• 대한금속재료학회지
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• 제50권1호
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• pp.64-70
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• 2012

Samples of pure Mg, 76.5 wt%Mg-23.5 wt%Ni, and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ were prepared by reactive mechanical grinding and their hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and to shorten diffusion distances of hydrogen atoms. After hydriding-dehydriding cycling, the 76.5 wt%Mg-23.5 wt%Ni and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ samples contained $Mg_2Ni$ phase. In addition to the effects of the creation of defects and the decrease in particle size, the addition of Ni increases the hydriding and dehydriding rates by the formation of $Mg_2Ni$. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of particles. The reactive mechanical grinding of Mg-Ni alloy with $Fe_2O_3$ is considered to decrease the particle size.

• 한국수소및신에너지학회논문집
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• 제4권2호
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• pp.29-40
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• 1993

Intensive studies on the electrochemical characteristics of TiFe type alloy electrodes have been carried out to clarify the mechanism of electrochemical hydrogen absorption and desorption. It was found that electrochemical activation of the TiFe type alloys is difficult and that charge efficiencies are very low even after a decade of activation cycles. However, by the pretreatment of the powders such as gas activation and/or Ni chemical plating, charge efficiencies fairly increased, especially for the $TiFe_{0.8}Ni_{0.2}$ alloy. It was considered that difficulties to activation and lower charge efficies of the alloys are due to the presence of the passivation films, which prohibit inward diffusion of hydrogen and promote the combination of adsorbed hydrogen atom to gas bubbles during the electrochemical charge. In addition, lower diffusivity of hydrogen in the alloys may be played an important role lowering the charge efficiencies.

• 대한금속재료학회지
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• 제50권12호
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• pp.949-953
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• 2012

$MgH_2$ was employed as a starting material instead of Mg in this work. A sample with a composition of 94 wt% $MgH_2-6$ wt% Ni (called $MgH_2-6Ni$) was prepared by reactive mechanical grinding. The hydriding and dehydriding properties were then examined. An $MgH_2-Ni$ hydrogen storage alloy that does not require an activation process was developed. The alloy was prepared in a planetary ball mill by grinding for 4 h at a ball disc revolution speed of 250 rpm under a hydrogen pressure of about 12 bar. The sample absorbed 3.74 wt% H for 5 min, 4.07 wt% H for 10 min, and 4.41 wt% H for 60 min at 573 K under 12 bar $H_2$, and desorbed 0.93 wt% H for 10 min, 1.99 wt% H for 30 min, and 3.16 wt% H for 60 min at 573 K under 1.0 bar $H_2$. $MgH_2-6Ni$ after reactive mechanical grinding contained ${\beta}-MgH_2$ (a room temperature form of $MgH_2$), Ni, ${\gamma}-MgH_2$ (a high pressure form of $MgH_2$), and a very small amount of MgO. Reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation, and to reduce the particle size of Mg. $Mg_2Ni$ formed during reactive mechanical grinding also increases the hydriding and dehydriding rates of the sample.

• 한국태양에너지학회 논문집
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• 제25권4호
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• pp.13-19
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• 2005

The reaction of steam reforming of methane with commercial catalysts was conducted for thermochemical heat storage. The reaction conditions were investigated for temperature range of 700 to $900\;^{\circ}C$ and steam to carbon mole ratios between 3.0 and 5.0. The reactor was made of stainless steel and it's dimension was 12 cm inside diameter and 6cm long. The effects of space velocity and reactants mole ratio and temperature on the methane conversion and CO selectivity were examined. Optimum reaction condition was determined. There was not a significant difference of methane conversion and CO selectivity compared to conventional reactor.

• 한국수소및신에너지학회논문집
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• 제28권6호
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• pp.712-720
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• 2017

As Korean government has activated the renewable portfolio standard (RPS) since 2012, producers have been seeking and using the various renewable resources to meet the RPS quota. One of these efforts, Power Bio-Fuel oil demonstration project is being conducted to check the operability and compatibility with fossil fuel, Fuel oil (B-C) from 2014. The oil is a mixture of vegetable oil and animal fat or fatty acid ester of them and should satisfy some specification to use the power generation. The oil's quality and combustion characteristics are different from conventional oil, Fuel oil (B-C) in current power plant facility. In this study, it was investigated the storage stability and malodor intensity of Bio-Fuel oil.

• 한국수소및신에너지학회논문집
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• 제13권2호
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• pp.135-142
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• 2002

본 연구는 Chemical hydride 형태의 수소발생제를 포함한 액체연료를 이용한 신개념의 알칼라인 연료전지의 특성을 분석하였다. Chemical hydride는 연료전지의 수소공급원으로써 사용될 수 있으며, 본 연구팀은 KOH 전해질에 수소발생제인 Sodium Borohydride ($NaBH_4$)를 첨가하여 제조된 액체연료를 알칼라인 연료전지에 공급함으서 상온에서 매운 우수한 전기 화학적 성능결과를 얻을 수 있었다. 이때 음극 찰물질로 $ZrCr_{0.8}Ni_{1.2}$ 수소저장합금이 사용되었으며, 양극은 방수처리된 카본지 위에 분산된 Pt/C 가 사용되었고, air가 latm으로 양극에 공급되었다. 음극에 대한 XRD 분석결과 음극에서의 산화에 의해 Sodium Borohydride ($NaBH_4$)가 분해되어 수소가 발생되며, 연속적으로 액체연료가 주입되어도 전지가 작동하는 것을 확인할 수 있었다. 이때 에너지밀도는 6,000 Ah/kg (for $NaBH_4$ or $KBH_4$)이다.

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.550-554
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• 2023

탄화수소기반의 화석연료 에너지원은 이산화탄소 배출로 인한 지구온난화 문제로 지속적인 이용 및 확장에 제한이 있다. 수소는 전통적인 화석연료에 대한 유망한 대안으로 여겨지고 있다. 수소의 안정적인 장기저장을 위해서 극저온인 포화상태에서 수소의 열역학적 물성에 대한 예측이 요구된다. 따라서 본 연구에서는 비교적 간단한 관계식을 보이는 3차 상태방정식들을 이용하여 포화상태의 열역학적 물성들(포화증기압, 액체 및 기체의 밀도, 엔탈피 및 엔트로피)을 모사하였다. 포화상태 수소에 대한 여러가지 열역학적 물성들을 비교한 결과 3 종류(Redlich-Kwong (RK), Soave-Redlich-Kwong (SRK), Peng-Robinson (PR))의 상태방정식 중 SRK 모델이 비교적 정확한 예측결과를 보였다.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.787-793
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• 2011

A 76.5wt%Mg - 23.5wt%Ni (Mg-23.5Ni) sample was prepared by reactive mechanical grinding (RMG) and its hydriding and dehydriding properties were then investigated. Activation of the Mg-23.5Ni sample was completed only after two hydriding (under 12 bar $H_2$) - dehydriding (under 1.0 bar $H_2$) cycles at 593K. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and shorten diffusion distances of hydrogen atoms. After hydriding - dehydriding cycling, the Mg-23.5Ni sample contained Mg2Ni phase.

• 조명전기설비학회논문지
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• 제20권7호
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• pp.46-52
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• 2006

[ $Mg_2Ni$ ]계 합금 입자의 수소저장 특성에 대한 표면처리 효과가 마이크로 전극 측정법에 의해 검토되었다. 카본-섬유로 된 마이크로 전극을 KOH 수용액 속에서 조정자를 사용하여 수소 단일입자에 접촉시켰다. 상온에서 $Mg_2Ni$ 합금의 수소저장 특성은 니켈 도금용액에 의한 표면 처리에 의해 크게 개선되었다. 니켈 도금용액 속에 있는 함유된 나트륨염(sodium phosphate 및 sodium dihydrogen citrate)이 합금을 아몰퍼스와 같은 형태로 만들었으며, 그 결과 상온에서 수소 흡장/방출 용량이 최초의 17[mAh/g]에서 150[mAh/g]로 향상되었다. 합금 입자 내에서 수소원자의 겉보기 화학적 확산계수를 계산하기 위하여 Potential-step 실험을 실시하였으며 데이터 해석을 위해 구형확산 모델을 적용하였다. 실험결과로서 겉보기 확산계수($D_{app}$)는 수소 흡장 및 방출되는 전 과정에서 $10^{-8}{\sim}10^{-9}[cm^2/s]$ 수준인 것으로 확인되었다.

• 한국재료학회지
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• 제29권12호
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• pp.798-803
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• 2019

The self-discharge behavior of zinc-air batteries is a critical issue induced by corrosion and hydrogen evolution reaction (HER) of zinc anode. The corrosion reaction and HER can be controlled by a gelling agent and concentration of potassium hydroxide (KOH) solution. Various concentrations of KOH solution and polyacrylic acid have been used for gel electrolyte. The electrolyte solution is prepared with different concentrations of KOH (6 M, 7 M, 8 M, 9 M). Among studied materials, the cell assembled with 6 M KOH gel electrolyte exhibits the highest specific discharge capacity and poor capacity retention. Whereas, 9 M KOH gel electrolyte shows high capacity retention. However, a large amount of hydrogen gas is evolved with 9 M KOH solution. In general, the increase in concentration is related to ionic conductivity. At concentrations above 7 M, the viscosity increases and the conductivity decreases. As a result, compared to other studied materials, 7 M KOH gel electrolyte is suitable for Zn-air batteries because of its higher capacity retention (92.00 %) and specific discharge capacity (351.80 mAh/g) after 6 hr storage.