• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.74-82
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• 2002

Ni nanoparticles이 표면에 분산된 mutiwall carbon nanotubes (MWNTs)의 수소저장 특성을 분석하였다. Metal nanoparticles의 분산 방법은 incipient wetness impregnation procedure을 사용하였는데, 이러한 Ni catalysts의 역할은 기존에 알려진 Li, K doping과 같은 개념으로 기상의 수소를 분해하여 carbon 표면에 chemical adsorption 시키는 역할을 하게 된다. 실제로 Ni nanoparticles이 6wt% loading된 경우에는 thermal desorption spectra를 분석한 결과 ~2.8wt% hydrogen이 ~340-520K의 온도범위에서 방출되는 것을 관찰할 수 있었다. Kissingers plot을 통해서 MWNTs와 hydrogen과 interaction energy를 구한 결과 ${\sim}31kJ/molH_2$를 얻을 수 있었으며 이 값은 기존의 SWNTs에 hydrogen이 physi-sorption에서 실험적으로 얻을 수 있었던 값보다 1.5배 큰 값이라고 할 수 있다. 자세한 수소저장 기구를 분석하기 위해서 FT-IR분석을 한 결과 C-Hn stretching vibrations이 관찰되었으며 mono-hydride와 weak di-hydride $sp^3$가 형성된 것으로 해석 될 수 있었다. 이와 같은 결과는 Ni nanoparticle들이 예상과 같이 hydrogen molecules을 dissociation하는 역할을 하는 것을 의미한다. 연속적인 thermal desorption 실험을 통해 가역성도 평가하였다.

• Journal of Powder Materials
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• v.16 no.1
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• pp.28-32
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• 2009

The activation temperatures and hydrogen sorption rates of $Ti_{80-X}Zr_{20}V_X$ alloys were evaluated at room temperature. The alloy powders were prepared by arc melting and then hydride-dehydride(HDH) process. The alloy powders were apt to activate by increase of vanadium in Ti-Zr-V alloys. The easy activation was explained in terms of surface oxygen content which decreased with increase of vanadium on Ti-Zr-V alloys.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.5
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• pp.428-436
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• 2013

Attrition characteristics of $CO_2$ absorbents for pre-combustion $CO_2$ capture were investigated to check attrition loss of those absorbents and to determine solid circulation direction and the better $CO_2$ absorbent. The cumulative attrition losses of two absorbents increased with increasing time. However, attrition loss under a humidified condition was lower than that under a non-humidified condition case. Between two absorbents, attrition loss of PKM1-SU absorbent was higher than that of P4-600 absorbent. The average particle sizes of the attrited particles were less than $2.5{\mu}m$ for two absorbents under a non-humidified condition case, and therefore, we could conclude that the main mechanism of attrition for two absorbents is not fragmentation but abrasion. Based on the results from the test for the effect of humidity on the attrition loss, we selected solid circulation direction from SEWGS reactor to regeneration reactor because the SEWGS reactor contains more water vapor than regeneration reactor. Attrition loss and make-up rate of two absorbents were compared based on the results from $CO_2$ sorption capacity tests and attrition tests. Required make-up rate of P4-600 absorbent was lower than that of PKM1-SU absorbent. However, more detail investigation on the optimum regeneration temperature, manufacturing cost, solid circulation rate, regeneration rate, and long-term sorption capacity should be considered to select the best $CO_2$ absorbent.

• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.689-695
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• 2017

This study was carried out to investigate the physicochemical and adsorptive characteristics of black carbon (BC) materials for cesium in case of severe nuclear accidents. The BC was prepared with a xylem of oak and pine trees incompletely combusted with different ramp rate and final temperature. Carbon (C), hydrogen (H) and oxygen (O) atomic ratios, BET, pore structure, and zeta potential were characterized for the produced BC. A low cesium concentration ($C_w{\approx}10^{-7}M$) was used for sorption batch experiments. The H/C and O/C ratios of BC decreased with the increase of final temperature, which indicates a carbonization of the wood materials regardless of ramp rate and tree species. However, SEM images showed different pore structures depending on tree species such as steric and plate-like for oak-BC and pine-BC, respectively. The greatest sorption distribution coefficients of $K_{d,Cs}{\approx}1,200{\sim}1,800L\;kg^{-1}$ were observed for the oak-BC produced at $400^{\circ}C$, while comparatively low $K_{d,Cs}$ < $100L\;kg^{-1}$ for pine-BC. In addition, the sorption capabilities of BC declined with the increase of combustion temperature up to $600^{\circ}C$, because high temperature destroyed surface functionalities with the rise of ash components in the BC. Therefore, the sorption processes of BC for radioactive cesium are predominantly controlled by final production temperature of BC as well as raw materials (e.g., tree species).

• Journal of Powder Materials
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• v.14 no.1 s.60
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• pp.56-62
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• 2007

Getter property of nano-sized metallic powders was evaluated as a possible candidate for the future getter material. For the purpose, Ti powders of about 50 nm were prepared by electrical wire explosion. Commercial Ti powders of about 22 micrometer were tested as well for comparison. The room-temperature hydrogen-sorption speed of nano-sized Ti powders was $1.34\;L/sec{\cdot}cm^{2}$ which was more than 4 times higher than that of micron-sized ones. The value is comparable to or even higher than those of commercial products. Its sorption speed increases with activation temperature up to $500^{\circ}C$ above which it deteriorates due to low-temperature sintering effect of nano-sized particles.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.377-382
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• 2014

Micro-/macroporous carbons (MMCs) were prepared using a hollow mesoporous silica capsule (HMSC) as a sacrificial hard template. The carbonization process after the infiltration of furfuryl alcohol into the template-free HMSC material afforded MMC materials in high yield. The hard template HMSC could be removed by HF etching without deteriorating the structure of MMC. The MMC materials were fully characterized by SEM, TEM, PXRD, XPS, and Raman spectroscopy. The replication processes were so successful that MMCs exhibited a hollow capsular structure with multimodal microporosity. Detailed textural properties of MMC materials were investigated by volumetric $N_2$ adsorption-desorption analysis at 77 K. To explore the gas sorption abilities of MMCs for other gases, $H_2$ and $CO_2$ sorption analyses were also performed at various temperatures. The multimodal MMC materials were found to be good sorbents for both $H_2$ and $CO_2$ at low pressure.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.2
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• pp.168-178
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• 2009

To check feasibility of SEWGS(Sorption Enhanced Water Gas Shift) system, conceptual design and sensitivity analysis of operating variables have been investigated based on a design program of two-interconnected fluidized bed. Based on the conceptual design results, the optimum configuration for SEWGS was considered. Among three configurations, bubbling beds system was selected as the best configuration. Process design results indicate that the SEWGS system is compact and feasible. Based on the selected operating conditions, the effects of variables such as pressure, $CO_2$ capture capacity, solid inventory, CO conversion and $CO_2$ capture efficiency have been investigated as well.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.399-405
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• 2007

The hyper-eutectic Mg-33.5%Ni alloy was rapidly solidified by melt spinning process. The melt-spun Mg-33.5%Ni has amorphous structure and crystallization occurred above $162^{\circ}C$. The hydriding and dehydriding rates of melt-spun Mg-33.5%Ni increased with cycle and high rate of hydrogen storage occurred at 3rd cycle. The maximum hydrogen amount absorbed in melt-spun Mg-33.5%Ni at $300^{\circ}C$ is about 4.5%.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.655-659
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• 2020

Hydrogen isotopes (i.e. deuterium and tritium) are supplied to the tokamak in the International Thermonuclear Experimental Reactor (ITER) fuel cycle. One important part of the ITER fuel cycle is the recycling of unused fuel back to the tokamak, as almost 99 % of fuel is unburned during fusion reaction. For this, cryogenic distillation has been used in the isotope separation system (ISS) of ITER, but this technique tends to be energy-intensive and to have low selectivity (typically below 1.5 at 24 K). Recently, efficient isotope separation by porous materials has been reported in the so-called quantum sieving process. Hence, in this study, hydrogen isotope adsorption behavior is studied using chemically stable ZIF-11. At low temperature (40 K ~ 70 K), the adsorption increases and the sorption hysteresis becomes stronger as the temperature increases to 70K. Molar ratio of deuterium to hydrogen based on the isotherms shows the highest (max. 14) ratio at 50 K, confirming the possibility of use as a potential isotope separation material.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.780-786
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• 2011

Mg hydride had high hydrogen capacity (7.6%), lightweight and low cost materials and it was promising hydrogen storage material at high temperature. However, commercial applications of the Mg hydride are currently hindered by its high absorption/desorption temperature, and very slow reaction kinetics. one of the approaches to improve the kinetic is $MgH_x$ intermixed with carbon. And it shows that carbon and carbon allotropes have a beneficial effect on hydrogen sorption in Mg. The graphene is a kind of carbon allotropes which is easily desorbed reaction at low temperatures because its reaction is exothermic. In this work, the effect of graphene concentration on the kinetics of Mg hydrogen absorption reaction was investigated. The $MgH_x$-Graphene composites has been prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD and simultaneous TG, DSC analysis. The hydrogenation behaviors were evaluated by using a sievert's type automatic PCT apparatus. In this research, results of kinetic profiles exhibit hydrogen absorption rate of $MgH_x$-5wt.% and 10wt.% graphene composite, as 1.25wt.%/ms, 10.33wt.%/ms against 0.88wt.%/ms for $MgH_x$ alone at 473K.