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舩津, 賢人 ; 伊藤, 一磨 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />In order to investigate the effectiveness as a heat shield of SiC-based and carbon-based materials, the ablation experiments were performed in micro-air plasma-jet at an atmospheric
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pressure. Test materials are SiC/SiC, SiC, C/C, and C. These materials were inserted into the plasma-jets and ablation properties were measured, that is weight loss rate and the heat of ablation. In order to investigate the physical behaviors of the materials in the plasma-jets, the ablating C/C and C were observed by a high-speed video camera. In addition, the surface of the ablated materials was observed with a scanning electron microscope and was analyzed quantitatively with an electron probe microanalyzer. It was found that SiC-based materials might be effective as an ablation material because of its small weight loss. The heats of ablation of C/C and C were almost the same. The surface observation and quantitative analyses showed that the ablated surfaces of SiC-based materials were covered with silicon oxides.
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| 2.
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舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets were performed at an atmospheric pressure in the wavelength region of 280 to 420nm where N^+_21- and N_22+ bands were
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predominant. The spectra were measured at many radial and axial points to obtain its radiative characteristics in detail. Abel inversion method was applied to all the experimental data measured laterally to obtain true spectral intensity distribution at all radial points. The comparison of the experimental and Abel-inverted spectra showed that the experimental data could not be used directly to deduce temperatures without the Abel inversion except around the flow axis. Temperatures of the plasma jets were estimated by applying the spectral matching method to N^+_21- bands. Rotational temperature for N^+_21- bands was about 8000K, and was almost independent of radial positions. Vibrational temperature was about 28000K in the core region with much higher in the outermost region.
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| 3.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets were performed at an atmospheric pressure in the wavelength region of 280 to 420nm where N^+_21- and N_22+ bands were
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predominant. The spectra were measured at many radial and axial points to obtain its radiative characteristics in detail. Abel inversion method was applied to all the experimental data measured laterally to obtain true spectral intensity distribution at all radial points. The comparison of the experimental and Abel-inverted spectra showed that the experimental data could not be used directly to deduce temperatures without the Abel inversion except around the flow axis. Temperatures of the plasma jets were estimated by applying the spectral matching method to N^+_21- bands. Rotational temperature for N^+_21- bands was about 8000K, and was almost independent of radial positions. Vibrational temperature was about 28000K in the core region with much higher in the outermost region.
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Igarashi, Akira ; Hayashi, Hiroshi ; Yamanobe, Takeshi ; Komoto, Tadashi
概要:
application/pdf<br />Journal Article<br />In order to investigate the structure and morphology of diamond-like carbon (DLC) film coated on a polymer alloy prepared by a particular four-steps method in the plasma-based ion implantation
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and deposition (PBIID) process, studies were made on the structure and properties of the DLC film with special reference to its surface morphology by scanning (SEM) and transmission (TEM) electron microscopies. It is revealed from TEM microscopy that the amorphous structure of the DLC film consists of a silicon-implanted layer on the polymer substrate, a hard acetylene-implanted layer and a flexible acetylene/toluene-deposited layer. Some properties of the DLC film can be accounted for by the morphology examined in this study.
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| 5.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets generated at low pressures were performed at several points on flow axis, using a spectrometer in the wavelength region of 200 to 900
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nm. The N_22+ bands and N_2^+1- bands were predominant in the region of 280 to 480nm, and atomic lines of N and O in the visible and infrared regions. Temperatures of the plasma-jets were estimated by applying a spectral matching method to N_2^+1- bands along a flow axis for low-pressure conditions. Rotational temperatures for N_2^+1- bands were 6000 to 7000K, and vibrational temperatures 25000 to 28000K, almost independent of pressures and axial positions. It was found that the rotational temperatures measured had great difference from the gas temperature based upon an empirical formula for supersonic free jets, and also the vibrational temperatures were much higher than those expected.
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| 6.
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澁澤, 健二 ; 舩津, 賢人 ; 白井, 紘行 ; 久保田, 聖
概要:
application/pdf<br />Journal Article<br />The characteristic intensity distribution in the N_2 second positive bands obs
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erved in high-temperature air plasmas generated by a micro-air plasma-jet generator was reconstructed by the theoretical spectra with predissociation and non-Boltzmann rotational population distribution. In order to construct the precise theoretical spectra, collisional transition rate coefficient that was applicable at high temperatures was proposed based upon a simple collision theory. In addition, the effect of the radiative transition from C ^3Π_u to B ^3Π_g state was included in the master equation. The theoretical spectra with non-Boltzmann rotational population distribution calculated with such factors agreed very well with the experimental ones.
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| 7.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 田部井, 勝稲
概要:
application/pdf<br />Journal Article<br />A micro-air plasma-jet, whose size was 3.0mm in length and about 0.7mm in diameter, was measured spectroscopically in the wavelength region of 200 to 900nm using a spectrometer. The N_2 2+ and N^+_2
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1- bands were predominant in the region of 280 to 500nm and intense atomic lines of N and O in the infrared region. Temperatures of the plasma-jet were determined by applying a spectral matching method to those band spectra. There was a very good agreement between the theoretical and experimental spectra in the main part of the measured wavelength region. It was found that the rotational temperature was 7,000 to 9.000K depending on the band, vibrational temperature about 28,000K for both the bands, and the jet was remarkably in thermal non-equilib-rium state.
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| 8.
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澁澤, 健二 ; 舩津, 賢人 ; 白井, 紘行 ; 久保田, 聖
概要:
application/pdf<br />Journal Article<br />The N_2 second positive bands observed in high-temperature air plasmas are con
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sidered to be useful to determine internal states of high-temperature plasmas. In the experiments with a microair plasma-jet, the N_2 second positive bands with higher vibrational levels (v'≧2) were found to show a characteristic intensity distribution. The intensity distribution could not be explained by a usual equilibrium radiation theory. In order to investigate the phenomenon, theoretical spectra were calculated by taking account of two effects, that is, predissociation of N_2 C 3^II_u state through C' 3^II-u state and non-Boltzmann rotational population distribution. This calculated spectra with such effects agreed very well with the experiments.
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| 9.
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FUNATSU, Masato ; SHIRAI, Hiroyuki ; KASUYA, Koichi
概要:
application/pdf<br />Journal Article<br />The equilibrium composition and spectral absorption coefficient of SiC ablation layer plasmas have been calculated for temperature of 5000 to 7000 K, layer thickness of 0 to 7.5mm, and
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pressure of 0.1 to 1.0MPa. The radiations included were molecular bands, atomic lines, and continuum processes. The absorption coefficient thus calculated was applied to a simplified shock layer model for the Jupiter entry probe to investigate the effectiveness of the ablation layer in reducing the radiative heating from a shock layer to a body surface. It was found that the SiC ablation layer is very effective to protect the body from radiative heating and that the photoionization processes of atomic carbon and silicon were mainly responsible for radiative absorption at high photon energy range. Furthermore the molecular carbon bands were effectively absorptive in relatively low photon energy range, particularly at low temperatures.
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| 10.
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舩津, 賢人 ; 糟谷, 紘一 ; 白井, 紘行
概要:
application/pdf<br />Journal Article<br />The equilibrium composition and spectral absorption coefficient of SiC ablation layer plasmas have been calculated for temperature of 5000 to 7000 K, layer thickness of 0 to 7.5mm, and
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pressure of 0.1 to 1.0 MPa. The radiations included were molecular bands, atomic lines, and continuum processes. The absorption coefficient thus calculated was applied to a simplified model of the ablation layer for Jupiter entry probe. It was found that the molecular carbon bands were very effective in reducing the high-temperature radiative flux from a stagnation shock layer at low ablation-layer temperature, and the photoionization process in atomic elements (carbon, silicon) at high ablation-layer temperature.
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