• 한국수소및신에너지학회논문집
• /
• 제10권2호
• /
• pp.131-139
• /
• 1999

The objective of this works was to synthesize the$Mg_2Ni$ hydrogen storage materials economically and to eliminate the intial activation process. $Mg_2NiH_x$ was mechanically alloyed under purified hydrogen gas atmosphere using pure Mg and Ni chips. M.A(Mechanical Alloying) was carried out using planetary ball mill for times varying from 12h to 96h under 20bars of hydrogen gas pressure. $Mg_2NiH_x$ started to form after 48h and the homogeneous $Mg_2NiH_x$ composites was synthesized after 96h. From TG analysis, the dehydriding reaction of $Mg_2NiH_x$ started at around $200^{\circ}C$. The result of P-C-T at $300^{\circ}C$ revealed the hydrogen storage capacity of $Mg_2NiH_c$ reached 3.68 wt% and the effective hydrogen storage was 2.38 wt%. The enthalpy difference of absorption-desorption cycling for the hydride formation and the hysteresis were reduced and the plateau flatness and the sloping were improved according to M.A time.

• 한국수소및신에너지학회논문집
• /
• 제32권3호
• /
• pp.156-162
• /
• 2021

Mg hydride has a relatively high hydrogen storage amount of 7.6wt%, and inexpensive due to abundant resources, but has high reaction temperature and long reaction time because of treble oxidation reactivity and upper activation energy. Their range of applications could be further extended if their hydrogenation kinetics and degradation behavior could be improved. Therefore, the effect of CaO has improved the hydrogenation kinetics and slowed down the degradation. This study focused on investigating whether to improve the hydrogenation kinetics by synthesizing Mg₂NiH_x-5wt% CaO composites. The Mg₂NiH_x-5wt% CaO composites have been synthesized by hydrogen induced mechanical alloying. The synthesized composites were characterized by performing X-ray diffraction, Scanning Electron Microscopy, Brunauer-Emmett-Teller, Thermogravimetric, and Sivert's type automatic pressure-composition-temperature analysis. Hydriding kinetics were performed using an automatic PCT measurement system and evaluated over the temperature range of 423 K, 523 K, and 623 K. As a result of calculating the hydrogen adsorption amount through the hydrogenation kinetics curve, it was calculated as about 0.42wt%, 0.91wt%, and 1.15wt%, the highest at 623 K and the lowest at 423 K.

• 청정기술
• /
• 제27권2호
• /
• pp.107-114
• /
• 2021

Mg₂NiH_x-5 wt% CaO 수소 저장 복합재료의 합성 공정에 대한 환경 영향 특성을 분석하기 위해 물질전과정평가(material life cycle assessment, MLCA)를 수행하였다. MLCA는 Gabi 소프트웨어를 사용하였으며, Eco-Indicator 99' (EI99)와 CML 2001 방법론을 기반으로 하여 분석하였다. Mg₂NiH_x-5 wt% CaO 복합재료는 수소 가압형 기계적 합금화법(hydrogen induced mechanical alloying, HIMA)에 의해 합성되었다. X-선 회절분석기(X-ray diffraction, XRD), 주사전자현미경(scanning electron microscopy, SEM), 에너지 분산형 X-선 분광법(energy dispersive X-ray spectroscopy, EDS), 비표면적 분석(Bruner-Emmett-Teller, BET), 열중량 분석(thermogravimetric analysis, TGA)을 이용하여 복합재료의 야금학적, 열화학적 특성을 분석하였다. CML 2001 및 EI99 방법론을 토대로 MLCA를 수행하여 분석한 정규화 결과, Mg₂NiH_x-5 wt% CaO 복합재료는 지구온난화(GWP)와 화석연료의 환경 부하 값에서 가장 높은 수치를 나타내었다. 이는 CaO 첨가에 따른 제조 공정에서의 추가적인 전기 사용으로 인한 것으로 판단된다. 따라서 향후 합금 설계 시에 제조 공정 시간 단축을 통한 공정 최적화 및 친환경적인 대체물질을 탐구하여 환경적인 요인을 고려한 연구를 모색해 볼 필요가 있다.

• 한국수소및신에너지학회논문집
• /
• 제25권1호
• /
• pp.19-27
• /
• 2014

Mg hydride has a high hydrogen capacity (7.6%), at high temperature, and is a lightweight and low cost material, thus it a promising hydrogen storage material. However, its high operation temperature and very slow reaction kinetics are obstacles to practical application. In order to overcome these disadvantages of Mg hydride, graphene powder was added to it. The addition of graphene has been shown to reduce the operating temperature of dehydrogenation. Moreover, in this report the environmental aspects of $MgH_x$-Graphene composites are investigated by means of the environmental life cycle assessment (LCA) method. $MgH_x$-Graphene mixture was prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD(X-ray Diffraction). The hydrogenation behaviors were evaluated by using a Sievert's type automatic PCT apparatus. Such evaluation of Materials also conducted in the LCA. From the result of P-C-T(Pressure-Composition-Temperature) curves, the $MgH_x$-3wt.% graphene composite was evaluated as having a 5.86wt.% maximum hydrogen storage capacity, at 523K. From absorption kinetic testing, the $MgH_x$-7wt.% graphene composite was evaluated as having a maximum 6.94wt.%/ms hydrogen absorption rate, at 573K. Environment evaluation results for the $MgH_x$-graphene composites and other materials indicated environmental impact from the electric power used and from the materials themselves.

• 한국수소및신에너지학회논문집
• /
• 제31권6호
• /
• pp.553-557
• /
• 2020

It is possible that hydrogen could replace coal and petroleum as the predominant energy source in the near future, but several challenges including cost, efficiency, and stability. Mg and Mg alloys are attractive hydrogen storage materials because of their lightweight and high absorption capacity. Their range of applications could be further extended if their hydrogenation properties could be improved. The main emphasis of this study was to investigate their hydrogenation properties for Synthesis of 10wt.% CaF2 in Mg2NiHx systems. The effect of BCR (66:1) and MA time (96 hours) on the hydrogenation properties of the composite was investigated. also, Mg2NiHx-10wt% CaF2 composites prepared by Mechanical Alloying are used in this work to illustrate the effect of catalysts on activation energy and kinetics of Magnesium hydride.

• 한국수소및신에너지학회논문집
• /
• 제33권2호
• /
• pp.148-157
• /
• 2022

Research on hydrogen storage is active to properly deal with hydrogen, which is considered a next-generation energy medium. In particular, research on metal hydride with excellent safety and energy efficiency has attracted attention, and among them, magnesium-based hydrogen storage alloys have been studied for a long time due to their high storage density, low cost, and abundance. However, Mg-based alloys require high temperature conditions due to strong binding enthalpy, and have many difficulties due to slow hydrogenation kinetics and reduction in hydrogen storage capacity due to oxidation, and various strategies have been proposed for this. This research manufactured Mg₂Ni to improve hydrogenation kinetics and synthesize about 5, 10, 20 wt% of CaF₂ as a catalyst for controlling oxidation. Mg₂NiHx-CaF₂ produced by hydrogen induced mechanical alloying analyzed hydrogenation kinetics through an automatic PCT measurement system under conditions of 423 K, 523 K, and 623 K. In addition, material life cycle assessment was conducted through Gabi software and CML 2001 and Eco-Indicator 99' methodology, and the environmental impact characteristics of the manufacturing process of the composites were analyzed. In conclusion, it was found that the effects of resource depletion (ARD) and fossil fuels had a higher burden than other impact categories.

• 한국수소및신에너지학회논문집
• /
• 제33권1호
• /
• pp.8-18
• /
• 2022

With rapid industrialization and population growth, fossil fuel use has increased, which has a significant impact on the environment. Hydrogen does not cause contamination in the energy production process, so it seems to be a solution, but it is essential to find an appropriate storage method due to its low efficiency. In this study, Mg-based alloys capable of ensuring safety and high volume and hydrogen storage density per weight was studied, and Mg₂NiH_x synthesized with Ni capable of improving hydrogenation kinetics. In addition, in order to improve thermal stability, a hydrogen storage composite material synthesized with CaO was synthesized to analyze the change in hydrogenation reaction. In order to analyze the changes in the metallurgical properties of the materials through the process, XRD, SEM, BET, etc. were conducted, and hydrogenation behavior was confirmed by TGA and hydrogenation kinetics analysis. In addition, in order to evaluate the impact of the process on the environment, the environmental impact was evaluated through "Material Life Cycle Assessments" based on CML 2001 and EI99' methodologies, and compared and analyzed with previous studies. As a result, the synthesis of CaO caused additional power consumption, which had a significant impact on global warming, and further research is required to improve this.

• 한국수소및신에너지학회논문집
• /
• 제20권6호
• /
• pp.512-518
• /
• 2009

Mg 및 Mg합금은 수소 저장량이 7.6wt.%로 비교적 높고 자원도 풍부하여 값이 싼 장점을 가지고 있으나 산화반응성이 높고 활성화 에너지가 크기 때문에 반응온도가 높고 반응시간이 긴 단점을 가지고 있다. 이러한 단점을 극복하기 위해 일반적으로 Mg 및 Mg합금의 표면 개질화, 금속간 화합물 형성, 전이금속 첨가에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 전이금속인 Nb를 촉매제로 사용하여 수소화 특성을 개선하고자 기계적 합금화법(MA;Mechanical Alloying)을 실시하여 복합재료를 합성한 후 수소화 반응을 평가하였다. XRD, SEM, TEM, PSA, TG/DSC 분석을 수행하였으며 Sievert's 형 PCT를 이용하여 온도 및 압력 변화에 따른 특성평가를 하였다. 전이금속인 Nb의 첨가로 수소화 반응개시온도가 낮아지고 수소 저장량이 향상되는 거동을 보였다. 특히, 5mass%Nb가 10mass%Nb 보다 수소 저장량 및 반응속도가 좋은 결과를 보였다.