• Journal of Korean Society for Atmospheric Environment
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• v.32 no.3
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• pp.248-255
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• 2016

The leaves of three plant species, such as soybean, raspberry, and kudzu, exposed to hydrogen fluoride was collected in an area surrounding an emission source where the release accident occurred. The ultrasonic-assisted extraction and analysis of fluoride by ion chromatography was carried out. The mean concentration of fluoride in the leaves of three plant species exposed to hydrogen fluoride was $5,409{\pm}1,198mg\;F/kg\;dry\;wt$ and $788{\pm}339mg\;F/kg\;dry\;wt$, respectively. The mean fluoride concentration in ambient air were estimated to be $2.36{\pm}0.65mg/m^3$ ($2.89{\pm}0.79ppm$) and $0.35{\pm}0.15mg/m^3$ ($0.43{\pm}0.19ppm$) in exposed and unexposed sites, respectively. It seems likely that the passive monitoring using plant leaves could identify with respect to plant risk by fluoride in atmosphere.

• Journal of Powder Materials
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• v.16 no.4
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• pp.262-267
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• 2009

Disk type porous nickel membrane was fabricated by in-situ reduction/sintering process using compacted NiO/PMMA (PMMA; Polymethyl methacrylate) mixture at $800^{\circ}C$ in hydrogen atmosphere. The porosity (49$\sim$58%) of these membrane was investigated as an amount of PMMA additive. The thermal decomposition and reduction behavior of NiO/PMMA were analyzed by TG/DTA in hydrogen atmosphere and the activation energy for the hydrogen reduction of NiO and thermal degradation of PMMA was calculated as 61.1 kJ/mol, evaluated by Kissinger method. Finally, the filtering performance and pressure drop were measured by particle counting system.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1993.11a
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• pp.3-3
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• 1993

In mechanical testing of W-Ni-Pe heavy alloys, the cracks nucleate at W/W interface and propagate through W/ Imatrix interface or through matrix phase together with the cleavage of W grains. The mechanical properties can therefore be improved by control of the interfacial strength and area. In this presentation, some experimental result and techniques on this subject will be reviewed and discussed. The hydrogen embrittlement caused by the hydrogen segregation at interfaces during sintering in an hydrogen atmosphere can be removed by an heat-treattnent in vacuum or in an inert atmosphere. The heat-treatment condition can be estimated by using a diffusion equation for a cylindrical shape. The mechanical properties, in particular the impact property, are degraded by the segregation of non-metallic impurities, such as Sand P. The degradation can be prevented by adding a fourth element, such as La or Ca, active with the non-metallic impurities. The cyclic heat-treatment at usual heat-treattnent tempemture causes the penetration of matrix between W/W grain boundaries and results in remarkable increase in impact energy. This is due to an increase in the area of ductile failure during the impact test. The instability of W/matrix interface casued by addition of Mo or Re can be controlled by using W powders of different size. The increase in the interfacial area in found to be related to the presence of non-equilibrium pure W gmins among W(Mo or Re) solid solution gmins.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.187-191
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• 2011

In order to obtain a suitable back contacting electrode for $Cu(InGa)Se_2$-based photovoltaic devices, a molybdenum thin film was deposited using a chemical vapor transport (CVT) during the hydrogen reduction of $MoO_3$ powder. A $MoO_2$ thin film was successfully deposited on substrates by using the CVT of volatile $MoO_3(OH)_2$ at $550^{\circ}C$ for 60 min in a $H_2$ atmosphere. The Mo thin film was obtained by reduction of $MoO_2$ at $650^{\circ}C$ in a $H_2$ atmosphere. The Mo thin film on the substrate presented a low sheet resistance of approximately $1{\Omega}/sq$.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.315-316
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• 2003

대기중 광화학반응에서 생산되는 이차 생성물중의 하나인 $H_2O$$_2$(hydrogen peroxide)는 peroxy radicals간의 결합에 의해 생성된다. HO$_2$ + HO$_2$ $\longrightarrow$ $H_2O$$_2$+ $O_2$ 이렇게 생성된 $H_2O$$_2$는 대기중에서 주요 산화제로 작용하며, pH 4.5 이하 수용액 내에서 S(IV)를 S(VI)로 산화시켜 H$_2$SO$_4$(sulfuric acid)를 생성 한다. 또한 $H_2O$$_2$는 대기중에서 odd-hydrogen radicals(OH, HO$_2$, and RO$_2$)의 저장고 역할과 함께 odd-hydrogen radical의 생성과 소멸에 작용하여 대기의 산화력을 반영한다(Lee et al. 2000). (중략)

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.318-327
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• 1998

The deuterium uptake behavior of Zr-2.5Nb pressure tubes in Wolsong Unit 1 was analyzed in terms of longitudinal location, operation time, and coolant temperature. The results were compared with those obtained from Canadian CANDU reactors. The amount of deuterium uptake was higher at the outlet part than at the inlet part and was also higher when subjected to a longer operation time and a higher coolant temperature. The hydrogen uptake of Zr-2.5Nb in a hydrogen gas atmosphere was dependent on the microstructure of the alloy. The aged Zr-2.5Nb consisting of $\alpha$-Zr and $\beta$-Nb phases showed higher hydrogen uptake than that consisting of $\alpha$-Zr and $\beta$-Zr phases. The hydrogen in the alloy decreased the rate of oxidation. This could be explained in terms of the cathodic controlled reaction of Zr-2.5Nb oxidation.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2007.10a
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• pp.268-268
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• 2007

See Full Text

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.48-48
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• 2000

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.61-66
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• 1986

The gas mixtures ($H_2$/$N_2$, He/$N_2$) having a high thermal conductivity allow the heat generated by the nitriding exotherm to be dissipated from the compact in to the nitriding atmosphere permitting a more accurate control of temperature and produces a more uniform microstructure. In order to observe the effect of the mixed gas atmosphere on the microsturcture of RBSN. the specimen was nitrided in the mixed gas atmosphere which was containe up to 50vol% $H_2$ or He for 0-12 hrs at 135$0^{\circ}C$. The addition of hydrogen to nitrogen gas resulted in the growth of a-needle at the early stage of nitrding increase of the reaction rate and a finer and more uniform microstructure. in case of the addition of helium the behaviour of reaction was similar to the one with pure nitrogen. As the amount of helium was increased a coarse microstructure was formed.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.179-188
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• 1991

The semiconducting BaTiO3 ceramics used in this study were sintered in the reducing atomosphere(hydrogen gas) and neutral atmosphere(nitrogen gas), then were heat-treated in air to vary defect concentrations. In this experiment, the correlations between the composition analysis and electrical characteristics of these samples were investigated. When the BaTiO3 ceramics were sintered in N2 atmosphere, it was observed that the Ba contents near the interface were lower than that of the grain center, and these samples showed superior PTCR effects. From analysis of the resistivities of grains and grain boundaries by CIRM(Complex Impedance Resonance Method), it was confirmed that the PTCR effects were caused by the resistivity of grain boundaries. And from measurement of the capacitance at each temperature, the samples sintered in N2 atmosphere show the increase of room temperature resistance and the decrease of capacitance as a result of the increase of the charge depletion layers. This phenomenon agrees well with the cation deficiencies in the analytical results.