• 제목, 요약, 키워드: Carbothermal reduction

검색결과 89건 처리시간 0.026초

분무건조법에 의해 제조된 Ti-Co-O계 산화물 분말의 고체 탄소에 의한 환원/침탄 (Carbothermal Reduction of Spray Dried Titanium-Cobalt-Oxygen Based Oxide Powder by Solid Carbon)

  • 이길근;문창민;김병기
    • 한국분말야금학회지
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    • v.11 no.1
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    • pp.28-33
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    • 2004
  • In the present study, the focus is on the analysis of carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fined TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. The synthesized titanium-cobalt-oxygen based oxide powder has a mixture of $TiO_2$ and $CoTiO_3$. This oxide powder was transformed to a mixed state of titanium car-bide and cobalt by solid carbon through four steps of carbothermal reduction steps with increasing temperature; reduction of $CoTiO_3$ to $TiO_2$ and Co, reduction of $TiO_2$, to the magneli phase($Ti_nO_{2n-1}$, n>3), reduction of the mag-neli phase($Ti_nO_{2n-1}$, n>3) to the $Ti_nO_{2n-1}$(2$\leq$n$\leq$3) phases, and reduction and carburization of the $Ti_nO_{2n-1}$(2$\leq$n$\leq$3) phases to titanium carbide.

분무건조법에 의해 제조된 Ti-Co-O계 산화물 분말의 환원/침탄반응에 미치는 코발트 산화물의 영향 (Effect of Cobalt Oxide on Carbothermal Reduction of Spray Dried Titanium-Cobalt-Oxygen Based Oxide Powder)

  • 이길근;김찬영
    • 한국분말야금학회지
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    • v.12 no.5
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    • pp.336-344
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    • 2005
  • In the present study, the focus is on the effect of cobalt oxide powder in the carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fine TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under flowing argon atmosphere. Changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. Titanium-cobalt-oxygen based oxide powder desalted at $600^{\circ}C$ had a mixture of $TiO_2\;and\;Co_{3}O_4$. And the one desalted at $800^{\circ}C$ had a mixture of $TiO_2\;and\;CoTiO_3$. In the case of the former powder, the reduction of cobalt oxide powder in the titanium-cobalt-oxygen based oxide powder occurred at lower temperature than the latter one. However, the carbothermal reduction of titanium dioxide powder in the titanium-cobalt-oxygen based oxide powder with a mixture of $TiO_2\;and\;Co_{3}O_4$ occurred at higher temperature than the one with a mixture of $TiO_2\;and\;CoTiO_3$. And also, the former powder showed a lower TiC formation ability than the latter one.

WC/Co 초경 스크랩 산화물의 고체탄소에 의한 환원/침탄 (Carbothermal Reduction of Oxide Powder Prepared from Waste WC/Co Hardmetal by Solid Carbon)

  • 이길근;하국현
    • 한국분말야금학회지
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    • v.12 no.2
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    • pp.112-116
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    • 2005
  • In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste $WC-8 wt.\%Co$ hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste $WC-8wt.\%Co$ hardmetal has a mixture of $WO_{3} and CoWO_{4}$. This oxide powder reduced at about $850^{\circ}C$, formed tungsten carbides at about $950^{\circ}C$, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about $1100^{\circ}C$ by solid carbon under a stream of argon. The WC/Co composite powder synthesized at $1000^{\circ}C$ for 6 hours from oxide powder of waste $WC-8wt.\%Co$ hardmetal has an average particle size of $0.3 {\mu}m$.

산화알루미늄 분말의 탄소열환원 및 직접 질화반응을 통한 질화알루미늄 나노분말의 합성 (Synthesis of Aluminum Nitride Nanopowders by Carbothermal Reduction of Aluminum Oxide and Subsequent In-situ Nitridization)

  • 서경원;이승용;박종구;김성현
    • 한국분말야금학회지
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    • v.13 no.6
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    • pp.432-438
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    • 2006
  • Aluminum nitride (AlN) nanopowders with low degree of agglomeration and uniform particle size were synthesized by carbothermal reduction of alumina and subsequent direct nitridization. Boehmite powder was homogeneously admixed with carbon black nanopowders by ball milling. The powder mixture was treated under ammonia atmosphere to synthesize AlN powder at lour temperature. The effect of process variables such as boehmite/carbon black powder ratio, reaction temperature and reaction time on the synthesis of AlN nanopowder was investigated.

카올린의 환원 열탄화법에 의한 베타 탄화규소 휘스커의 합성 (Synthesis of $\beta$-SiC Whiskers by the Carbothermal Reduction of Kaolin)

  • 오세정;류종화;조원승;최상욱
    • 한국세라믹학회지
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    • v.35 no.12
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    • pp.1249-1256
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    • 1998
  • ${\beta}$-Silicon carbide(${\beta}$-SiC) whiskers could be synthesized by the carbothermal reduction of kaolin at tem-peratures between 1400 and 1500$^{\circ}C$. The whiskers were grown up to about 1150 of aspect ratio by VS mechanism (showing tapering tips) and to about 45 of that by VLS mechanism (showing round droplet tips) respectively. Hydrocarbon like methane in the reaction atmosphere promoted the formation of gaseous il-icon monoxide(SiO) from silicon dioxide(SiO2) and subsequently reacted with it to form whiskers. The for-mation of ${\beta}$-SiC whiskers increased with increasing carbon content(to 30 wt%) and reaction temperatures. The max. yield of ${\beta}$-SiC whiskers was 15% at 1500$^{\circ}C$ under 20%CH4/80%H2.

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ZnO 나노선의 합성에서의 미량산소의 영향 (Effect of Oxygen in the Synthesis of ZnO Nanowires)

  • 박경수;최영진;박재관;강교성;임동건;박재환
    • 한국재료학회지
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    • v.17 no.9
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    • pp.458-462
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    • 2007
  • The effect of oxygen in the synthesis of oxide nanowires by using carbothermal reduction process have been studied thermodynamically and kinetically. By using laboratory air, ZnO nanowires could be fabricated in the carbothermal reduction process and a metal oxidation process. As the processing pressure decreases, the diameter of the nanowires decreases and the oxygen vacancy increases. As the processing pressure increases, the oxygen vacancy decreases and the shape of the ZnO becomes plate-like.

Raman Spectroscopy Study of Carothermal Reactions in Double-layer Graphene on $SiO_2$ Substrates

  • 박민규;류순민
    • 한국진공학회:학술대회논문집
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    • pp.387-387
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    • 2012
  • 그래핀(graphene)의 가장자리(edge)는 결정구조의 배향성에 따라 지그재그(zigzag)와 안락의자 (armchair) 형태로 구분되는데, 나노미터 크기의 그래핀의 전자적 성질은 이러한 가장자리의 배향성에 의해 크게 영향을 받는다고 알려져 있다. 단일층 그래핀 가장자리 사이에서 일어나는 산화실리콘($SiO_2$)의 carbothermal reduction은 선택적으로 지그재그 형태의 가장자리를 생성한다고 알려져 있다. 본 연구에서는 라만 분광법과 원자 현미경(atomic force microscopy)을 이용하여 기계적 박리법으로 만들어진 이중층 그래핀에서 일어나는 carbothermal reaction을 연구하였다. 고온 산화 방법으로 이중층 그래핀에 원형 식각공(etch pit)을 만들고 Ar 기체 속에서 700도 열처리를 진행한 후, 원형 식각공이 육각형으로 확장된 것을 관찰하였다. 이것은 이중층 그래핀도 산화실리콘의 carbothermal reduction을 유발한다는 사실을 보여준다. 그러나 이중층 그래핀의 반응속도는 단일층보다 느린 것이 확인되었는데, 이는 이중층 그래핀의 탄소 원자와 산화제로 작용하는 산화실리콘 간의 평균 거리가 단일층보다 더 크다는 사실로 설명할 수 있다. 또한 본 연구에서는 반응기 내의 압력이 반응 속도에 미치는 영향과 식각공이 육각형으로 변해가는 과정에 대한 라만 분광 특성을 조사 및 분석하였다.

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구형 초미립 금속산화물의 Carbothermal 환원에 의한 Sn-Sb계 분말 합성 및 리튬 이차 전지 음극재료 특성 평가 (Fabrication of Sn-Sb Based Powder by Carbothermal Reduction of Spherical Ultrafine Metal Oxides)

  • 홍성현;배종수;진영미;권해웅
    • 한국수소및신에너지학회논문집
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    • v.17 no.3
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    • pp.324-330
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    • 2006
  • In this study, carbothermal reduction method was employed to synthesis Sn-Sb alloy powders from chief metal oxides with ultrafine sizes. The Sn-Sb powders consisting of ultrafine particles were formed at $800{\sim}900^{\circ}C$ by reduction of oxides. Those powders have high initial discharge capacities ($570{\sim}637\;mAh/g$) and discharge capacities of those powders maintain initial capacity after 20 cycle due to existence of ultrafine particles in powders and alloying effect of Sn-Sb.