Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Manabu Tanaka Last modified date:2019.06.24

Assistant Professor / Product System Engineering / Department of Chemical Engineering / Faculty of Engineering


Papers
1. Manabu Tanaka, Hirohiko Soeda, Takayuki Watanabe, Tomohiro Koga, Plasma Jet Characteristics in Long DC Arc with Ring-Shaped Anode, Journal of Fluid Science and Technology, https://doi.org/10.1299/jfst.2018jfst0027, 13, 4, 2018.11, Fluctuation characteristics of plasma jet flow in an innovative long DC arc system with ring-shaped anode were successfully clarified on the basis of the high-speed camera visualization. The long DC arc with long electrode gap distance more than 350 mm has been applied to gas decomposition due to its advantages such as large plasma volume and long residence time of treated gas. However, large heat loss at a conventional hemispherical-shaped anode was critical issue in the long DC arc system. Therefore, a ring-shaped anode was utilized to convert large energy loss at the anode into the plasma jet flow. Two kinds of the experiments were conducted. One was the estimation of energy balance in the long DC arc system. Calorimetric measurements were carried out. Another was the high-speed camera observation of the arc fluctuation and the plasma jet fluctuation. Results indicated that the 60% of heat loss at the conventional hemispherical-shaped anode was converted into the plasma jet flow when the ring-shaped anode was utilized. High-speed camera observation revealed that the plasma jet fluctuation with sharp FFT peak in the range of 25-500Hz was attributed to the arc fluctuation, which originated from the restrike phenomena of the anode spot. In contrast, results also suggested that the plasma jet fluctuation with broad FFT peaks in the range of 100-300Hz was attributed to the eddy formation due to the entrainment of ambient cold gas. To understand and control the fluctuation phenomena in the plasma jet enables to establish the innovative waste treatment by thermal plasmas..
2. Fengmei Su, Xuechao Qiu, Feng Liang, Manabu Tanaka, Tao Qu, Yaochun Yao, Wenhui Ma, Bin Yang, Yongnian Dai, Katsuro Hayashi, Takayuki Watanabe, Preparation of nickel nanoparticles by direct current arc discharge method and their catalytic application in hybrid Na-air battery, Nanomaterials, 10.3390/nano8090684, 8, 9, 2018.09, Nickel nanoparticles were prepared by the arc discharge method. Argon and argon/hydrogen mixtures were used as plasma gas; the evaporation of anode material chiefly resulted in the formation of different arc-anode attachments at different hydrogen concentrations. The concentration of hydrogen was fixed at 0, 30, and 50 vol% in argon arc, corresponding to diffuse, multiple, and constricted arc-anode attachments, respectively, which were observed by using a high-speed camera. The images of the cathode and anode jets were observed with a suitable band-pass filter. The relationship between the area change of the cathode/anode jet and the synchronous voltage/current waveform was studied. By investigating diverse arc-anode attachments, the effect of hydrogen concentration on the features of nickel nanoparticles were investigated, finding that 50 vol% H
2
concentration has high productivity, fine crystallinity, and appropriate size distribution. The synthesized nickel nanoparticles were then used as catalysts in a hybrid sodium–air battery. Compared with commercial a silver nanoparticle catalyst and carbon black, nickel nanoparticles have better electrocatalytic performance. The promising electrocatalytic activity of nickel nanoparticles can be ascribed to their good crystallinity, effective activation sites, and Ni/NiO composite structures. Nickel nanoparticles prepared by the direct current (DC) arc discharge method have the potential to be applied as catalysts on a large scale..
3. Takafumi Okuma, Hiroki Maruyama, Taro Hashizume, Manabu Tanaka, Takayuki Watanabe, Hisao Nagai, Takeshi Koiwasaki, Hiroshi Nasu, Effects of the Driving Frequency on Temperature in a Multiphase AC Arc, IEEE Transactions on Plasma Science, 10.1109/TPS.2018.2832286, 2018.05, Effects of the driving frequency on temperature in a multiphase ac arc were successfully clarified. A multiphase ac arc is one of the thermal plasmas, which is suitable for producing functional materials such as nanoparticles, in-flight glass melting, and waste treatment in terms of its large plasma volume, high-energy efficiency, and low flow velocity. The temperature and arc behavior in various driving frequencies were investigated by the observation system consisting of a high-speed video camera and bandpass filters for plasma spectroscopy. The temperature measurement was conducted on the basis of the Boltzmann plot method. The obtained results indicated that the arc behavior and its temperature field were strongly influenced by the driving frequency. An increase of the frequency led to concentrated arc region, higher arc temperature at the center of electrode region and lower arc fluctuation. The temperature and its distribution can be controlled depending on the material properties to be treated and the purpose of the process..
4. Takafumi Okuma, Tomoyuki Imatsuji, Taro Hashizume, Manabu Tanaka, Takayuki Watanabe, Hisao Nagai, Takeshi Koiwasaki, Hiroshi Nasu, Effects of working pressure on temperature characteristics in multiphase AC arc, Journal of Fluid Science and Technology, 10.1299/jfst.2018jfst0024, 13, 4, 2018.01, Temperature characteristics of a multiphase AC arc in various working pressures were investigated by an innovative observation system consisting of a high-speed video camera and band-pass filters. Thermal plasmas have been widely applied to many industrial fields because of their unique advantages such as high temperature, high enthalpy, and rapid quenching capability. In particular, the multiphase AC arc is advantageous in terms of large plasma volume and high energy efficiency. Therefore, this heat source has been applied to innovative material processing such as in-flight glass melting, and functional nanoparticles fabrication. However, the temperature field and its fluctuation characteristics in the multiphase AC arc have not been understood because of the difficulties of temperature measurement due to their rapid fluctuation in millisecond timescale as well as the axisymmetric spatial characteristics. To understand and control the fluctuation phenomena is important to realize this method as industrial technology. Temperature measurement system using a high-speed camera was constructed to visualize the temperature fields of the multiphase AC arc. The fluctuations in the two-dimensional intensity distributions of particular line emissions from atomic argon were successfully observed. By analyzing these images using the Boltzmann plot method, the temperature distribution was estimated. The experimental results indicated that the arc temperature fluctuated in the range from 6,000 to 12,000 K. Higher temperature, smaller arc existence area, and decrease in the diameter of the arc were observed with an increase of working pressure. The arc temperature in the multiphase AC arc is sufficiently high to treat the refractory metals and ceramics powders at high processing rate..
5. Yutaro Ozeki, Tsuyoshi Matsuo, Manabu Tanaka, Takayuki Watanabe, Characteristics of water thermal plasma for biomass utilization system, Journal of Fluid Science and Technology, 10.1299/jfst.2017jfst0022, 12, 3, 2017.12, The purpose of the present work is to visualize the temperature fluctuation of water thermal plasma for biomass gasification. Another purpose is to investigate D-glucose decomposition mechanism in water thermal plasma because D-glucose is one of the main components in general biomass products. Arc temperature distributions of water thermal plasma with and without D-glucose injection were successfully visualized by high-speed camera. Two synchronized arc images in different wavelengths of Hα and Hβ were observed owing to appropriate optical band-pass filters with negligible other emissions from the arc. The arc temperature was measured based on Boltzmann-plot method. Measured arc temperature without D-glucose was 9000 K, and that with D-glucose was 7500 K. These temperatures were sufficiently high to decompose D-glucose completely. Furthermore, frequency analysis of arc fluctuation revealed that the time period of arc fluctuation was sufficiently shorter than that of the time constant of D-glucose decomposition. These results implied that the influence of arc fluctuation on D-glucose decomposition was negligible. In addition, the decomposition mechanism of D-glucose was discussed on the basis of the analyses of the products in vapor, liquid, and solid phases. They were converted from D-glucose through the water thermal plasma. Decomposition rate of D-glucose reached 99%. Gaseous product contains more than 86% of syngas, H2 and CO. This ratio is much higher than that in conventional gasification device. From these characteristics, water plasma system is suitable device for biomass utilization..
6. Manabu Tanaka, Tomoyuki Imatsuji, Taro Hashizume, Takayuki Watanabe, Hisao Nagai, Takeshi Koiwasaki, Takafumi Okuma, Investigation of temperature characteristics of multiphase AC arc by high-speed visualization, Journal of Fluid Science and Technology, 10.1299/jfst.2017jfst0024, 12, 3, 2017.12, The objective of the present study is to understand fluctuation phenomena in a multiphase AC arc as a heat source for material processing based on the high-speed visualization technique of the temperature field. The multiphase AC arc is one of the most attractive thermal plasmas which possess extremely high temperature, high chemical reactivity, rapid quenching capability, and selectivity of the reaction atmosphere in accordance with required chemical reaction. In particular, the multiphase AC arc has a strong advantage on higher energy efficiency compared with other thermal plasmas. Therefore, this heat source has been applied to innovative material processing such as in-flight glass melting. However, the temporal and spatial characteristics of the multiphase AC arc have not been clarified although these are essential to control the characteristics of the products such as particle size distribution, yields of the desired materials. The high-speed visualization of the temperature field of the multiphase AC arc was conducted at 1x104 fps as typical framerate to observe the dynamic behavior of the multiphase AC arc in millisecond time scale. An optical system including the band-pass filters was combined with the high-speed camera to observe particular line emissions from atomic argon with negligible emissions from thermal plasma. The obtained experimental results indicated that the temperature of the multiphase AC arc was around 1.0x104 K. The arc temperature fluctuated in the range from 0.6x104 to 1.3x104 K. Consequently, the arc temperature in the multiphase AC arc is sufficiently high to treat the refractory metals and/or ceramics powders. Furthermore, the obtained temperature was well-validated by the conventional spectroscopic method with high accuracy..
7. Manabu Tanaka, Taro Hashizume, Koki Saga, Tsugio Matsuura, Takayuki Watanabe, Diode-rectified multiphase AC arc for the improvement of electrode erosion characteristics, Journal Physics D: Applied Physics, 10.1088/1361-6463/aa8cac, 50, 46, 2017.10, An innovative multiphase AC arc (MPA) system was developed on the basis of a diode-rectification technique to improve electrode erosion characteristics. Conventionally, electrode erosion in AC arc is severer than that in DC arc. This originated from the fact that the required properties for the cathode and anode are different, although an AC electrode works as the cathode and the anode periodically. To solve this problem, a separation of AC electrodes into pairs of thoriated tungsten cathode and copper anode by diode-rectification was attempted. A diode-rectified multiphase AC arc (DRMPA) system was then successfully established, resulting in a drastic improvement of the erosion characteristics. The electrode erosion rate in the DRMPA was less than one-third of that in the conventional MPA without the diode rectification. In order to clarify its erosion mechanism, electrode phenomena during discharge were visualized by a high-speed camera system with appropriate band-pass filters. Fluctuation characteristics of the electrode temperature in the DRMPA were revealed..
8. Feng Liang, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Formation of different arc-anode attachment modes and their effect on temperature fluctuation for carbon nanomaterial production in DC arc discharge, Carbon, 10.1016/j.carbon.2017.02.084, 117, 100-111, 2017.06, Diffuse and multiple arc-anode attachment modes were observed when using DC arc discharge to prepare carbon nanomaterials. The effects of arc current and electrode gap distance on the formation of different attachment modes were investigated. The formation of different attachment modes is explained by the competition of the cathode jet and the anode jet. During the arc discharge, the surface temperature of the carbon electrode was measured by two-colour pyrometry combined with a high-speed camera employing appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature fluctuation of the electrode surface was investigated. Due to the unbalanced Lorenz force, the rotation of arc spot was severe in diffuse arc-anode attachment mode, which led to relatively large temperature fluctuations on the anode surface, resulting in low purity of synthesised multi-wall carbon nanotubes on the anode deposit..
9. Taro Hashizume, Manabu Tanaka, Takayuki Watanabe, Effect of arc current on droplet ejection from tungsten-based electrode in multiphase AC arc, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.056101, 56, 5, 2017.05, The dynamic behavior of droplet ejection from a tungsten electrode was successfully visualized using a high-speed camera and an appropriate band-pass filter. The effect of arc current on droplet ejection was investigated to understand the electrode erosion mechanism in the multiphase AC arc. The rate of erosion by droplet ejection increased with increasing current. This result was examined on the basis of the time variation in forces on a pending droplet at the electrode tip during the AC cycle. The relationship among electromagnetic force, surface tension, and ion pressure on the molten tip during the cathodic period is crucial for controling droplet ejection. The molten tip becomes hemispherical forming the pending droplet with an increase in the instantaneous value of arc current during the AC cycle. The pending droplet detaches from the electrode surface when electromagnetic force becomes the dominant force. Consequently, a higher rate of erosion by droplet ejection with a higher arc current resulted from a stronger electromagnetic force..
10. Takayuki Watanabe, T. Hashizume, T. Imatsuji, Manabu Tanaka, High-speed visualization of thermal plasma characteristics, 31st International Congress on High-Speed Imaging and Photonics Selected Papers from the 31st International Congress on High-Speed Imaging and Photonics, 10.1117/12.2269401, 10328, 2017.01, Thermal plasmas are expected to be utilized for a number of industrial applications, such as nanomaterial synthesis and waste treatment. The thermal plasma generation and its characteristics remain to be explored for more attractive processing. In particular, the electrode dynamics are one of the most considerable issues for the practical use of industrial applications, because it determines the electrode lifetime and the performance of materials in thermal plasmas. High-speed imaging provides a powerful tool to reveal the plasma dynamics. High-speed video camera with bandpass filter system was used to measure the electrode temperature as well as the arc fluctuation. Electrode temperature was evaluated from the radiation intensities at 785 nm and 880 nm from the electrode thermal emission. This system can be also applied to observe the dynamic behavior of vapor generation from the electrode on the millisecond time scale. Emissions from tungsten vapor were observed at the wavelength of 393 nm. The tungsten electrode started to evaporate just after the peak top of the arc current in the anodic period. The tungsten vapor became the main species in the anodic arc when the electrode started to evaporate. In contrast, a small amount of tungsten evaporation was observed during the cathodic period. These experimental studies enable us to understand the electrode erosion mechanism of the multiphase AC arc. Fundamental researches for electrode phenomena determining thermal plasma characteristics lead to the development of innovative industrial applications of material processing and waste treatment..
11. Tsuyoshi Matsuo, Manabu Tanaka, Takayuki Watanabe, Analysis of fluctuation phenomena in water plasma, IEEJ Transactions on Power and Energy, 10.1541/ieejpes.136.749, 136, 9, 749-754, 2016.09, A water plasma was generated by DC arc discharge with a hafnium cathode and a cupper anode. Arc fluctuation in water plasma was examined by arc image observation synchronized with voltage measurement. The main parameters that cause arc fluctuation was a feed rate of solution. The dynamic behavior of the arc as a restrike mode has faster fluctuation than the decomposition process in the water plasma. Axial and radial extent of the arc is increased with increasing in the feed rate. Therefore, effective energy of the arc is decreased with increasing in the feed rate. Decomposition rate of the treated material can be improved by controlling the arc fluctuation in the anode nozzle..
12. Hirotaka Sone, Takuya Kageyama, Manabu Tanaka, Daisuke Okamoto, Takayuki Watanabe, Induction Thermal Plasma Synthesis of Lithium Oxide Composite Nanoparticles with A Spinel Structure, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 55, 7S2, 2016.06, Li–Mn composite oxide nanoparticles are synthesized using an induction thermal plasma, and the formation mechanism is investigated on the basis of the homogenous nucleation rate and thermodynamic considerations. Under a high O2 partial pressure, MnO crystals nucleate and Li oxide condenses on MnO nuclei at a relatively high rate, forming LiMn2O4 in a single phase. On the other hand, under a low partial pressure of O2, LiMnO2 is obtained owing to the low condensation rate of Li oxide. This study presents the successful selective synthesis of LiMn2O4 nanoparticles by controlling the partial pressure of O2..
13. Manabu Tanaka, Taro Hashizume, Tomoyuki Imatsuji, Yushi Nawata, Takayuki Watanabe, Investigation of erosion mechanism of tungsten-based electrode in multiphase AC arc by high-speed visualization of electrode phenomena, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 55, 2016.06, Electrode phenomena in a multiphase AC arc were successfully visualized using a high-speed observation system with a bandpass filter system to understand the erosion mechanisms of tungsten-based electrodes due to the droplet ejection and electrode evaporation. The obtained results indicated that both droplet ejection and electrode evaporation contributed to the electrode erosion in the multiphase AC arc. The erosion by droplet ejection mainly occurred during the cathodic period, while electrode evaporation mainly occurred during the anodic period. The rates of erosion by droplet ejection and evaporation were estimated to be 6 and 3 g/min, respectively, when the arc current was 100 A. The results of an evaluation of the possible forces acting on the electrode tip suggested that the electromagnetic force was the dominant force in the cathodic period, resulting in droplet ejection..
14. Manabu Tanaka, Takuya Kageyama, Hirotaka Sone, Shuhei Yoshida, Daisuke Okamoto, Takayuki Watanabe, Synthesis of lithium metal oxide nanoparticles by induction thermal plasmas, Nanomaterials, 10.3390/nano6040060, 6, 4, 2016.04, Lithium metal oxide nanoparticles were synthesized by induction thermal plasma. Four different systems-Li-Mn, Li-Cr, Li-Co, and Li-Ni-were compared to understand formation mechanism of Li-Me oxide nanoparticles in thermal plasma process. Analyses of X-ray diffractometry and electron microscopy showed that Li-Me oxide nanoparticles were successfully synthesized in Li-Mn, Li-Cr, and Li-Co systems. Spinel structured LiMn2O4 with truncated octahedral shape was formed. Layer structured LiCrO2 or LiCoO2 nanoparticles with polyhedral shapes were also synthesized in Li-Cr or Li-Co systems. By contrast, Li-Ni oxide nanoparticles were not synthesized in the Li-Ni system. Nucleation temperatures of each metal in the considered system were evaluated. The relationship between the nucleation temperature and melting and boiling points suggests that the melting points of metal oxides have a strong influence on the formation of lithium metal oxide nanoparticles. A lower melting temperature leads to a longer reaction time, resulting in a higher fraction of the lithium metal oxide nanoparticles in the prepared nanoparticles..
15. Feng Liang, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Investigation of the relationship between arc-anode attachment mode and anode temperature for nickel nanoparticle production by a DC arc discharge, Journal Physics D: Applied Physics, 10.1088/0022-3727/49/12/125201, 49, 12, 2016.02, Multiple and constricted arc-anode attachment modes were observed in helium arc discharge to prepare nickel nanoparticles. The electron overheating instability resulted in the formation of multiple attachment modes. The effects of hydrogen concentration and shield gas flow rate on the characteristics of nickel nanoparticles were investigated. The evaporation rate of anode material contributed to forming different arc-anode attachments. The surface temperature of the electrode was measured during the arc discharge by two-color pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature behavior of the anode surface was investigated by using two synchronized high-speed cameras. The waveform of anode jet area variation with time follows that of the highest temperature variation of anode surface with time. The fluctuation of the highest anode temperature increased when the arc anode attachment changed from multiple into constricted mode. The highest temperature fluctuation and stability of the arc contributed to nanoparticle size distribution. Nickel nanoparticles with large productivity and narrow size distribution were obtained when shield gas was employed by controlling the residence time of nanoparticle growth. The formation mechanism of different arc-anode attachment modes was explained..
16. Taro Hashizume, Manabu Tanaka, Takayuki Watanabe, Investigation of Droplet Ejection Mechanism from Electrode in Multi-Phase AC Arc, Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society, 33, 2, 44s-48s, 2016.01.
17. Yaping Liu, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Investigation of In-Flight Glass Melting by Controlling the High-Temperature Region of Multiphase AC Arc Plasma, International Journal of Applied Glass Science, 10.1111/ijag.12081, 5, 4, 443-451, 2014.12, A large volume discharge produced by a stable 12-phase alternating current (AC) arc plasma is preferable to melt the granulated glass materials for time and energy saving. The discharge behavior and the high-temperature region of the plasma system can be controlled by the electrode configurations. In this study, the spatial characteristics of the arc discharge were examined by image analysis with a high-speed camera. The melting characteristics of alkali-free glass particles were investigated by microscope and X-ray diffractometry. This is the first time to investigate the relationship between spatial characteristics of plasma and glass particle property. Results show the arc existence area is strongly related to the electrode configuration. Distributions of in-flight powders and the spatial characteristics of arc are important factors when using multiphase AC arc for in-flight melting. This study provides information of efficient particle treatment according to the electrode configuration..
18. F. Liang, Manabu Tanaka, S. Choi, Takayuki Watanabe, Effect of arc behaviour on the temperature fluctuation of carbon electrode in DC arc discharge, Journal of Physics: Conference Series, 10.1088/1742-6596/518/1/012027, 518, 1, 2014.06, Diffuse and multiple arc-anode attachment modes were observed in a DC arc discharge with a carbon electrode. During the arc discharge, the surface temperature of the electrode was successfully measured by two-colour pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature fluctuation of electrode surface was investigated. The diffuse arc-anode attachment mode leads to relatively large temperature fluctuation on anode surface due to the rotation of the arc spot. In the case of diffuse mode, the purity of synthesized multi-wall carbon nanotube was deteriorated with temperature fluctuation..
19. Y. Cheng, Manabu Tanaka, Takayuki Watanabe, S. Y. Choi, M. S. Shin, K. H. Lee, Synthesis of Ni2B nanoparticles by RF thermal plasma for fuel cell catalyst, Journal of Physics: Conference Series, 10.1088/1742-6596/518/1/012026, 518, 1, 2014.06, The catalyst of Ni2B nanoparticles was successfully prepared using nickel and boron as precursors with the quenching gas in radio frequency thermal plasmas. The generating of Ni2B needs adequate reaction temperature and boron content in precursors. The quenching gas is beneficial for the synthesis of Ni2B in RF thermal plasma. The effect of quenching rate, powder feed rate and boron content in feeding powders on the synthesis of nickel boride nanoparticles was studied in this research. The high mass fraction of 28 % of Ni2B nanoparticles can be generated at the fixed initial composition of Ni:B 2:3. Quenching gas is necessary in the synthesis of Ni2B nanoaprticles. In addition, the mass fraction of Ni2B increases with the increase of quenching gas flow rate and powder feed rate..
20. Manabu Tanaka, J. Noda, Takayuki Watanabe, J. Matsuno, A. Tsuchiyama, Formation mechanism of metal embedded amorphous silicate nanoparticles by induction thermal plasmas, Journal of Physics: Conference Series, 10.1088/1742-6596/518/1/012025, 518, 1, 2014.01, The purpose of this paper was to synthesize metal embedded amorphous silicate nanoparticles by induction thermal plasmas. Powder of Fe, Ni, Sn, and Zn were used as precursor as well as SiO2 and MgO. In the case of Fe, Ni, and Sn, metal embedded nanoparticles were successfully synthesized. While most of Zn nanoparticles were attached on the surface of the amorphous silicate nanoparticles. Internal rate of each metal in the synthesized nanoparticles and nucleation temperature were evaluated to understand the formation mechanism of the metal embedded amorphous silicate nanoparticles. Results indicated that the relationship between the nucleation temperature of silicon and the melting temperature of each metal has important role on the metal embedded nanoparticles formation..
21. Feng Liang, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Investigation of carbon nanomaterials growth on anode surface by Arc discharge method, Journal of Chemical Engineering of Japan, 10.1252/jcej.13we174, 47, 3, 296-300, 2014.01, Multi-wall carbon nanotube (MWNT), highly textured pyrolytic graphite, necklace-like carbon, and spherical carbon particle were prepared by arc discharge method under atmospheric pressure. These carbon nanomaterials were characterized by field emission scanning electron microscope (FE-SEM), transition electron microscopy (TEM), and Raman spectroscopy. Two-color pyrometry was conducted to measure the temperature of anode surface by high-speed camera. The deposition temperature of MWNT is in the range of 2,400-2,700 K, which indicates that a suitable quenching effect is a necessary condition for the formation of MWNT on the anode surface. The growth mechanism of carbon nanomaterials on the anode surface was estimated, quenching effect playing an important role in the formation of these carbon nanomaterials..
22. Takayuki Watanabe, Yaping Liu, Manabu Tanaka, Investigation of electrode phenomena in an innovative thermal plasma process for glass melting, Plasma Chemistry and Plasma Processing, 10.1007/s11090-014-9530-8, 34, 3, 443-456, 2014.01, A multi-phase alternating current (AC) arc has been applied to glass melting technology. The large volume discharge produced by a stable multi-phase AC arc is preferable to melt the granulated glass materials. The discharge behavior and the high-temperature region of the plasma can be controlled by the electrode configurations. In this study, the spatial characteristics of the arc discharge were examined by image analysis of high-speed camera. Results show arc existence area is related with electrode configuration. This study provides the useful information of efficient particle treatment in the preferred electrode configuration. However, the electrode erosion is one of the most considerable issues to be solved. The combination of high-speed video camera and band-pass filters was introduced to measure the electrode temperature to investigate the erosion mechanism of the multi-phase AC arc. The dynamic behavior of the electrode vapors in the arc was investigated by using the same high-speed camera system. Results show the tungsten electrode mainly evaporates at the anodic period during AC cycle..
23. Feng Liang, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Measurement of anode surface temperature in carbon nanomaterial production by arc discharge method, Materials Research Bulletin, 10.1016/j.materresbull.2014.08.029, 60, 158-165, 2014.01, Nano-graphite particles, multi-wall carbon nanotube (MWNT), and pyrolytic graphite were prepared at different positions of the anode surface in an arc discharge. Graphite electrodes were employed for the arc discharge under helium environment at atmospheric pressure. Nano-sized carbon products were characterized by scanning electron microscopy and transmission electron microscopy. During the arc discharge, two-color pyrometry combined with a high-speed camera was conducted to measure the temperature distribution of the anode surface. The growth temperature of pyrolytic graphite, MWNT, and nano-graphite particles were in the ranges of 2400-2600 K, 2600-2700 K, and 2700-3500 K, respectively. The local temperature of anode surface is a critical parameter to determine the products with different morphologies. The formation mechanism of these carbon nanomaterials is suggested based on the local temperature of anode surface and their thermodynamic stability..
24. Yaping Liu, Manabu Tanaka, Tomoki Ikeba, Sooseok Choi, Takayuki Watanabe, Fluctuation measurement of multi-phase AC arc and in-flight particle temperature, Journal of Chemical Engineering of Japan, 10.1252/jcej.13we098, 46, 10, 672-676, 2013.10, A stable 12-phase alternating current (AC) arc has been successfully applied to melt granulated glass materials. The discharge behavior and the high temperature region of the plasma system can be controlled by the electrode configurations. In this study, the temporal characteristics of the arc discharge were examined by image analysis with a high-speed camera. The instabilities of particle surface temperature were investigated by a high-speed camera equipped with a band-pass filter system. This is the first time that particle temperature measurement of millisecond order has been performed by high-speed camera. Results show the amplitude of the variation in the in-flight particle temperature depends on the amplitude of the arc fluctuation. The periodicity of arc fluctuation is strongly related with transition of discharge pattern..
25. Manabu Tanaka, Yaping Liu, Sooseok Choi, Takayuki Watanabe, High-speed visualization of electrode erosion in multi-phase alternating current arc, Journal of Fluid Science and Technology, 8, 160-171, 2013.09.
26. Takayuki Watanabe, Manabu Tanaka, Tasuku Shimizu, Feng Liang, Metal nanoparticle production by anode jet of argon-hydrogen DC arc, 2012 International Conference on Manufacturing Engineering and Technology for Manufacturing Growth, METMG 2012 Manufacturing Engineering and Technology for Manufacturing Growth, 10.4028/www.scientific.net/AMR.628.11, 11-14, 2013.02, The purpose of this paper is to prepare nickel particles by arc plasma method with hydrogen addition. The effect of anode jet formation on the nanoparticle production was investigated by high-speed camera observations. The high-speed camera system with appropriate band-pass filters successfully provides the observation of anode jet image without cathode jet image. The areas of the anode jet and the cathode jet were separately estimated from the high-speed images. From these observations, the periodical fluctuation of the anode jet was confirmed. Higher hydrogen concentration leads to larger anode jet area, resulting from the enhanced evaporation of the anode material..
27. Manabu Tanaka, Takayuki Watanabe, Mechanism of enhanced vaporization from molten metal surface by argon-hydrogen Arc plasma, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.52.076201, 52, 7 PART 1, 2013.01, A DC arc with hydrogen addition is one of the promising routes to prepare nanoparticles with high productivity. The purpose of this study is to investigate the mechanism of vaporization enhancement of a particular metal from a molten metal mixture by the DC arc method with hydrogen addition. The selective enhanced vaporization of Sn from a Sn-Ag molten mixture by an Ar-H2 arc was confirmed. Spectroscopic measurements were conducted to investigate the vaporization mechanism on the anode boundary region. The obtained results indicated that Sn was mainly vaporized as SnH from the molten Sn-Ag mixture, which decomposed to H and Sn vapor soon after SnH was vaporized. The mechanism of the vaporization enhancement of particular metal from a molten metal mixture by an Ar-H2 arc is mainly attributed to the formation of the metal hydride..
28. Feng Liang, Tasuku Shimizu, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Preparation of polyhedral graphite particles by arc discharge under atmospheric pressure, Japanese Journal of Applied Physics, 10.7567/JJAP.52.01AK01, 52, 1 PART2, 2013.01, Polyhedral graphite particles (PGPs) were synthesized by arc discharge method under atmospheric pressure in the relatively short electrode gap distance of 1 mm, while graphene flakes and turbostratic graphite were found by increasing the electrode gap distance. The selective synthesis of nano-sized carbon allotropes was controlled by the contribution of carbon ions and carbon radicals with the change of the electrode gap distance. The formation mechanism of PGPs and other carbon allotropes were proposed according to the experimental results. The low concentration of carbon ions to carbon radicals contributes to the formation of PGPs. In contrast, relatively high concentration of carbon ions to carbon radicals contributes to the formation of graphene flakes and turbostratic graphite..
29. Manabu Tanaka, T. Ikeba, Y. Liu, S. Choi, Takayuki Watanabe, Investigation of electrode erosion mechanism of multi-phase AC arc by high-speed video camera, Journal of Physics: Conference Series, 10.1088/1742-6596/441/1/012015, 441, 1, 2013.01, A multi-phase AC arc has been applied to the glass melting technology. However, the electrode erosion is one of the most considerable issues to be solved. In order to investigate the erosion mechanism of the multi-phase AC arc, the combination of the high-speed video camera and the band-pass filters was introduced to measure the electrode temperature. Results indicated the tip temperature of the electrode surface in the 12-phase arc was lower than that in the 2-phase arc, while erosion rate in 12-phase arc was higher than that in the 2-phase arc. Furthermore, the dynamic behaviour of the vapours in the arc was investigated by using the same high-speed camera system. The tungsten electrode mainly evaporates at the anodic period during AC cycle. The oxygen concentration in the arc increases with larger number of the phases, resulting in the higher erosion rate in the 12-phase arc..
30. Manabu Tanaka, Yaping Liu, Yosuke Tsuruoka, Takayuki Watanabe, Experimental investigation of in-flight melting by hybrid heating of multi-phase alternating current arc with oxygen burner for alkali-free glass raw materials, Thin Solid Films, 10.1016/j.tsf.2012.07.064, 523, 67-71, 2012.11, An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of multi-phase AC arc combined with an oxygen burner. A multi-phase AC arc and hybrid plasma were compared to study the in-flight melting efficiency of the granulated raw materials. The effects of the input energy and the primary size of SiO 2 in the glass raw materials on the characteristics of the in-flight melted particles were investigated. The reaction rate inside the individual in-flight particles was enhanced with decreasing the primary size of SiO 2 particles, resulting in the more effective in-flight melting by the hybrid plasma..
31. Feng Liang, Tasuku Shimizu, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, Selective preparation of polyhedral graphite particles and multi-wall carbon nanotubes by a transferred arc under atmospheric pressure, Diamond and Related Materials, 10.1016/j.diamond.2012.09.004, 30, 70-76, 2012.11, High-purity polyhedral graphite particles (PGPs) and multi-wall carbon nanotubes (MWNTs) were selectively synthesized by a transferred arc discharge method under atmospheric pressure. PGPs and MWNTs were characterized by the field emission scanning electron microscope (FE-SEM), transition electron microscopy (TEM), and Raman spectroscopy. The products were successfully controlled by varying the arc current and the anode diameter. PGPs were the main products in the case of a relatively high arc current of 100 A or a large anode diameter of 30 mm, while MWNTs were the main products when the arc current was reduced to 80 A or the anode diameter was decreased to 15 and 10 mm. The ratio of carbon ions to carbon radicals near the cathode tip was employed to explain the mechanisms of PGP and MWNT formation. Relatively high ratio of carbon ions to carbon radicals contributed to the formation of PGPs. In contrast, relatively low ratio of carbon ions to carbon radicals led to the formation of MWNTs..
32. Yaping Liu, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, In-flight Particle Measurement of Alkali-Free Glass Raw Materials in 12-Phase AC Arc Plasma, Journal of Thermal Spray Technology, 21, 863-872, 2012.09.
33. Yaping Liu, Manabu Tanaka, Sooseok Choi, Takayuki Watanabe, In-flight particle measurement of alkali-free glass raw materials in 12-phase AC Arc plasma, Journal of Thermal Spray Technology, 10.1007/s11666-012-9758-x, 21, 5, 863-872, 2012.09, In-flight particle measurements of the surface temperature and velocity are important for understanding of melting behavior of glass particles during in-flight melting by multi-phase AC arc plasma. However, the use of optical pyrometry for particle surface temperature has inevitable uncertainties due to non-thermal emissions signals from the plasma plume. This work presents spectroscopic measurements of the non-thermal signals which were found to be caused mainly by the plasma emissions scattered by the particles and the radiation emitted by vapor. After that, the accuracy of thermal radiation measurement was estimated and surface temperature of in-flight glass particle was corrected..
34. Manabu Tanaka, T. Ikeba, Y. Liu, T. Matsuura, Takayuki Watanabe, Electrode temperature measurements of multi-phase AC arc by high-speed video camera, Journal of Physics: Conference Series, 10.1088/1742-6596/406/1/012008, 406, 1, 2012.01, The multi-phase AC arc plasma has been applied in the glass melting technology as a promising heat source. The electrode erosion of the multi-phase arc is one of the most important issues to be solved. In the present work, the theory of the two-colour pyrometry by using the high-speed video camera with band-pass filters was applied to the electrode temperature measurements. First, the spectroscopic measurements of the electrode region in the multi-phase arc were conducted to select the appropriate wavelengths of band-pass filters. Then, the electrode temperatures of 2-phase, 6-phase, and 12-phase arcs were measured. The electrode tip temperature and the molten area were evaluated from the obtained 2-dimensional temperature distributions. Results indicated that the increase of the number of the phases leads to the lower tip temperature and the larger molten area. Observation of the multiple arcs further revealed the particular characteristics of the multi-phase arc, such as the periodical arc motion has important role on the electrode molten state..
35. Y. Liu, Manabu Tanaka, T. Ikeba, S. Choi, Takayuki Watanabe, In-flight particle measurement of glass raw materials in hybrid heating of twelve-phase AC arc with oxygen burner, Journal of Physics: Conference Series, 10.1088/1742-6596/406/1/012022, 406, 1, 2012.01, The high temperature provided by a 12-phase AC arc plasma is beneficial to finish vitrification reaction in milliseconds. Another heating method called "hybrid plasma" combines multi-phase AC arc and oxygen burner are expected to improve glass quality and increase productivity with minimum energy consumption. In this study, recent works on the development of in-flight particle measurement in hybrid plasma system are presented. Two-colour pyrometry offers considerable advantages for measuring particle temperatures in flight. A high-speed camera equipped with a band-pass filter system was applied to measure the in-flight temperatures of glass particles. The intensity recorded by the camera was calibrated using a tungsten halogen lamp. This technique also allows evaluating the fluctuation of the average particle temperature within millisecond in plasma region..
36. Manabu Tanaka, Yosuke Tsuruoka, Yaping Liu, T. Matsuura, Takayuki Watanabe, Investigation of multiphase ac arc behavior by high-speed video observation, IEEE Transactions on Plasma Science, 10.1109/TPS.2011.2149545, 39, 11 PART 1, 2904-2905, 2011.11, A stable multiphase ac arc was generated by transformers at a commercial electric system. The arc discharge behavior is investigated by high-speed video camera observation synchronized with voltage waveform analysis. The multiphase ac arc-generating system enables one to obtain wide high-temperature region, which is expected to be suitable for powder heat treatment such as in-flight glass production..
37. Manabu Tanaka, Y. Tsuruoka, Y. Liu, Takayuki Watanabe, Investigation of in-flight melting behaviour of granulated glass raw material by multi-phase ac arc plasma and hybrid plasma, IOP Conference Series: Materials Science and Engineering, 10.1088/1757-899X/18/11/112010, 18, SYMPOSIUM 8, 2011.11, An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by twelve-phase AC arc and that combined with an oxygen burner. The particle measurement was carried out to investigate the in-flight melting behavior of glass raw materials during the in-flight melting by twelve-phase AC arc. Obtained results show the mean particle velocity was about 9 m s-1 and mean temperature was about 2600 K. The high vitrification degree achieved within several milliseconds reveals that the new in-flight melting technology of hybrid plasma treating can reduce energy consumption and shorten the glass production cycle..
38. Manabu Tanaka, Yosuke Tsuruoka, Yaping Liu, Tsugio Matsuura, Takayuki Watanabe, Stability analysis of multi-phase AC arc discharge for in-flight glass melting, Current Applied Physics, 10.1016/j.cap.2011.05.037, 11, 5 SUPPL., 2011.09, A stable multi-phase AC arc was generated to by transformers at a commercial electric system. The arc discharge behavior and the stability were investigated by the high-speed video camera observation synchronized with the voltage waveform analysis. The effect of the number of phase and the flaming gas addition into the arc region on the arc behavior and the arc stability were studied. Results showed that the re-ignition occurred between adjacent electrodes periodically. Two kinds of the stability analysis methods were introduced. The estimated fluctuation degree showed that an increase of the number of the phase leads to the stable multi-phase AC arc. The deviation of the arc voltage from the average arc voltage was estimated to evaluate the uniformity of the multi-phase AC arc. Although an addition of the oxygen flame into the arc region leads to lower uniformity, the modification of the electrode position can improve the uniformity of the multi-phase AC arc..
39. Yaping Liu, Yosuke Tsuruoka, Manabu Tanaka, Toshio Ichihashi, Tetsuji Yano, Takayuki Watanabe, In-flight melting behavior of different glass raw materials by hybrid heating of twelve-phase ac arc with oxygen burner, Thin Solid Films, 10.1016/j.tsf.2010.11.056, 519, 20, 7005-7008, 2011.08, An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of twelve-phase ac arc combined with an oxygen burner. X-ray diffraction analysis showed that all carbonates in raw materials were decomposed and > 94% SiO2 (quartz) was reacted into a noncrystalline state. The high vitrification degree achieved within several milliseconds reveals that the new in-flight melting technology of hybrid plasma treating can reduce energy consumption and shorten the glass production cycle..
40. Manabu Tanaka, Teisuke Hiyama, Takayuki Watanabe, Control of Size and Composition of Sn Based Nanoparticles Prepared by Ar-H2 Arc, Transactions on Materials Research Society of Japan, 33, 3, 687-690, 2008.09.
41. Manabu Tanaka, Takayuki Watanabe, Vaporization mechanism from Sn-Ag mixture by Ar-H2 Arc for nanoparticle preparation, Thin Solid Films, 10.1016/j.tsf.2007.11.096, 516, 19, 6645-6649, 2008.08, The purpose of this paper was to describe the synthesis of Sn-Ag nanoparticles by an arc plasma method. Sn-Ag nanoparticles have been successfully prepared by DC arc plasma with hydrogen addition. The prepared nanoparticles were characterized by X-Ray diffraction, transmission electron microscopy and inductively coupled plasma-atomic emission spectrometry. The obtained results indicated that the nanoparticles have high-purity and spherical shape. The average diameter of the nanoaprticles with 100%-Ar arc was 19.8 nm and that with 50%-H2 arc was 56.5 nm. Another purpose of this work is to investigate the vaporization behavior from molten Sn-Ag mixture with Ar and Ar-H2 arc. We confirmed the vaporization enhancement of Sn from Sn-Ag mixture by hydrogen in arc plasma..
42. Manabu Tanaka, Takayuki Watanabe, Growth mechanism of Sn-Ag nanoparticles prepared by Ar-H2 arc, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.55.446, 55, 6, 446-451, 2008.06, The purpose of this paper was to investigate the growth mechanism of the Sn-Ag nanoparticles prepared by Ar -H2 arc. The effects of the H 2 concentration in the arc, initial composition of raw materials, and gas flow rate of circulation gas on particle diameter was investigated. Numerical analysis was conducted for the growth process with nucleation and co-condensation. Tin vapor was consumed by nucleation and condensation, followed by the condensation of silver vapor. Tin and silver were well synthesized in a liquid state in the co-condensation process since the particles grow at higher temperature than the melting point of Sn-Ag alloy..