• 제목/요약/키워드: Chemical reduction

검색결과 3,584건 처리시간 0.03초

Electrochemical Reduction of SiO2 Granules to One-Dimensional Si Rods Using Ag-Si Eutectic Alloy

  • Lee, Han Ju;Seo, Won-Chul;Lim, Taeho
    • Journal of Electrochemical Science and Technology
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    • 제11권4호
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    • pp.392-398
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    • 2020
  • Producing solar grade silicon using an inexpensive method is a key factor in lowering silicon solar cell costs; the direct electrochemical reduction of SiO2 in molten salt is one of the more promising candidates for manufacturing this silicon. In this study, SiO2 granules were electrochemically reduced in molten CaCl2 (850℃) using Ag-Si eutectic droplets that catalyze electrochemical reduction and purify the Si product. When Ag is used as the working electrode, the Ag-Si eutectic mixture is formed naturally during SiO2 reduction. However, since the Ag-Si eutectic droplets are liquid at 850℃, they are easily lost during the reduction process. To minimize the loss of liquid Ag-Si eutectic droplets, a cylindrical graphite container working electrode was introduced and Ag was added separately to the working electrode along with the SiO2 granules. The graphite container working electrode successfully prevented the loss of the Ag-Si eutectic droplets during reduction. As a result, the Ag-Si eutectic droplets acted as stable catalysts for the electrochemical reduction of SiO2, thereby producing one-dimensional Si rods through a mechanism similar to that of vapor-liquid-solid growth.

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.

화학환원법(化學還元法)을 이용(利用)해 제조(製造)한 20% Pt/C 캐소드 촉매(觸媒)의 열처리(熱處理)에 따른 산소환원반응(酸素還元反應) 평가(評價) (Oxygen Reduction Reaction Evaluation of Synthesized 20% Pt/C with Beat Treatment by Chemical Reduction Method)

  • 김진환;강석민;;류호진
    • 자원리싸이클링
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    • 제18권5호
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    • pp.12-18
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    • 2009
  • 고분자전해질 연료전지용 캐소드 촉매로서 화학환원법을 이용하여 20% Pt/C 제조하고 다양한 온도($300-600^{\circ}C$)열처리하여 산소환원반응을 평가하였다 $300-400^{\circ}C$에서 열처리한 20% Pt/C가 높은 산소환원반응 활성을 나타냈으며, 특히 $300^{\circ}C$에서 열처리한 촉매를 0.6V에서의 정전위를 측정한결과, 열처리하지 않은 촉매에 비해서 산소환원 반응 활성정도가 2배 높게 나타났다. TEM 및 XRD 분석을 이용하여 조사한 결과, 열처리 온도가 높아짐에 따라서 백금 입자 크기가 커지고 결정화도가 증가하는 것을 확인하였다. 이러한 결과에서 산소환원반응 활성을 위한 백금의 입자 크기와 결정화도가 $300^{\circ}C$에서 최적화되는 것으로 판단된다.

음식물 쓰레기 소멸화에 관한 연구 (A Study on Reduction of Food Waste)

  • 서명교;이상봉;이국의;이상훈
    • 한국환경보건학회지
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    • 제27권1호
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    • pp.14-19
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    • 2001
  • The physical and chemical transformation and reduction degree of food waste were investigated in a food waste reduction machine using thermophilic bacteria. The first operation of the reduction machine for grain, vegetables, fishes and flesh wastes proceeded during three weeks. The first and second reduction percentages of the wastes were 98.3% and 93.2%, respectively. The residue of food waste was composed of fruits, fish, and vegetables. The temperature distribution of the reduction machine ranged between 30 and 6$0^{\circ}C$ appropriate for growth of thermophilic bacteria. At initial stage the pH in the reduction machine decreased with organic acids produced, but increased as the organic acids decomposed by different thermophilic bacteria. In the reduction machine, the moisture content of the food waste was reduced from 80-90% to 10-20% after 24 hours, and the salinity of residue was 0.29% after the second operation. The degree of odor was most high between 2 and 4 hours.

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Electrocatalytic Reduction of Dioxygen by Cobaltporphyrin in Aqueous Solutions

  • 전승원;이효경;김송미
    • Bulletin of the Korean Chemical Society
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    • 제19권8호
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    • pp.825-830
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    • 1998
  • The electrocatalytic reduction of dioxygen by Co(TTFP)(Y)2 {Y=H2O or HO-} is investigated by cyclic voltammetry, spectroelectrochemistry, hydrodynamic voltammetry at a glassy carbon electrode in dioxygen-saturated aqueous solutions. Electrocatalytic reduction of dioxygen by CoⅡ(TTFP)(Y)2 establishes a pathway of 2e- reduction to form hydrogen peroxide, and then the generated hydrogen peroxide is reduced to water by CoⅠ(TTFP)(Y)2 at more negative potential. CoⅡ(TTFP)(Y)2 may bind dioxygen to produce the adduct complex [CoⅡ-O2 or CoⅢ-O2] which exhibits a Soret band at 411 nm and Q band at 531 nm.

Convenient Procedure for the Reduction of Carboxylic Acids via Acyloxyborohydrides

  • Cho, Byung-Tae;Yoon, Nung-Min
    • Bulletin of the Korean Chemical Society
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    • 제3권4호
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    • pp.149-152
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    • 1982
  • A new convenient method for the reduction of carboxylic acids to the corresponding alcohols via acyloxyborohydrides was explored. Acyloxyborohydrides, prepared from the reaction of various carboxylic acids and sodium borohydride, underwent reduction to the corresponding alcohols readily by the addition of dimethyl sulfate or Lewis acids, such as boron trifluoride etherate and triphenyl borate, presumably through acyloxyboranes. By utilizing this procedure, aliphatic and aromatic acids are rapidly and quantitatively reduced to the corresponding alcohols in terahydrofuran either at room temperature (or at $65^{\circ}$). This procedure provides selective reduction of carboxylic acids in the presence of halogen, nitro, and heterocyclic rings such as furan and thiophene.

Facile Preparation of Silver Nanoparticles and Application to Silver Coating Using Latent Reductant from a Silver Carbamate Complex

  • Kim, Kyung-A;Cha, Jae-Ryung;Gong, Myoung-Seon
    • Bulletin of the Korean Chemical Society
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    • 제34권2호
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    • pp.505-509
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    • 2013
  • A low temperature ($65^{\circ}C$) thermal deposition process was developed for depositing a silver coating on thermally sensitive polymeric substrates. This low temperature deposition was achieved by chemical reduction of a silver alkylcarbamate complex with latent reducing agent. The effects of acetol as a latent reducing agent for the silver 2-ethylhexylcarbamate (Ag-EHCB) complex and their blend solutions were investigated in terms of reducing mechanism, and the size and shape of silver nanoparticles (Ag-NPs) as a function of reduced temperature and time, and PVP stabilizer concentration were determined. Low temperature deposition was achieved by combining chemical reduction with thermal heating at $65^{\circ}C$. A range of polymer film, sheet and molding product was coated with silver at thicknesses of 100 nm. The effect of process parameters and heat treatment on the properties of silver coatings was investigated.

Electro-Chemical Reduction에 의한 $Hg_{1-x}Cd_{x}$Te재료의 특성 고찰 (A Research of the Characteristics of $Hg_{1-x}Cd_{x}$Te material by using Electro - Chemical Reduction)

  • 이상돈;김봉흡;강형부
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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    • pp.38-41
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    • 1994
  • The method of passivation for protecting the $Hg_{1-x}Cd_{x}$Te surface is important device fabrication process. Because the surface components are highly reactive leading to its chemical and electrical instability. Especially. the material of detecting for infrared radiation, of which composition is x=0.2 or 0.3, is narrow bandgap semi- conductor. The narrow bandgap semi conductors are largely governed by the properties of the semiconductor surface. The narrow bandgap semi-conductors are largely governed by the properties of the semiconductor surface. The electro-chemical processing of $Hg_{1-x}Cd_{x}$Te allows rigorous control of the surface chemistry and provides an in-suit monitor of surface reaction. So electro-chemical reduction at specific potential can be selectively eliminated the undesirable species on the surface and mainpulated to reproducibly attain the desired stoichiometry. This method shows to assess the quality of chemically treated good $Hg_{1-x}Cd_{x}$Te surface.

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