• 대한금속재료학회지
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• 제56권12호
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• pp.878-884
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• 2018

In the present work, we selected a polymer, polyvinylidene fluoride (PVDF), as an additive to improve the hydrogenation and dehydrogenation properties of Mg. 95 wt% Mg + 5 wt% PVDF (designated Mg-5PVDF) samples were prepared via milling in hydrogen atmosphere (reactive milling), and the hydrogenation and dehydrogenation characteristics of the prepared samples were compared with those of Mg milled in hydrogen atmosphere. The dehydrogenation of magnesium hydride formed in the as-prepared Mg-5PVDF during reactive milling began at 681 K. In the fourth cycle (n=4), the initial hydrogenation rate was 0.75 wt% H/min and the quantity of hydrogen absorbed for 60 min, $H_a$ (60 min), was 3.57 wt% H at 573 K and in 12 bar $H_2$. It is believed that after reactive milling the PVDF became amorphous. The milling of Mg with the PVDF in hydrogen atmosphere is believed to have produced defects and cracks. The fabrication of defects is thought to ease nucleation. The fabrication of cracks is thought to expose fresh surfaces, resulting in an increase in the reactivity of the particles with hydrogen and a decrease in the diffusion distances of hydrogen atoms. As far as we know, this investigation is the first in which a polymer PVDF was added to Mg by reactive milling to improve the hydrogenation and dehydrogenation characteristics of Mg.

• 분석과학
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• 제25권6호
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• pp.402-409
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• 2012

연속흐름 수소화물 생성-유도결합 플라스마 원자 방출 분광기(FI-HG-ICP-AES) 이용하여 플라스틱 소재에 함유된 비소를 정량하기 위한 조건을 얻었다. 플라스틱 시료를 습식 산 분해 방법 및 마이크로파 산 분해 방법으로 전처리하여 시험 용액을 조제하였다. 인증표준물질(CRM)인 CRM-EC680k 및 CRM-EC681k를 사용하여 측정한 값과 인증값을 비교하여 분석 방법의 재현성 및 정확성을 확인하였다. 습식 산 분해 방법 및 마이크로파 산 분해 방법으로 전처리하여 FI-HG-ICP-AES로 측정한 결과 CRM-EC680k의 경우에는 4.1~4.3 mg/kg (인증값 $4.1{\pm}0.5$ mg/kg)이고, CRM-EC681k의 경우에는 28.9~30.6 mg/kg (인증값 $29.1{\pm}1.8$ mg/kg)이었다.

• 한국재료학회지
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• 제20권10호
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• pp.543-549
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• 2010

The hydrogen energy had recognized clean and high efficiency energy source. The research field of hydrogen energy was production, storage, application and transport. The commercial storage method was using high pressure tanks but it was not safety. However metal hydride was very safety due to high chemical stability. Mg and Mg alloys are attractive as hydrogen storage materials because of their lightweight and high absorption capacity (about 7.6 wt%). Their range of applications could be further extended if their hydrogenation properties and degradation behavior could be improved. The main emphasis of this study was to find an economical manufacturing method for Mg-Ti-Ni-H systems, and to investigate their hydrogenation properties. In order to examine their hydrogenation behavior, a Sievert's type automatic pressure-compositionisotherm (PCI) apparatus was used and experiments were performed at 423, 473, 523, 573, 623 and 673 K. The results of the thermogravimetric analysis (TGA) revealed that the absorbed hydrogen contents were around 2.5wt.% for (Mg8Ti2)-10 wt.%Ni. With an increasing Ni content, the absorbed hydrogen content decreased to 1.7 wt%, whereas the dehydriding starting temperatures were lowered by some 70-100 K. The results of PCI on (Mg8Ti2)-20 wt.%Ni showed that its hydrogen capacity was around 5.5 wt% and its reversible capacity and plateau pressure were also excellent at 623 K and 673 K.

• 한국분말재료학회지
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• 제13권3호
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• pp.199-204
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• 2006

We manufactured the metal hydrides of $(Ti_{0.88}Mg_{0.12})H_2$ using a very easy and cheap way that Ti-12%Mg blending powder was mechanically milled with liquid milling media such as isopropyl alcohol ($C_3H_8O$, containing oxygen) and hexane ($C_6H_{14}$, no oxygen) as hydrogen source. The $(Ti_{0.88}Mg_{0.12})H_2$ synthesized in isopropyl alcohol contained the high oxygen of 11.2%, while one in hexane had the low oxygen content of 0.7%. Such a difference of oxygen content affected the dehydriding behavior, phase transformation, and microstructural evolution at high temperature, which was investigated through X-ray diffraction and DSC measurements, and electron microscope observations.

• 한국수소및신에너지학회논문집
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• 제10권1호
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• pp.9-17
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• 1999

기계적인 합금처리된 여러 Mg-Ni 혼합물 중에서 가장 우수한 수소저장 성질을 가지고 있는 Mg-25wt.%Ni 혼합물의 수소화물 형성 및 분해 반응에 대한 반응속도론적 연구를 하였다. 수소화물 형성 및 분해 속도를 측정하여 이론적인 반응 속도식과 비교함으로써 율속 단계를 결정하였다. Mg-25wt.%Ni의 수소화물 형성의 율속단계는 $H_a$ = 4.0 미만의 여러 $H_a$ 범위에서는 입자간 통로 (interparticle channel), 입자의 갈라진 틈(crack) 등을 통한 수소 분자의 이동 단계인 Knudsen 유동과 보통의 기체 확산이고, 4.0 < $H_a{\leq}4.25$ 범위에서는 성장하는 수소화물 층을 통한 수소 원자의 확산으로 생각된다. Mg-25wt.%Ni의 수소화물 분해의 율속 단계는 전 $H_d$ 범위에 걸쳐 수소 분자의 이동 단계인 Knusden 유동과 보통의 기체 확산이다.

• 한국수소및신에너지학회논문집
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• 제21권1호
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• pp.58-63
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• 2010

Mg and Ma-based alloys are promising hydrogen storage materials for renewable clean energy applications. It has high hydrogen storage capacity (7.6wt.%), lightweight and low economical materials. However, commercial applications of the Mg hydride are currently hindered by its high operating temperature, and very slow reaction kinetics. In this work, we are aimed at studying the hydrogenation properties of the $MgH_x-V_2O_5$ composite prepared by hydrogen induced mechanical alloying. The absorption capacity of the sample is found to be about 4.7wt.% at 623K under 3 MPa $H_2$ pressure. The absorption characteristics observed have been compared with prepared $MgH_x$.

• 한국수소및신에너지학회논문집
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• 제16권3호
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• pp.238-243
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• 2005

Mg and Mg-based alloys are most important hydrogen storage materials. It is a lightweight and low-cost materials with high hydrogen storage capacity. However, the formation of hydride at high temperature, the deterioration effect, the hydriding and dehydriding kinetics are bad factor for application. In this study, Mg and Ni have been produced by hydrogen induced mechanical alloying(HIMA) process. The raw materials, Mg(purity 99.9%) chip and Ni(purity 99.95%) chip was prepared by using a planetary ball mill apparatus(FRITSCH pulverisette 5). The balls to chips mass ratio(BCR) are 30:1. The hydrogen pressure induced 2.0MPa and milling times were 12, 24, 48, 72, 96 hours with a rotating speed of 200rpm. X-ray diffraction(XRD) analysis was made to characterize the crystallite size and misfit strain. The crystallite size measured by laser particle size analysis(PSA). Microstructure changes were investigated by scanning electron microscopy(SEM) and the transmission electron microscopy(TEM). The hydrogen storage properties were evaluated by using an Sivert's type automatic pressure-composition-therm(PCT) apparatus.

• 한국수소및신에너지학회논문집
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• 제18권1호
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• pp.26-31
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• 2007

Hydrogen has a high potential to be a renewable substitute for fossil fuels, because of its high gravimetric energy density and environment friendliness. In particular, Magnesium have attracted much interest since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve the kinetic is addition of metal oxide. In this paper, the effect of $Fe_2O_3$ concentration on the kinetics of Mg hydrogen absorption reaction was investigated. $MgH_x-Fe_2O_3$ composites have been synthesized by hydrogen induced mechanical alloying. The powder synthesized was characterized by XRD, SEM and simultaneous TG, DSC analysis. The hydrogenation behaviors were evaluated by using a sievert's type automatic PCT apparatus. Absorption and desorption kinetics of Mg catalyzed with 5,10 mass% $Fe_2O_3$ are determined at 423, 473, 523, 573, 623K.

• Journal of Ceramic Processing Research
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• 제13권spc1호
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• pp.128-131
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• 2012

The selective area growth light emitting diode on GaN substrate was grown using mixed-source HVPE method with multi-sliding boat system. The GaN substrate was grown using mixed-source HVPE system. Te-doped AlGaN/AlGaN/Mg-doped AlGaN/Mg-doped GaN multi-layers were grown on the GaN substrate. The appearance of epi-layers and the thickness of the DH was evaluated by SEM measurement. The DH metallization was performed by e-beam evaporator. n-type metal and p-type metal were evaporated Ti/Al and Ni/Au, respectively. At the I-V measurement, the turn-on voltage is 3 V and the differential resistance is 13 Ω. It was found that the SAG-LED grown on GaN substrate using mixed-source HVPE method with multi-sliding boat system could be applied for developing high quality LEDs.

• 한국식품과학회지
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• 제31권2호
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• pp.273-279
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• 1999

국내외에서 재배, 유통되고 있는 다류소재 식물류 40종에 대하여 총 페놀성 물질과 비타민 C 함량은 비색법으로, ${\alpha}-tocopherol$과 ${\beta}-carotene$ 함량은 HPLC에 의해, 셀레늄 함량은 원자흡광법을 이용하여 분석하였다. 시료 100 g당(건량) 들어있는 총 페놀성 물질 함량은 녹차잎, 홍차잎, 우롱차잎, 인스탄트커피 등이 약 7g으로 가장 높았고 셀레늄 함량은 산수유와 칡이 약 $4{\mu}g$으로 가장 높았다. ${\beta}-carotene$ 함량은 두충$(8587{\mu}g)$, 감잎$(6222{\mu}g)$, 녹차잎$(3652{\mu}g)$ 등이 매우 높았다. ${\alpha}-tocopherol$ 함량은 감잎(33 mg), 두충(26 mg), 녹차잎(16 mg), 홍차잎(13 mg) 순으로 높았으며, 비타민 C 함량은 녹차잎(199 mg)과 홍차잎(117 mg)이 가장 높았다.