• Journal of Hydrogen and New Energy
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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 Soil and Groundwater Environment
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• v.20 no.5
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• pp.11-15
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• 2015

The three processes of 1) high- & low-temperature microwave heatings, 2) the soil washing, and 3) the thermal desorption processes in soil remediation are analysed on the treatment cost data for 2003-2012 years. The cost of microwave heating method with at temperature 500-700℃, for 30 minutes, and at 4-6 kW is approximately 10 $/ton (13,000 ₩) due to the deep through heating of micro-wave, the soil washing with chemicals is about 80 $/ton (85,000 ₩) due to the chemicals & duration, and the thermal desorption process is around 40 $/ton (41,000 ₩) from the less efficiency. Furthermore the sustainability has been assessed, and suggestions are made. 1) Green; the minimal environmental footprint, 2) Growth; the least cost, 3) Shared; the social & environmental justice, 4) Smart; the microwave characteristics of deep through irradiation & heating, and 5) Mutuality; the flexibility of the technology. More additives including water, the government support, and public relation are suggested realizing the microwave in this condition is not harmful to human beings.

• Journal of the Korean Society of Tobacco Science
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• v.36 no.1
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• pp.26-33
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• 2014

Simultaneous determination of crop protection agents(CPAs) in food are done with multi-residue methods, which are composed of sample clean-up, concentration, chromatographic separation and detection. Stir Bar Sorptive Extraction(SBSE) technique is used for sample preparation of various analytes in several fields. The aim of this study was to develop a sensitive and fast method based on SBSE followed by thermal desorption - gas chromatography - mass spectrometry(TD - GC/MS) to determine CPAs in tobacco sample. For the analysis of tobacco sample prior to the SBSE method, solvent extraction or ultrasound-assisted solvent extraction was performed. methanol was used as the extraction solvent. The extract was then diluted with water. Finally, the sample was subjected to SBSE. A method for fast screening of crop protection agents in tobacco using SBSE-TD - GC/MS has been developed. About 17 CPAs including organochlorine, organophosphorous and others were identified and quantified. This method showed good linearity and high sensitivity for most of the target CPAs. The method was applied to the determination of CPAs at ng/mL levels in tobacco sample. This method is simple, rapid and may be applied in detection of other components.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.513-513
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• 2012

핵 융합로의 대면재질(Plasma Facing Material; PFM)은 고온의 플라즈마와 고 에너지의 이온들에 지속적으로 노출 된다. 특히 PFM은 흡착되는 기체 등에 의한 부식과 변형이 발생할 수 있다. 현재 핵 융합로 내부의 PFM으로 고려되고 있는 재질 중 하나인 고순도 탄소타일의 경우 고온의 수소동위원소 플라즈마에 직접적으로 노출되므로 이에 의한 탄소타일에 흡착되는 수소 등의 기체에 대한 정량적인 분석방법이 필요하다. 본 연구는 고순도 탄소타일 등과 같은 플라즈마 대면재료에 흡착되어 있는 물질의 정량적 분석이 가능한 TDA (Thermal Desorption Analyzer)의 개념 설계에 관한 것이다. TDA는 고온 가열($800^{\circ}C$ 이상) 및 시료 장착부 및 초고진공(~10-9 torr) 및 측정부의 두 부분으로 구성 하였다. TDA 설계시 고온 가열 및 시료 장착부는 시료 내부에 흡착되어 있는 기체의 효과적 탈착을 위한 가열 및 시료의 모양에 영향을 받지 않는 장착방법, 시료 장착부의 outgassing rate를 최소화 하는 재질 선정 등을 고려하였으며, 초고진공(~10-9 torr) 및 측정부는 초고진공 유지방법, 터보펌프 배기속도 실측을 위한 구조, 진공측정 ion 게이지, 잔류가스분석기(Residual Gas Analyzer)의 최적위치 설정 등을 고려하여 설계하였다. 개념 설계된 TDA에 대하여 발표하고자 한다.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.145-153
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• 2024

In the automotive industry, the hole expanding test is widely used to assess the formability of punched holes in sheets. This test provides a good representation of formability within the framework defined by the ISO 16630 standard. During hole expanding tests on galvanized high strength steels, a negative effect was observed when there was a delay between hole punching and expansion, as compared to performing both operations directly. This effect is believed to be caused by hydrogen aging, which occurs when hydrogen diffuses towards highly-work hardened edges. Therefore, the aim of this study is to demonstrate the migration of hydrogen towards work-hardened edges in high strength Zn-coated steel sheets using a novel Thermal Desorption Analyzer (TDA) designed for small samples. This newly-developed TDA setup allows for the quantification of local diffusible hydrogen near cut edges. With its induction heating and ability to analyze Zn-coated samples while reducing artifacts, this setup offers flexible heat cycles. Through this method, a hydrogen gradient is observed over short distances in shear-cut galvanized steel sheets after a certain period of time following punching.

• Analytical Science and Technology
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• v.24 no.3
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• pp.200-211
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• 2011

In this study, 13 compounds including four volatile fatty acids (VFA) and nine volatile organic compounds (VOC) were analyzed by cryogenic trapping-thermal desorption technique. In order to evaluate the analytical method for VFA, calibration experiments were performed using five different sorbent materials. When the calibration results are compared between different sorbents, sampling tube filled with Carbopack X showed the highest response factor (RF) for both VFA and VOC. To validate this new analytical method for VFA using cryogenic trapping-thermal desorption technique, this method was compared with alkali absorption method recommended by the odor prevention law of the Korea Ministry of Environment (KMOE). For this purpose, unknown samples were analyzed by two different methods, i.e., cryogenic trapping-thermal desorption (TD) and alkali absorption with solid phase microextraction (SPME). When the results of two different methods were compared, ratios of concentrations determined by the two analytical methods (TD/SPME) was found as 0.46 (valeric acid) ~ 0.71 (isovaleric acid). Therefore, additional study is required to properly establish and find stable analytical conditions for VFA analysis. Furthermore, comparison between two different methods should be made with more reliable calibration approaches.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.111-114
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• 2001

Thermal desorption process is valuable for the remediation of oil contaminated site. The system is physical separation process by volatizing oil contaminants from soil matrixes and is not designed to provide high levels of oil destruction. The process is not incineration, because the decomposition of oil materials is not the desired result, although some decomposition may occur. The physical and chemical properties that influence the design and operation of the system include boiling points, soil sorption characteristics, aqueous phase solubility, thermal stability, contaminating oil concentration, moisture contents, particle size distribution and etc.

• Journal of Hydrogen and New Energy
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• v.6 no.1
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• pp.43-52
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• 1995

Hydrogen storage alloy powder compacts were prepared by using automatic press, with PTFE as a binder. Hydrogen absorption and desorption characteristics and thermal conducting property of the compacts were studied using test hydrogen cylinder, comparing with bare alloy powder. The compacts showed better rate capability and activation characteristics than bare powder. Effective thermal conductivity and diffusivity of the compact bed were $1.0{\times}10^{-2}W/cmK$ and $2.0{\times}10^{-2}cm^2/S$, respectively, which were similar to that of bare powder bed. A good rate capability of the compacts was interpreted in terms of hydrogen permeation rather than thermal conductivity in the beds.

• Journal of Hydrogen and New Energy
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• v.30 no.1
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• pp.8-13
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• 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 $0.15{\pm}0.05atm$.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.70.4-70.4
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• 2019

Complex organic molecules (COMs) are increasingly observed in the environs of young stellar objects (YSOs), including hot cores/corinos around high-mass/low-mass protostars and protoplanetary disks. It is widely believed that COMs are first formed in the ice mantle of dust grains and subsequently released to the gas by thermal sublimation at high temperatures (T>100 K) in strong stellar radiation fields. In this paper, we report a new mechanism that can desorb COMs from icy grain mantles at low temperatures (T<100K), which is termed rotational desorption. The rotational desorption process of COMs comprises two stages: (1) ice mantles on suprathermally rotating grains spun-up by radiative torques (RATs) are first disrupted into small fragments by centrifugal stress, and (2) COMs and water ice then evaporate rapidly from the tiny fragments (i.e., radius a <1nm) due to thermal spikes or enhanced thermal sublimation due to increased grain temperature for larger fragments (a>1 nm). We discuss the implications of rotational desorption for releasing COMs and water ice in the inner region of protostellar envelopes (hot cores and corinos), photodissociation regions, and protoplanetary disks (PPDs). In shocked regions of stellar outflows, we find that nanoparticles can be spun-up to suprathermal rotation due to supersonic drift of neutral gas, such that centrifugal force can be sufficient to directly eject some molecules from the grain surface, provided that nanoparticles are made of strong material. Finally, we find that large aggregates (a~ 1-100 micron) exposed to strong stellar radiations can be disrupted into individual icy grains via RAdiative Torque Disruption (RATD) mechanism, which is followed by rotational desorption of ice mantles and evaporation of COMs. In the RATD picture, we expect some correlation between the enhancement of COMs and the depletion of large dust grains in not very dense regions of YSOs.