• 제목/요약/키워드: Particle Size Reduction

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Development of volume reduction method of cesium contaminated soil with magnetic separation

  • Yukumatsu, Kazuki;Nomura, Naoki;Mishima, Fumihito;Akiyama, Yoko;Nishijima, Shigehiro
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.1
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    • pp.10-13
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    • 2016
  • In this study, we developed a new volume reduction technique for cesium contaminated soil by magnetic separation. Cs in soil is mainly adsorbed on clay which is the smallest particle constituent in the soil, especially on paramagnetic 2:1 type clay minerals which strongly adsorb and fix Cs. Thus selective separation of 2:1 type clay with a superconducting magnet could enable to reduce the volume of Cs contaminated soil. The 2:1 type clay particles exist in various particle sizes in the soil, which leads that magnetic force and Cs adsorption quantity depend on their particle size. Accordingly, we examined magnetic separation conditions for efficient separation of 2:1 type clay considering their particle size distribution. First, the separation rate of 2:1 type clay for each particle size was calculated by particle trajectory simulation, because magnetic separation rate largely depends on the objective size. According to the calculation, 73 and 89 % of 2:1 type clay could be separated at 2 and 7 T, respectively. Moreover we calculated dose reduction rate on the basis of the result of particle trajectory simulation. It was indicated that 17 and 51 % of dose reduction would be possible at 2 and 7 T, respectively. The difference of dose reduction rate at 2 T and 7 T was found to be separated a fine particle. It was shown that magnetic separation considering particle size distribution would contribute to the volume reduction of contaminated soil.

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

  • Yuna, Ki-Seok;Park, Young-Chul;Yang, Beom-Seok;MIn, Hyun-Hong;Won, Chang-Whan
    • Journal of Powder Materials
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    • v.12 no.1
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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.

Effects of Driving Force and Surfactant on the Formation of Ag Powders (Ag 입자의 형성에서 구동력 및 계면활성제의 효과)

  • Lee, Chang Geun;Kim, Donggyu;Lee, Sang Hwa;Lee, Hae Woo;Lee, Hyo Jong;Kim, Insoo
    • Korean Journal of Metals and Materials
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    • v.49 no.11
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    • pp.860-867
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    • 2011
  • This study was performed to investigate the effects of the driving force for reduction and the surfactant (polyacrylic acid) on the size of Ag particles. As the driving force for reduction increases, the size of particles decreases due to a decrease of initial nuclei-size. Also, an increase of pH increases the amount of ionized surfactant, which leads to a decrease of particle size due to the prevention of particle growth. Both the driving force and the surfactant may affect the particle size, but the surfactant appeared to be a more dominant factor than reduction potential in terms of controlling the particle size. An increase of surfactant in the range of pH=3-4 decreases the size of Ag particles, although the reduction potential also decreases.

The Effect of Reduction Temperature on the Characteristic Variation of Niobium Powder During Metallothermic Reduction Process (금속열환원 공정에서 반응온도가 니오븀 분말 특성에 미치는 영향)

  • Yoon, Jae-Sik;Lee, Young-Mi;Hwang, Sun-Ho;Kim, Byung-Il
    • Journal of Powder Materials
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    • v.16 no.2
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    • pp.104-109
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    • 2009
  • Niobium powder was made from potassium heptafluoroniobite ($K_2NbF_7$) as the raw material using sodium (Na) as a reducing agent based on the hunter process. The apparatus for the experiment was designed and built specifically for the present study. The niobium particle size greatly increased as the reduction temperature increased from $710^{\circ}C$ to $800^{\circ}C$. The particle size was fairly uniform, varying from $0.09{\mu}m$ to $0.4{\mu}m$ depending on the reduction temperatures. The niobium powder morphology and particle size are very sensitive to a reaction temperature in the metallothermic reduction process. The yield of niobium powder increased from 55% to 80% with a increasing a reaction temperature.

Electrocatalyst for the Oxygen Reduction Reaction: from the Nanoscale to the Macroscale

  • Chung, Dong Young;Sung, Yung-Eun
    • Journal of Electrochemical Science and Technology
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    • v.5 no.3
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    • pp.65-72
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    • 2014
  • The use of nanoscale electrocatalysts is a promising strategy for achieving high catalyst activity due to their large surface area. However, catalyst activity is not directly correlated to particle size. To understand this discrepancy, many studies have been conducted, but a full understanding has still not been achieved, despite the importance of particle size effects in designing an active catalyst. In this review, we focus on the discussion of particle size effects on the oxygen reduction reaction, and also discussed the nanoscale design beyond the nanoparticle to the meso and macroscale design.

Characteristics of Powder with Change of Temperature in Production of Tantalum Powder by MR-EMR Combination Process (MR-EMR 복합공정에 의한 탄탈륨분말의 제조시 온도변화에 따른 분말의 특성)

  • 배인성;윤재식;박형호;윤동주;이민호;설경원;김병일
    • Journal of Powder Materials
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    • v.10 no.6
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    • pp.395-405
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    • 2003
  • In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of $K_2$TaF$_{7}$. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

Effect of High Temperature Treatment and Subsequent Oxidation anil Reduction on Powder Property of Simulated Spent Fuel

  • Song, Kun-Woo;Kim, Young-Ho;Kim, Bong-Goo;Lee, Jung-Won;Kim, Han-Soo;Yang, Myung-Seung;Park, Hyun-Soo
    • Nuclear Engineering and Technology
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    • v.28 no.4
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    • pp.366-372
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    • 1996
  • The simulated spent PWR fuel pellet which is corresponding to the turnup of 33,000 MWD/MTU is prepared by adding 11 fission-product elements to UO$_2$. The simulated spent fuel pellet is treated at 40$0^{\circ}C$ in air (oxidation), at 110$0^{\circ}C$ in air (high-temperature treatment), and at $600^{\circ}C$ in hydrogen (reduction). The product is treated through additional addition and reduction up to 3 cycles. Pellets are completely pulverized by the first oxidation, and the high-temperature treatment causes particle and crystallite to grow and surface to be smooth, and thus particle size significantly increases and surface area decreases. The reduction following the high-temperature treatment decreases much the particle size by means of the formation of intercrystalline cracks. The particle size decreases a little during the second oxidation and reduction cycle and then remains nearly constant during the third and fourth cycles. Surface area of pounder increases progressively with the repetition of oxidation and reduction cycles, mainly due to the formation of Surface cracks. The degradation of surface area resulting from high-temperature treatment is restored by too subsequent resulting oxidation and reduction cycles.

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Preparation of Ultrafine Nickel Powders by Wet Reduction Process (습식 환원법에 의한 니켈 미분말의 제조)

  • Lee, Yoon-Bok;Moon, Young-Tae;Shin, Dong-Woo;Kim, Kwang-Ho
    • Korean Journal of Materials Research
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    • v.12 no.10
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    • pp.803-808
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    • 2002
  • Nickel powders were prepared from nickel chloride solution by wet reduction process, and the size control of the particles was investigated with reactant concentration, dispersant agent, and the addition of ethanol as an organic solvent in NiCl$_2$ aqueous solution. The size of the particle decreased with the increase of nickel chloride concentration. Their average particle size were 1.9$\mu\textrm{m}$, 1.6$\mu\textrm{m}$ and $1.5\mu\textrm{m}$ with 0.5M, 0.8M and 1.0M of nickel chloride concentration respectively. The spherical particle was easily controlled by the addition of ethanol as an organic solvent. Especially, in 30 vol% of ethanol, the average particle size and specific surface area were about 0.2$\mu\textrm{m}$ and 8.98m$^2$/g, respectively.

High Fastness Dyeing Technology of Polyester Microfiber with Several Disperse Dyes and Vat dye (수종의 분산 염료 및 환원염료에 의한 Polyester microfiber의 고견뢰 염색기술)

  • 백진주;권오대;손아름;이난형;김삼수
    • Textile Coloration and Finishing
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    • v.15 no.6
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    • pp.1-7
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    • 2003
  • Polyester microfiber has usually greater dye uptake than normal denier polyester fiber in same dyeing condition. In spite of this high dye uptake dyed microfiber fabric has not only low visual colour depth but also poor washing fastness property. In order to study high colouring dyeing technology and high washing fastness of polyester microfiber, dyeing property of polyester microfiber was investigated according to the dye solubility and particle size of used disperse dyes in aqueous dye solution. After disperse dyeing, dyed fabric with disperse dye was redyed with a vat dye without reduction clearing in order to obtain a high washing fastness property. The result were as followings ; A small particle sized disperse dyes such as C. I. Disperse Blue 56 and Red 60 showed high rate of initial exhaution compared with a large particle sized disperse dyes like C. I. Disperse Blue 165 and Red 343. In study of dyeing property of polyester microfiber with C. I. Vat Blue 1, polyester microfiber could achieve high dye uptake at a given optimum vatting process conditions. On the other hand, in consecutive dyeing with disperse and vat dye, K/S value of polyester microfiber with a small particle sized disperse dye increased without reduction clearings, but K/S value of polyester microfiber with a large particle sized disperse dye decreased with reduction clearings.