• Title/Summary/Keyword: Gas Atomization

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Synthesis and Characterization of (AgSbTe2)15(GeTe)85 Thermoelectric Powder by Gas Atomization Process (가스분무공정을 이용한 (AgSbTe2)15(GeTe)85 열전분말의 제조 및 특성평가)

  • Kim, Hyo-Seob;Lee, Jin-Kyu;Koo, Jar-Myung;Chun, Byong-Sun;Hong, Soon-Jik
    • Journal of Powder Materials
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    • v.18 no.5
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    • pp.449-455
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    • 2011
  • In this study, p-type $(AgSbTe_2)_{15}(GeTe)_{85}$: TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous $AgSbTe_2$ + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group $R_{3m}$. The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral ($R_{3m}$) at low-temperature to cubic ($F_{m-3m}$) at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.

Control of Grain Refinement and Anisotropy of NdFeB Alloy Powder by Severe Plastic Deformation Fabricated by the Gas Atomization Process (가스분무로 제조된 NdFeB 합금분말의 강소성변형을 통한 결정립 미세화 및 이방성 제어)

  • Cho, J.Y.;Park, S.M.;Hussain, J.;Song, M.S.;Kim, T.S.
    • Transactions of Materials Processing
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    • v.31 no.3
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    • pp.124-128
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    • 2022
  • NdFeB magnets have been positioned as the core materials in advanced technologies such as MRI (magnetic resonance imaging), FA (factory automation system), robot, motors, and so on based on the highest magnetic properties. To effectively improve the refined microstructure, the plastic deformation has been known as the good alternatives by the recrystallization. However, it has been regarded as being impossible because of the few slip systems in the RE-Fe-B magnets at room temperature. The purpose of this study was to investigate the possibility of control of grain refinement and magnetic anisotropy of NdFeB alloy powder by the severe plastic deformation. The NdFeB magnet powder was fabricated by gas atomization process, and the powder was pre-compacted at high temperature. The pre-compacted billets were deformed by HPT (high pressure torsion), and then the deformed billets were observed microstructure and magnetic properties. After the HPT process at room temperature, the grain size decreased with increasing because of the melted Nd-rich phase, and the anisotropy of Nd2Fe14B phase was formed after the HPT process.

Assessment of Prediction Ability of Atomization and Droplet Breakup Models on Diesel Spray Dynamic (디젤분무에서 미립화 및 액적분열모델의 예측능력평가)

  • Kim, J.I.;No, S.Y.
    • Journal of ILASS-Korea
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    • v.5 no.2
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    • pp.35-42
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    • 2000
  • A number of atomization and droplet breakup models have been developed and used to predict the diesel spray characteristics. Of the many atomization and droplet breakup models based on the breakup mechanism due to aerodynamic liquid and gas interaction, four models classified as mathematical models, such as TAB, modified TAB, DDB, WB and one of the hybrid model based on WB and TAB models were selected for the assessment of prediction ability of diesel spray dynamics. The assessment of these models by using KIVA-II code was performed by comparing with the experimental data of spray tip penetration and sauter mean diameter(SMD) from the literature. It is found that the prediction of spray tip penetration and SMD by the hybrid model was only influenced by the initial parcel number. All the atomization and droplet breakup models considered here was strongly dependent on the grid resolution. Therefore it is important to check the grid resolution to get an acceptable results in selecting the models. At low injection pressure, modified TAB model could only give the good agreement with experimental data of spray tip penetration and both of modified TAB and DDB models were recommendable for the prediction of SMD. At high injection pressure, hybrid model could only give the good agreement with the experimental data of spray tip penetration and the prediction of all of the selected models did not match the experimental data. Spray tip penetration was increased with the increase the $B_1$ and the increase of $B_1$ did not affected the prediction of SMD.

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Spark Plasma Sintering of the Ductile Cu-Gas-atomized Ni Bulk Metallic Glass Composite Powders (연질 Cu 분말-가스분무 Ni계 벌크 비정질 복합분말의 방전플라즈마 소결에 관한 연구)

  • Kim, Jin-Chun;Kim, Yong-Jin;Kim, Byoung-Kee;Kim, Ji-Soon
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.351-359
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    • 2006
  • Ni based($Ni_{57}Zr_{20}Ti_{18}Si_2Sn_3$) bulk metallic glass(BMG) powders were produced by a gas atomization process, and ductile Cu powders were mixed using a spray drying process. The Ni-based amorphous powder and Cu mixed Ni composite powders were compacted by a spark plasma sintering (SPS) processes into cylindrical shape. The relative density varied with the used SPS mold materials such as graphite, hardened steel and WC-Co hard metal. The relative density increased from 87% to 98% when the sintering temperature increased up to $460^{\circ}C$ in the WC-Co hard metal mold.

Microstructure and Mechanical Properties of Al-Ni-Mm-(Cu, Fe) Alloys Hot-Extruded from Gas-Atomized Powders (가스분사 분말로부터 고온 압출된 Al-Ni-Mm-(Cu, Fe)합금들의 미세구조 및 기계적 성질)

  • Kim, Hye-Sung
    • Korean Journal of Materials Research
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    • v.16 no.2
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    • pp.137-143
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    • 2006
  • The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

Effects of Hydrogen Reduction in Microstructure, Mechanical and Thermoelectric Properties of Gas Atomized n-type Bi2Te2.7 Se0.3 Material

  • Rimal, Pradip;Yoon, Sang-Min;Kim, Eun-Bin;Lee, Chul-Hee;Hong, Soon-Jik
    • Journal of Powder Materials
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    • v.23 no.2
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    • pp.126-131
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    • 2016
  • The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type $Bi_2Te_{2.7}Se_{0.3}$ material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at $360^{\circ}C$. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

SELF-PULSATION CHARACTERISTICS OF A SWIRL COAXIAL INJECTOR WITH VARIOUS INJECTION AND GEOMETRIC CONDITIONS

  • Im, Ji-Hyuk;Kim, Dong-Jun;Yoon, Young-Bin;Bazarov, V.
    • Journal of ILASS-Korea
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    • v.10 no.3
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    • pp.29-37
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    • 2005
  • The spray and acoustic characteristics of a gas/liquid swirl coaxial injector are studied experimentally. The self-pulsation is defined as a pressure and flow rate oscillations by a time-delayed feedback between liquid and gas phase. Self-pulsation has strong influences on atomization and mixing processes and accompanies painful screams. So. the spray and acoustic characteristics are investigated. Spray patterns are observed by shadow photography technique in order to determine the onset of self-pulsation. And self-pulsation boundary with Injection conditions and recess length is get. To measure the frequency of the spray oscillation. oscillation of the laser intensity which passes through spray is analyzed by Fast Fourier Transform. For acoustic tests, a PULSE System was used. Acoustic characteristics of a swirl coaxial injector are investigated according to the injection conditions. such as the pressure drop or the liquid and gas phase. and injector geometries. such as recess length and gap size between the inner and outer injector. Front the experimental results. the increase of recess length leads to the rapid increase of the sound pressure level. And as the pressure drop of the liquid phase increases. the frequency of the self?pulsation shifts to the higher frequency. The frequency of spray oscillations is the same as that of the acoustic fields by self-pulsation.

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Design and Spray Characteristics of Coaxial injector using GCH4/LOx (가스메탄/액체산소를 추진제로 이용한 동축인젝터 설계 및 분무 특성)

  • Kim, Bo-Yeon;Lee, Yank-Suk;Park, Jin-Ho;Ko, Young-Sung;Kim, Sun-Jin;Kim, Yoo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.11a
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    • pp.577-580
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    • 2010
  • Coaxial injectors using GCH4/LOx as propellants was designed with shear(gas)/shear(liquid) type and shear(gas)/swirl(liquid) type. Spray characteristics were investigated by cold flow test. Spray patterns of the shear/shear and the shear/swirl type injectors were like a spout of water and hollow cone, respectively. Atomization efficiency of the shear/swirl type injector was better than atomization efficiency of the shear/shear type injector.

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The effect of gas density on the drop trajectory and drop size distribution in high speed gas stream (고속기류에 분사된 액적궤적 및 입경분포에 미치는 주위 기체밀도의 영향)

  • Lee, C.H.
    • Journal of ILASS-Korea
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    • v.5 no.3
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    • pp.37-44
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    • 2000
  • High velocity, gas-assisted liquid drop trajectories were investigated under well-controlled experimental conditions at elevated gas densities and room temperature. A monodisperse stream of drops which are generated by a vibrating-orifice drop generator were injected into a transverse high velocity gas stream. The gas density and air jet velocity were adjusted independently to keep the Weber numbers constant. The Weber numbers studied were 72, 148, 270, 532. The range of experimental conditions included studied the three drop breakup regimes previously referred as bag, stretching/thinning and catastrophic breakup regimes. High-magnification photography and conventional spray field photographs were taken to study the microscopic breakup mechanisms and the drop trajectories in high velocity gas flow fields, respectively. The parent drop trajectories were affected by the gas density and the gas jet velocities and do not show similarity with respect to the either Weber or the Reynolds number, as expected.

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Mass Distribution and Spray Characteristics to Liquid-Gas Line Selection of Unlike Triplet Impinging Injector (비동질 3중 충돌형 인젝터의 기체-액체 라인 선택에 따른 분무특성)

  • Lee, I.C.;Lee, C.J.;Koo, J.Y.
    • Journal of ILASS-Korea
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    • v.11 no.4
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    • pp.205-211
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    • 2006
  • Impinging angle, impinging distance, length eve. diameter and injection pressure of a triplet injector were tested to evaluate the spray characteristics injected by liquid/gas combinations. Two different kinds of unlike triplet sprays were produced by changing the gas and liquid feed lines. One was the G-L-G(Gas-Liquid-Gas) type, and the other was L-G-L(Liquid-Gas-Liquid) type. Spray angles were wider with the G-L-G type than with L-G-L type. Mass distributions in spray were obtained with a, mechanical patternator. Mass distributions were not circular but elliptical distributions. When the range of mechanical patternator to injector decreased, mass distributions were more concentrated in the center region.

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