• Title/Summary/Keyword: Nanosized powder

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Microstructural and Magnetic Characterization of Fe Nanosized Powder Synthesized by Pulsed Wire Evaporation

  • Kim, Deok Hyeon;Lee, Bo Wha
    • Journal of Magnetics
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    • v.22 no.1
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    • pp.100-103
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    • 2017
  • We studied the microstructure and magnetic properties of Fe nanosized powder synthesized by the pulsed wire evaporation method. The x-ray diffraction spectrum confirmed that this powder had a pure ${\alpha}$-Fe phase. Scanning electron microscope and transmission electron microscope measurements indicated that the prepared powder had uniform spherical shape with core-shell structure. The mean powder size was about 35 nm and the thickness of the surface passivation layer was about 5 nm. Energy dispersive X-ray spectroscopy measurement indicated that the surface passivation layer was iron oxide. Magnetic field dependent magnetization measurement at room temperature showed that the maximum magnetization of the prepared powder was 177.1 emu/g at 1 T.

Preparation of Nanosized WO3 Powder by Chemical Vapor Condensation Process

  • Kim, Jin-Chun;Kim, Byoung-Kee
    • Journal of Powder Materials
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    • v.10 no.3
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    • pp.186-189
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    • 2003
  • A chemical vapor condensation (CVC) process using the pyrolysis of metal-organic precursors was applied to produce the nanosized $WO_3$ powders. Morphology and phase changes of the synthesized $WO_3$ powder as a function of CVC parameters were investigated by XRD, BET and TEM. The agglomerated nanosized monoclinic $WO_3$ powders with nearly spherical shape and 10-38 nm in mean diameter could be obtained. Conditions to produce the $WO_3$ nanopowders are presented in this paper.

Facile Synthesis of Highly Dispersed Ultra-fine ZrC Powders by Carbothermal Reduction Method Using Nanosized ZrO2 and Nanosized Graphite Powder Mixtures (나노크기의 ZrO2와 Graphite 분말 혼합체의 열탄소환원법에 의한 고분산 초미립 ZrC 분말의 합성)

  • Lee, Wha-Jun;Ryu, Sung-Soo
    • Journal of Powder Materials
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    • v.20 no.2
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    • pp.100-106
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    • 2013
  • Ultra-fine zirconium carbide (ZrC) powder with nano-sized primary particles was synthesized by the carbothermal reduction method by using nano-sized $ZrO_2$ and nano-sized graphite powders mixture. The synthesized ZrC powder was well dispersed after simple milling process. After heat-treatment at $1500^{\circ}C$ for 2 h under vacuum, ultra-fine ZrC powder agglomerates (average size, $4.2{\mu}m$) were facilely obtained with rounded particle shape and particle size of ~200 nm. Ultra-fine ZrC powder with an average particle size of 316 nm was obtained after ball milling process in a planetary mill for 30 minutes from the agglomerated ZrC powder.

Production of Nanosized WC Powder by Vapor Phase Reaction

  • Cho, Gi-Chul;Lee, Gil-Geun;Ha, Gook-Hyun;Kim, Byung-Kee
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.625-626
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    • 2006
  • In the present study, the focus is on the synthesis of nanosized WC powder by the chemical vapor condensation proces. The synthesized W-C system powder by the CVC process shows W2C, W, WO3 phases and can not shows WC phase. After recarburization heat treatment under mixture gas atmosphere of argon and hydrogen gases, the synthesized W-C system powder fully transformed to the pure WC. The synthesized WC powder after recarburization heat treatment has an average particle size of 20 nm. The nano-sized WC powder can be prepared by the combination of the CVC process and heat treatment methods.

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Synthesis and Microstructural Changes of Nanostructured Tungsten Carbide Powder by Chemical Vapor Condensation Process (화학기상응축법에 의한 나노구조 텅스텐카바이드 분말의 제조와 미세구조 변화)

  • ;;;;O.V.Tolochko
    • Journal of Powder Materials
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    • v.9 no.3
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    • pp.174-181
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    • 2002
  • Nanosized tungsten carbide powders were synthesized by the chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl($W(CO)_6$). The effect of CVC parameters on the formation and the microstructural change of as-prepared powders were studied by XRD, BET and TEM. The loosely agglomerated nanosized tungsten-carbide($WC_{1-x}$) particles having the smooth rounded tetragonal shape could be obtained below $1000^{\circ}C$ in argon and air atmosphere respectively. The grain size of powders was decreased from 53 nm to 28 nm with increasing reaction temperature. The increase of particle size with reaction temperature represented that the condensation of precursor vapor dominated the powder formation in CVC reactor. The powder prepared at $1000^{\circ}C$ was consisted of the pure W and cubic tungsten-carbide ($WC_{1-x}$), and their surfaces had irregular shape because the pure W was formed on the $WC_{1-x}$ powders. The $WC_{1-x}$ and W powders having the average particles size of about 5 nm were produced in vacuum.

Microstructure and Elevated Temperature Strength of W-ZrC Composites with Micrometric and Nanosized ZrC Particles (서로 다른 입자크기의 ZrC가 첨가된 W-ZrC 복합체의 미세구조 및 고온강도에 관한 연구)

  • Han, Yoon Soo;Ryu, Sung-Soo
    • Journal of Powder Materials
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    • v.21 no.6
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    • pp.415-421
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    • 2014
  • W-10vol.%ZrC composites reinforced by micrometric and nanosized ZrC particles were prepared by hot-pressing of 25 MPa for 2 h at $1900^{\circ}C$. The effect of ZrC particle size on microstructure and mechanical properties at room temperature and elevated temperatures was investigated by X-ray diffraction analysis, scanning electron microscope and transmission electron microscope observations and the flexural strength test of the W-ZrC composite. Microstructural analysis of the W-ZrC composite revealed that nanosized ZrC particles were homogeneously dispersed in the W matrix inhibiting W grain growth compared to W specimen with micrometric ZrC particle. As a result, its flexural strength was significantly improved. The flexural strength at room temperature for W-ZrC composite using nanosized ZrC particle being 740 MPa increased by around 2 times than that of specimen using micrometric ZrC particle which was 377 MPa. The maximum strength of 935 MPa was tested at $1200^{\circ}C$ on the W composite specimen containing nanosized ZrC particle.

Synthesis of Nanosized TiO$_2$ Powder by Chemical Vapor Condensation Process(1) (화학기상응축법에 의한 TiO$_2$ 나노분말의 합성 (1))

  • 김신영;유지훈;이재성;김종렬;김병기
    • Journal of the Korean Ceramic Society
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    • v.36 no.7
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    • pp.742-750
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    • 1999
  • Nanosized TiO2 powders were synthesized using the chemical vapor conduensation (CVC) process with various precursor feeding rates (0.37 and 0.752 ml/min) and oxygen flow rates(1-2slm) conditions and powder characteristics were investigated in terms of formation of nanosized powder varying with the above processing conditions. For this study the main thermodynamic and fluid dynamic factors -supersaturation ratio collision frequency and residence time-were theoretically established and compared to the characteristics of formed TiO2 powder. The loosely combined anatase phase powders (including less than 3%of rutile phase) having 20-30nm crystallite size were obtained at overall conditions. The particle size and th degree of agglomeration for a precursor flow rate of 0.376 ml/min turn out to be smaller than for a flow rate of 0.742ml/min. And the decreasing of particles size and particle size distribution were observed with increasing oxygen flow rate as the residence time and collision frequency were reduced by increasing oxygen flow rate,. It appears that further scrutiny is needed to elucidate the influence of the individual thermodynamic and kinetic parameters mdependently.

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Synthesis of Nanosized Powders by Wire Explosion (전기폭발(wire explosion)에 의한 나노분말 제조)

  • Cho, Chu-Hyun;Rim, Geun-Hie;Lee, Hong-Sik;Jiang, WeiHua
    • Proceedings of the KIEE Conference
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    • 2005.07c
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    • pp.2057-2059
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    • 2005
  • Silver nanosized powder have been synthesized using wire explosion technology. The discharge system of 10kw (10uF, 20kV, 0.5 shots/s) was set up for mass production of 300g/h. The high purity silver powder was collected and separated by cyclone and fabric filters.

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