• Title/Summary/Keyword: Mg and Mg-based materials

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Hydrogenation Properties on MgHx-Sc2O3 Composites by Mechanical Alloying (MgHx-Sc2O3 복합재료의 수소화 특성)

  • Kim, Kyeong-Il;Kim, Yong-Sung;Hong, Tae-Whan
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.2
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    • pp.81-88
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    • 2010
  • Hydrogen energy applications have recognized clean materials and high energy carrier. Accordingly, Hydrogen energy applies for fuel cell by Mg and Mg-based materials. Mg and Mg-based materials are lightweight and low cost materials with high hydrogen storage capacity. However, commercial applications of the Mg hydride are currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. Therefore one of the most methods to improve kinetics focused on addition transition metal oxide. Addition to transition metal oxide in $MgH_x$ powder produce $MgH_x$-metal oxide composition by mechanical alloy and it analyze XRD, EDS, TG/DSC, SEM, and PCT. This report considers kinetics by transition metal oxide rate and Hydrogen pressure. In this research, we can see behavior of hydriding/dehydriding profiles by addition catalyst (transition metal oxide). Results of PCI make a excellent showing $MgH_x$-5wt.% Sc2O3 at 623K, $MgH_x$-10wt.% $Sc_2O_3$ at 573K.

Fabrication and hydrogen storage property of eutectic Mg-Ni based alloy powder (공정 Mg-Ni계 합금 분말의 제조 및 수소저장 특성)

  • Hong, Seong-Hyeon;Bae, Jong-Soo;Yim, Chang-Dong;Na, Young-Sang;Song, Myoung-Youp
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.2
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    • pp.174-180
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    • 2006
  • The eutectic Mg-23.5%Ni alloy was casted by melting and solidification. The powders of Mg-23.5%Ni and (Mg-23.5%Ni)-10% iron oxide were prepared by mechanical grinding of casted Mg-Ni alloy and casted Mg-Ni alloy+oxide, respectively. As milling time increases, hydriding and dehydriding rates of Mg-Ni and Mg-Ni-oxide alloy powders increase. The additions of iron oxide to Mg-Ni alloy and Mg-Ni-oxide increase hydriding rates and slightly decrease dehydriding rates.

Improving the Efficiency of SnS Thin Film Solar Cells by Adjusting the Mg/(Mg+Zn) Ratio of Secondary Buffer Layer ZnMgO Thin Film (2차 버퍼층 ZnMgO 박막의 Mg/(Mg+Zn) 비율 조절을 통한 SnS 박막 태양전지 효율 향상)

  • Lee, Hyo Seok;Cho, Jae Yu;Youn, Sung-Min;Jeong, Chaehwan;Heo, Jaeyeong
    • Korean Journal of Materials Research
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    • v.30 no.10
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    • pp.566-572
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    • 2020
  • In the recent years, thin film solar cells (TFSCs) have emerged as a viable replacement for crystalline silicon solar cells and offer a variety of choices, particularly in terms of synthesis processes and substrates (rigid or flexible, metal or insulator). Among the thin-film absorber materials, SnS has great potential for the manufacturing of low-cost TFSCs due to its suitable optical and electrical properties, non-toxic nature, and earth abundancy. However, the efficiency of SnS-based solar cells is found to be in the range of 1 ~ 4 % and remains far below those of CdTe-, CIGS-, and CZTSSe-based TFSCs. Aside from the improvement in the physical properties of absorber layer, enormous efforts have been focused on the development of suitable buffer layer for SnS-based solar cells. Herein, we investigate the device performance of SnS-based TFSCs by introducing double buffer layers, in which CdS is applied as first buffer layer and ZnMgO films is employed as second buffer layer. The effect of the composition ratio (Mg/(Mg+Zn)) of RF sputtered ZnMgO films on the device performance is studied. The structural and optical properties of ZnMgO films with various Mg/(Mg+Zn) ratios are also analyzed systemically. The fabricated SnS-based TFSCs with device structure of SLG/Mo/SnS/CdS/ZnMgO/AZO/Al exhibit a highest cell efficiency of 1.84 % along with open-circuit voltage of 0.302 V, short-circuit current density of 13.55 mA cm-2, and fill factor of 0.45 with an optimum Mg/(Mg + Zn) ratio of 0.02.

Effect of calcium addition on creep properties in Mg-Zn-Y alloys (Mg-Zn-Y 합금의 크리프 저항성에 미치는 칼슘의 영향)

  • Lee, Yoon-Hee;Lim, Hyun-Kyu;Kim, Do-Hyung;Kim, Do-Hyang
    • Journal of Korea Foundry Society
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    • v.27 no.5
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    • pp.198-202
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    • 2007
  • In the present study, the high temperature mechanical properties and creep resistance of Mg-Zn-Y-Ca alloys has been investigated. The Mg-4Zn-0.8Y alloy consists of ${\alpha}$-Mg matrix and icosahedral quasicrystalline phase. Calcium addition into Mg-4n-0.8Y based alloy results in the formation of ${\tau}(Ca_{2}Mg_{6}Zn_{3})$ and $Mg_{2}Ca$ as the second solidification phases. Creep properties of the Mg-Zn-Y and Mg-Zn-Ca based alloys measured at applied stresses between 65 MPa and 85 MPa are significantly improved with adding calcium and yttrium, respectively. The improved creep resistance is due to the formation of thermally stable $Mg_{2}Ca$ phase.

Influence of hot deformation and composition on microstructure development of magnesium-stannide alloys

  • Pandel, Divija;Banerjee, Malay K.
    • Advances in materials Research
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    • v.9 no.3
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    • pp.171-187
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    • 2020
  • The microstructural evolution of different compositions of Mg-Sn alloys (30%Sn-70%Mg, 40%Sn-60%Mg and 50%Sn-50%Mg) is studied at first to understand the changes observed with change in tin content and deformation conditions. The Mg2Sn phase increases with increase in tin content and a significant substructure development is found in 50%Sn-50%Mg alloy. The above observation led to further deformation studies on Mg2Sn based thermoelectric materials with higher tin percentage. The microstructure in terms of Electron backscatter diffraction (EBSD)measurements is studied in detail followed by the determination of thermoelectric properties i.e., Seebeck coefficient and electrical conductivity for both as cast and extruded Mg(2+x)Sn-Ag alloys. The electrical conductivity of the extruded Mg(2+x)Sn-.3wt%Ag {x =1} alloy was found to be more than its as cast counterpart while the Seebeck coefficient values remained almost the same.

Thermoelectric Properties of Porous Mg3Sb2 Based Compounds Fabricated by Reactive Liquid Phase Sintering (반응성 액상 소결법으로 제조한 다공성 Mg3Sb2계 화합물의 열전물성)

  • Jang, Kyung-Wook;Kim, In-Ki;Kim, Il-Ho
    • Korean Journal of Materials Research
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    • v.25 no.2
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    • pp.68-74
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    • 2015
  • The porous $Mg_3Sb_2$ based compounds with 60~70% of relative density were prepared by powder compaction at room temperature and reactive liquid phase sintering at 1023 K for 4hrs. The stoichiometric $Mg_3Sb_2$ compounds were synthesized from elemental Sb and Mg powder in the mixing range of 61~63 at% Mg. The increased scattering effect due to the micro-pores reduced the mobility of the charge carrier and the phonon, which caused the electrical conductivity and the thermal conductivity to decrease, respectively. But the scattering effect was greater for the electrical conductivity than for the thermal conductivity. Excess Mg alloyed in the $Mg_3Sb_2$ compounds decreased the electrical conductivity, but had no effect on the thermal conductivity. On the other hand, the large increase of the Seebeck coefficient was the result of a decrease in the charge carrier density due to the excess Mg. Dimensionless figure of merit of the porous $Mg_3Sb_2$ compound reached a maximum value of 0.28 at 61 at% Mg. The obtained value was similar to that of $Mg_3Sb_2$ compounds having little pores.

Corrosion protection behavior of AZ31 magnesium alloy with cathodic electrophoretic coating pretreated by cerium based conversion coatings at various pH

  • Fazal, Basit Raza;Phuong, Nguyen Van;Moon, Sungmo
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2015.11a
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    • pp.268-268
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    • 2015
  • The corrosion protection behavior of AZ31 magnesium alloy (Mg alloy) with cathodic electrophoretic coating (E-coating) pretreated by cerium-based conversion coatings at various pH was investigated in this study. Cerium-based conversion coatings (CeCCs) were deposited on AZ31 Mg alloy by immersion treatment in the nitrate-based cerium salt solution. The morphology and composition of the CeCCs were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion properties of the AZ31 Mg alloy pretreated with cerium coating and subsequently E-coated were studied during salt-spray testing. The surface morphologies of the E-coated Mg alloy were examined in detail after different testing times using digital photography. It was found that the protective properties of the E-coating on AZ31 Mg alloy generated are heavily dependent upon the CeCC factors such as treatment time, coating thickness and pH of the solution.

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Development of an Mg-Based Alloy with a Hydrogen-Storage Capacity over 6 wt% by Adding Graphene

  • Choi, Eunho;Kwak, Young Jun;Song, Myoung Youp
    • Metals and materials international
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    • v.24 no.6
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    • pp.1403-1411
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    • 2018
  • Graphene (multilayer graphene) was chosen as an additive to improve the hydrogen uptake and release properties of magnesium (Mg). Five weight percent of graphene was added to pre-milled Mg by milling in hydrogen (reaction-involving milling). The hydrogen uptake and release properties of the graphene-added Mg were investigated. The activation of Mg-5graphene, which was prepared by adding 5 wt% graphene to Mg pre-milled for 24 h, was completed after the second cycle (cycle number, CN=2). Mg-5graphene had a high effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of 6.21 wt% at CN=3 at 593 K in 12 bar $H_2$. At CN=1, Mg-5graphene released 0.46 wt% hydrogen for 10 min and 4.99 wt% hydrogen for 60 min. Milling in hydrogen is believed to create defects (leading to facilitation of nucleation), produce cracks and clean surfaces (leading to increase in reactivity), and decrease particle size (leading to diminution of diffusion distances or increasing the flux of diffusing hydrogen atoms). The added graphene is believed to have helped the sample have higher hydrogen uptake and release rates, weakly but partly, by dispersing heat rapidly.

Enhanced superconducting properties of MgB2 by doping the carbon quantum dots

  • K.C., Chung;S.H., Jang;Y.S., Oh;S.H., Kang
    • Progress in Superconductivity and Cryogenics
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    • v.24 no.4
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    • pp.55-58
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    • 2022
  • Carbon-based doping to MgB2 superconductor is the simplest approach to enhance the critical current densities under magnetic fields. Carbon quantum dots is synthesized in this work as a carbon provider to MgB2 superconductors. Polyvinyl Pyrrolidone is pyrolyzed and dispersed in dimethylfomamide solvent as a dopant to the mixture of Mg and B powders. Doped MgB2 bulk samples clearly show the decrease of a-axis lattice constant, grain refinements, and broadening of FWHM of diffraction peaks compared to un-doped MgB2 possibly due to the carbon substitution and/or boron vacancy at the boron site in MgB2 lattice. Also, high-field Jc for the doped MgB2 is enhanced significantly with the crossover about 3 T at 5 & 20 K when increasing the doping of carbon quantum dots.

Bi-materials of Al-Mg Alloy Reinforced with/without SiC and Al2O3 Particles; Processing and Mechanical Properties

  • Chang, Si-Young;Cho, Han-Gyoung;Kim, Yang-Do
    • Journal of Powder Materials
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    • v.14 no.6
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    • pp.354-361
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    • 2007
  • The bi-materials with Al-Mg alloy and its composites reinforced with SiC and $Al_2O_3$ particles were prepared by conventional powder metallurgy method. The A1-5 wt%Mg and composite mixtures were compacted under $150{\sim}450\;MPa$, and then the mixtures compacted under 400 MPa were sintered at $773{\sim}1173K$ for 5h. The obtained bi-materials with Al-Mg/SiCp composite showed the higher relative density than those with $Al-Mg/Al_2O_3$ composite after compaction and sintering. Based on the results, the bi-materials compacted under 400 MPa and sintered at 873K for 5h were used for mechanical tests. In the composite side of bi-materials, the SiC particles were densely distributed compared to the $Al_2O_3$ particles. The bi-materials with Al-Mg/SiC composite showed the higher micro-hardness than those with $Al-Mg/Al_2O_3$ composite. The mechanical properties were evaluated by the compressive test. The bi-materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. Their compressive strength was lower than that of Al-Mg alloy. Moreover, impact absorbed energy of bi-materials was smaller than that of composite. However, the bi-materials with Al-Mg/SiCp composite particularly showed almost similar impact absorbed energy to $Al-Mg/Al_2O_3$ composite. From the observation of microstructure, it was deduced that the bi-materials was preferentially fractured through micro-interface between matrix and composite in the vicinity of macro-interface.