• Journal of Hydrogen and New Energy
• /
• v.2 no.1
• /
• pp.1-6
• /
• 1990

The desorption kinetics of $Mg_2Cu$ hydride were studied by thermal analysis technique in order to study desorption behavior and to relate thermal desorpton spectra to occuption site of hydrogen. It is suggested that a continuous ${\alpha}/{\beta}$ interface boundary is formed at the initial absorption stage. And the desorption kinetics were analysed by the theoretical equation which was derived on the basis of continous moving boundary model. The number of thermal desorption peak corresponds to the occupation sites of hydrogen. The apparent activation energy for the desorption of $Mg_2Cu$ hydride is 91 KJ/mol.

• Korean Journal of Metals and Materials
• /
• v.48 no.12
• /
• pp.1123-1129
• /
• 2010

In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the dehydrogenation of the Mg-H system was investigated. As the initial wt% of hydrogen was increased to 4.4, the peak temperature of evolution rate shifted to higher temperature. However, with the initial wt% of hydrogen higher than 4.4, peak temperature of evolution rate did not change. The peak temperatures of evolution rate obtained by automatic apparatus were almost the same as those measured by a manual apparatus. As the heating rate was increased, the peak temperatures increased; the peak temperatures for heating rates 1, 2 and 3 K/min were 664, 687 and 702 K, respectively. The activation energy for the decomposition of Mg hydride was 101 kJ/mol. The Sievert's type automatic apparatus can be successively applied to the thermal analysis of metal hydride.

• Journal of Hydrogen and New Energy
• /
• v.26 no.4
• /
• pp.308-317
• /
• 2015

To investigate the effect of microstructure on the formation of the desorption peak, the volumetric thermal analysis technique (VTA) was applied to the Mg-13.5 wt% Ni hydride system. The sample made by the HCS (hydriding combustion synthesis) process had two kinds of Mg microstructures. Linear heating was started with various constant heating rates. Only one peak was appeared in the case of the small initial hydrogen wt% (0.83 wt%). Yet, two peaks were appeared with increasing initial hydrogen wt% (1.85 and 3.73 wt%) when only Mg was hydrogenated. The first peak was formed through the evolution of hydrogen from $MgH_2$, made by eutectic Mg. The second peak was formed through the evolution of hydrogen from $MgH_2$, made by primary Mg. Therefore, this result shows that the microstructure also has a considerable effect on forming the desorption peak. We have also derived the hydrogen desorption equations by VTA to get apparent activation energy when the rate-controlling step for the desorption of the hydrided system is the diffusion of hydrogen through the ${\alpha}$ phase and the chemical reaction ${\beta}{\rightarrow}{\alpha}$.

• Korean Journal of Materials Research
• /
• v.7 no.8
• /
• pp.707-713
• /
• 1997

HVPE(hydride vapor phase epitaxy)법으로 (111)MgAI$_{2}$ $O_{4}$기판위에 GaN 후막을 성장하였다. GaN를 성장하기 전에 기판에 표면을 GaCI로 처리한 수 성장하였을 때 이중 X선 회절 피크의 반치폭이 710 arcsec로서 N $H_{3}$로 처리한 후 성장한 GaN에 비하여 작았으며, 무색 투명의 경면상태가 얻어\ulcorner다. 113$0^{\circ}C$의 온도에서 성장한 GaN 의 광루미네센스(PL)특성과 동일하게 나타났다. 10K의 온도에서 측정된 PL 스펙트럼은 자유여기자와 속박여기자의 재결합천이에 의한 피크들과 Mg과 관련된 도너-억셉터 쌍 사이의 재결합 및 이의 1LO, 2LO, 3LO 및 4 LO 포논복제에 의한 피크들이 나타났다. 성장된 GaN는 n형의 전도성을나타내었으며, 캐리어 이동도와 농도는 각각 21.3$\textrm{cm}^2$/V ㆍsec와 4.2 x $10^{18}$$cm^{-3}$이었다.

• Journal of Hydrogen and New Energy
• /
• v.2 no.1
• /
• pp.69-75
• /
• 1990

The effect of thermal cycling on the hydrogenation characteristics of the $Mg_2Cu-H$ system was investigated in order to study of intrinsic degradation of the system. The hydrogen storage capacity decreased with thermal cycling from $573^{\circ}K$ to $663^{\circ}K$. By the thermal analysis it is found that stable $MgH_2$ hydride is formed during thermal cycling. With a heat treatment at $693^{\circ}K$ at a hydrogen pressure of 16 atm, the hydrogenation rate drastically decreased. From these observation, it suggested that the intrinsic degradation of $Mg_2Cu$ system results from mainly the formation of stable $MgH_2$ hydride phase.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2000.11a
• /
• pp.168-168
• /
• 2000

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.41 no.5
• /
• pp.674-680
• /
• 2012

As(III) and As(V) were analyzed in bamboo salts by hydride generation ICP-AES. In order to quantify the total amount of As in bamboo salts, $AsH_3$ was producted by reacting with 6 mol/L hydrochloric acid and $NaBH_4$, which was then analyzed by hydride generation ICP-AES. As(V) was quantified simultaneously after selectively quantifying As(III). As(III) was quantified by determining the total amount of As and then correcting for the amount of As(III). To improve the reliability of the analysis we repeated the experiment several times to check the detection limit, quantification limit, and measurements of our testing methods. According to the result of our quantification analysis of As existing in bamboo salt, the range of total As content was 0.05 mg/kg~0.2 mg/kg and As(V) was over 90% of the total As.

• Journal of Hydrogen and New Energy
• /
• v.30 no.1
• /
• pp.8-13
• /
• 2019

In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the Sievert's type automatic apparatus was modified in my laboratory. In this study, an experiment was conducted to see if hydrogen absorption and desorption reactions are possible under near constant pressure (${\pm}0.05atm$) using this device. The hydrogenation and dehydrogenation of the Mg-H system was investigated. And the program was also modified for the kinetics. It was found that it is possible to measure the hydrogen absorption rate under near constant pressure of Mg by using the modified Sievert's type automatic apparatus at 573 K and 598 K. And using this system, the hydrogen desorption rate of Mg hydride under near constant pressure at 623 K was also measurable. However, since the hydrogen desorption rate of Mg hydride is fast at 648 K, the hydrogen desorption reaction did not proceed within a constant pressure range of $0.15{\pm}0.05atm$.

• Journal of Industrial Technology
• /
• v.3
• /
• pp.47-51
• /
• 1983

The fragmentation of Mg and Mg-25(w/o) Al alloy particles in hydriding-dehydriding was studied. The formation of hydride was made in autoclave, and formed hydrides were $MgH_2$ in both pure Mg and Mg-25(w/o) Al alloy particles. Pure Mg was more fractured than Mg-25(w/o) Al alloy in hydriding. The addition of Al exhibited fragmentation in hydriding, but displayed the same fragmentation as Mg in dehydriding.

• Journal of Hydrogen and New Energy
• /
• v.21 no.2
• /
• 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.