• Journal of the Korean Institute of Gas
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• v.5 no.2 s.14
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• pp.62-68
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• 2001

Overpressure in pipeline attached to outlet of LPG vaporizer has been studied to provide countermeasures to prevent it. The cause of liquefaction in pipeline was reviewed using vapor pressure curve with temperature, pressure, and composition to suggest method of controlling such parameters. Performance of vaporizer has been tested to detect defective design of float ball, and then improved scheme was suggested. Trouble of regulator attached to vaporizer was also studied to give countermeasures.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.617-623
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• 2002

In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{x}$ (x=0, 0.025, 0.05, 0.1), are prepared by adding the excess Zr in $MmNi_{4.5}$ $Mn_{0.5}$ / alloy for the strong resistance to intrinsic degradation. The hydrogen storage alloys of rare-earth metal such as $LaNi_{5}$ , and $MmNi_{5}$X and $MmNi_{4.5}$ /$_Mn{0.5}$ alloys which substituted La by misch metal properties were characterized as well. The hydrogen storage alloys were produced by melting each metal mixture in arc melting furnace, and the as-cast alloys were heat-treated at $1100^{\circ}C$ for 10 hr. The major elements of misch metal(Mm) were La, Ce, Pr and Nd with some impurities less than 1wt.% determined by ICP-AES. X-ray diffraction indicated that the structure for these samples was a single phase of hexagonal with $CaCu^{5}$ type. As the Zr contents increases, the activation time and the plateau pressure decrease and sloping of the plateau pressure increase. Amount of the 2nd phases increases with increase in Zr contents in $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{0.1}$ alloy, This phenomenon indicated that $ZrNi_3$ in this phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage..

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.79-84
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• 2005

The lowest activation temperature of a commercial vacuum getter reported so far in literature was about $400^{\circ}C$. Recently, $Ti_{0.3}Zr_{0.2}V_{0.5}$ alloy has been reported to exhibit the activation temperature lower than $200^{\circ}C$ when they are prepared as thin film. In this study, the alloy was prepared as bulk form and its activation temperature and hydrogen sorption properties were investigated in compliance with a standard method. The alloy powder was prepared by arc melting and subsequent HDH(Hydride-DeHydride) process. The activation temperature of the alloy was estimated from the ultimate pressure-temperature curve and located between $150^{\circ}C\;and\;200^{\circ}C$. The hydrogen sorption speed measured by an orifice method was 0.895 liter/sec which is comparable to thin film of same composition.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.4
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• pp.189-202
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• 2000

$AB_2$ type Zr-based Laves phases alloys have been studied for potential application as a negative electrode in a Ni-MH battery. The $AB_2$-type electrodes have a much higher energy density than $AB_5$-type electrodes per weight, however they have some disadvantages such as poor activation behavior and cycle life etc. Nonetheless, the $AB_2$-type electrodes have been studied very extensively due to their high energy density. In this study, in order to develop the cycle life, the Mn of $AB_2$ alloy composition was substituted partially by Mo. The alloys were melted by arc furnace and remelted 4-5 times for homogeneity. The alloy powder was used below 200-325 mesh for experiments. The structures and phases of the alloys were analyzed by XRD, SEM and EDS, and measured the curve of a pressure-composition isotherms. The electrodes were prepared by cold pressing of the copper-coated(25 wt%) alloy powders, and tested by a half cell. The results are summarized as follows. The cycle life was improved with the increase of Mo amount in $Zr_{1-x}Ti_xV_{0.4}Ni_{1.2}Mn_{0.4}Mo_y$(x=0.3, 0.4) and the activation was faster, whereas the discharge capacity decreased.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.39-48
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• 2018

This study presents optimal design of gas lift considering composition of reservoir oil and injected gas which can affect gas lift performance in offshore oil reservoir. Reservoir simulation was conducted by using reservoir models which were built in accordance with API gravity of oil. The results of simulation reveal that oil production rate is considerably increased by gas lift when the reservoir productivity decrease. As a results of response curve analysis for gas lift using well models, gas injection rate to improve the production rate increases as the API gravity of oil decreases and the specific gravity of injected gas increases. The optimal design of gas lift was carried out using multiple lift valves. Consequently, gas lift can be operated at relatively low injection pressure because of decrease in injection depth in comparison to the single lift valve design. The improved oil production rates were analyzed by coupling between reservoir model and well model. As a results of the coupling, it is expected that natural gas injection in the heavy oil reservoir is the most efficient method for improving oil production by gas lift.

• Membrane Journal
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• v.25 no.2
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• pp.191-201
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• 2015

We have studied on the preparation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy, the characteristics of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloy by X-ray diffractometer (XRD), pressure composition temperature (PCT) curve, scanning electron microscopy (SEM) and the $H_2-N_2$ gas mixture separation of $TiCo_xFe_{1-x}$(x=0.50~1.00)- stainless steel (SS) composite membranes. The formation of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys with cubic crystal same as TiCo was confirmed by X-ray diffractometer. $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys showed the hysteresis at $120^{\circ}C$. As the Fe content of $TiCo_xFe_{1-x}$(x=0.50~1.00) system alloys increased, the hysteresis was increased both range x=0.90~1.00 and x=0.55~0.60, and the range x=0.55~0.90 gave decreased hysteresis. $TiCo_{0.55}Fe_{0.45}$ alloy was the one showed the lowest hysteresis among them. The lowest value of hydrogen permeation pressure of $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membrane was $TiCo_{0.55}Fe_{0.45}$-SS composite membrane with the value of 2.5 atm at $120^{\circ}C$; otherwise, $TiCo_{0.90}Fe_{0.10}$-SS composite had the highest pressure value among the membranes with the value of 10 atm. $TiCo_{0.55}Fe_{0.45}$-SS composite membrane was the best to separate the $H_2-N_2$ gas mixture excellently among the $TiCo_xFe_{1-x}$(x=0.50~1.00)-SS composite membranes since $TiCo_{0.55}Fe_{0.45}$ had the least hysteresis, and hydrogen permeation pressure was the lowest with value of 2.5 atm.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.380-385
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• 2011

$MgH_2$ was synthesized by hydriding chemical vapor deposition (HCVD). In this study, we examined the hydrogen storage property of $MgH_2$ synthesized by HCVD. The results of pressure-composition-temperature (PCT) measurement showed that the HCVDed $MgH_2$ reversibly absorbed hydrogen as much as 6 wt%. Each hydrogenation rate was very greater than the conventional alloy methods. The reason was that the particle size made by HCVD was small as approximately 1 ${\mu}m$. The PCT of $MgH_2$ made by HCVD methode was similar to a commercial $MgH_2$. The ${\Delta}H$ and ${\Delta}S$ value are respectively -76.8 $kJ/mol{\cdot}H_2$ and -137.4 $kJ/mol{\cdot}H_2$. Mg made by HCVD methode was activated easily than commercial Mg. Also the initial reaction rate was faster than that of commercial $MgH_2$. 70% of the total storage were stored during 400s.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.3
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• pp.156-162
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• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.2
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• pp.122-129
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• 2005

The characteristics of hydrogen storage have been investigated in the Ti-Cr-Mo and Ti-Cr-V ternary alloys with bcc structure. The alloys were melted by arc furnace and remelted 4-5 times for homogeneity. The lattice parameters, microstructures and phases of the alloys were examined by SEM, EDX and XRD, and the Pressure-Composition isotherms of the alloys were measured. From these data the relationship of the maximum and effective hydrogen storage capacities vs. chemical composition, lattice parameter and the radius of tetrahedral site were analyzed and discussed. The results showed that all of these alloy, in the range of the this study, had mainly bcc solid solutions with small amount of Ti segregation due to a lower melting point of Ti compared with other elements. Lattice parameters of the alloys were very near to the atomic average values of lattice parameters of the constituent elements. It was also found that maximum hydrogen storage capacities of the Ti-Cr-Mo alloys increased with increasing Ti content and the radius of tetrahedral site but the effective hydrogen storage capacities decreased after showing the maximum. The hydrogen storage capacities of the Ti-Cr-V alloys were almost same even though the V contens were quite different from alloy to alloy and this could be attributed to the almost same Ti/Cr ratio of the alloys. The maximum effective hydrogen storage capacity of the Ti-Cr-Mo alloys was revealed at Ti content of about 40${\sim}$50 at% and radius of tetrahedral site of 0.43${\sim}$0.45 nm. The Ti-Cr-V alloys showed the hydrogen storage capacities of 3.0 wt% and effective hydrogen storage capacities of 1.5 wt%.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.185-189
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• 2012

We report plasma-assisted molecular beam epitaxy of $In_XGa_{1-X}N$ films on c-plane sapphire substrates. Prior to the growth of $In_XGa_{1-X}N$ films, GaN film was grown on the nitride c-plane sapphire substrate by two-dimensional (2D) growth mode. For the growth of GaN, Ga flux of $3.7{\times}10^{-8}$ torr as a beam equivalent pressure (BEP) and a plasma power of 150 W with a nitrogen flow rate of 0.76 sccm were fixed. The growth of 2D GaN growth was confirmed by $in-situ$ reflection high-energy electron diffraction (RHEED) by observing a streaky RHEED pattern with a strong specular spot. InN films showed lower growth rates even with the same growth conditions (same growth temperature, same plasma condition, and same BEP value of III element) than those of GaN films. It was observed that the growth rate of GaN is 1.7 times higher than that of InN, which is probably caused by the higher vapor pressure of In. For the growth of $In_xGa_{1-x}N$ films with different In compositions, total III-element flux (Ga plus In BEPs) was set to $3.7{\times}10^{-8}$ torr, which was the BEP value for the 2D growth of GaN. The In compositions of the $In_xGa_{1-x}N$ films were determined to be 28, 41, 45, and 53% based on the peak position of (0002) reflection in x-ray ${\theta}-2{\theta}$ measurements. The growth of $In_xGa_{1-x}N$ films did not show a streaky RHEED pattern but showed spotty patterns with weak streaky lines. This means that the net sticking coefficients of In and Ga, considered based on the growth rates of GaN and InN, are not the only factor governing the growth mode; another factor such as migration velocity should be considered. The sample with an In composition of 41% showed the lowest full width at half maximum value of 0.20 degree from the x-ray (0002) omega rocking curve measurements and the lowest root mean square roughness value of 0.71 nm.