日本金属学会誌
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
63 巻, 1 号
選択された号の論文の21件中1~21を表示しています
  • 吉田 豊信
    1999 年 63 巻 1 号 p. 1
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
  • 作田 忠裕, 田中 康規, 香月 真, 石垣 隆正
    1999 年 63 巻 1 号 p. 2-8
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    We have newly designed a thermal plasma system which can be operated with a pulse modulated mode for the control of plasma power in the time domain and for creating non-equilibrium effects such as fast heating or quenching of the plasma to produce new functional materials at a high rate. The system consists of a solid state power supply with a maximum peak power of 30 kW (20 kW continuous), an induction plasma torch with a 13-turns coil of 55 mm diameter and 85 mm length and a vacuum chamber. The pulse modulated plasma was successfully produced at a plasma power of 11 kW and a pressure from 27 kPa to 101 kPa (from 200 to 760 Torr). The on and off time were each 5 ms, which corresponds to a duty factor of 50%. Measurements were carried out on the time variation of the spectral lines emitted from the ArI species. The dynamic behavior of the plasma temperature in an on-off cycle was estimated by the Boltzman plot method as an average value for eight emission lines. The excitation temperature of the ArI atom changed periodically from 5000 K to 14000 K during the cycle at 27 kPa. The magnitude of this temperature change was weakened at higher pressure of 101 kPa. The minimum duty factor to sustain the pulse modulated thermal plasma was found to be 30%, which corresponds to the pulse off time of 10 to 12 ms.
  • 牛尾 誠夫, 田中 学
    1999 年 63 巻 1 号 p. 9-14
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    In order to make clear the deviations of the plasma state from LTE (Local Thermodynamic Equilibrium)in the arc column of an argon gas-tungsten-arc plasma at the atmospheric pressure, axial profiles of heavy particle temperature, electron temperature and electron number density were measured by using of line-profile analysis of the laser scattering method which yielded each temperature and the density without the assumption of LTE. The experimental results showed that the arc column which was in the center of the arc significantly deviated from LTE state under both conditions of the arc current of 50 A and 150 A. As a result, it is suggested that the deviations from LTE in the arc column should be affected strongly by the mass flow of cold gas induced by the arc constriction at the cathode, namely, cathode jet.
  • 岩尾 徹, 石田 貴之, 林 龍也, 平野 貴裕, 遠藤 正雄, 稲葉 次紀
    1999 年 63 巻 1 号 p. 15-20
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Calculation of the radiation power emitted from Ar long plasmas produced by a torch has been carried out.
    At first, the radial and axial temperature distributions in appearance plasmas have been calculated by using the measured electric field strength and photo-radius. Then, radiation power has been calculated by making use of the radiation power density of high-temperature Ar and then compared with the measured radiation power as a function of plasma length.
  • 松丸 幸司, 福山 博之, 須佐 匡裕, 永田 和宏
    1999 年 63 巻 1 号 p. 21-27
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Samples of 40 mass%SiO2-40CaO-20Al2O3(Glass) and 36 mass%SiO2-36CaO-18Al2O3-10Fe2O3(Fe-Glass) were melted by argon plasma arc, with iron rods used for arc ignition. A direct current transferred type plasma generator was used with an output power of 6 kW. During arc melting, the iron rod located in the centre of the molten glass was melted. During Glass melting, the oxygen partial pressure was kept constant in the chamber. On the other hand, during Fe-Glass melting, the oxygen partial pressure steeply increased in the initial stage and then gradually decreased. The chemical state of iron ion in Fe-Glass was changed from Fe3+ to Fe2+ rapidly. The evaporation rates from Glass and Fe-Glass were 3.8×10−7 kg/s and 2.0×10−7 kg/s, respectively. It has been concluded that the rate of evaporation from the molten glasses is affected by the oxygen partial pressure which is determined by the state of the iron oxides in the samples during the melting.
  • 竹内 章浩, 渡辺 隆行
    1999 年 63 巻 1 号 p. 28-33
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Peculiar reactions are known to occur using the features of arc plasmas, high temperature and high chemical activity, according to circumstances that are very effective. However few chemical reactions of arc plasmas have been unknown. Researches in the field of arc plasma reactions have been used hydrogen plasma gas to reduce metal oxides and to add heat to samples excessively, but there are very few thermodynamic data on hydrides which cause the plasma reactions. We have investigated the arc plasma reactions with chlorine because it reacts with metal to form chlorides which have high vapor pressure to be separated peculiarly and there are many available thermodynamic data on chlorides to study the reaction mechanism theoretically, and succeeded in separating iron component from Fe-Co-Ni alloys.
  • 田原 弘一, 吉川 孝雄
    1999 年 63 巻 1 号 p. 34-40
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Spectroscopic measurements were carried out to understand the plasma feature inside and outside a direct-current nitrogen arcjet generator with a supersonic expansion nozzle. In the expansion nozzle, the plasma was in thermodynamical nonequilibrium because the pressure drastically decreased downstream, although the plasma in the throat was expected to be nearly in a temperature-equilibrium condition. The radial profiles of the physical properties showed that there existed a core flow with high vibrational and rotational temperatures and large electron number densities on the center axis, even at the nozzle exit. The vibrational temperature at the nozzle exit ranged from 6000 to 10000 K in input powers of 5-11 kW and the rotational temperature from 500 to 2000 K. In the exhaust flow, the temperatures and the electron density were approaching some values downstream. Nitriding of titanium was conducted using the nitrogen plasma jets under a low pressure environment below 3 kPa. Plasma was accelerated smoothly with an optimally designed supersonic expansion nozzle because a shock diamond was not observed in the plasma flame. Even under a low pressure below 3 kPa, a titanium nitride layer was constructed on the surface of a titanum sample by only 5-min plasma jet irradiation. Although nitride formation decreased with decreasing pressure at the center of the irradiated region, the nitrided area became larger.
  • 武田 紘一, 竹内 順
    1999 年 63 巻 1 号 p. 41-47
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    The interesting properties of cathode spots were investigated in the removal of an oxide layer on metal substrate by a vacuum arc. The cathode spots attack the oxides selectively and remove them by evaporation. The observed removal rate of the oxide layer increases in proportion to the arc current and in inverse proportion to the thickness of the oxide layer. Considering the energy balance at the cathode spot, the authors have developed a simplified model to predict the removal rate. The theoretical results agree with the experimental ones qualitatively. The modeling reveals that there exists a critical current density below which the removal of oxides does not occur. The current density of the cathode spots produced in vacuum exceeds the critical value.
  • 伊藤 健一, 松本 修
    1999 年 63 巻 1 号 p. 48-54
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    The deposition of diamond from the Ar-H2 plasma jets comprising benzene (C6H6) and benzene derivatives, such as cyclohexane (C6H12) and phenol (C6H5OH), as carbon sources was investigated.
    First, the diamond deposition from the Ar-C6H6-H2 plasma jet had been carried out and the results obtained were compared with those in the C6H6-H2 microwave plasma. The deposit from the Ar-C6H6-H2 plasma jet exhibited crystalline habit planes and it was identified as the diamond by means of scanning electron microscope observation, X-ray diffraction method, and Raman spectroscopy. However, the diamond deposited from the C6H6-H2 microwave plasma was covered with amorphous components according to scanning electron micrograph, though the diamond was identified in the deposit by means of X-ray diffraction method. Emission band due to C6H6 was observed in the emission spectrum from the C6H6-H2 microwave plasma, but it was not observed in the spectrum from the Ar-C6H6-H2 plasma jet. The dissociation of C6H6 would be promoted in the plasma jet and the diamond could be deposited from the Ar-C6H6-H2 plasma jet.
    Second, the diamond was deposited from the Ar-C6H12-H2 plasma jet and the Ar-C6H5OH-H2 plasma jet. The better-faceted and higher-quality diamond was formed from both plasma jets than the deposit from the Ar-C6H6-H2 plasma jet. In the plasma jets, C6H12 and C6H5OH were dissociated and a large amount of H atom and a trace of OH radical were identified. These species prepared in the plasma jets and the adsorbed species on the surface of the deposits would give rise to the deposition of the larger and purer diamond like in the diamond deposition from Ar-chlorinated benzenes-H2 plasma jets.
  • 崎山 智司, 福政 修
    1999 年 63 巻 1 号 p. 55-61
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    To realize the large area deposition of diamond films at a high rate, synthesis of diamond with the use of plasma jets under medium pressure, which are in the transition region from thermal plasmas to cold plasmas, is studied. Under low pressure, the morphology of deposited particles strongly depends on the ratio of methane gas flow rate to hydrogen gas flow rate, CH4/H2, and on the distance from the feed ring exit to the substrate, L. The euhedral diamond particles are synthesized when CH4/H2 is lower and L is shorter. To clarify the relationship between the morphology of the prepared particles and the chemical species in the plasma jet, emission spectra from the plasma jet have been studied. The spectra of the Balmer series of hydrogen, hydrocarbons and dicarbon have attracted special interest. Among these spectra, the spectral intensity ratio of CH to Hα at 1 mm above the substrate has a strong correlation with the quality of synthesized diamond and its deposition area.
  • 永田 真吾, 脇谷 尚樹, 篠崎 和夫, 増田 善男, 水谷 惟恭
    1999 年 63 巻 1 号 p. 62-67
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    PbTiO3 thin films were prepared by low-pressure thermal plasma deposition method on (100)MgO substrates. The mists of the mixed solution of each metal alkoxides and 2-methoxyethanol were introduced into a plasma flame and deposited onto substrates. The constituent phases, the crystal texture and the surface morphology were drastically changed by the chamber pressure. Over 13332 Pa, single phase PbTiO3 films were obtained. They were grown epitaxially and their surface morphology was composed of rectangular shaped grains. The remnant polarization and coercive field of the film from the hysteresis loop were about 0.104 C·m−2 and 5.12 MV·m−1, respectively.
  • 服部 伴之, 山口 哲央, 間嶋 俊雄, 寺嶋 和夫, 吉田 豊信
    1999 年 63 巻 1 号 p. 68-73
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Hot cluster epitaxy (HCE) is a novel high-rate epitaxial growth mechanism discovered in the study of the plasma flash evaporation method. In HCE, the main deposition species are thermally activated, nanometer-scale clusters (hot clusters), which have unique characteristics such as high internal energy and high sticking probability even at high substrate temperature. Actually, with HCE, deposition of YBa2Cu3O7−x epitaxial films at a growth rate of 16 nm/s on the SrTiO3 substrate has been achieved. However, films thicker than 2 μm could not be obtained so far. In this paper, we discuss the “charge-up” effect of clusters and insulating substrates in a plasma environment as a retarding factor for film growth. Probe measurements and the biasing deposition clarified the charge-up of clusters were charged up during deposition. It was found that more than 60% of the clusters were negatively charged. By using conductive substrates of Nb doped SrTiO3, or changing Ar composition in Ar-O2 plasma, we could deposit monolayer-smooth epitaxial YBa2Cu3O7−x films thicker than 3 μm, with excellent properties; the full width less than 0.14° at half maximum of the X-ray rocking curve of the (005) peak, and the superconducting transition temperature of 92 K. These results suggest the future role of HCE in epitaxial thick film deposition.
  • 奥山 秀男, 本間 一廣, 大野 悟
    1999 年 63 巻 1 号 p. 74-81
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Ultrafine Particles (UFP) of TiO2 have been synthesized by oxidation of Ti vapor in the tail flame of an argon RF-Plasma, and their activity for photocatalytic hydrogen evolution in aqueous suspensions has been investigated.
    Synthesized TiO2 UFP are composed of a mixture of the rutile and anatase phases, and the anatase content in UFP varies from about 35 to 75 mass% depending on the oxygen content and the injection point of a reaction gas. The photocatalytic activity of TiO2 UFP increases drastically with decreasing anatase content, and reaches a maximum at about 40 mass% anatase. The maximum activity is 1000 times larger than that of a commercial anatase UFP.
  • 石垣 隆正, 佐藤 忠夫, 田中 順三, 目 義雄, 守吉 佑介
    1999 年 63 巻 1 号 p. 82-89
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    In order to investigate the influence of plasma treatment on the powder properties, titanium carbide powder with an average particle size of 1.35 μm was modified by the in-flight induction plasma treatment generated at the plate power of 45 kW and reactor pressure of 26.7 kPa. The treatment in Ar-H2 induced the formation of carbon-site vacancies. The tail injection of Ar-NH3 to the Ar-H2 plasma resulted in the partial substitution of carbon by nitrogen. Also, the treatment in Ar-N2 plasma gave rise to the partial nitridation. A large amount of oxygen incorporated into the plasma-treated powders stored in air. The original and plasma-treated powders were dispersed in an alumina matrix, and the pressureless sintering of Al2O3-TiC composites was tried to elucidate the influence of plasma modification. The composites with the dispersion of plasma-treated titanium carbide powders showed an increase in sintered density.
  • 植松 進, 高橋 千織
    1999 年 63 巻 1 号 p. 90-97
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    The collection of flying particles in plasma spraying has been performed by use of a chemical filter and a carbon adhesive tape and subjected to scanning electron microscopy (SEM). The observation reveals that the fusion mechanism of large and thick ceramic particles is different from that of smaller ceramic or metal particles. After introducing alumina particles into plasma jet, the separation occurs at the 1-2 micron under the surface of particles by the thermal stress. This separated thin layer prevents the internal thermal conduction in the particle and is heated up to completely melted by plasma flame. The melted part moves to the end of solid part and remains at the side edges of solid. At the same time the next separation and melting sequence starts at the solid surface followed by the melting parts apart from the solid to be a single and connected sphere particles before impact the substrate. This observation also provides an excellent method visualizing the particle melting process in the plasma jet without a special equipment.
  • 渡辺 隆行, 薄井 宗光
    1999 年 63 巻 1 号 p. 98-102
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Wire arc spraying is one of the most economical thermal plasma coating processes. The disadvantage of wire arc spraying is larger porosity and larger oxide content of the coatings. The purpose of this study is to reduce the oxidation of droplets, and to investigate the effect of atomizing gas on the droplet formation. Lower oxidation at the electrodes results in the stability of the arcing process, and in a decrease in production of AlO in gas phase. The stable arcing process resulting from the lower oxidation leads to the improvement of the coatings. Argon used as the atomizing gas leads to the smallest diameter of the droplets. This is due to the highest temperature of the atomizing gas. Oxidation during the droplet flight is stronger than that at the droplet formation from the electrodes. Argon or nitrogen used as the atomizing gas cannot decrease the oxide content of the droplets.
  • 天田 重庚, 春山 昌広, 大谷木 貴司
    1999 年 63 巻 1 号 p. 103-111
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    Plasma sprayed coatings are formed by a continuous deposition of numerous and molten droplets, which lead to a lamella structure. So that, it is very crucial to understand the interaction between molten droplets and substrates. This report presents the influence of wettability of substrates by molten metal droplets with on flattening degree of splats. Using a free-fall droplets apparatus, the metal Sn, Pb, Cu, and Fe are used for the experiments. Taking an equilibrium contact angle of metals into the energy balance for impingement of molten droplets, the relationship between the theoretical and experimental results shows approximately a good agreement in some Re and We regions.
  • 松原 学, 花田 修治
    1999 年 63 巻 1 号 p. 112-117
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    In order to improve the oxidation resistance of Nb base alloys as a promising high temperature structural material in the next generation, plasma sprayed ceramic coatings were prepared on Nb and their oxidation behavior and thermal shock property were investigated. Al2O3, MoSi2 and Al2O3-MoSi2 were chosen as the coatings by considering the oxidation resistance and the difference in thermal expansion. The plasma sprayed Al2O3 was laser-treated for densification. Oxidation test was carried out in air at 1473 K for 100 h and mass change during exposure was measured. The thermal shock test was performed by water quenching after holding for 50 h at 1473 K using Nb coated with Al2O3-30 vol%MoSi2. To investigate the effect of reacted phases between a coating and Nb on thermal shock properties, Al2O3 under-coating was employed.
    Laser-treatment on a porous Al2O3 coating leads to densification due to elimination of most pores but yields many macrocracks. The oxidation test of Nb plasma sprayed with Al2O3 or MoSi2 indicates that the coatings are spalled at an early stage. In contrast, Al2O3-MoSi2 coated Nb exhibits excellent oxidation resistance and mass change after 100 h exposure is less than 5 mg/cm2. It is suggested that SiO2 formed on MoSi2 acts as a protective layer against oxygen penetration, and porous Al2O3 in the layered Al2O3/MoSi2 structure relaxes the thermal stress generated in the coating. In the thermal shock test of Al2O3-MoSi2 coated Nb, spalling occurs at a reaction layer consisting of Mo5Si3 and Nb5Si3 which form between Nb and the coating. A lot of Kirkendall voids are produced in the Mo5Si3 reaction layer probably because of higher diffusivity of Si than Nb. The spalling is caused by propagation of cracks due to thermal stress throughout the voids. In the Al2O3 under-coated sample, there exists no reaction layer after the thermal shock test, thereby resulting in no spalling.
  • 榊原 紀幸, 納富 啓, 小椋 謙, 近藤 雅之, 藤原 力, 関川 貴洋, 河内山 治朗, 三保 和之
    1999 年 63 巻 1 号 p. 118-125
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    For high temperature oxidation resistant coating on C/C composites, multi layer system composed of a Y2SiO5 outer layer and a SiC inner layer is proposed. Atmospheric plasma spraying (APS) technology is employed to form Y2SiO5 coating. Influences of two spraying parameters, (1) particle size and (2) plasma secondary gas (H2) flow rate, on microstructure and gas tightness of Y2SiO5 coating are investigated. To improve adhesion between Y2SiO5 layer and SiC layer, forming an interlayer is examined. High temperature oxidation resistance of the coating system is investigated. The results are summarized as follows:
    (1) In a condition that median particle size is 14.51 μm and H2 flow rate is 2SLPM, Y2SiO5 coating has low porosity and gas permeability of Y2SiO5 coating is 1.49×10−13 m2/(Pa·s).
    (2) Y2SiO5 layer adheres to SiC layer by forming YSix interlayer.
    (3) The coating system in this study show high temperature oxidation resistance at 2073 K.
  • 村田 裕, 竹内 純一, 原田 良夫, 富田 友樹, 呉 徹, 中浜 修平
    1999 年 63 巻 1 号 p. 126-134
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    In oder to improve density and bond strength of atmospheric plasma sprayed Cr3C2-NiCr coatings, chromium diffusion treatments have been carried out in the range of 1073 to 1373 K. In this work, the change of structure and hardness were examined by SEM, EDX, XRD and micro vickers hardness tester. The results obtained are as follows.
    (1) Thin Cr23C6 carbide layer which slightly contains Cr2C has been formed on the sprayed coating surface by the chromium diffusion treatment. This carbide layer is extremely high desity and high micro vickers hardness, HV1500.
    (2) The thickness of this carbide layer became large (about 20 μm at 1373 K for 57.6 ks), as the temperature and period for chromium diffusion treatment incereased. It is found that at higher temperature than 1203 K this carbide layer covered the sprayed coating surface with nearly unform thickness. The growth rate of this carbide layer goes with a parabolic rule and the activity energy for the growth is 113.9 kJ/mol.
  • 浜谷 秀樹, 小原 昌弘, 藤 雅雄
    1999 年 63 巻 1 号 p. 135-143
    発行日: 1999年
    公開日: 2008/04/24
    ジャーナル フリー
    This study is aimed at developing a high power hybrid plasma spraying device with a maximum radio frequency input power of 300 kW, in order to improve the strength and adhesion strength of sprayed coating. The stability of plasma, energy efficiency, and melting state of particles were investigated under several conditions, and then characterization of coating was carried out. The stability of plasma condition is strongly influenced by gas flow rate of Ar, N2, and H2 mixture against the power supplied. The energy efficiency of equipment is approximately 14%. The energy is lost mainly by joule’s heat in the oscillator circuit. Using this device, the maximum particle diameter for full melting is approximately 250 μm. In the plasmas praying by not fully melted particles, the strength of coating decreases with increasing particle diameter because of increased porosity size. On the other hand, in the spraying by fully melted particles, it is found that the high strength of coating and the high adhesion strength at the interface between substrate and coating is obtained at large diameter particles. This tendency is explained by easy remelting or sintering at the interface between large particles. Actually, our experiment demonstrates that the maximum strength of coating and adhesion strength is more than 1300 and 250 MPa respectively, by using fully melted particles with maximum diameter.
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