• Korean Journal of Materials Research
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• v.19 no.12
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• pp.657-660
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• 2009

Optical characteristics and structural changes depending on CuO content in phosphate glasses that are used in near-infrared (near-IR) filters were investigated. With phosphate glasses that contain 1-9 mol% CuO, changes in optical transmittance, optical absorption, and color coordinate were measured with a UV-VIS spectrophotometer. An XPS (X-ray photoelectron spectroscopy) analysis was performed to determine valence of copper ion that influences optical characteristics in near-IR filter glasses. Structural changes in glasses depending on CuO content were also analyzed by FT-IR (Fourier transform infrared) and Raman spectrophotometers. From the UV-VIS spectrophotometer results, strong absorption peaks at 220 & 900 nm were found and transmittance was decreased. The color coordinates of the glasses were shifted to the green color direction with CuO addition for increasing absorption of long wavelength range spectra, in spite of the amount of $Cu^{2+}$, which gives a blue color to glasses, and which was increased in XPS results. Also, structural de-polymerization of glasses with CuO addition were found by FT-IR and Raman results.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.87-88
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• 2012

Metal oxide nanostructures have been applied to various fields such as energy, catalysts and electronics. We have freely designed one and two-dimensional (1 and 2-D) metal (transition metals and lanthanides) oxide nanostructures, characterized them using various techniques including scanning electron microscopy, transmission electron microscopy, X-ray diffraction crystallography, thermogravimetric analysis, FT-IR, UV-visible-NIR absorption, Raman, photoluminescence, X-ray photoelectron spectroscopy, and temperature-programmed thermal desorption (reaction) mass spectrometry. In addition, Ag- and Au-doped metal oxides will be discussed in this talk.

• Journal of the Korean Chemical Society
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• v.57 no.6
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• pp.721-725
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• 2013

Reaction between 2-pyridinecarboxylic acid (Hpic) and $K_3[Cr(O_2)_4]$ give complex $[Cr(pic)_3].H_2O$ (1) which is characterized by elemental analysis and spectroscopic methods (FT-IR, Raman) and X-ray crystallography. In the crystal structure of 1, chromium atom with coordinated by three nitrogen and three oxygen atoms has a distorted octahedral geometry. Also a water molecule is incorporated in crystal network. Each water molecule acts as hydrogen bond bridging and connects two adjacent complexes by two $O-H{\cdots}O$ hydrogen bonds.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.301-301
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• 2013

전도성 고분자인 PEDOT은 PSS와 활용도를 높게 하기 위해 PSS와 함께 쓰이며, 다양한 분야에서 넓게 활용되고 있다. 하지만 박막 형성시 전도성이 작은 문제점이 있기 때문에 이를 개선할 필요성이 있다. 이에 본 연구에서는 용매를 사용한 PEDOT:PSS 박막의 처리 과정을 통하여 물성의 변화를 관찰하였으며, 전도성 향상을 관찰 하였다. 이를 위해 4-point probe장비를 이용하여 면저항을 측정하였으며, 동시에 Fe-SEM을 사용하여 박막의 무께를 알아 보았다. 또한 분자 수준의 관찰을 위해 Raman spectroscopy를 이용하였으며 동시에 FT-IR과 XPS장비를 사용하였다.

• Journal of the Korean Ceramic Society
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• v.52 no.2
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• pp.165-170
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• 2015

We employed the high-pressure high temperature (HPHT) process to enhance the colors of natural sapphires to obtain a vivid blue. First, we analyze the content of the coloring agent $Fe_2O_3$ using the wavelength dispersive X-ray fluorescence (WD-XRF) method. The HPHT procedure operates under 1 GPa at various temperatures of 1700, 1750, and $1800^{\circ}C$ for 5 minutes using a cubic press. We determine the color changes using the optical microscopic images, UV-VIS near-infrared (NIR) spectra, micro-Raman spectra, and Fourier transform-infrared (FT-IR) spectra for all sapphire samples before and after the treatment. The optical microscopic results indicate that the HPHT process can enhance the sapphire color to a vivid blue at temperatures above $1750^{\circ}C$. The UV-VIS-NIR spectra identify the color changes explicitly and quantitatively through providing the Lab color scales and color differences. Both results demonstrate that the colors of natural sapphires can be enhanced to a vivid blue using the HPHT process above $1750^{\circ}C$ under 1 GPa for 5 minutes.

• Advances in environmental research
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• v.9 no.3
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• pp.161-173
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• 2020

The removal of two dyes, namely Methylene Blue (MB) and Reactive Brillant Red (RR) from aqueous solution was investigated using magnetite iron coated pumice (MIP) composite in the Fenton-like oxidation process. A weight ratio of 2.5 g (with the molar ratio of Fe³⁺ to Fe²⁺ to be 2) (5%) of iron to the total pumice (50 g) was enabled during synthesis of catalyst. Surface composition and characteristics of the catalyst were assessed by SEM-EDX, FT-IR, Raman spectral analysis. The effect of the amount of pumice solely used or MIP, H₂O₂ concentration, pH and initial concentration of MB or RR dyes on Fenton-like process efficiency was investigated. EDAX spectrums of pumice and MIP showed that oxygen and silisium are the major elements. The Fe content of MIP increased to 2.24%. SEM, FT-IR and Raman spectrums confirmed the impregnation of Fe on pumice surface. The experimental results revealed that high removal rates of dyes could be obtained using MIP that demonstrated a higher stability for removal of MB dye. pH affected the removal efficiency of both dyes and the degradation of both dyes was sharply dropped when pH was increased above 4. The removal of dyes did not significantly change with increasing H₂O₂ concentration. Degradation rates of both MB and RR dyes increased 3.3 and 2.8 times with the use of MIP compared to pumice alone, respectively. Furthermore, MIP enabled a good removal efficiency at higher dye concentrations. It can be emphasized that MIP composite can be used in the heterogeneous Fenton-like systems considering the economic and easily separation aspects.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2769-2773
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• 2013

Red phosphors $Ca_{(1-1.5x)}Eu_xWO_4$ and $Ca_{(1-2x)}Eu^_xNa_xWO_4$ were synthesized with various concentrations x of $Eu^{3+}$ ions by using a solid-state reaction method. The crystal structure of the red phosphors were found to be a tetragonal scheelite structure with space group $I4_1/a$. X-ray diffraction (XRD) results show the (112) main diffraction peak centered at $2{\theta}=28.71^{\circ}$, and indicate that there is no basic structural deformation caused by the vacancies ${V_{Ca}}^{{\prime}{\prime}}$ or the $Eu^{3+}$ (and $Na^+$) ions in the host crystals. Densities of $Ca_{(1-1.5x)}Eu_xWO_4$ were measured on a (helium) gas pycnometer. Comparative results between the experimental and theoretical densities reveal that $Eu^{3+}$ (and $Na^+$) ions replace the $Ca^{2+}$ ions in the host $CaWO_4$. Also, the photoluminescence (PL) emission and photoluminescence excitation (PLE) spectra show the optical properties of trivalent $Eu^{3+}$ ions, not of divalent $Eu^{2+}$. Raman spectra exhibit that, without showing any difference before and after the doping of activators to the host material $CaWO_4$, all the gerade normal modes occur at the identical frequencies with the same shapes and weaker intensities after the substitution. However, the FT-IR spectra show that some of the ungerade normal modes have shifted positions and different shapes, caused by different masses of $Eu^{3+}$ ions (or $Na^+$ ions, or ${V_{Ca}}^{{\prime}{\prime}}$ vacancies) from $Ca^{2+}$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.38.1-38.1
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• 2011

최근 중동정세의 변화와 유류 소비의 증가에 따른 유가의 급등과, 일본 지진사태로 일어난 원자력 발전의 안정성에 대한 문제로 인하여 안전하고 깨끗하게 에너지를 생산할 수 있는, 저탄소 녹색성장을 구현할 수 있는 신재생 에너지에 관련된 연구에 많은 관심이 모아지고 있다. 특히 태양광 에너지를 전기로 변환하여 사용하는 것은 최근 가장 큰 관심사 중 하나이다. 나노결정 Si (nc-Si) 박막은 이러한 광전자 산업 및 태양 에너지 분야에서의 폭넓은 응용 가능성으로 많은 연구가 진행되고 있다. 이러한 nc-Si 박막의 발광 특성은 비정질 박막내 Si 나노결정에 기인한 양자제한효과(quantum confinement effect)에 의한 것으로 알려져 있다. 본 연구에서는 증착시 기판에 AC (alternating current) Bias를 인가하여 PE CVD 기법으로 nc-Si:H 박막을 증착하였다. H2와 SiH4를 각기 45, 20 sccm으로, 100 W의 RF 전압을 주어 플라즈마를 생성하였으며, 60~900 Hz의 주파수 범위에서 60 V의 Bias를 인가하여 박막을 증착하였다. 이들 박막의 결정 크기, 결정화도, 나노 구조 및 광학적, 화학적, 기계적 특성을 XRD, FT-IR, Raman spectroscopey, AFM, PL, Nano indenter 등을 사용하여 조사하였으며, 기판에 인가된 전압과 주파수에 따른 결정크기와 박막의 광학적 특성과 상관관계를 고찰하였다. Bias 전압에 따라 ~1에서 ~4 nm의 크기를 갖는 나노 크리스탈이 생성 되었으며, 최고 10%의 나노결정 분율을 가지는 박막을 증착하였다. 이는 광학적 특성에도 영향을 주어 PL (photoluminescence)의 피크는 470~710 nm의 영역에서 관찰되었다. 또한 AC-Bias의 영향으로 박막 내 응력 해소에도 영향을 주어 박막내 존재하는 응력이 결정에 미치는 영향도 알 수 있었다. 이번 발표에선 증착 조건에 따른 박막의 나노구조 및 광학적 특성의 변화와 이들 간의 상관관계를 발표하고자 한다.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.194-198
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• 2002

Various composition of $K_2O{\cdot}CaO{\cdot}P_2O_5$ glasses were studied by melting process to identify glass forming region. Thermal properties were observed by DSC and TG-DTA, structural properties were investigated by FT-IR and Raman Spectroscopy. The glass transition temperature (Tg) and softening temperature (Ts) were decreased with increasing $K_2O\;and\;P_2O_5$ contents. The basic structural unit of phosphate glasses is the $PO_2\;and\;PO_4^{3-}$ groups to make a cross-link and P-O-P group to form skeleton structure. As CaO content was increased, the P-O-P field strength in these glass was increased and intensity of $PO_2\;and\;PO_4^{3-}$ stretch was decreased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.5
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• pp.181-188
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• 2006

Rutile single crystals grown by skull melting method were cut parallel and perpendicular to growth axis, and both sides of the cut wafers (${\phi}5.5mmx1.0mm$) were then polished to be mirror surfaces. The black wafers were changed into pale yellow color by annealing in air at 1200 and $1300^{\circ}C$ for $3{\sim}15\;and\;10{\sim}50$ hours, respectively. After annealing, structural and optical properties were examined by specific gravity (S.G), SEM-electron backscattered pattern (SEM-EBSP), X-ray diffraction (XRD), FT-IR transmittance spectra, laser Raman spectroscopy (LRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). These results are analyzed increase of weight in air, decrease of weight in water and specific gravity, shown secondary phase of needle shape, diffusion of oxygen ion and increase of $Ti^{3+}$. From the above results, we suggest that the skull melting method grown rutile single crystals contain defect centers such as $O_v,\;Ti^{3+},\;O_v-Ti^{3+}$ interstitials and $F^+-H^+$.