• 제목/요약/키워드: Powder metallurgy

검색결과 3,649건 처리시간 0.024초

Synthesis of Nanocrystalline ZnFe2O4 by Polymerized Complex Method for its Visible Light Photocatalytic Application: An Efficient Photo-oxidant

  • Jang, Jum-Suk;Borse, Pramod H.;Lee, Jae-Sung;Jung, Ok-Sang;Cho, Chae-Ryong;Jeong, Euh-Duck;Ha, Myoung-Gyu;Won, Mi-Sook;Kim, Hyun-Gyu
    • Bulletin of the Korean Chemical Society
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    • 제30권8호
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    • pp.1738-1742
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    • 2009
  • Nanocrystalline Zn$Fe_2O_4$ oxide-semiconductor with spinel structure was synthesized by the polymerized complex (PC) method and investigated for its photocatalytic and photoelectric properties. The observation of a highly pure phase and a lower crystallization temperature in Zn$Fe_2O_4$ made by PC method is in total contrast to that was observed in Zn$Fe_2O_4$ prepared by the conventional solid-state reaction (SSR) method. The band gap of the nanocrystalline Zn$Fe_2O_4$ determined by UV-DRS was 1.90 eV (653 nm). The photocatalytic activity of Zn$Fe_2O_4$ prepared by PC method as investigated by the photo-decomposition of isopropyl alcohol (IPA) under visible light (${\geq}$ 420 nm) was much higher than that of the Zn$Fe_2O_4$ prepared by SSR as well as Ti$O_{2-x}N_x$. High photocatalytic activity of Zn$Fe_2O_4$ prepared by PC method was mainly due to its surface area, crystallinity and the dispersity of platinum metal over Zn$Fe_2O_4$.

Energy Band Structure and Photocatalytic Property of Fe-doped Zn2TiO4 Material

  • Jang, Jum-Suk;Borse, Pramod H.;Lee, Jae-Sung;Lim, Kwon-Taek;Jung, Ok-Sang;Jeong, Euh-Duck;Bae, Jong-Seong;Won, Mi-Sook;Kim, Hyun-Gyu
    • Bulletin of the Korean Chemical Society
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    • 제30권12호
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    • pp.3021-3024
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    • 2009
  • $Zn_2Ti_{1-x}Fe_xO_4\;(0\;{\leq}\;x\;{\leq}\;0.7)$ photocatalysts were synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. $Zn_2Ti_{1-x}Fe_xO_4$ can absorb not only UV light but also visible light region due to doping of Fe in the Ti site of $Zn_2TiO_4$ lattice because of the band transition from Fe 3d to the Fe 3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $Zn_2TiO_4$ samples for hydrogen production under UV light irradiation decreased with an increase in Fe concentration in $Zn_2TiO_4$. Consequently, there exists an optimized concentration of iron for improved photocatalytic activity under visible light (${\lambda}{\leq}$420 nm)

용탕교반법에 의한 $Al_2O_{3(p)}$/LXA복합재료의 기계적 성질에 관한 연구 (A study on the Mechanical Properties of $Al_2O_{3(p)}$/LXA Composites by Melt-stirring Method)

  • 이현규;공창덕
    • 한국추진공학회지
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    • 제4권1호
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    • pp.65-73
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    • 2000
  • 금속기지 복합재료의 주조는 폭넓은 재료의 선택과 공정조건들을 제공하는 좋은 공정이다. 용탕교반기술은 압착주조 또는 분말야금과 비교하면 매우 간단하고 값이 싸기 때문에 주조방법중에서 산업응용에 가장 널리 쓰이는 좋은 방법이다. 최근에는 $\alpha$ -$Al_2O_{3(p)}$/Lo-Ex alloy 복합재료의 입자크기, 입자의 부피 분율, 기계적 성질에 있어서 Mg첨가 그리고 열팽창계수 등이 연구되어 왔다. $\alpha$ -$Al_2O_3$는 입자계면과 기지에 형성되어 기계적 성질에 중요한 역할을 하였다 대부분 복합재료의 인장강도는 증가하지 않지만 16$\mu\textrm{m}$ $\alpha$ -$Al_2O_3$ 입자를 5vol%로 첨가한 경우, 3wt.% Mg를 첨가한 복합재료의 인장강도는 증가한다. 강화재의 부피분율과 mg은 복합재료의 열팽창계수를 감소시켰다.

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다공성 3차원 Ti 지지체의 제조 및 알카리처리에 따른 생체활성 평가 (Fabrication of Porous 3-Dimensional Ti Scaffold and Its Bioactivity by Alkali Treatment)

  • 안상현;김승언;김교한;윤희숙;현용택
    • 한국재료학회지
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    • 제19권7호
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    • pp.362-368
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    • 2009
  • Ti scaffolds with a three-dimensional porous structure were successfully fabricated using powder metallurgy and modified rapid prototyping (RP) process. The fabricated Ti scaffolds showed a highly porous structure with interconnected pores. The porosity and pore size of the scaffolds were in the range of 66$\sim$72% and $300\sim400\;\mu$m, respectively. The sintering of the fabricated scaffolds under the vacuum caused the Ti particles to bond to each other. The strength of the scaffolds depended on the layering patterns. The compressive strength of the scaffolds ranged from 15 MPa to 52 MPa according to the scaffolds' architecture. The alkali treatment of the fabricated scaffolds in an aqueous NaOH solution was shown to be effective in improving the bioactivity. The surface of the alkali-treated Ti scaffolds had a nano-sized fibre-like structure. The modified surface showed a good apatite forming ability. The apatite was formed on the surface of the alkali treated Ti scaffolds within 1 day. The thickness of the apatite increased when the soaking time in a simulated body fluid (SBF) solution increased. It is expected that the surface modification of Ti scaffolds by alkali treatment could be effective in forming apatites in vivo and can subsequently enhance bone formation.

REACTION STEPS OF A FORMATION OF THE BLACK LAYER BEIWEEN IRON NTIRIDE AND TiN COATING

  • Baek, W.S.;Kwon, S.C.;Lee, J.Y.;Rha, J.J.;Lee, S.R.;Kim, K.H.
    • 한국표면공학회지
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    • 제32권3호
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    • pp.312-316
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    • 1999
  • The interfacial structure of duplex treated AISI 4140 consisting of iron nitride and TiN layer was characterized by optical microscope, SEM and XRD. A black layer was formed from the decomposition of iron nitride during Ti ion bombardment. The black layer was characterized as an a-Fe phase transformed from the iron nitride by XRD. In order to identify the formation mechanism of the black layer, a thermal analysis of iron nitride undertaken by DSC method. As an iron nitride was mostly consisted of ${\gamma}$'-Fe$_4$N and $\varepsilon$-$Fe_3$N phase after plasma nitriding, in this study, a ${\gamma}$'$-Fe_4$N and $\varepsilon$-$Fe_3$N powders were separately prepared by the different processing conditions of gas nitriding of iron powder in the fluidized bed. From the DSC thermal analysis, the phase transformation of ${\gamma}$'$-Fe_4$N, $\varepsilon$-$Fe_3$N was followed the path of transformation; $ \Upsilon{'}-Fe_4$Nlongrightarrow${\gamma}$-Felongrightarrowa-Fe and of $\varepsilon$-$Fe_3$Nlongrightarrow$\varepsilon$-$Fe_{2.5}$ /N+${\gamma}$'$-Fe_4$Nlongrightarrow${\gamma}$'-Fe$_4$Nlongrightarrow${\gamma}$longrightarrowFelongrightarrowalongrightarrowFe, respectively. It explains the reason why the $\varepsilon$ $-Fe_3$N phase disappeared in the first time and then ${\gamma}$'-Fe$_4$N in the formation of the black layer in the duplex coating.

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통전가압활성소결에 의한 생체재료용 Ti-HA복합재료 제조 및 특성 (Fabrication and Properties of Ti-HA Composites Produced by Pulsed Current Activated Sintering for Biomaterials)

  • 우기도;강덕수;권의표;문민석;손인진
    • 대한금속재료학회지
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    • 제47권8호
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    • pp.508-515
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    • 2009
  • Ti-6Al-4V biomaterial is widely used as a bone alternative. However, Ti-6Al-4V ELI alloy suffers from numerous problems such as a high elastic modulus and high toxicity. Therefore, non-toxic biomaterials with low elastic moduli need to be developed. Ti-HA(hydroxyapatite) composites were fabricated in the present work by pulsed current activated sintering (PCAS) at $1000^{\circ}C$ under 60 MPa using mixed Ti and HA powders. The effects of HA content on the physical and mechanical properties of the sintered Ti-HA composites have been investigated. X-ray diffraction(XRD) analysis of the Ti-HA composites, including Ti-40 wt%HA in particular, revealed new phases, $Ti_{2}O$, CaO, $CaTiO_3$, and TixPy, formed by chemical reactions between Ti and HA during sintering. The hardness of the Ti-HA composites decreased with an increase in HA content. The corrosion resistance of these composites was observed to be an excellent candidate as a commercial Ti-6Al-4 V ELI alloy. A Ti-5 wt%HA composite fabricated by PCAS is recommended as a new biomaterial, because it offers good corrosion resistance, compressive strength, wear resistance, and biocompatibility, and a low Young's modulus.

열간가압성형기술을 이용한 Ai-SiC 금속기 복합재료 개발 (Development of Al-SiC Metal Matrix Composites by using Hot Press Forming Technologies)

  • 전호진;김태원
    • Composites Research
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    • 제20권4호
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    • pp.9-17
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    • 2007
  • 분말야금법 및 고온진공가압기술, 열간등가압성형기술을 이용하여 알루미늄 금속기 복합재료를 제작하였으며 이들과 관련한 미시역학 기반 강화공정 모델을 개발하였다. 고온, 가압 성형공정은 기지재료의 비탄성거동과 성형체 내부의 기공 제거를 통한 충진을 수반하게 되며 이러한 공정은 압력, 온도 및 강화재의 체적분률 등과 같은 공정변수의 영향을 받게 된다. 따라서 개발된 강화공정 모델을 유한요소해석 프로그램에 적용함으로써 고온진공가압과 열간등가압 동안 기공의 상대밀도 변화에 따른 충진거동을 예측하였고 다양한 공정조건 하에서 실험결과와 잘 일치함을 확인하였다. 완성된 알루미늄 금속기 복합재료의 건전성 평가와 관련하여 인장시험을 수행하였으며 초기 잔존하는 기공의 영향에 따른 제반 기계적 특성을 고찰할 수 있었다.

Formation of Layered Bi5Ti3FeO15 Perovskite in Bi2O3-TiO2-Fe2O3 Containing System

  • Borse, Pramod H.;Yoon, Sang-Su;Jang, Jum-Suk;Lee, Jae-Sung;Hong, Tae-Eun;Jeong, Euh-Duck;Won, Mi-Sook;Jung, Ok-Sang;Shim, Yoon-Bo;Kim, Hyun-Gyu
    • Bulletin of the Korean Chemical Society
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    • 제30권12호
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    • pp.3011-3015
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    • 2009
  • Structural and thermo-analytical studies were carried out to understand the phase formation kinetics of the single phase $Bi_5Ti_3FeO_{15}$ (BTFO) nanocrystals in $Bi_2O_3-Fe_2O_3-TiO_2$, during the polymerized complex (PC) synthesis method. The crystallization of Aurivillius phase $Bi_5Ti_3FeO_{15}$ layered perovskite was found to be initiated and achieved under the temperature conditions in the range of ${\sim}$800 to 1050$^{\circ}C$. The activation energy for grain growth of $Bi_5Ti_3FeO_{15}$ nanocrystals (NCs) was very low in case of NCs formed by PC (2.61 kJ/mol) than that formed by the solid state reaction (SSR) method (10.9 kJ/mol). The energy involved in the phase transformation of Aurivillius phase $Bi_5Ti_3FeO_{15}$ from $Bi_2O_3-Fe_2O_3-TiO_2$ system was ${\sim}$ 69.8 kJ/mol. The formation kinetics study of $Bi_5Ti_3FeO_{15}$ synthesized by SSR and PC methods would not only render a large impact in the nanocrystalline material development but also in achieving highly efficient visible photocatalysts.

고에너지 밀링분말과 급속소결을 이용한 Ti-Nb-Zr-HA 생체복합재의 기계적 성질 및 생체적합성 (Mechanical Properties and Bio-Compatibility of Ti-Nb-Zr-HA Biomaterial Fabricated by Rapid Sintering Using HEMM Powders)

  • 박상훈;우기도;김상혁;이승민;김지영;고혜림;김상미
    • 한국재료학회지
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    • 제21권7호
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    • pp.384-390
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    • 2011
  • Ti-6Al-4V ELI (Extra Low Interstitial) alloy has been widely used as an alternative to bone due to its excellent biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity. Therefore, nontoxic biomaterials with a low elastic modulus should be developed. However, the fabrication of a uniform coating is challenging. Moreover, the coating layer on Ti and Ti alloy substrates can be peeled off after implantation. To overcome these problems, it is necessary to produce bulk Ti and Ti alloy with hydroxyapatite (HA) composites. In this study, Ti, Nb, and Zr powders, which are biocompatible elements, were milled in a mixing machine (24h) and by planetary mechanical ball milling (1h, 4h, and 6h), respectively. Ti-35%Nb-7%Zr and Ti-35%Nb-7%Zr-10%HA composites were fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70MPa using mixed and milled powders. The effects of HA addition and milling time on the biocompatibility and physical and mechanical properties of the Ti-35%Nb-7%Zr-(10%HA) alloys have been investigated. $Ti_2O$, CaO, $CaTiO_3$, and $Ti_xP_y$ phases were formed by chemical reaction during sintering. Vickers hardness of the sintered composites increases with increased milling time and by the addition of HA. The biocompatibilty of the HA added Ti-Nb-Zr alloys was improved, but the sintering ability was decreased.