• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.568-580
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• 1998

A sodium-concrete reaction facility with a test chamber of 0.226㎥($\Phi$0.6m$\times$H0.8m) was constructed to carry out experiments of sodium-concrete reaction which might take place in sodium metal fast-breeder reactor Utilizing this facility, several experiments were conducted to closely examine the characteristics of sodium-concrete reactions under different conditions : Sodium mass : 100, 250g ; Sodium temperature : 450, 550, $650^{\circ}C$ ; Concrete age = 30, 45, 50, 90days. Our experiments show that the amount of the H2 generated by sodium-concrete reaction has increased up to its flammable range as the amount of spilled sodium and its temperature have increased. The maximum hydrogen concentration was 31mo1% at the concrete age of 30days, sodium temperature : 55$0^{\circ}C$, and sodium mass : 250g. The major components of sodium-concrete reaction products were also determined as Na$_2$SiO$_3$ and NaAlO$_2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.183-184
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• 2013

Two main MBE growth techniques have been used: plasma-assisted MBE (PA-MBE), which utilizes a rf plasma to supply active nitrogen, and ammonia MBE, in which nitrogen is supplied by pyrolysis of NH3 on the sample surface during growth. PA-MBE is typically performed under metal-rich growth conditions, which results in the formation of gallium droplets on the sample surface and a narrow range of conditions for optimal growth. In contrast, high-quality GaN films can be grown by ammonia MBE under an excess nitrogen flux, which in principle should result in improved device uniformity due to the elimination of droplets and wider range of stable growth conditions. A drawback of ammonia MBE, on the other hand, is a serious memory effect of NH3 condensed on the cryo-panels and the vicinity of heaters, which ruins the control of critical growth stages, i.e. the native oxide desorption and the surface reconstruction, and the accurate control of V/III ratio, especially in the initial stage of seed layer growth. In this paper, we demonstrate that the reliable and reproducible growth of GaN on Si (110) substrates is successfully achieved by combining two MBE growth technologies using rf plasma and ammonia and setting a proper growth protocol. Samples were grown in a MBE system equipped with both a nitrogen rf plasma source (SVT) and an ammonia source. The ammonia gas purity was ＞99.9999% and further purified by using a getter filter. The custom-made injector designed to focus the ammonia flux onto the substrate was used for the gas delivery, while aluminum and gallium were provided via conventional effusion cells. The growth sequence to minimize the residual ammonia and subsequent memory effects is the following: (1) Native oxides are desorbed at $750^{\circ}C$ (Fig. (a) for [$1^-10$] and [001] azimuth) (2) 40 nm thick AlN is first grown using nitrogen rf plasma source at $900^{\circ}C$ nder the optimized condition to maintain the layer by layer growth of AlN buffer layer and slightly Al-rich condition. (Fig. (b)) (3) After switching to ammonia source, GaN growth is initiated with different V/III ratio and temperature conditions. A streaky RHEED pattern with an appearance of a weak ($2{\times}2$) reconstruction characteristic of Ga-polarity is observed all along the growth of subsequent GaN layer under optimized conditions. (Fig. (c)) The structural properties as well as dislocation densities as a function of growth conditions have been investigated using symmetrical and asymmetrical x-ray rocking curves. The electrical characteristics as a function of buffer and GaN layer growth conditions as well as the growth sequence will be also discussed. Figure: (a) RHEED pattern after oxide desorption (b) after 40 nm thick AlN growth using nitrogen rf plasma source and (c) after 600 nm thick GaN growth using ammonia source for (upper) [110] and (lower) [001] azimuth.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.599-610
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• 2005

Purpose: The success of the bonding between electroformed gold and ceramic is dependent on the surface treatment of the pure gold coping. The purpose of this study was to evaluate the bonding strength between the electroformed gold and ceramic with varying surface treatment. Materials and methods: A total of 32 disks,8 were using conventional ceramometal alloy, 24 were using electroforming technique as recommended by manufacturer, were prepared. 24 electroformed disks were divided 3 groups according to surface treatment, i.e. 50 microns aluminium oxide sandblasting(GES-Sand), gold bonder treatment(GES-Bond) and $Rocatec^{TM}$ system(GES-Rocatec). For control group of conventional alloy 50 microns aluminium oxide treatment was done(V-Supragold). Energy dispersive x-ray analysis and scanning electron microscope image were observed. Using universal testing machine, shear bond strength and bonding failure mode at metal-porcelain interface were measured. Results and Conclusion: The following conclusions were drawn: 1. In the energy dispersive x-ray analysis, the Au was main component in electroformed gold(99.9wt%). After surface treatment, a little amount of $Al_2O_3(2.4wt%)$ were found in GES-Sand, and $SiO_2(4wt%)$ in GES-Bond. In GES-Rocatec, however, a large amount of $SiO_2(17.4wt%)$ were found. 2. In the scanning electron microscopy, similar pattern of surface irregu larities were observed in V-Supragold and GES-Sand. In GES-Bond, surface irregularities were increased and globular ceramic particles were observed. In GES-Rocatec, a large amount of silica particles attached to metal surface with increased surface irregularities were observed. 3. The mean shear bond strength values(MPa) in order were $22.9{\pm}3.7(V-Supragold),\;22.1{\pm}3.8(GES-Bond),\;20.1{\pm}2.8(GES-Rocatec)\;and\;13.0{\pm}1.4(GES-Sand)$. There was no significant difference between V-Supragold, GES-Bond, and GES-Rocatec. (P>0.05) 4. Most bonding failures modes were adhesive type in GES-Sand. However, in V-Supragold, GES-Bond and GES-Rocatec, cohesive and combination failures were commonly observed. From the result, with proper surface treatment method electroformed gold may have enough strength compare to conventional ceramometal alloy.

• Resources Recycling
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• v.2 no.2
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• pp.27-38
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• 1993

In this study, we investigated the grinding and sedimentation(elutriation) process of the dusts for the effective separation of high purity iron and iron oxides. For characterization of the dust, particle size distribution and chemical composition, were examined. The results obtained in this study may be summarized as follows : 1. The converter CF(clarifier) dust of the Pohang 1st, 2nd steel making factory and EC(Evaporation Cooler), EP(Eltrostatic precititator) dust of the Kwangyang 2nd steel making factory are composed $\alpha$-Fe(21~50%), FeO(wustite)$Fe_3$$O_4$(magnetite), $Fe_2$$O_3$, CaO, $Al_2$$O_3$, $SiO_2$, and etc. 2. Pure iron has ductile characteristic in nature, particle size of the pure iron increase by increasing the grinding time. On the other hand, it is conformed that bo고 particles of hematite and magnetite become less than 325 mesh after 10 minutes grinding. 3. By applying the elutriation technique for the EC dust of the Kwangyang 2nd steel making factory, the iron powder of high content more than 99.17% of pure Fe was recovered with 37.8% yield at grinding time for 40 minutes. 4. By applying the elutriation technique for the CF dust of the Pohang 2nd steel making factory, the iron powder of high content more than 98.38% of pure Fe was recovered with 44.42% yield at grinding time for 40 minutes. 5. When magnetic separation was performed using plastic bonding magnet of 70 gauss, more than 98% Fe grade of iron powder was recovered in the size range +65 -200 mesh but the recovery of it was low.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.312-320
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• 2013

Particulates in drinking water distribution system (DWDS) are mostly influenced by internal corrosion of metal pipes and sediment in pipelines due to the solution of this effect is limited. The particle size, component and properties of compounds for particulates in distributed water are different and the difference of these characteristics will be occurred by the kind of facilities, pipe condition, external factors and supply system etc. In this study, conducting the investigation of water quality in DWDS researches with particulates in the water. Monitoring sites were each water supply reservoir and the end of water supply area in DWDS. To collect particulate material at each sampling site, $47{\phi}$ glass microfiber filter type GF/C was performed using a filtration. Substances that the effect of the turbidity in the water according to particulate suspended solids and inorganic materials is due to the increasing particulates in the end of DWDS were increased. The result of compounds analysis by using X-ray diffraction (XRD) were Goethite (${\alpha}$-FeOOH), Magnetite ($Fe_3O_4$) in the end of DWDS and Quartz ($SiO_2$), Yeelimite ($Ca_4Al_6O_{12}SO_4$) at the effluent of waterworks and reservoirs. There were differences the compounds and sediments in the releasing or remaining water distribution facilities.

• Journal of Environmental Health Sciences
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• v.33 no.6
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• pp.502-505
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• 2007

To estimate the soil quality of Miryang area, soil analysis were conducted according to the city and out of city of soil expenses at according to analysis components and heavy metal pollution of irradiation sampling sites. The through soil components the principal element about the 71% $SiO_2\;and\;Al_2O_3$, the pH of field area near the city center was lower than that of the other field area, which indicated that this acidification was probably attributed to the acid rain caused by the traffic exhaust gas such as $SO_x\;and\;NO_x$. Acidification was more severe in the field area than in the farming land. The concentration of five heavy metals such as Cu, Cd, Pb, As and Cr were found to be lower than the standard of soil pollution. An assessment using the SPI(Soil Pollution Index), which was developed to estimate an overall soil quality, was performed. Each SPS(Soil Pollution Score) were evaluated with the results of the data from this study. The soil quality of most area of Miryang land was determined to Class 1, which indicated that the soil was healthy.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.27-28
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• 1997

최근 들어 분리공정의 발달과 산업의 고도화에 따라 기체 및 액체분리의 중요성이 강조되면서 열적, 화학적 그리고 기계적 안정성이 좋으며, 수명이 길고, 세척과 재생이 용이하며, 미생물에 의한 손상이 없는 무기막에 대한 연구가 진행중이다. 무기막은 기공의 크기에 따라 크게 다공성 막과 비다공성 막의 두 종류로 구분된다. 비다공성 금속막은 특정 기체에만 투과성을 가지며, 이때 기체는 용해-확산(solution-diffusion)기구에 의해 금속막을 투과하므로 특정기체에 대한 선택도는 매우 크나 투과도가 매우 작고 가격이 비싼 단점을 가지고 있다. 다공성 막은 기체 투과율이 큰 반면 기체 선택도가 작은 단점을 가지고 있다. 현재 기체분리에 사용되고 있는 무기막은 기공크기가 40${\AA}$ 이상으로 기체 분리가 Kundsen diffusion에 의해 이루어지므로, 기체 투과도는 큰 반면에 기체에 대한 선택도는 그리 크지 않다. 따라서 최근 들어서는 다공성 담체에 기공이 작은 ($d_{pore}<20{\AA}$)박막을 담지시켜 기체의 분리 선택도를 향상시키기 위한 연구가 활발히 이루어지고 있다. 본 연구에서는 유기금속 화학증착법(metal-organic chemical vapor deposition:MOCVD)을 이용하여 수소 선택성을 가지는 $SiO_2/Al_2O_3$ 복합막을 비율별로 제조하여 증착속도를 알아보고, 열과 수분에 노출시켜 박막의 기체투과도 변화를 살펴보았다.

• Ocean and Polar Research
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• v.36 no.4
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• pp.407-421
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• 2014

The benthic environmental impact experiment addresses environmental impacts at a specific site related to deep-sea mineral resource development. We have acquired several tens of multi- or box core samples at 31 sites within the Benthic environmental Impact Site (BIS) since 2010, aiming to examine the basic properties of surficial deep-sea sediment as a potential source for deep-water plumes. In this study, we present the geochemical properties such as major elements, rare earth elements (REEs), and heavy metal contents at the BIS. Such proxies vary distinctly according to the Facies association. The lithology of all core sediments in the BIS corresponds to both Association Ib and Association IIIb. The vertical profiles of some major elements ($SiO_2$, $Fe_2O_3$, CaO, $P_2O_5$, MgO, MnO) show noticeable differences between Association Ib and IIIb, while others ($Al_2O_3$, $TiO_2$, $Na_2O$, and $K_2O$) do not vary between Association Ib and IIIb. REEs are also distinctly different for Associations Ib and IIIb; in Association Ib, REY and HREE/LREE are uniform through the sediment section, while they increase downward in Association IIIb like the major elements; below a depth of 8 cm, REY is over 500 ppm. The metal enrichment factor (EF) evaluates the anthropogenic influences of some metals (Cu, Ni, Pb, Zn, and Cd) in marine sediments. In both Associations, the EF for Cu is over 1.5, the EF for Ni and Pb ranges from 0.5 to 1.5, and the EF for Zn and Cd are less than 0.5, indicating Cu is enriched but Zn and Cd are relatively depleted in the BIS. The vertical variations of geochemical properties between Association Ib and IIIb are shown to be clearly different, which seems to be related to the global climate changes such as the shift of Intertropical convergence zone (ITCZ).

• Journal of the Mineralogical Society of Korea
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• v.29 no.4
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• pp.209-220
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• 2016

Clay minerals are a major player to determine geochemical cycles of trace metals and carbon in the critical zone which covers the atmosphere down to groundwater aquifers. Molecular dynamics (MD) simulations can examine the Earth materials at an atomic level and, therefore, provide detailed fundamental-level insights related to physicochemical properties of clay minerals. In the current study, we have applied classical MD simulations with clayFF force field to dioctahedral clay minerals (i.e., gibbsite, kaolinite, and pyrophyllite) to analyze and compare structural parameters (lattice parameter, atomic pair distance) with experiments. We further calculated vibrational power spectra for the hydroxyls of the minerals by using the MD simulations results. The MD simulations predicted lattice parameters and interatomic distances respectively deviated less than 0.1~3.7% and 5% from the experimental results. The stretching vibrational wavenumber of the hydroxyl groups were calculated $200-300cm^{-1}$ higher than experiment. However, the trends in the frequencies among different surface hydroxyl groups of each mineral was consistent with experimental results. The angle formed by the surface hydroxyl group with the (001) plane and hydrogen bond distances of the surface hydroxyls were consistent with experimental result trends. The inner hydroxyls, however, showed results somewhat deviated from reported data in the literature. These results indicate that molecular dynamics simulations with clayFF can be a useful method in elucidating the roles of surface hydroxyl groups in the adsorption of metal ions to clay minerals.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.306-308
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• 2007

Poly(ethylene glycol) dimethyl ether (PEGDME)/fumed silica/ 1-methyl -3-propylimidazolium iodide (MPII)/$I_2$ mixtures were used as polymer electrolytes in solid state dye-sensitized solar cells (DSSCs). The contents of MPII were changed and the concentration of $I_2$ was fixed at 0.1 mole% with respect to the MPII. The maximum ionic conductivity was obtained at [EG]:[MPII]:[$I_2$]=10:1.5:0.15. It was supposed that the maximum of ionic conductivities would match with that of cell efficiencies, if the ionic conductivity is a rate determining step in the sol id state DSSCs. However, the maximum composition did not show the maximum solar cell performance, indicating the mismatch between ionic conductivity and cell performance. This suggests that the ionic conductivity may not be the rate controlling step in determining the cell efficiency in these experimental conditions, whereas other parameters such as the electron recombination might play an important role. Thus, we tried to modify the surface of the $TiO_2$ particles by coating a thin metal oxide such as $Al_2O_3$ or $Nb_2O_5$ layer to prevent electron recombination. As a result, the maximum of the cell efficiency was shifted to that of the ionic conductivity. The peak shifts were also attempted to be explained by the diffusion coefficient and the lifetime of electrons in the $TiO_2$ layer.