• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.292-300
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• 2001

The paper describes spectroscopic characteristics of plasma induces in the pulsed YAG laser welding of alloys containing a large amount of volatile elements. The authors have conducted the spectroscopic analyses of laser induced Al-Mg alloys plasma in the air and argon atmosphere. In the air environment, the identified spectra were atomic lines of Al, Mg, Cr, Mn, Cu, Fe and Zn, and singly ionized Mg lines, as well as the intense molecular spectra of A10 and Mg0 formed by chemical reactions of evaporated Al and Mg atoms from the pool surface with oxygen in the air. In argon atmosphere, Mg0 and AI0 spectra vanished, but AIH spectrum was detected. The hydrogen source was presumably hydrogen dissolved in the base metals, water absorbed on the surface oxide layer, or $H_2$ and $H_2O$ in the shielding gas. The resonant 1ines of Al and Mg were strongly self-absorbed, in particular, self-absorption of the Mg 1ine was predominant. These results show that the laser induced plasma was made of metal1ic vapor with relatively low temperature and high density.

• 반도체디스플레이기술학회지
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• 제15권1호
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• pp.41-46
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• 2016

In this study, gas flow and temperature distribution in the multi-wafer planetary CVD reactor for the Si epitaxial growth were analyzed. Although the structure of the reactor was simplified as the first step of the study, the three-dimensional analysis was performed taking all these considerations of the revolution of the susceptor and the rotation of satellites into account. From the analyses, a reasonable velocity field and temperature field were obtained. However, it was found that analyses including the upper structure of the reactor were required in order to obtain more realistic temperature results. DCS mole fraction above the satellite surface and the susceptor surface without satellite was compared in order to check the gas species mixing. We found that satellite rotation helped gases to mix in the reactor.

• Korean Chemical Engineering Research
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• 제49권3호
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• pp.271-276
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• 2011

대면적 대기압 플라즈마 반응 장비를 플라즈마-용액 시스템에 적용하여 액상 내부에 잠입된 폴리프로필렌(PP) 필름의 표면손상 없이 관능기 도입 가능성을 탐색하였다. 액상으로 1-butyl-3-methylimidazolium tetrafluoroborate: $[BMIM]^{+}[BF_{4}]^{-}$ 이온성 액체 수용액을 사용한 경우, 안정적으로 플라즈마를 발생시킬 수 있었다. PP 필름의 플라즈마 처리 결과, PP 표면에 다양한 산소 함유 관능기들이 도입되었음을 확인할 수 있었다. 플라즈마 처리 후 PP의 표면 자유에너지는 처리시간, 전압의 증가에 따라서 증가하며, 1.5M 이온성 액체 수용액 농도에서 가장 큰 값을 나타내었다. ATR-FTIR 분석 결과, 다양한 카르보닐 기(1,726 $cm^{-1}$, 1,643 $cm^{-1}$)와 하이드록시 기$(3,100{\sim}3,500\;cm^{-1})$의 흡광도가 증가하였고, XPS 분석은 ATR-FTIR 분석 결과를 뒷받침하여 주었다.

• 한국세라믹학회지
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• 제41권6호
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• pp.435-438
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• 2004

MOCVD is one of the major deposition techniques for Cu thin films and Ta-Si-N is one of promising barrier metal candidates for Cu with high thermal stability. Effects of hydrogen plasma pretreatment of the underlying Ta-Si-N film surface on the Cu nucleation in Cu MOCVD were investigated using scanning electron microscopy, X-ray photoelectron spectroscopy and Auger electron emission spectrometry analyses. Cu nucleation in MOCVD is enhanced as the rf-power and the plasma exposure time are increased in the hydrogen plasma pretreatment. The optimal plasma treatment process condition is the rf-power of 40 Wand the plasma exposure time of 2 min. The hydrogen gas flow rate in the hydrogen plasma pretreatment process does not affect Cu nucleation much. The mechanism through which Cu nucleation is enhanced by the hydrogen plasma pretreatment of the Ta-Si-N film surface is that the nitrogen and oxygen atoms at the Ta-Si-N film surface are effectively removed by the plasma treatment. Consequently the chemical composition was changed from Ta-Si-N(O) into Ta-Si at the Ta-Si-N film surface, which is favorable for Cu nucleation.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.449-453
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• 2009

A mesoporous assembly of layered titanate with well-dispersed Pt cocatalysts has been synthesized via a restacking of exfoliated titanate nanosheets and a simultaneous adsorption of Pt nanoparticles. According to powder X-ray diffraction analysis, the obtained mesoporous assembly shows amorphous structure corresponding to the disordered stacking of layered titanate crystallites. Field emission-scanning electron microscopy and $N_2$ adsorption-desorption isotherm measurement clearly demonstrate the formation of mesoporous structure with expanded surface area due to the house-of-cards type stacking of the titanate crystallites. From high resolution-transmission electron microscopy and elemental mapping analyses, it is found that Pt nanoparticles with the size of ~2.5 nm are homogeneously dispersed in the mesoporous assembly of layered titanate. In comparison with the protonated titanate, the present mesoporous assembly of layered titanate exhibits better photocatalytic activity for the photodegradation of organic molecules. This finding underscores that the restacking of exfoliated nanosheets is quite useful not only in creating mesoporous structure but also in improving the photocatalytic activity of titanium oxide.

• Journal of Electrochemical Science and Technology
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• 제14권3호
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• pp.222-230
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• 2023

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g^-1 in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260^th to the 530^th cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g^-1. Detailed surface characterization and electrochemical analyses are conducted.

• 대한화학회지
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• 제56권2호
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• pp.217-227
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• 2012

Syntheses of some novel oxomolybdenum(V) and dioxomolybdenum(VI) complexes with an azo dye methoxyphenolazoantipyrine (HL) derived from 4-aminoantipyrine and 2-methoxyphenol are reported. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility data, IR, UV-Vis, $^1H$ NMR, EPR and FAB mass spectral studies. The physicochemical studies and spectral data indicate that HL acts as a bidentate chelating ligand. The complexes have the general formulae [$MoO(HL)XCl_2$] and [$MoO_2(HL)XCl$],where X=Cl, NCS or $NO_3$. All the complexes are found to have distorted octahedral geometry. Structural and morphological characterization of the complexes [$MoO(HL)Cl_3$](1) and [$MoO_2(HL)Cl_2$](4) before and after gamma ray irradiation,was performed by X-ray diffraction and scanning electron microscopy( SEM).The ligand and the complexes were screened for their possible antimicrobial activities.

• 한국수소및신에너지학회논문집
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• 제20권4호
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• pp.317-322
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• 2009

To investigate degradation mechanism of PEMFC operated with repetitive startup/shutdown cycling, i-V characteristics, impedance, cyclic voltamograms were measured. OCV decreased from 0.967 to 0.951 V while the cell voltage at 800mA/$cm^2$ from 0.657 to 0.563V, implying that the electrodes rather than membrane electrolyte was damaged during the cycling operation. Electrochemical analyses supported that the performance degradation could be mainly attributed to degradation of the electrodes such as a decrease in electrochemical active surface area rather than degradation of membrane.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.73-78
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• 2003

The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

• Bulletin of the Korean Chemical Society
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• 제21권7호
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• pp.690-696
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• 2000

Epoxy copolymers containing oxime urethane groups were prepared by the polymerization of glycidyl methacrylate and N-[5-(benzophenoneoximinocarbonylamino)pentanyl]maleimide (BOPM). Their physical properties were characterized by GPC, DSC and TGA analyses. Photochemical changes of the copolymers were studied by UV, IR spectroscopy, and contact angle measurements. A photoinduced cross-linking reaction in copolymer films was observed by measuring the insoluble fraction. Irradiation of the copolymers at 254 nm UV light leads to the formation of pendant amino groups by photodissociation of the oxime-urethane groups. Treatment of the amino groups with HCl resulted in the formation of ammonium salts, which changed the polymer surface to be hydrophilic. An insoluble fraction of the copolymers increased with irradiation time, heating time, and heating temperature. Cross-linking of the epoxy resin effectively catalyzed by the photogenerated pendant amines upon heating.