• Title, Summary, Keyword: Microwave microscopy

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NH3-SCR performance and characterization over magnetic iron-magnesium mixed oxide catalysts

  • Xu, Liting;Niu, Shengli;Lu, Chunmei;Wang, Dong;Zhang, Kang;Li, Jing
    • The Korean Journal of Chemical Engineering
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    • v.34 no.5
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    • pp.1576-1583
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    • 2017
  • A series of magnetic iron-magnesium mixed oxide catalysts ($Fe_{1-x}Mg_xO_z$) were synthesized via a novel co-precipitation method with microwave thermal treatment, and their activity in $NH_3$-SCR was tested on a quartz fixedbed reactor. Physical and chemical properties of the catalysts were characterized by X-ray diffraction (XRD), $N_2$-adsorption-desorption, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). $Fe_{0.8}Mg_{0.2}O_z$ with excellent $N_2$ selectivity and resistance to $SO_2$ and $H_2O$ was validated as the proper SCR catalyst, with the maximum $NO_x$ conversion of 99.1% fulfilled at $325^{\circ}C$. Activity was strongly influenced by the ${\gamma}-Fe_2O_3$ crystalline phase, and magnesium existed in an amorphous phase and interacted with iron oxide intensively to form solid solution in favor of SCR. For $Fe_{0.8}Mg_{0.2}O_z$ catalyst, optimum pore diameter distribution, appropriate surface area, pore volume and abundant lattice oxygen on the surface could be guaranteed, which is good for the diffusion process and enhances the activity.

In-vitro and In-vivo Biocompatibility Evaluation of Silica Based Bio-active Glass Prepared by Hydrothermal Method

  • Sarkar, Swapan Kumar;Nguyen, Phuong Thi;Lee, Byong-Taek
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.53.1-53.1
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    • 2011
  • Bioactive glass powders were synthesized by hydrothermal chemical route by the use of ultrasonic energy irradiation. We used sodalime, calcium nitrate tetra hydrate and di ammonium hydrogen phosphate as the precursor material to synthesize $SiO_2$ rich bio-active glass materials. The $SiO_2$ content was varied in the precursor mixture to 60, 52 and 45 mole%. Dense compacts were obtained by microwave sintering at $1,100^{\circ}C$. Mechanical properties were characterized for the fabricated dense bioactive glasses and were found to be comparable with conventional CaO-$SiO_2$-$Na_2O$-$P_2O_5$ bioactive glass. Detailed biocompatibility evaluation of the glass composition was investigated by in-vitro culture of MG-63 cell and mesenchyme stem cell. Cell adhesion behavior was investigated for both of the cell by one cell morphology for 30, 60 and 90 minutes. Cell proliferation behavior was investigated by culturing both of the cells for 1, 3 and 7 days and was found to be excellent. Both SEM and confocal laser scanning microscopy were used for the investigation. Western blot analysis was performed to evaluate the bimolecular level interaction and extent and rate of specific protein expression. The ability to form biological apatite in physiological condition was observed with simulated body fluid (SBF). In-vivo bone formation behavior was investigated after implanting the materials inside rabbit femur for 1 and 3 month. The bone formation behavior was excellent in all the bioglass compositions, specially the composition with 60% $SiO_2$ content showed most promising trend.

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Growth and electrical properties of $MgTiO_3$ thin films ($MgTiO_3$산화물 박막의 성장 및 전기적 특성 연구)

  • 강신충;임왕규;안순홍;노용한;이재찬
    • Journal of the Korean Vacuum Society
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    • v.9 no.3
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    • pp.227-232
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    • 2000
  • $MgTiO_3$thin films have been grown on various substrates by pulsed laser deposition (PLD) to investigate the application for microwave dielectrics and optical devices. Epitaxial $MgTiO_3$thin films were obtained on sapphire (c-plane$A1_2O_3$$MgTiO_3$thin films deposited on $SiO_2/Si$ and platinized silicon ($Pt/Ti/SiO_2/Si$) substrates were highly oriented. $MgTiO_3$thin films grown on sapphire were transparent in the visible and had a sharp absorption edge about 290 nm. These $MgTiO_3$thin films had extremely fine feature of surface morphology, i.e., rms roughness of 0.87 nm, which was examined by AFM. We have investigated the dielectric properties of the $MgTiO_3$thin films in $MIM(Pt/MgTiO_3/Pt)$ capacitors. Dielectric constant and loss of $MgTiO_3$thin films deposited by PLD were about 24 and 1.5% at 1 MHz, respectively. These $MgTiO_3$thin films also exhibited little dielectric dispersion.

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Effect of Surfactants on ZnO Synthesis by Hydrothermal Method and Photocatalytic Properties (계면활성제 첨가에 의한 산화아연의 수열합성과 광촉매 특성)

  • Hyeon, Hye-Hyeon;Lee, Dong-Kyu
    • Journal of the Korean Applied Science and Technology
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    • v.34 no.1
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    • pp.50-57
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    • 2017
  • Zinc oxide is, one of metal oxide semiconductor, harmless to human and environment-friendly. It has excellent chemical and thermal stability properties. Wurtzite-zinc oxide is a large band gap energy of 3.37 eV and high exciton binding energy of 60 meV. It can be applied to various fields, such as solar cells, degradation of the dye waste, the gas sensor. The photocatalytic activity of zinc oxide is varied according to the particle shape and change of crystallinity. Therefore, It is very important to specify the additives and the experimental variables. In this study, the zinc oxide were synthesized by using a microwave assisted hydrothermal synthesis. The precursor was used as the zinc nitrate, the pH value was controlled as 11 by NaOH. Surfactants are the ethanolamine, cetyltrimethylammonium bromide, sodium dodecyl sulfate, sorbitan monooleate was added by changing the concentration. The composite particles had the shape of a star-like, curcular cone, seed shape, flake-sphere. Physical and chemical properties of the obtained zinc oxide was characterized using x-ray diffractometer, field emission scanning electron microscopy, thermogravimetric analysis and optical properties was characterized using UV-visible spectroscopy, photoluminescence and raman spectroscopy.

Effects of Macrophage on Biodegradation of β-tricalcium Phosphate Bone Graft Substitute (대식세포가 β-tricalcium Phosphate 뼈이식제의 생분해에 미치는 영향)

  • Kim, Young-Hee;Jyoti, Anirban;Byun, In-Sun;Oh, Ik-Hyun;Min, Young-Ki;Yang, Hun-Mo;Lee, Byong-Taek;Song, Ho-Yeon
    • Journal of the Korean Ceramic Society
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    • v.45 no.10
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    • pp.618-624
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    • 2008
  • Various calcium phosphate bioceramics are distinguished by their excellent biocompatibility and osteoconductivity. Especially, the exceptional biodegradability of $\beta$-TCP makes it a bone graft substitute of choice in many clinical applications. The activation of osteoclasts, differentiated from macrophage precursor cells, trigger a cell-mediated resorption mechanism that renders $\beta$-TCP biodegradable. Based on this evidence, we studied the biodegradation process of granular-type $\beta$-TCP bone graft substitute through in vitro and in vivo studies. Raw 264.7 cells treated with RANKL and M-CSF differentiated into osteoclasts with macrophage-like properties, as observed with TRAP stain. These osteoclasts were cultured with $\beta$-TCP nano powders synthesized by microwave-assisted process. We confirmed the phagocytosis of osteoclasts by observing $\beta$-TCP particles in their phagosomes via electron microscopy. No damage to the osteoclasts during phagocytosis was observed, nor did the $\beta$-TCP powders show any sign of cytotoxicity. We also observed the histological changes in subcutaneous tissues of rats implanted with granule-type $\beta$-TCP synthesized by fibrous monolithic process. The $\beta$-TCP bone graft substitute was well surrounded with fibrous tissue, and 4 months after implantation, 60% of its mass had been biodegraded. Also, histological findings via H&E stain showed a higher level of infiltration of lymphocytes as well as macrophages around the granule-type $\beta$-TCP. From the results, we have concluded that macrophages play an important role in the biodegradation process of $\beta$-TCP bone graft substitutes.

Analysis of Surface Plasmon Resonance on Periodic Metal Hole Array by Diffraction Orders

  • Hwang, Jeong-U;Yun, Su-Jin;Gang, Sang-U;No, Sam-Gyu;Lee, Sang-Jun;Urbas, Augustine;Ku, Zahyun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.176-177
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    • 2013
  • Surface plasmon polaritons (SPPs) have attracted the attention of scientists and engineers involved in a wide area of research, microscopy, diagnostics and sensing. SPPs are waves that propagate along the surface of a conductor, usually metals. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of conductor. In this interaction, the free electrons respond collectively by oscillating in resonance with the light wave. The resonant interaction between the surface charge oscillation and the electromagnetic field of the light constitutes the SPPs and gives rise to its unique properties. In this papers, we studied theoretical and experimental extraordinary transmittance (T) and reflectance (R) of 2 dimensional metal hole array (2D-MHA) on GaAs in consideration of the diffraction orders. The 2d-MHAs was fabricated using ultra-violet photolithography, electron-beam evaporation and standard lift-off process with pitches ranging from 1.8 to $3.2{\mu}m$ and diameter of half of pitch, and was deposited 5-nm thick layer of titanium (Ti) as an adhesion layer and 50-nm thick layer of gold (Au) on the semiinsulating GaAs substrate. We employed both the commercial software (CST Microwave Studio: Computer Simulation Technology GmbH, Darmstadt, Germany) based on a finite integration technique (FIT) and a rigorous coupled wave analysis (RCWA) to calculate transmittance and reflectance. The transmittance was measured at a normal incident, and the reflectance was measured at variable incident angle of range between $30^{\circ}{\sim}80^{\circ}$ with a Nicolet Fourier transmission infrared (FTIR) spectrometer with a KBr beam splitter and a MCT detector. For MHAs of pitch (P), the peaks ${\lambda}$ max in the normal incidence transmittance spectra can be indentified approximately from SP dispersion relation, that is frequency-dependent SP wave vector (ksp). Shown in Fig. 1 is the transmission of P=2.2 um sample at normal incidence. We attribute the observation to be a result of FTIR system may be able to collect the transmitted light with higher diffraction order than 0th order. This is confirmed by calculations: for the MHAs, diffraction efficiency in (0, 0) diffracted orders is lower than in the (${\pm}x$, ${\pm}y$) diffracted orders. To further investigate the result, we calculated the angular dependent transmission of P=2.2 um sample (Fig. 2). The incident angle varies from 30o to 70o with a 10o increment. We also found the splitting character on reflectance measurement. The splitting effect is considered a results of SPPs assisted diffraction process by oblique incidence.

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RF and Optical properties of Graphene Oxide

  • Im, Ju-Hwan;Rani, J.R.;Yun, Hyeong-Seo;O, Ju-Yeong;Jeong, Yeong-Mo;Park, Hyeong-Gu;Jeon, Seong-Chan
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.68.1-68.1
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    • 2012
  • The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

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