• Title/Summary/Keyword: Spectroscopy

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$CO_2$ Sensing Characteristics of Carbon-nanofibers Based on Effects of Porosity and Amine Functional Group (다공성 및 아민 작용기에 따른 탄소나노섬유의 $CO_2$ 감응특성)

  • Kim, Jong Gu;Kang, Seok Chang;Shin, Eunjeong;Kim, Da Young;Lee, Jin Hee;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.23 no.1
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    • pp.47-52
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    • 2012
  • Porous carbon nanofibers were prepared as a gas sensor electrode to study the $CO_2$ sensing property based on effects of porosity and introduced amine functional groups. Electrospun fibers were obtained by using electrospinning method with polyacrylonitrile precursor and they were treated by the thermal treatment and chemical activation. Amine functional groups were introduced by the liquid state treatment using diethylenetriamine. The specific surface area increased up to $2000m^2/g$ by the chemical activation. The Introduced amine functional group was identified using FT-IR spectroscopy. $CO_2$ gas sensing property was improved as four folds via introduced amine functional groups on the activated carbon nanofiber. In conclusion, the gas sensing property was improved based on the developed porosity by the chemical activation and the chemical attraction of $CO_2$ gas by introduced functional groups.

Low Temperature Selective Catalytic Reduction of NO with $NH_3$ over Mn/$CeO_2$ and Mn/$ZrO_2$ (Mn/$CeO_2$와 Mn/$ZrO_2$ 촉매 상에서 $NH_3$를 사용한 NO의 선택적 촉매 산화 반응)

  • Ko, Jeong Huy;Park, Sung Hoon;Jeon, Jong-Ki;Sohn, Jung Min;Lee, See-Hoon;Park, Young-Kwon
    • Applied Chemistry for Engineering
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    • v.23 no.1
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    • pp.105-111
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    • 2012
  • Manganese (Mn) catalysts were generated using $CeO_2$ and $ZrO_2$supports synthesized by the supercritical hydrothermal method and two different Mn precursors, aimed at an application for a low-temperature selective catalytic reduction process. Manganese acetate (MA) and manganese nitrate (MA) were used as Mn precursors. Effects of the kind and the concentration of the Mn precursor used for catalyst generation on the NOx removal efficiency were investigated. The characteristics of the generated catalysts were analyzed using $N_2$ adsorption-desorption, thermo-gravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. De-NOx experiments were carried out to measure NOx removal efficiencies of the catalysts. NOx removal efficiencies of the catalysts generated using MA were superior to those of the catalysts generated using MN at every temperature tested. Analyses of the catalyst characteristics indicated that the higher NOx removal efficiencies of the MA-derived catalysts stemmed from the higher oxygen mobility and the stronger interaction with support material of $Mn_2O_3$ produced from MA than those of $MnO_2$ produced from MN.

A Study on the Molecular Weight Control and Rheological Properties of Branched Polycarbonate (분지형 폴리카보네이트의 분자량 조절 및 유변학적 특성 연구)

  • Lee, Bom Yi;Dahal, Prashanta;Kim, Hee Seung;Yoo, Seung Yoon;Kim, Youn Cheol
    • Applied Chemistry for Engineering
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    • v.23 no.4
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    • pp.388-393
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    • 2012
  • Branched polycarbonates (B-PCs) were synthesized using melt polymerization method with four different end capping agents and vaying concentrations. The chemical structure of the synthesized PC was determined by FT-IR and $^{1}H-NMR$ spectroscopy, and the reaction of the end capping agent was confirmed by the existence of hydroxy group in FT-IR spectrum. The average molecular weight and distribution, glass transition and degradation temperatures were determined by GPC, DSC and TGA. The average molecular weight changed with the chemical structure of end capping agent, and 4-tert-butylphenol was estimated as the optimum end capping agent. The average molecular weights of B-PCs decreased with the increase of the concentration of the agent, the number average molecular weight represented 20000 when 0.05 mol% of 4-tert-butylphenol was added to B-PCs. The melt viscosities of the B-PCs decreased with the decrease of the molecular weight of B-PCs, and adding of the agent was not effected to shear thinning tendency.

Fluorination of Polymethylmethacrylate (PMMA) Film and Its Surface Characterization (폴리메틸메타아크릴레이트(PMMA) 필름의 불소화 및 그 표면특성)

  • Jung, Min-Jung;Lim, Jae-Won;Park, In-Jun;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.21 no.3
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    • pp.317-322
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    • 2010
  • In this study, poly(methyl methacrylate) (PMMA) was treated with changing mixing ratios of $F_2$ and $O_2$ using oxyfluorination method for hydrophilic modification of PMMA film. For the characterizations of oxyfluorinated PMMA surface, contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS) and optical transmittance (UV-vis) were carried out. After the oxyfluorination, PMMA surface became more hydrophilic showing the decrease of water contact angle from $69^{\circ}$ to $44^{\circ}$. So, surface free energy of oxyfluorinated PMMA film was increased from 46 to $58\;mN\;m^{-1}$. These results are attributed to hydrophilic functional groups such as hydroxyl group formed oxyfluorination method on the PMMA surface. From XPS results, it was confirmed that O/C concentration ratio on the surface of PMMA was increased, the amount of C-OH bonding which shows hydrophilicity was also largely increased from 6.7 to 24.8% with increasing fluorine partial-pressure via the oxyfluorination, The oxyfluorination conditions, room temperature, 1 bar with one mixture ratio of $F_2$ to $O_2$ had little influence on optical transmittance properties of PMMA film but enhanced its surface hydrophilicity. This result suggests that oxyfluorination method could be useful to change hydrophobic PMMA surface to hydrophilic.

Synthesis of MnO2 Nanowires by Hydrothermal Method and their Electrochemical Characteristics (수열합성법을 이용한 망간 나노와이어 제조 및 이의 전기화학적 특성 연구)

  • Hong, Seok Bok;Kang, On Yu;Hwang, Sung Yeon;Heo, Young Min;Kim, Jung Won;Choi, Bong Gill
    • Applied Chemistry for Engineering
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    • v.27 no.6
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    • pp.653-658
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    • 2016
  • In this work, we developed a synthetic method for preparing one-dimensional $MnO_2$ nanowires through a hydrothermal method using a mixture of $KMnO_4$ and $MnSO_4$ precursors. As-prepared $MnO_2$ nanowires had a high surface area and porous structure, which are beneficial to the fast electron and ion transfer during electrochemical reaction. The microstructure and chemical structure of $MnO_2$ nanowires were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller measurements. The electrochemical properties of $MnO_2$ nanowire electrodes were also investigated using cyclic voltammetry and galvanostatic charge-discharge with a three-electrode system. $MnO_2$ nanowire electrodes showed a high specific capacitance of 129 F/g, a high rate capability of 61% retention, and an excellent cycle life of 100% during 1000 cycles.

Analytical Characteristics of Electron Spin Resonance for Identifying Irradiated Ramen Soup with Radiation Sources (방사선 조사된 라면수프의 조사선원에 따른 전자스핀공명 분석특성)

  • Ahn, Jae-Jun;Lee, Ju-Woon;Chung, Hyung-Wook;Kwon, Joong-Ho
    • Korean Journal of Food Science and Technology
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    • v.41 no.2
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    • pp.131-135
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    • 2009
  • The identification characteristics of irradiated commercial Ramen soup were investigated depending on radiation sources and doses by electron spin resonance (ESR) spectroscopy. Two commercial powder soups (RS-1, RS-2) were irradiated at 0 to 20 kGy under ambient conditions by both a Co-60 gamma irradiator and an electron beam (EB) accelerator, respectively. Crystalline sugar-induced multi-component signals with g-values of 2.010/2.011, 2.006, 2.002 and 1.999 were detected in the irradiated Ramen soup (RS-1, RS-2), whereas $Mn^{2+}$ signals were observed in non-irradiated samples, thereby distinguishing each other. Under the same analytical conditions, the intensity of ESR signals was higher in EB-irradiated samples than the gamma-irradiated ones. Determination coefficients ($R^2$) between irradiation doses and corresponding ESR responses were above 0.9665 in all the samples, and the magnetic field of specified g-value remained constant. The predominant ESR signals of $g_2$ (2.010-2.011) and $g_3$ (2.002) increased with corresponding doses of irradiation ($R^2$= 0.9750-0.9981).

Structural and Solubility Characteristics of Coenzyme Q10 Complexes Including Cyclodextrin and Starch (사이클로덱스트린과 전분을 이용한 coenzyme Q10 복합체의 특성 연구)

  • Lee, Joon-Kyoung;Lee, Hyun-Joo;Lim, Jae-Kag
    • Korean Journal of Food Science and Technology
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    • v.46 no.2
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    • pp.180-188
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    • 2014
  • This study focused on assessing the solubility and structural characteristics of two types of coenzyme $Q_{10}$ ($CoQ_{10}$) complexes: the $CoQ_{10}$-starch and the $CoQ_{10}$-cyclodextrin complexes. The solubility of $CoQ_{10}$-starch complex increased significantly as the temperature was increased. However, the solubility of $CoQ_{10}$-cyclodextrin complex reached a peak at $37^{\circ}C$, and strong aggregation occurred at $50^{\circ}C$. When the temperature was raised to $80^{\circ}C$, the $CoQ_{10}$-cyclodextrin complex dissociated owing to the weakening of bonds, resulting in $CoQ_{10}$ emerging at the surface of water. Therefore, $CoQ_{10}$-cyclodextrin complexes have lower solubility, due to their reduced heat-stability, than do the $CoQ_{10}$-starch complexes. Structural differences between the two $CoQ_{10}$ complexes were confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), and differential scanning calorimeter (DSC). The $CoQ_{10}$-cyclodextrin complex included an isoprenoid chain of $CoQ_{10}$, while the $CoQ_{10}$-starch complex included both the benzoquinone ring and the isoprenoid chain of $CoQ_{10}$. These results suggest that $CoQ_{10}$-starch complexes possess higher heat-stability and solubility than do the $CoQ_{10}$-cyclodextrin complexes.

Effect of Metal Interlayers on Nanocrystalline Diamond Coating over WC-Co Substrate (초경합금에 나노결정질 다이아몬드 코팅 시 금속 중간층의 효과)

  • Na, Bong-Kwon;Kang, Chan Hyoung
    • Journal of the Korean institute of surface engineering
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    • v.46 no.2
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    • pp.68-74
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    • 2013
  • For the coating of diamond films on WC-Co tools, a buffer interlayer is needed because Co catalyzes diamond into graphite. W and Ti were chosen as candidate interlayer materials to prevent the diffusion of Co during diamond deposition. W or Ti interlayer of $1{\mu}m$ thickness was deposited on WC-Co substrate under Ar in a DC magnetron sputter. After seeding treatment of the interlayer-deposited specimens in an ultrasonic bath containing nanometer diamond powders, $2{\mu}m$ thick nanocrystalline diamond (NCD) films were deposited at $600^{\circ}C$ over the metal layers in a 2.45 GHz microwave plasma CVD system. The cross-sectional morphology of films was observed by FESEM. X-ray diffraction and visual Raman spectroscopy were used to confirm the NCD crystal structure. Micro hardness was measured by nano-indenter. The coefficient of friction (COF) was measured by tribology test using ball on disk method. After tribology test, wear tracks were examined by optical microscope and alpha step profiler. Rockwell C indentation test was performed to characterize the adhesion between films and substrate. Ti and W were found good interlayer materials to act as Co diffusion barriers and diamond nucleation layers. The COFs on NCD films with W or Ti interlayer were measured as less than 0.1 whereas that on bare WC-Co was 0.6~1.0. However, W interlayer exhibited better results than Ti in terms of the adhesion to WC-Co substrate and to NCD film. This result is believed to be due to smaller difference in the coefficients of thermal expansion of the related films in the case of W interlayer than Ti one. By varying the thickness of W interlayer as 1, 2, and $4{\mu}m$ with a fixed $2{\mu}m$ thick NCD film, no difference in COF and wear behavior but a significant change in adhesion was observed. It was shown that the thicker the interlayer, the stronger the adhesion. It is suggested that thicker W interlayer is more effective in relieving the residual stress of NCD film during cooling after deposition and results in stronger adhesion.

A STUDY ON THE DEGREE OF CONVERSION OF LIGHT CURING COMPOSITE RESIN ACCORDING TO THE DEPTH OF CURE AND LIGHT CURING TIME (수종 광중합 복합 레진의 중합 깊이와 광조사 시간에 따른 중합률에 관한 연구)

  • Kim, Kyung-Hyun;Kwon, Oh-Sung;Kim, Hyun-Gee;Baek, Kyu-Chul;Um, Chung-Moon;Kwon, Hyuk-Choon
    • Restorative Dentistry and Endodontics
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    • v.22 no.1
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    • pp.35-60
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    • 1997
  • Physical properties of composite resins such as strength, resistance to wear, discoloration, etc, depend on the degree of conversion of the resin components. The clinical behavior of restorative resins varies brand to brand. Part of this variation is associated with the filler and differences in the polymer matrix. The polymer matrix of resins may differ because the involved monomers are dissimilar and because of variation in the catalyst system. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the depth of cure and light curing time. 7mm diameter cylindrical aluminum molds were filled with each of five different hybrid light curing composite resins(Z-100, Charisma, Herculite XRV, Prisma TPH, Veridonfil) on the thin resin films. The molds were 1mm, 2mm, 3mm, 4mm, and 5mm in depth to produce resin films of various heights. Each sample was given 20sec, 40sec, and 60sec illumination with a light source. The degree of conversion of carbon double bonds to single bonds in the resin films was examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows; 1. There was difference in the degree of conversion among five light curing composite resins according to the depth of cure for 20sec, 40sec, and 60sec illumination with light source with statistical significance(P<0.05). 2. Five light curing composite resins show lower degree of conversion at surface of the resin than depth of 1mm. 3. The degree of conversion of five light curing composite resins was siginificantly reduced from the maximum for the resin film when the light passed through as little as 1mm of each composite. 4. The degree of conversion of five light curing composite resins decrease significantly at the depth of 4mm, and polymerization was not occured at the depth of 5mm except for Prisma TPH. 5. The degree of conversion of five light curing composite resins was increased with increased light curing time, and there was no significant differences in the degree of conversion above 4mm in Z-100, 3mm in Charisma, and at depth of 5mm in Herculite XRV and Veridonfil(P>0.05).

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Development of Prediction Model by NIRS for Anthocyanin Contents in Black Colored Soybean (근적외분광분석기를 이용한 검정콩 안토시아닌의 함량 분석)

  • Kim, Yong-Ho;Ahn, Hyung-Kyun;Lee, Eun-Seop;Kim, Hee-Dong
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.53 no.1
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    • pp.15-20
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    • 2008
  • Near infrared reflectance spectroscopy (NIRS) is a rapid and accurate analytical method for determining the composition of agricultural products and feeds. This study was conducted to measure anthocyanin contents in black colored soybean by using NIRS system. Total 300 seed coat of black colored soybean samples previously analyzed by HPLC were scanned by NIRS and over 250 samples were selected for calibration and validation equation. A calibration equation calculated by MPLS(modified partial least squares) regression technique was developed in which the coefficient of determination for anthocyanin pigment C3G, D3G and Pt3G content was 0.952, 0.936, and 0.833, respectively. Each calibration equation was applied to validation set that was performed with the remaining samples not included in the calibration set, which showed high positive correlation both in C3G and D3G content file. In case Pt3G, the prediction model was needed more accuracy because of low $R^2$ value in validation set. This results demonstrate that the developed NIRS equation can be practically used as a rapid screening method for quantification of C3G and D3G contents in black colored soybean.