーダーの過熱度を持った沸騰現象を液中に容易に発生させることができる．

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液中プラズマ化学蒸着法におけるダイヤモンドの生成には，基板の材質や基板の表面処理方法が重要である．本研究では基板の材質や表面処理方法を変化させ，液中プラズマ化学蒸着法における適切な基板の材質と表面処理方法の実験を行った．適切な基板の材質と表面処理方法はSiにダイヤモンドパウダーを用いて研磨を行った基板が良好な結果が得られた．また，実験に用いた基板の温度における線膨張係数を比較し，ダイヤが成膜できた基板ではダイヤモンドの線膨張係数の曲線に近いことが分かった．またSiがダイヤモンドの線膨張係数の曲線に最も近似しており最適だと考えられる．

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高速度カメラを用いて高周波水中プラズマの励起温度分布の測定を行った．プラズマの発光の様子をダイクロックミラーで波長の違いにより２つの像に分解し，２つの像からバンドパスフィルターによりHαとHβの発光のみを取り出し，並べられた２つの発光の様子を高速度カメラで撮影した．励起温度は２つの発光強度の関係から求められた．励起温度の時間変化はプラズマの周囲の水の蒸発によってできる気泡の生成・成長・離脱の周期と同期した．気泡の離脱直前に励起温度は最大となり温度分布は細長く伸びることが明らかとなった．

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純水中に高周波を照射する電極を設置し，電極先端でプラズマを発生させる．高速度カメラでプラズマを内包する気泡の挙動を観察する．気泡の生成様式は，水温と供給電力により4つに分類され，加熱沸騰の場合との比較を行った．供給電力に対して，水温の上昇に消費される熱は約90%，蒸発として消費される熱は約10%，気泡表面から水中へと伝導される熱は約30%，さらに，化学反応により消費される熱は1%以下となることがわかった．

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The purpose of this research is to develop a process to use the plasma decomposition of clathrate hydrates to produce fuel gas. An ordinary microwave (MW) oven is used as the source of 2.45 GHz MW radiation under atmospheric-pressure. The plasma decomposition of the hydrates could pave the way for a new utilization of atmospheric pressure plasma. Cyclopentane (CP) hydrate formed at atmospheric pressure was decomposed by plasma in a MW oven generating gas with a content of 65% hydrogen, 12% CO, and 8% CO_2. About 32% of the MW input power was consumed to decompose the hydrate.

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The purpose of this experiment is conversion of cellulose dispersed in water as fuel using in-liquid plasma. 27.12 MHz high-frequency plasma was generated in aqueous suspension of cellulose powder or aqueous solution of glucose which is monosaccharide. The gas production rate was measured and the components of the gas production were analyzed. When the concentration of cellulose was 40wt% or higher, the production rate became remarkably high because the ball-like aggregation of hydrous cellulose fell into the plasma and the cellulose was decomposed directly by plasma. On the other hand, the glucose and cellulose with 27wt% or lower was decomposed indirectly by plasma, because the emission spectrum from the species which comprises carbon atom was not detected by spectroscopic analysis.

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The purpose of this research is the industrialization of hydrogen production using a commercial microwave oven by generating plasma in waste oil. N-dodecane, engine oil and cooking oil were used as a liquid. N-dodecane can be circulated in the experimental device to assume continuous production of hydrogen. The gas production rate was measured, the content of the produced gas was analyzed. The energy efficiency which was expressed as the ratio of the consumed power for the chemical reaction to the microwave power was calculated. The energy efficiency increased with decrease of the microwave power, and reached 14% at the maximum. To improve the energy efficiency the reaction vessel was decompressed. The gas production rate became approximately 2 times larger and the ratio of hydrogen in the produced gas.

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The purpose of this report is to investigate the heating effect of agar phantom containing ferrite powder by applying external AC magnetic field. Mg ferrite is most applicable for local hyperthermia. When using AC magnetic field with a frequency of 190 to 700kHz, the higher the frequency can increase the temperature of agarphantom containing 3.0 and 5.0% Mg ferrite powder. Even to the same weight of ferrite powder, the lager heat generation is obtained at the larger powder size. Moreover, a slight difference of distribution of ferrite powder has marked effects on the maximum temperature in vivo.

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A stable plasma within cavitation bubble created in a liquid can be achieved by applying microwave and ultrasonic irradiation simultaneously. We refer to the latter plasma using ultrasonic vibration as sono-plasma. We propose that plasma in a liquid be applied as a new technique to replace the gas-phase. To control the plasma for practical application, it is important to clarify the behavior of bubbles in liquid. The behavior of a single air bubble in water, n-dodecane and benzene with ultrasound was visualized by use of stroboscope, and calculated by numerical simulation. Single bubble sonoluminescence was observed in the case of using water. However the luminescence phenomenon was not observed in liquid hydrocarbon. When the bubble size is minimum, the deformation of the spherical bubble occured in liquid hydrocarbon. Ultrasonic wave had to be irradiated with much lower amplitude of sound pressure than that in water to hold the bubble, which moved and became unstable with increased of sound pressure. The numerical analysis results are compared with that of the observation data to check the reliability of the analysis.

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液中プラズマは気相プラズマとは異なる特徴をもち，応用研究は活発に行われている．一方，基礎的な発生メカニズムや物性に関する研究報告は少ない．本研究では，プラズマ発生と同時に，プラズマを内包しながら発生し成長する泡の挙動を高速度ビデオカメラで撮影し，画像から気泡内部の圧力を求め，熱電対を用いてプラズマ周辺の温度を測定する．液中プラズマの気泡は系圧力が小さいほど大きく成長し，気泡が膨張，収縮する周期が長くなる．周辺温度はプラズマが消費するエネルギー量が大きく，系圧力が大きいほど上昇する．

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液体中で亜鉛の電極を利用しマイクロ波プラズマを発生させて電極を原料としたナノ粒子の合成を行った。エタノール中でプラズマを発生させると10-200nmの六角柱または球体の亜鉛ナノ粒子が合成され、純水中で発生させると亜鉛ナノ粒子と酸化亜鉛ナノ粒子が凝集した約200nmの花びら型をした粒子が合成された。また、電極上部に設置された金属プレートの直径と位置を変え、ナノ粒子の合成に及ぼす影響を調べた。ナノ粒子の合成速度は金属プレートの直径が大きいほど、位置が電極先端に近いほど大きくなった。投入電力が230Wの場合、合成速度は5g/hourとなった。さらに、銅の電極を利用し放電開始電力を調べた。放電開始電力は金属プレートの位置が近いほど小さくなった。

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The purpose of this study is to produce hydrogen gas from saccharide efficiently using 27.12 MHz radio-frequency (RF) in-liquid plasma. In order to enhance the production rate of hydrogen gas, ultrasonic irradiation was added to the plasma. The experiments were conducted adopting two different ultrasonic frequencies, 29 kHz using a horn-type transducer and 1.6 MHz using a piezoelectric transducer. When 29 kHz ultrasonic irradiation was added to the RF plasma in 0 to 10wt% glucose solution, the hydrogen production rate increased 4-17% from that without ultrasonic irradiation. When 1.6 MHz ultrasonic irradiation was applied to the RF plasma in 5wt% glucose solution, the gas production rate increased 90-150% from that without ultrasonic irradiation. The effects of ultrasonic atomization and agitation in the solution of nonvolatile glucose enhance a chemical reaction of the in-liquid plasma.

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In the present study, two methods for methane hydrate decomposition were conducted, one was using 27.12 MHz radio-frequency plasma jet and another was radio-frequency plasma using a monopole antenna. The objective of this research is to investigate a method to enhance production of hydrogen gas by the plasma from methane hydrate. When the RF plasma irradiated to methane hydrate, the hydrogen production ratio was 42.6% and the hydrogen generation efficiency was 1.9 ml/kJ. On the other hand, the ratio of hydrogen in exhaust gas by the decomposition using plasma jet was decreased with increase of the flow rate from 0 to 150 mL/min. However, when the flow rate was 200 mL/min, the ratio of hydrogen had most greatly 15.6%. The hydrogen generation efficiency tended to be a similar analysis result.

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