• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.780-786
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• 2011

Mg hydride had high hydrogen capacity (7.6%), lightweight and low cost materials and it was promising hydrogen storage material at high temperature. However, commercial applications of the Mg hydride are currently hindered by its high absorption/desorption temperature, and very slow reaction kinetics. one of the approaches to improve the kinetic is $MgH_x$ intermixed with carbon. And it shows that carbon and carbon allotropes have a beneficial effect on hydrogen sorption in Mg. The graphene is a kind of carbon allotropes which is easily desorbed reaction at low temperatures because its reaction is exothermic. In this work, the effect of graphene concentration on the kinetics of Mg hydrogen absorption reaction was investigated. The $MgH_x$-Graphene composites has been prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD and simultaneous TG, DSC analysis. The hydrogenation behaviors were evaluated by using a sievert's type automatic PCT apparatus. In this research, results of kinetic profiles exhibit hydrogen absorption rate of $MgH_x$-5wt.% and 10wt.% graphene composite, as 1.25wt.%/ms, 10.33wt.%/ms against 0.88wt.%/ms for $MgH_x$ alone at 473K.

• 한국세라믹학회지
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• 제35권9호
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• pp.923-932
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• 1998

Al2O3/Al composites were produced by displacement reaction method which was carried out by imm-ersing the sintered silica preform which was prepared form fused silica powder in molten aluminu. an ac-tivation energy of 94kJ/mole was calculated from Al-SiO2 reaction data in 1000-130$0^{\circ}C$ temperature range With increase of reaction temperature the alumina particle in the Al2O3/Al composites produced with pur metal Al showed grain growth and the growth of alumina particle in Al2O3/Al composite produced by using of Mg contained Al alloy was inhibited. The flexural strength of Al2O3/Al composites produced at 100$0^{\circ}C$ showed the highest value as 393 MPa. Flexural strength of the composite fabricated at 85$0^{\circ}C$ showed higher deviation than that of the composite produced at above 100$0^{\circ}C$ Low flexural strength of the composite fa-bricated at 120$0^{\circ}C$ due to the growth of pore and alumina particle size. The hardness of composites de-pended on alumina content in Al2O3/Al composite decreased with increasing of aluminium content in case the same alumina content and increased with increasing of silicon content in composite.

• 대한금속재료학회지
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• 제49권3호
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• pp.264-269
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• 2011

Hydrogen and hydrogen energy have been recognized as clean energy sources and high energy carrier. Mg and Mg alloys are attractive hydrogen storage materials because of their lightweight and low cost materials with high hydrogen capacity (about 7.6 wt.%). However, the commercial applications of the Mg hydrides are currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. However, Ti and Ti based hydrogen storage alloys have been thought to be the third generation of alloys with a high hydrogen capacity, which makes it difficult to handle because of high reactivity. One of the most methods to develope kinetics was addition of transition metal. Therefore, Mg-Ti-Cr-Nb alloy was fabricated to add TiCrNb by hydrogen induced mechanical alloying. TiCrNb systems have included transition metals, low operating temperatures and hydrogen storage materials. As-received specimens were characterized using X-ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) and Thermo Gravimetric analysis/Differential Scanning Calorimetry (TG/DSC). $Mg-TiCr_{10}Nb$ systems were evaluated for hydrogen kinetics by Sievert's type Pressure-Composition-Isotherm (PCI) equipment. The operating temperature range was 473, 523, 573 and 623 K.

• Composites Research
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• 제13권6호
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• pp.1-8
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• 2000

무가압함침법에 의한 $Al_2O_{3p}$/AC8A 복합재료의 제조와, 제조법과 관련하여 부가적인 Mg의 첨가와 강화상의 부피분율이 $Al_2O_{3p}$/AC8A복합재료의 기계적 성질과 마모저항에 미치는 영향을 조사하였다. 강화상 입자와 기지재료의 일부를 분말로 조합한 혼합분말 속으로 기지금속을 자발적으로 침투시켜 부피분율이 20~40%인 $Al_2O_{3p}$/AC8A 복합재료를 제조할 수 있었다. 그러나 강화상의 부피분율이 40%인 복합재료의 경우 기공율의 상승으로 복합재료의 강도는 저하하였다. Mg의 첨가량이 5~7wt% 일 때 가장 높은 강도를 나타냈으며, 경도는 Mg 첨가량의 증가에 따라 점진적으로 상승하였다. $Al_2O_{3p}$/AC8A복합재료는 저속에서 기지재료에 비해 내마모성이 저하하였으나, 고속에서는 AC8A합금에 비해 약 5.5배의 우수한 내마모성을 나타냈다. 마모기구의 관찰에 의해 부피분율 20% $Al_2O_{3p}$/AC8A복합재료의 경우 연삭마모가 주된 마모기구임을 알 수 있었으며, 부피분율 40% $Al_2O_{3p}$/AC8A복합재료는 높은 기공율로 인한 마모 가중으로 저속에서도 경미한 응착마모가 관찰됐고 마찰 속도가 증가함에 따라 격심한 마모로 진행되었다.

• 한국재료학회지
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• 제8권8호
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• pp.672-677
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• 1998

오원계 AI-합금의 용융산화에 의한 $AI_2O_3$ 복합재료의 형성속도와 미세구조에 대하여 연구하였다. AI-1Mg-3Si-3Zn 합금과 AI-1Mg-3Si-5Zn합금에 Cu, Ni 각각을 1% 무게비로 첨가하였다. 각 오원계 합금은 1373K, 1473K에서 최대 20시간 동안 산화시켰으며, 산화속도는 무게증가 측정을 통하여 조사하였다. 산화층의거시적 형상과 미세구조를 광학현미경으로 관찰하였다. AI-1Mg-3Si-5Zn-1Cu 합금이 가장 우수한 산화거동을 보였으나, 산화층이 불균일하였다. 합금위에 $SiO_2$를 도포하였더니 산화속도가 증진되었으며, 균일하고 조직이 친밀한 산화층이 얻어졌다.

• 한국주조공학회지
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• 제20권4호
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• pp.254-259
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• 2000

Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partioel sizes(50 and 100 ${\mu}m$) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of $Al-5Mg-X(Si,Cu,Ti)/SiC_p$ composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound $Al-5Mg-X(Si,Cu,Ti)/SiC_p$(50 and 100 ${\mu}m$) composites were fabricated by pressureless infiltration method. The $Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p$ composite with $50 {\mu}m$ size of SiC particle has higher hardness and better wear property than any other composite with $100{\mu}m$ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of $Al-5Mg/SiC_p$(50 and 100 ${\mu}m$) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.429-436
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• 2012

Mg and Mg-based alloys are regarded as strong candidate hydrogen storage materials since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogenation properties of Mg-based hydrogen storage composites. The effect of transition metal oxides, such as $Nb_2O_5$ on the kinetics of the Magnesium hydrogen absorption kinetics was investigated. $MgH_x$-5wt.% $Nb_2O_5$ composites have been synthesized by hydrogen induced mechanical alloying. The powder fabricated was characterized by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (Fe-SEM), Energy Dispersive X-ray (EDX), BET and simultaneous Thermo Gravimetric Analysis / Differential Scanning Calorimetry (TG/DSC) analysis. The Absorption / desorption kinetics of $MgH_x$-5wt.% $Nb_2O_5$ (type I and II) are determined at 423, 473, 523, 573 and 623 K.

• 대한금속재료학회지
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• 제49권2호
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• pp.145-152
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• 2011

Mechanical and property corrosion resistance of Mg-Zn-Y alloys with an atomic ratio of Zn/Y of 6.8 are investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, uniaxial tensile test and corrosion test with immersion and dynamic potentiometric tests. The alloys showed an in-situ composite microstructure consisting of ${\alpha}$-Mg and icosahedral phase (I-phase) as a strengthening phase. As the volume fraction of the I-phase increases, the yield and tensile strengths of the alloys increase while maintaining large elongation (26~30%), indicating that I-phase is effective for strengthening and forms a stable interface with surrounding ${\alpha}$-Mg matrix. The presence of I-phase having higher corrosion potential than ${\alpha}$-Mg, decreased the corrosion rate of the cast alloy up to I-phase volume fraction of 3.7%. However further increase in the volume fraction of the I-phase deteriorates the corrosion resistance due to enhanced internal galvanic corrosion cell between ${\alpha}$-Mg and I-phase.

• Composites Research
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• 제21권6호
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• pp.8-14
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• 2008

가로등은 운전자의 안전을 위한 필수적인 도로 부속구조물이며, 대부분 강재 등주를 사용하고 있다. 강재등주는 부식이 발생하여 내구성을 감소시키고, 도시미관을 저해하므로 스테인레스 제품이나 주철재 등을 사용하기도 한다. 그러나 주철재 및 스테인레스 등주를 사용하더라도 부식에 대한 위험성을 완전히 배제할 수 없고, 높은 강도와 강성은 충돌시 운전자의 안전을 위협하는 요인이 되고 있다. 따라서 새로운 형태의 등주 시스템의 개발이 요구되고 있다. 기존 등주의 문제점을 보완하기 위해 최근 알루미늄 합금을 사용한 등주가 개발되어 사용되고 있다. 알루미늄은 재료적 특성상 단위중량당 강도가 높고 부식에 대한 저항성이 매우 커서 그 활용성을 크게 증대될 것으로 예측되나 강계에 비해 강성과 강도가 낮기 때문에 구조적 안전성에서 문제점이 제기되고 있어 구조거동에 대한 연구가 필요하다. 이 연구는 현재 가로등 등주로 사용되고 있는 강재 및 알루미늄 등주에 대한 휨, 압축실험 등을 수행하여 알루미늄 등주의 구조거동을 조사하였고, 기존 강재등주와 비교하여 효율성 및 안전성을 평가하였다.

• Steel and Composite Structures
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• 제22권4호
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• pp.745-752
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• 2016

An investigation has been done to study the evolution of the microstructure, mechanical and electrical properties of AlMgSi alloy destined for the transport of electric energy, in function of the deformation caused by the cold drawing process. We identified that drawing of aluminum wire causes development of a fibrous texture of type <111> and <100>. We notice also that the electrical resistivity and mechanical resistance increases with the increasing of the deformation level. Characterization methods used in this work is: The Electron Back Scattered Diffraction EBSD, X-Ray diffraction, Vickers microhardness, Tensile test, Measuring electrical resistivity, the Scanning Electron Microscope (SEM) and Energy Diffraction Spectrum (EDS).