• 제목/요약/키워드: Reduction of Materials

검색결과 4,990건 처리시간 0.036초

염화동 수용액으로부터 Cu 미립자의 합성 (Synthesis of Uniform Cu Particles from Copper Chloride Solution)

  • 윤지희;권현우;유연태;김병규;김광수
    • 한국재료학회지
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    • 제15권4호
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    • pp.263-270
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    • 2005
  • In order to prepare the uniform copper particles from copper chloride solution, the reduction behavior of copper particles from copper chloride and the effects of reduction agent and dispersing agent was investigated. In the case that 2.56 M of $C_6H_8O_6$ was used as a reduction agent, the highly dispersed Cu particles with sharp size distribution were generated from 0.96M of copper chloride solution, and the size of Cu particles was $6\~10\;{\mu}m$. To form $Cu(NH_3)_4Cl_2$ complex solution, $NH_4OH$ was added in the copper chloride solution before the reductive reaction of Cu ion. The generated Cu particles have a two kind of shape, spherical and rod-like. In the case that $N_2H_4{\cdot}H_2O$ was used as a reduction agent, the very fine spherical Cu particles with the size of $0.2\~0.5\;{\mu}m$ was obtained. Arabic gum as a dispersing agent was more effective than $Na_4P_2O_7{\cdot}10H_2O$.

Effect of Cu During Non-isothermal Hydrogen Reduction of $MoO_3$

  • Kim, Gil-Su;Kim, Dae-Gun;Oh, Sung-Tag;Suk, Myung-Jin;Kim, Young-Do
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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    • pp.1329-1330
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    • 2006
  • The effect of Cu on the hydrogen reduction of $MoO_3$ powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of $MoO_3\rightarrowMo_4O_{11}\rightarrowMoO_2$, which comprised the contained chemical vapor transport of $MoO_x(OH)_2$. This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of $MoO_x(OH)_2$ to $MoO_2$ particles from $MoO_3$ or $Mo_4O_{11}$. Such an activated reduction process results in the deposition of Mo and $MoO_2$ particles on the surface of the Cu.

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습식 화학적 환원법에 의한 AgNO3로부터 Ag 분말의 제조 1. 균일한 구형 Ag 분말의 제조를 위한 최적 반응계 확립 (Preparation of Ag Powder from AgNO3 by Wet Chemical Reduction Method1. The Establishment of Optimum Reaction System for the Preparation of Spherical Ag Powder)

  • 윤기석;박영철;양범석;민현홍;원창환
    • 한국분말재료학회지
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    • 제12권1호
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    • pp.56-63
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    • 2005
  • Ag powder was prepared from $AgNO_3$ by wet chemical reduction method using various reduction agent system involving $AgNO_3$, $AgNO_2$(AgCl) and Ag complex ion aqueous solution. The pure Ag powder could be prepared regardless of reaction system but the particle shape and distribution were affected very much according to the kind of reduction agents and reaction systems. The optimum reaction system for the preparation of the silver powder having the uniform particle shape and size distribution was Ag complex ion aqueous solution-reduction agent system and in particular, $H_2O_2$ and $C_6H_8O_6$as a reduction agent leaded the more uniform particle shape and size distribution.

일산화탄소탈수소화효소를 이용한 이산화탄소의 전기화학적 환원에 미치는 pH와 온도의 영향 (Effect of pH and Temperature on the Electrochemical Reduction of Carbon Dioxide by Carbon Monoxide Dehydrogenase)

  • 신준원;김유성;이상희;이상필;이호준;임미란;송지은;신운섭
    • 전기화학회지
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    • 제10권4호
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    • pp.265-269
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    • 2007
  • 일산화탄소탈수소화효소를 이용한 이산화탄소의 전기화학적 환원 반응의 최적화를 위해 pH와 온도의 영향을 살펴보았다. pH는 이산화탄소의 환원반응 용이성과 효소의 안정도 효과가 함께 반영되는 6.3에서 최적의 조건을 보였고, 온도는 이산화탄소의 용해도가 적어지더라도 효소의 활성이 가장 좋은 60도에서 최적 조건을 보였다. 일산화탄소탈수소화효소의 안정성 및 활성이 가장 중요한 조건임을 알 수 있었다.

고분자전해질 연료전지용 20% Pt/C 캐소드 촉매 제조 및 산소환원반응 평가 (Synthesis and Oxygen Reduction Reaction Evaluation of 20% Pt/C for Polymer Electrolyte Fuel Cell)

  • 김진환;강석민;;류호진
    • 대한금속재료학회지
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    • 제47권7호
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    • pp.454-459
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    • 2009
  • In order to commercialize Polymer Electrolyte Fuel Cell (PEFC), the cathode catalyst such as Platinum supported Carbon (Pt/C) need to have a high activity of Oxygen Reduction Reaction (ORR). In this study, the 20% Pt/C was synthesized using the chemical reduction method while the crystallinity of Platinum (Pt) particles were controlled under heat treatment conditions. The activity of synthesized Pt catalysts was evaluated using electrochemical measurement. Compared with the $i_{ORR}$ at 0.8 V of 20% Pt/C heat-treated at $500^{\circ}C$ and the 20% Pt/C that were not heated and commercial 20% Pt/C, the $i_{ORR}$ at 0.8 V of 20% Pt/C heattreated at $500^{\circ}C$ was 9.5 and 1.7 times higher than those of the 20% Pt/C and commercial 20% Pt/C that were not heated. It was considered that the crystallinity and particle size affect the ORR activity of the Pt/C catalysts.

광촉매시멘트의 배기가스 저감 특성에 관한 연구 (A Study on the Properties of Waste Gas Reduction in the Photocatalytic Cement)

  • 이원암;양진;유재상;이종열
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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    • pp.355-360
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    • 2003
  • Recently, a cement plays an important roll in the materials field. So, in this research we would like to study on the properties of waste gas reduction in the photocatalytic cement. The fundamental phenomena of waste gas reduction in the photocatalytic cement were observed by the NOx analyzer with reaction chamber, UV Lamp, MFC, and humidity control bath. As a result of this study, the photocatalytic cement used photocatalytic powder, admixture and other materials can obtain NOx gas reduction and its photocatalytic efficiency. Developing for the photocatalytic cement, we need a various study.

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도전체 매개반응(EMR)법에 의한 Ti 분말 제조 (Production of Titanium Powder by Electronically Mediated Reaction (EMR))

  • 박일;추용호;이철로;이오연
    • 한국재료학회지
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    • 제14권12호
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    • pp.857-862
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    • 2004
  • Production of titanium powder directly from tantalum oxides ($TiO_2$) pellet through an electronically mediated reaction (EMR) by calciothermic reduction has been investigated. Feed material ($TiO_2\;pellet$) and reductant (Ca-Ni alloy) were charged into electronically isolated locations in a molten calcium chloride ($CaCl_2$) bath at $950^{\circ}C$. The current flow through an external circuit between the feed (cathode) and reductant (anode) locations was monitored during the reduction of $TiO_2$. The current approximately 3.2A was measured during the reaction in the external circuit connecting cathode and anode location. After the reduction experiment, pure titanium powder with low nickel content was obtained even though Ca-Ni alloy was used as a reductant. These results demonstrate that titanium powder can be produced without direct physical contact between the feed and reductant. In certain experimental conditions, pure titanium powder with approximately $99.5\;mass\%$ purity was successfully obtained.

초음파 분무 열분해법에 의한 산화물 환원 공정의 구형 Bi2Te3 분말 합성 (Spherical Bi2Te3 Powder Synthesized by Oxide-Reduction Process via Ultrasonic Spray Pyrolysis)

  • 송철한;장대환;진연호;공만식
    • 한국표면공학회지
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    • 제50권2호
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    • pp.114-118
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    • 2017
  • Bismuth telluride ($Bi_2Te_3$) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic $Bi_2Te_3$ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical $Bi_2Te_3$ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above $375^{\circ}C$ for 6h. The reduced $Bi_2Te_3$ powders have a mean particle size of $1.5{\mu}m$. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

황산동 수용액으로부터 hydrazine 환원에 의한 Cu 미립자의 합성 (Synthesis of Uniform Cu Particles by Hydrazine Reduction from Copper Sulfate Solution)

  • 유연태;최영윤
    • 한국재료학회지
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    • 제13권8호
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    • pp.524-530
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    • 2003
  • In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of $NH_4$OH and $Na_4$$P_2$$O_{7}$ on the formation of uniform copper particles were discussed. ($NHCu_3$)$_4$$SO_4$was completely formed at over pH 11 by adding $NH_4$OH in copper sulfate solution. The fine $Cu_2$O with the particle size of 50 nm was produced in the initial reduction process of (NH$Cu_3$)$_4$$SO_4$solution with $Na_4$$P_2$$O_{ 7}$ and then the Cu$_2$O was converted into copper particles by inserting additional hydrazine. When Cu(NH$_3$)$_4$SO$_4$solution with $Na_4$$P_2$$O_{ 7}$ was reduced at $80^{\circ}C$ by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 $\mu\textrm{m}$ was obtained.

콜로이드 Ag 나노입자 합성시 계면활성제의 영향 (Effect of Surfactant on Synthesis of Colloidal Ag Nanoparticles)

  • 이종국;최남규;서동석
    • 한국재료학회지
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    • 제15권5호
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    • pp.340-347
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    • 2005
  • Silver nanoparticles were synthesized by chemical reduction method from aqueous silver nitrate solution ana hydrazine as a reduction agent. The morphology, particle size and shape were dependent on the mixing method, reaction temperature and time, molar ratio of hydrazine and silver nitrate, the kind of surfactant, and the addition of surfactant. The stability of the colloidal silver was achieved by the adsorption of surfactant molecules onto the particle. Silver nanoparticles have a characteristic absorption maximum at 430 nm under UV irradiation. It was found that the colloid was nanometer m size and formed very stable dispersion of silver. The Ag nanoparticles obtained showed the spherical shape with the size range of 10-30 nm.