• 제목/요약/키워드: reduction and diffusion process

검색결과 139건 처리시간 0.023초

환원확산법에 의한 TiFe 수소 흡장합금의 제조에 관한 기초적 연구 (Fundamental Study on the Production of TiFe Hydrogen Alloy by the Reduction-Diffusion Process)

  • 권호영;일본명;일본명
    • 한국안전학회지
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    • 제8권2호
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    • pp.3-9
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    • 1993
  • For comparison, we used Ca and Mg as reducers to produce TiFe hydrogen stroage alloy from Fe and TiO$_2$by the Reduction-Diffusion process. The results obtained were as follow. \circled1 Ca was found to be effective both for reduction and diffusion processes. Moreover, Ca oxide was easily removed in an NH$_4$Cl solution after the reaction. \circled2 In the case of using Ca as a reducer, the Reduction-Diffusion process is considered to take place in the foiling three steps. First, TiO$_2$is reduced to Ti by Ca over 100$0^{\circ}C$. Second, the atomic Ti drifts in the Ca melt and meets Fe particles. Finally, the atomic Ti diffuses in to the Fe particles. \circled3 In the case of using Mg as a reducer, We found that the reduction reaction of TiO$_2$went well. But the reduced Ti scarcely diffused into Fe particles. This was probably because no Mg melt was formed due to the high vapor pressure of Mg.

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Development of a Mass Transfer Model and Its Application to the Behavior of the Cs, Sr, Ba, and Oxygen ions in an Electrolytic Reduction Process for SF

  • 박병흥;강대승;서중석;박성원
    • 방사성폐기물학회지
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    • 제3권2호
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    • pp.85-93
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    • 2005
  • Isotopes of alkali and alkaline earth metals (AM and AEM) are the main contributors to the heat load and the radiotoxicity of spent fuel (SF) . These components are separated from the SF and dissolved in a molten LiCl in an electrolytic reduction process. A mass transfer model is developed to describe the diffusion behavior of Cs, Sr, and Ba in the SF into the molten salt. The model is an analytical solution of Fick's second law of diffusion for a cylinder which is the shape of a cathode in the electrolytic reduction process. And the model is also applied to depict the concentration profile of the oxygen ion which is produced by the electrolysis of Li$_{2}$O. The regressed diffusion coefficients of the model correlating the experimentally measured data are evaluated to be greater in the order of Ba, Cs, and Sr for the metal ions and the diffusion of the oxygen ion is slower than the metal ions which implies that different mechanisms govern the diffusion of the metal ions and the oxygen ions in a molten LiCl.

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The Influence of Mechanical Milling on the Structure and Magnetic Properties of Sm-Fe-N Powder Produced by the Reduction-Diffusion Process

  • Lee, Jung-Goo;Kang, Seok-Won;Si, Ping-Zhan;Choi, Chul-Jin
    • Journal of Magnetics
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    • 제16권2호
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    • pp.104-107
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    • 2011
  • In the present study, we systematically investigated the effect of mechanical milling on the magnetic properties of $Sm_2Fe_{17}N_x$ powders produced by the reduction-diffusion process. The Sm-Fe powders obtained by the reduction-diffusion process were composed of an $Sm_2Fe_{17}N_x$ single phase. After nitrogenation, the coercivity and saturation magnetization of the powders were 0.48 kOe and 13.32 kG, respectively. The particle size largely decreased down to less than $2\;{\mu}m$ in diameter after ball milling for 30 hours. However, there is no evidence that the $Sm_2Fe_{17}N_x$ was decomposed to Sm-N and ${\alpha}$-Fe even after ball milling for 30 hours. The coercivity was significantly improved up to 8.82 kOe after milling for 60 hours. However, the magnetization decreased linearly with the ball milling time.

Fe 나노분말을 사용한 환원-확산공정에서 Sm2Fe17 합금상형성에 미치는 공정온도의 영향 (Effect of Process Temperature on the Sm2Fe17 Alloying Process During a Reduction-Diffusion Process Using Fe Nanopowder)

  • 윤준철;이건용;이재성
    • 대한금속재료학회지
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    • 제48권11호
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    • pp.995-1002
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    • 2010
  • This study investigated the effect of process temperature on the alloying process during synthesis of $Sm_2Fe_{17}$ powder from ball-milled samarium oxide ($Sm_2O_3$) powders and a solid reducing agent of calcium hydrides ($CaH_2$) using iron nanopowder (n-Fe powder) by a reduction-diffusion (R-D) process. The $n-Fe-Sm_2O_3-CaH_2$ mixed powders were subjected to heat treatment at $850{\sim}1100^{\circ}C$ in $Ar-H_2$ for 5 h. It was found that the iron nanopowders in the mixed powders are sintered below $850^{\circ}C$ during the R-D process and the $SmH_2$ is synthesized by a reduced Sm that combines with $H_2$ around $850^{\circ}C$. The results showed that $SmH_2$ is able to separate Sm and $H_2$ respectively depending on an increase in process temperature, and the formed $Sm_2Fe_{17}$ phase on the surface of the sintered Fe nanopowder agglomerated at temperatures of $950{\sim}1100^{\circ}C$ in this study. The formation of the $Sm_2Fe_{17}$ layer is mainly due to the diffusion reaction of Sm atoms into the sintered Fe nanopowder, which agglomerates above $950^{\circ}C$. We concluded that nanoscale $Sm_2Fe_{17}$ powder can be synthesized by controlling the diffusion depth using well-dispersed Fe nanopowders.

환원·확산법에 의한 2-17형 고성능 희토류영구자석 재료의 제조에 있어서 첨가원소의 영향 (Effect of Addition Elements on the Production of the 2-17 Type High Performance of the Rare Earth Permanent Magnet Materials by the Reduction and Diffusion Process)

  • 송창빈;조통래
    • 열처리공학회지
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    • 제8권4호
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    • pp.333-339
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    • 1995
  • The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

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분무건조와 환원-확산 공정에 의한 Nd2Fe14B 분말의 합성 (Synthesis Of Nd2Fe14B Powders by Spray-Drying and Reduction-Diffusion Process)

  • 최철진;허민선;박병연;김성덕;하국현;김병기;박용호
    • 한국분말재료학회지
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    • 제10권6호
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    • pp.436-442
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    • 2003
  • The magnetic Nd-Fe-B powders were prepared by a thermochemical method, consisting of the processes of spray-drying, debinding, milling, H$_2$-reduction, Ca-reduction, and washing. The optimum process conditions were studied by microstructural and thermal analysis. The resultant Nd-Fe-B powder was spherical with the size of 1 ${\mu}{\textrm}{m}$. Effects of the process parameters of each step on the microstructure of the powders were investigated, and their magnetic properties were evaluated.

환원-확산법에 의해 제조된 Sm-Fe 합금분말의 질화거동 및 자기특성에 미치는 Mn첨가 효과 (The Effect of Mn Addition on Nitrogenation Behavior and Magnetic Properties of Sm-Fe Alloy Powder Produced by Reduction-diffusion Method)

  • 서영택;백연경;이정구;최철진
    • 한국분말재료학회지
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    • 제20권1호
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    • pp.13-18
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    • 2013
  • In the present study, we systematically investigated the effect of Mn addition on nitrogenation behavior and magnetic properties of Sm-Fe powders produced by reduction-diffusion process. Alloy powders with only $Sm_2(Fe,Mn)_{17}$ single phase were successfully produced by the reduction-diffusion process. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder rapidly increased during nitrogenation and reached the maximum of 637 Oe after 16 hours. After further nitrogenation, it decreased. In contrast, the coercivity of $Sm_2Fe_{17}$ powder gradually increased during nitrogenation for 24 hours. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder was higher than that of $Sm_2Fe_{17}$ powder at the same condition of nitrogenation. It was considered that the Mn addition facilitates the nitrogenation of $Sm_2Fe_{17}$ powder and enhances the coercivity.

환원/확산 공정에 의한 고성능 Nd-Fe-B 자성분말의 제조 (Preparation of Highly Efficient Nd-Fe-B Magnetic Powders by Reduction/Diffusion Process)

  • 김동수;진춘강;백연경;최철진
    • 한국분말재료학회지
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    • 제20권3호
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    • pp.197-202
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    • 2013
  • A novel route to prepare Nd-Fe-B magnetic particles by utilizing both spray drying and reduction/diffusion processes was investigated in this study. Precursors were prepared by spray drying method using the aqueous solutions containing Nd salt, Fe salt and boric acid with stoichiometric ratios. Precursor particles could be obtained with various sizes from 2 to $10{\mu}m$ by controlling concentrations of the solutions and the average size of $2{\mu}m$ of precursors were selected for further steps. After heat treatment of precursors in air, Nd and Fe oxides were formed through desalting procedure, followed by reduction processes in Hydrogen ($H_2$) atmosphere and with Calcium (Ca) granules in Argon (Ar) successively. Moreover, diffusion between Nd and Fe occurred during Ca reduction and $Nd_2Fe_{14}B$ particles were formed. With Ca amount added to particles after $H_2$ reduction, intrinsic coercivity was changed from 1 to 10 kOe. In order to remove and leach CaO and residual Ca, de-ionized water and dilute acid were used. Acidic solutions were more effective to eliminate impurities, but Fe and Nd were dissolved out from the particles. Finally, $Nd_2Fe_{14}B$ magnetic particles were synthesized after washing in de-ionized water with a mean size of $2{\mu}m$ and their maximum energy product showed 9.23 MGOe.

1.5wt%C 초고탄소 워크롤 제조를 위한 단조 공정 설계: 기공압착 및 접합강도 분석 (Process Design for Manufacturing 1.5wt%C Ultrahigh Carbon Workroll: Void Closure Behavior and Bonding Strength)

  • 임형철;이호원;김병민;강성훈
    • 소성∙가공
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    • 제22권5호
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    • pp.269-274
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    • 2013
  • Experiments and numerical simulations of the incremental upsetting test were carried out to investigate void closure behavior and mechanical characteristic of a 1.5wt%C ultra-high carbon steel. The experimental results showed that the voids become quickly smaller as the reduction ratio increases. The simulation results confirmed this behavior and indicated that the voids were completely closed at a reduction ratio of about 40~45% during incremental upsetting. After the completion of the incremental upsetting tests, the process of diffusion bonding was employed to heal the closed voids in the deformed specimens. To check the appropriate temperature for diffusion bonding, deformed specimens were kept at 800, 900, 1000 and $1100^{\circ}C$ for an hour. In order to investigate the effect of holding time for diffusion bonding at $1100^{\circ}C$, specimens were kept at 10, 20, 30, 40, 50 and 60minutes in the furnace. A distinction between closed and healed voids was clearly established using microstructural observations. In addition, subsequent tensile tests demonstrated that complete healing of a closed void was achieved for diffusion bonding temperatures in the range $900{\sim}1100^{\circ}C$ with a holding time larger than 1 hour.

환원-확산법에 의한 Sm-Fe-N계 자성분말 제조 (Synthesis of Magnetic Powder in the Sm-Fe-N System by the Reduction-Diffusion Process)

  • 이정구;강석원;박상준;오영우;최철진
    • 대한금속재료학회지
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    • 제48권9호
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    • pp.842-846
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    • 2010
  • In the present study, the reduction-diffusion method was employed to produce Sm-Fe alloy powder. It was confirmed that the amount of unreacted ${\alpha}-Fe$ in $Sm_2Fe_{17}$ matrix gradually decreased as the percentage of $Sm_2O_3$ increased. $Sm_2Fe_{17}$ single-phase powder was produced by the reduction-diffusion method with 40% excess $Sm_2O_3$. The Ca and Oxygen contents of the powder were approximately 300 ppm and 1600 ppm, respectively, after washing and acid treatment. By a subsequent nitrogenation, $Sm_2Fe_{17}N_x$ magnetic powders were produced. The coercivity of the powder increased with decreasing of the particle size by ball milling, and the highest coercivity of 2850 Oe was obtained after milling for 10 hours.