The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Hisanori Shinohara - One of the best experts on this subject based on the ideXlab platform.
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production of fullerenes and single wall carbon nanotubes by high temperature pulsed Arc Discharge
Journal of Chemical Physics, 2000Co-Authors: Toshiki Sugai, Hideki Omote, Nobuo Tanaka, Hisanori ShinoharaAbstract:Fullerenes and single-wall carbon nanotubes (SWNTs) have been produced for the first time by the high-temperature pulsed Arc-Discharge technique, which has developed in this laboratory. Fullerenes are identified quantitatively by high-performance liquid chromatography (HPLC), and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal a significant amount of production of bundles of SWNTs in soot. The pulse Arc production of fullerenes and SWNTs favors the high-temperature (⩾1000 °C), long pulses (⩾1 ms) and a heavy rare gas such as Ar or Kr as a buffer gas. We have found that fullerenes and SWNTs have complementary relationships in their early stage of production. The details of the pulsed Arc Discharge have been obtained by observing the transition from the pulsed Arc Discharge to the steady Arc Discharge while increasing the pulse width.
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Production of fullerenes by high-temperature pulsed Arc Discharge
European Physical Journal D, 1999Co-Authors: Toshiki Sugai, Hideki Omote, Hisanori ShinoharaAbstract:We have developed a high-temperature pulsed Arc Discharge apparatus, which can operate in a buffer gas heated up to 1000 °C, and have succeeded in producing fullerenes for the first time with this method. We have quantitatively analyzed the products, using high-performance liquid chromatography (HPLC), to estimate the concentration of fullerenes in soot. The results show that fullerenes are produced not at room temperature but at much higher temperatures such as 1000 °C for Ar. The concentration of fullerenes C70 and higher increases as the pulse width of the Discharge increases. In the pulsed Arc Discharge, the negative electrode is consumed by the sputtering of buffer gas ions.
Toshiki Sugai - One of the best experts on this subject based on the ideXlab platform.
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production of fullerenes and single wall carbon nanotubes by high temperature pulsed Arc Discharge
Journal of Chemical Physics, 2000Co-Authors: Toshiki Sugai, Hideki Omote, Nobuo Tanaka, Hisanori ShinoharaAbstract:Fullerenes and single-wall carbon nanotubes (SWNTs) have been produced for the first time by the high-temperature pulsed Arc-Discharge technique, which has developed in this laboratory. Fullerenes are identified quantitatively by high-performance liquid chromatography (HPLC), and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal a significant amount of production of bundles of SWNTs in soot. The pulse Arc production of fullerenes and SWNTs favors the high-temperature (⩾1000 °C), long pulses (⩾1 ms) and a heavy rare gas such as Ar or Kr as a buffer gas. We have found that fullerenes and SWNTs have complementary relationships in their early stage of production. The details of the pulsed Arc Discharge have been obtained by observing the transition from the pulsed Arc Discharge to the steady Arc Discharge while increasing the pulse width.
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Production of fullerenes by high-temperature pulsed Arc Discharge
European Physical Journal D, 1999Co-Authors: Toshiki Sugai, Hideki Omote, Hisanori ShinoharaAbstract:We have developed a high-temperature pulsed Arc Discharge apparatus, which can operate in a buffer gas heated up to 1000 °C, and have succeeded in producing fullerenes for the first time with this method. We have quantitatively analyzed the products, using high-performance liquid chromatography (HPLC), to estimate the concentration of fullerenes in soot. The results show that fullerenes are produced not at room temperature but at much higher temperatures such as 1000 °C for Ar. The concentration of fullerenes C70 and higher increases as the pulse width of the Discharge increases. In the pulsed Arc Discharge, the negative electrode is consumed by the sputtering of buffer gas ions.
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Preferential Arc-Discharge production of higher fullerenes
Chemical Physics Letters, 1995Co-Authors: Takumi Kimura, Toshiki Sugai, H. Shinohara, Goto Takashi, Kazuyuki Tohji, Isao MatsuokaAbstract:Abstract A new method for efficiently generating higher fullerenes is reported. By utilizing the Arc-Discharge of boron-doped graphite (bulk boronized graphite) electrodes, we have found that the yield of higher fullerenes (C 76 C 96 ) in toluene extracts becomes 35–40 wt% with an optimum boron doping, which is more than twice as large as that obtained in the conventional Arc-Discharge of 100% graphite rods. A typical absolute yield of the higher fullerenes in soot is 5–6 wt%. The results suggest that some boron-carbon binary clusters play an important role in an early stage of the formation of higher fullerenes.
Fei Xing - One of the best experts on this subject based on the ideXlab platform.
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Properties of surface Arc Discharge in a supersonic airflow
Plasma Sources Science and Technology, 2010Co-Authors: Jian Wang, Cheng Wang, Shengli Hou, Fei XingAbstract:An experimental study of a direct-current, surface Arc Discharge in a Mach 2 cold supersonic airflow is presented. The surface Arc Discharge is generated with cylindrical tungsten electrodes flush-mounted on a boron-nitride ceramic plate embedded in the lower wall of the supersonic test section. In the presence of airflow, gas breakdown voltage increases from 1.5 kV in stationary air to 2 kV due to particle number density augmentation in the flow. The surface Arc Discharge transforms from a continuous mode in stationary air to a pulsed-repetitive mode in the flow. The mean time interval between Discharge pulses is about 4.3 ms. For a single pulse, Arc Discharge occupies only about 60 µs. The Discharge photos taken by a high-speed CCD camera (framing rate 1125 Hz) validate this pulsed-repetitive process and indicate that the plasma channel of the surface Arc Discharge is blown downstream by the supersonic flow. As the length of the plasma channel increases, the Discharge voltage also increases. When the channel length reaches a critical value (~25 mm), the dc power supply (3 kV–4 kW) cannot sustain the Discharge voltage (~3 kV) and the Joule heating energy cannot balance the dissipation of constrained convection, and hence the Discharge quenches immediately. Current and voltage measurements demonstrate that the Discharge process in a single pulse can be separated into three distinct phases: strong-pulsed breakdown process, steady Discharge process and Discharge attenuation process. Finally, the underlying mechanism of the dynamic process of surface Arc Discharge in supersonic flow is discussed. This paper provides more insights into the mechanism of supersonic flow control (in particular, shock waves) by a surface Arc Discharge.
Andreas Markwitz - One of the best experts on this subject based on the ideXlab platform.
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Transition metal doped metal oxide nanostructures synthesized by Arc Discharge method
2013 International Conference on Manipulation Manufacturing and Measurement on the Nanoscale, 2013Co-Authors: F Fang, J. Futter, Andreas Markwitz, John Kennedy, Elayaperumal ManikandanAbstract:Doping metal oxides with metallic impurities has been the subject of previous studies for enhanced sensing performance. In this paper, we present a review on syntheses of transition metal doped metal oxide nanostructures using Arc Discharge method. Tungsten oxide was doped with Palladium, Scandium and Vanadium, respectively. Nickel was chosen to dope Zinc oxide by Arc Discharge method. It is demonstrated that dopants not only change the morphology of metal oxide nanostructures but also help to achieve an improved electrical conductivity. Because it is easy to tailor the morphology by adjusting the Arc Discharge parameters and dopant can be prescribed in the preparation of the anode material, the Arc Discharge is considered to be a fast and inexpensive synthesis method for doping which can be used to produce high quality doped metal oxide nanostructures for chemical sensing measurements.
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morphology and characterization of tio2 nanoparticles synthesized by Arc Discharge
Chemical Physics Letters, 2012Co-Authors: F Fang, J. Futter, J Kennedy, E Manikandan, Andreas MarkwitzAbstract:Abstract High quality titanium dioxide (TiO 2 ) nanoparticles have been successfully synthesized by Arc Discharge method. A mixture of anatase and rutile phase of TiO 2 crystal nanostructure with spherical shape was produced with an average diameter of 50 nm (range 10–100 nm). Integrated crystal form and high crystallinity were discovered. Besides a dominate UV emission at 409 nm originating from the radiative annihilation of excitation, a weak peak at 658 nm from the oxygen vacancies related emission is also detected. Due to its simplicity of synthesis, the proposed Arc Discharge is a promising technique for the fabrication of TiO 2 nanoparticles.
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Sensors based on metal oxide nanostructures synthesized by Arc Discharge
2011 Fifth International Conference on Sensing Technology, 2011Co-Authors: F Fang, J. Futter, John Kennedy, Andreas MarkwitzAbstract:Different synthetic methods have been developed to fabricate metal oxide nanostructures, but most of them require exotic reagents or are unsuitable for mass production. Till now, we've successfully synthesized zinc oxide (ZnO), tungsten oxide (WO 3 ) and titanium dioxide (TiO 2 ) nanostructures by Arc Discharge and the ability to tune the morphology of those nanostructures makes this method idea for fabrication of chemical sensing materials. In this paper, we present a review on metal oxide nanostructures synthesized by Arc Discharge demonstrating that Arc Discharge is a fast and inexpensive synthesis method which can be used to produce high quality metal oxide nanostructures for chemical sensing measurements. UV and gas sensing properties of ZnO nanostructures have been demonstrated as an example.
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Modulation of Field Emission Properties of ZnO Nanorods During Arc Discharge
Journal of Nanoscience and Nanotechnology, 2010Co-Authors: F Fang, J. Futter, P. Murmu, Donald A. Carder, J Kennedy, Andreas MarkwitzAbstract:Zinc oxide (ZnO) nanorods have been synthesized via the Arc Discharge method. Different oxygen partial pressures were applied in the Arc Discharge chamber to modulate the field emission properties of the as-synthesized ZnO nanorods. Scanning electron microscopy (SEM) was carried out to analyze the morphology of the ZnO nanorods. The ion beam analysis technique of proton induced X-ray emission (PIXE) was performed to probe the impurities in ZnO nanorods. SEM images clearly revealed the formation of randomly oriented ZnO nanorods with diameters between 10-50 nm. It was found that the morphology and the electrical properties of the ZnO nanorods were dependent on the oxygen partial pressure during Arc Discharge. In addition enhanced UV-sensitive photoconductivity was found for ZnO nanorods synthesized at high oxygen partial pressure during Arc Discharge. The field emission properties of the nanorods were studied. The turn-on field, which is defined at a current density of 10 microA cm(-2), was about 3 V microm(-1) for ZnO nanorods synthesized at 99% oxygen partial pressure during Arc Discharge. The turn-on field for ZnO nanorods increased with the decrease of oxygen partial pressure during Arc Discharge. The simplicity of the synthesis route coupled with the modulation of field emission properties due to the Arc Discharge method make the ZnO nanorods a promising candidate for a low cost and compact cold cathode material.
Michael Keidar - One of the best experts on this subject based on the ideXlab platform.
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Anodic Arc Discharge: Why pulsed?
Physics of Plasmas, 2020Co-Authors: Carles Corbella, Sabine Portal, Madhusudhan Kundrapu, Michael KeidarAbstract:Pulsed anodic Arc Discharge is a novel synthesis method of nanomaterials by means of low-temperature atmospheric plasma. The technique consists in periodically supplying DC power to two vertically aligned electrodes in the form of short unipolar pulses with peak currents of a few hundred Amperes in a helium atmosphere. The pulsed Arc plasmas are sustained at frequencies on the order of 1 Hz with around 10% of duty cycle. It constitutes a versatile technique thanks to a series of advantages compared to continuous DC Arc processes, in particular, flexibility in the experimental conditions, process stability and repeatability, better utilization of ablating anode material, lower production of macroparticles, and lower thermal loads. Such features are discussed in this article. A brief overview concerning the recent accomplishments of pulsed Arc Discharge on deposition of carbon nanostructures (graphene and carbon nanotubes) and few-layer flakes of molybdenum disulphide and an outlook on future applications of this method for the discovery of new materials with tailored functional properties are provided.
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Pulsed anodic Arc Discharge for the synthesis of carbon nanomaterials
Plasma Sources Science and Technology, 2019Co-Authors: Carles Corbella, Sabine Portal, Madhusudhan Kundrapu, Denis B. Zolotukhin, Luis Martinez, Li Lin, Michael KeidarAbstract:Pulsed Arc Discharges can improve Arc control and tailor the ablation process in the production of 1D and 2D nanostructures from carbon anodes. In this work, low-dimensional carbon nanoparticles have been generated by means of anodic Arc Discharge in helium atmosphere excited with a square-wave modulated signal (1–5 Hz, 10% duty cycle). The Discharges were performed between two graphite electrodes with maximal peak current of 250 A and maximal voltage of 65 V. The erosion rates and conversion efficiency of the ablated anode are compared to reference samples grown in DC steady Arc mode. Ablation rates in pulsed Arcs are typically of the order of 1 mg s−1. Combination of fast Langmuir probe diagnostics and optical emission spectroscopy provided plasma parameters of the Discharges at the Arc column. Ranges of 1016–1017 m−3 for electron density and 0.5–2.0 eV for electron temperature are estimated. The obtained samples were characterized with Raman spectroscopy and scanning electron microscopy. The deposit on the cathode after pulsed Arc consisted of carbon nanostructures such as graphene nano-platelets and carbon nanotubes. Erosion dynamics of pulsed Arc Discharge has been described in terms of a global model and compared to steady Arc Discharge. A correlation is identified among Discharge regimes, optical emission patterns and ablation modes. In conclusion, pulsed anodic Arc Discharge is a very efficient source of carbon nanomaterials. The large control of the Discharge characteristics will permit to tailor accurately the production and the properties of carbon nanotubes and graphene. This deposition method is promising for the fabrication of semiconducting nanomaterials with tuneable electrical and optical properties.