Spark Plasma Sintering Behavior of Pure Aluminum Depending on Various Sintering Temperatures

권한상,박대훈,박용하,Jean François Silvain,Akira Kawasaki,박용호 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.1

We have successfully fabricated high-density pure aluminum (Al) bulk by means of a spark-plasma-sintering (SPS) process. The relative density of Al was enhanced as the sintering temperature of the SPS process increased. During the SPS process for pure Al power, the Al oxide layer on the surface of the Al particle was partially broken by the microplasma and applied pressure. The microstructures of the spark-plasma-sintered compacts obtained at various temperatures were observed by optical microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. We believe that the pinning effect,rapid heating cycle, and applied pressure played an important role in restraining the particle growth despite the increase in sintering temperature. It is feasible that the employed SPS process could be very useful to achieve fully densified Al compact.

나노다이아몬드 소재산업 육성전략

권한상 부산연구원 2017 연구보고서 학연연구 Vol.2017 No.0

The nanomaterials industry is a high value-added industry with a high proportion of R&D investment. The world's major nations are investing enormous funds in nanomaterials and technology R&D to promote technological innovation. Nanodiamonds are single-crystal particles with a size of several to several tens of nanometers (10-9m), and are the advanced materials with the highest hardness among the existing materials. Nanodiamonds have excellent hardness, durability and chemical stability and excellent lubricity due to nanometer particle size. They show excellent characteristics in terms of erosion resistance, abrasion resistance, heat resistance and durability. Nanodiamonds can be applied to various industries by controlling its physical properties. This study shows technology and market trends of nanodiamonds and connectivity between advanced material(nanodiamond) and industries of Busan.

Fabrication of Single Crystalline Diamond Reinforced Aluminum Matrix Composite by Powder Metallurgy Route

권한상,Marc Leparoux,Jean-Marc Heintz,Jean-François Silvain,Akira Kawasaki 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.5

We have successfully fabricated highly densified aluminum (Al)-diamond composite materials by a simple hot press method. The thermal conductivity of the Al-diamond composite materials was measured. These materials had different types, sizes and fractions of diamond. These obtained values were discussed based on theoretically calculated values. The thermal conductivity of the composite materials, measured by Laser-Flash method, was found to have slightly increased compared to that of pure bulk Al. The obtained microstructures of the composite materials showed a lot of cleavage existing in the interface between the Al matrix and the diamond particles, which led to the low increment of the thermal conductivity. Moreover, Al-diamond bulk materials with different sintering temperatures in solid state, liquid phase, and transient region between solid and liquid of Al, have been synthesized.

흑연 함량에 따른 알루미늄 기지 복합재료의 방전플라즈마소결 거동 및 방열 특성

권한상,박재홍,주성욱,홍상휘,문지훈,Kwon, Hansang,Park, Jehong,Joo, Sungwook,Hong, Sanghwui,Mun, Jihoon 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.3

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

방전플라즈마 소결공정으로 제조된 단일벽탄소나노튜브 강화 금속기지 복합재료

권한상(Hansang Kwon) 한국동력기계공학회 2017 동력시스템공학회지 Vol.21 No.4

WC-Co 초경합금의 산화거동

이길근,권한상,하국현 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.2

The oxidation behavior of 91 WC-9Co hardmetal in weight percentage has been studied in the present work as a part of the development of recycling process. The morphological and compositional changes of the WC-Co hardmetal with oxidation time at 90$0^{\circ}C$ were analyzed by using surface observation and X-ray diffraction. respective]y. As the oxidation time increased, the WC-Co hardmetal was continuously expanded to form porous oxide mixtures of $CoWO_4$ and $WO_3$. The morphology of porous oxide mixture was basically dependent on initial shape of the WC-Co hardmetal. From thermo-gravimetric (TG) analysis, it was found that the oxidation rate was increased with increasing oxidation temperature and oxygen content in the flowing atmospheric gas. The fraction of oxidation versus time curves showed S-curve relationship at a given of oxidation temperature. These oxidation behaviors of the WC-Co hardmetal were discussed in terms of previously proposed kinetic models.

Fabrication of Core/Shell Structured SiO2/Zn2SiO4:Mn2+ Composite and Its Photoluminescence Properties

박재홍,김종수,권한상 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.7

Core/shell structured SiO2/Zn2SiO4:Mn2+ composite was prepared by thermal-diffusion reaction between SiO2 and Zn1−xMnxO particles, which is a low cost solid-state method. The X-ray diffraction and scanning electron microscope results showed that a 5-μm-thick dense Zn2SiO4:Mn2+ layer was successfully formed on the surface of the SiO2 particles. The PL spectrum of the SiO2/Zn2SiO4:Mn2+ composite revealed a green emission peak at 526 nm with PL intensity 20% higher than that of the conventional Zn2SiO4:Mn2+ particles. In addition, the decay time of the SiO2/Zn2SiO4:Mn2+ composite was shorter (10% = 7 ms) than that of the conventional Zn2SiO4:Mn2+ particles (10% =12 ms), which is owing to the relaxation of forbidden transition of Mn2+ ions due to the localized stress of Mn2+ ions arising from the surface tension in the SiO2/Zn2SiO4:Mn2+ composite.

가스압 함침 공정으로 제조된 TiB2-steel 금속복합재료의 미세조직 및 기계적 물성에 관한 연구

이지혜,이동현,조승찬,권한상,이상관,이상복,김정환 한국복합재료학회 2022 Composites research Vol.35 No.4

본 연구에서는 가스압 함침공정을 이용하여 고체적률 TiB2-steel 복합재료를 제조하였으며, 미세조직 분석과 압축강도 및 경도를 측정하였다. 복합재료의 미세조직과 기계적 물성과의 연관성을 고찰하고자, 압축시험 후 시편의 파면을 분석하고 압축시험 중 시편의 파괴 거동을 예측하였다. 파면 분석 결과, 기지금속과 강화상 입자간의 계면파괴 흔적이 관찰되었으며, 이에 기지금속과 강화상의 계면을 TEM을 사용하여 분석하였다. 제조된 복합재료의 미세조직 분석 결과, TiB2 강화상 및 steel 기지상 이외에 TiC 상과 조대한 (Fe,M)2B (M=Cr,Mn)상이 생성된 것을 확인할 수 있었으며, 열역학 계산을 통하여 공정조건에서 TiC와 (Fe,M)2B가 안정상으로 생성될 수 있음을 확인하였다. 제조된 TiB2-steel 복합재료는 기지 금속 대비 경도가 크게 상승하였으며, 상온 압축강도 및 탄성계수는 각각 3.07배, 1.95배 향상되었다. 복합재료 내부 전반에 생성된 조대한 (Fe,M)2B (M=Cr,Mn)상이 기계적 물성 저하를 일으키는 것으로 보이며, (Fe,M)2B (M=Cr,Mn)상의 생성을 제어함으로써 TiB2-steel 복합재료의 기계적 물성을 추가적으로 향상시킬 수 있을 것이라 생각한다.

cBN 입자상 강화재 첨가에 따른 중성자 흡수용 B4C/Al 복합재의 열전도도 변화 연구

강민우,이동현,이태규,김정환,이상복,권한상,조승찬 한국복합재료학회 2023 Composites research Vol.36 No.6

본 연구에서는 기존 사용후핵연료 운송/저장 용기에 사용되는 중성자 흡수용 B4C/Al 복합소재의 열전도도를 개선하기 위해 탄화붕소(B4C)와 입방정 질화붕소(cBN)를 동시에 강화재로 사용한 알루미늄(Al) 기지 복합소재를 제조 평가하였다. 이를 위해서 교반주조 공정을 통해 복합재 잉곳을 제조하고 이를 압연하여 실용이 가능한 중성자 흡수용 소재를 성공적으로 제조하였다. 제조된 소재의 평가를 위해 cBN 첨가에 따른 열전도도와 중성자 흡수능 변화를 관찰하였다. 열전도도 측정 결과, B4C 단일 입자만을 사용한 복합소재 대비 B4C, cBN을 함께 사용한 복합소재가 동일 체적율 조건 하에서 약 3%의 열전도도 증가가 발생하는 것을 확인하였으며 중성자 흡수 단면적 계산을 통해 중성자 흡수능이 무시할 수 있는 수준으로 저하가 발생하는 것을 확인하였다. 본 연구의 결과를 바탕으로, 중성자 흡수 소재의 새로운 설계 방안을 제시하고 고성능 운송/저장 용기의 개발에 기여할 수 있을 것으로 기대된다. This study aimed to enhance the thermal conductivity of B4C/Al composite materials, commonly used in transport/storage containers for spent nuclear fuel, by incorporating both boron carbide (B4C) and cubic boron nitride(cBN) as reinforcing agents in an aluminum (Al) matrix. The composite materials were successfully manufactured through a stir casting process and practical neutron-absorbing materials were obtained by rolling the fabricated composite ingot. The evaluation of the thermal conductivity of the fabricated composites was carried out because thermal conductivity is critical for neutron absorbing materials. The thermal conductivity measurement results indicated an approximately 3% increase in thermal conductivity under the same volume fraction when compared to composite materials using only B4C particles. Through neutron absorption cross-sectional area calculations, it was confirmed that the neutron absorption capability decreased to a negligible level. Based on the findings of this study, new design approaches for neutron absorption materials are proposed, contributing to the development of high-performance transport/storage containers.

알루미늄-스테인레스스틸-구리 경사기능재료의 제조 및 특성평가

박광재 ( Kwangjae Park ),김다솜 ( Dasom Kim ),권한상 ( Hansang Kwon ) 한국복합재료학회 2023 Composites research Vol.36 No.4

Aluminum (Al) and copper(Cu) are non-ferrous alloys with excellent electrical and thermal conductivity but have relatively lower mechanical properties than iron alloys. Stainless steel(STS), an iron alloy, is a high-strength industrial material due to its excellent mechanical properties and corrosion resistance compared to non-ferrous Al and Cu. In this research combined Al, Cu, and STS to fabricate as a functionally graded material (FGM) through a powder metallurgical process. The produced FGM exhibited lightweight and excellent surface hardness compared to copper and iron alloys and also showed higher thermal conductivity than single Al and STS materials.