• 한국수소및신에너지학회논문집
• /
• 제16권1호
• /
• pp.25-30
• /
• 2005

수소 분위기에서 10wt.%MnO와 기계적인 분쇄(반응성 기계적 분쇄)에 의해 Mg의 수소 저장 성질을 향상시켰다. 회전 속도는 250 rpm, 밀링시간은 2 h, 그리고 시료 대 볼 중량비는 1/45이었다. 준비한 Mg-10wt.%MnO 시료는 활성화를 위한 수소화물 형성 분해 싸이클링이 필요없었으며, 첫 번째 싸이클 593k 12 bar $H_2$에서, 10분 동안에 3.12wt.%, 60분 동안에 3.95wt.%의 수소를 흡수하였다. 또한 Mg-10wt.%MnO는 593k 0.8 bar $H_2$에서 60분 동안에 2.12wt.%의 수소를 방출하였다. MnO와 Mg의 방응성 분쇄는, 핵생성을 용이케하고 (Mg 입자의 표면에 결함 형성과 첨가물에 의해), Mg 입자의 표면에 crack을 만들어 Mg의 입자 크기를 줄여 그 결과 수소 원자의 확산 거리를 작게 함으로써 수소 흡수 방출 속도를 증가시킨다. 수소화물 형성 분해 싸이클링은 Mg 입자의 표면에 crack을 만들고 Mg의 입자 크기를 줄여 수소 흡수 방출 속도를 증가시킨다.

• 한국수소및신에너지학회논문집
• /
• 제16권3호
• /
• pp.238-243
• /
• 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
• /
• 제13권4호
• /
• pp.270-278
• /
• 2002

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 and degradation behavior could be improved, The main emphasis of this study was to find an economic manufacturing method for Mg-Ti-Ni-H systems, and to investigate their hydrogenation properties, In order to examine hydrogenation behavior, a Sieverts type automatic pressure-composition-isotherm(PCI) apparatus was used and the experiments were performed at 423, 473, 523, 573, 623 and 673K. The results of thermogravimetric analysis(TGA) reveal that the absorbed hydrogen contents are around 2.5 wt% for ($Mg_9Ti_1$)-10 wt% Ni. With increased Ni content, the absorbed hydrogen content decreases to 1.7 wt%, whereas the dehydriding starting temperatures are lowered by some 70-100K. The results of PCI on ($Mg_9Ti_1$)-20 wt% Ni show that its hydrogen capacity is around 5.3 wt% and its reversible capacity and plateau pressure are also excellent at 523K and 573K. In addition, the reaction enthalpy, $\Delta$HD.plateau, is $30.6{\pm}5.7kJ/molH_2$.

• 한국수소및신에너지학회논문집
• /
• 제24권5호
• /
• pp.367-372
• /
• 2013

Hydrogen storage as a metal hydride is the most promising alternative because of its relatively large hydrogen storage capacities near room temperature. TiMn2-based C14 Laves phases alloys are one of the promising hydrogen storage materials with easy activation, good hydriding-dehydriding kinetics, high hydrogen storage capacity and relatively low cost. In this work, multi-component, hyper-stoichiometric $Ti_{0.85}Zr_{0.13}(Fe_x-V)_{0.56}Mn_{1.47}Ni_{0.05}$ C14 Laves phase alloys were prepared by a vacuum induction melting for a hydrogen storage tank. Since pure vanadium (V) is quite expensive, the substitution of the V element in these alloys has been tried and some interesting results were achieved by replacing V by commercial ferrovanadium (FeV) raw material. In addition, the melt-spinning process, which was applied to the manufacturing of some of these alloys, could make the plateau slopes much flatter, which resulted in the increase of reversible hydrogen storage capacity. The improvement of sloping properties of melt-spun $Ti_{0.85}Zr_{0.13}(Fe_x-V)_{0.56}Mn_{1.47}Ni_{0.05}$ alloys was mainly attributed to the homogeneity of chemical composition.

• 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
• /
• 제23권5호
• /
• pp.455-460
• /
• 2012

This work describes the hydriding chemical vapor synthesis (HCVS) of the $MgH_2$ in a hydrogen atmosphere and the product's hydriding-dehydridng properties. Mg powder was used as a starting material to synthesize $MgH_2$ and uniformly heated to a temperature of $600^{\circ}C$ for Mg vaporization. The effects of hydrogen pressure on the morphology and the composition of HCVS-$MgH_2$ were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is clearly seen that after the HCVS process, the particle size of synthesized $MgH_2$ was drastically reduced to the submicron or micrometer-scale and these showed different shapes (needle-like nanofibers and angulated plate) depending on the hydrogen pressure. It was found that after the HCVS process, the $H_2$ desorption temperature of HCVS-$MgH_2$ decreased from 380 to $410^{\circ}C$, and the minimum hydrogen desorption tempreature of HCVS-$MgH_2$ powder with needle-like shape can be obtained. In addition, the enhanced hydrogen storage performance for needle-like $MgH_2$ was achieved during subsequent hydriding-dehydriding cycles.

• 한국수소및신에너지학회논문집
• /
• 제21권2호
• /
• pp.81-88
• /
• 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.

• 공업화학
• /
• 제9권2호
• /
• pp.255-260
• /
• 1998

금속수소화물 $LaNi_5$와 $LaNi_{4.5}Al_{0.5}$을 화학적 합성법으로 제조하여, 합성된 금속수소화물의 물성을 다양한 방법으로 확인하였다. $LaNi_5$와 $LaNi_{4.5}Al_{0.5}$은 2회 정도 수소화/탈수소화 반응을 시키면 활성화되었으며, 압력-농도-온도 곡선을 측정한 결과 각각 6개와 5.5개의 수소원자가 저장되었다. $LaNi_{4.5}Al_{0.5}$의 경우 수소화 반응속도를 초기속도법으로 구한 결과 비반응 수축핵모델이 잘 적용되었으며, 수소화반응의 율속단계는 $LaNi_{4.5}Al_{0.5}$의 표면에서 수소분자의 해리화학흡착임을 알 수 있었다. $LaNi_{4.5}Al_{0.5}$의 수소화반응 활성화에너지는 $9.506kcal/mol-H_2$이었으며, 반응속도식은 273~343K와 $P_o-P_{eq}=0.25{\sim}0.66atm$의 범위에서 아래와 같이 표시되었다. $\frac{dX}{dt}=4.636(P_o-P_{eq})$ exp$\frac{-9506}{RT}$).