• Title/Summary/Keyword: Microwave-hydrothermal

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Syntheses of FAPO-5 Molecular Sieves with Microwave Irradiation and Their Characterization (마이크로파 가열에 의한 FAPO-5 분자체의 합성 및 특성 분석)

  • Jang, Jong-San;Lee, Jin-Ho;Jeong, Seong-Hwa;Hwang, Jin-Su
    • Journal of the Korean Chemical Society
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    • v.50 no.1
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    • pp.53-59
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    • 2006
  • .FAPO-5 molecular sieves were synthesized starting from the same reactant gel at 170 oC using microwave irradiation technique and conventional hydrothermal reaction. The FAPO-5 molecular sieves were characterized by several techniques such as SEM, FTIR, UV/Vis, and ESR. Moreover, the oxidation of styrene over FAPO-5s was carried out, and compared to check the oxidation and epoxidation ability of the two FAPO-5s. FAPO-5 can be obtained easily by microwave irradiation within 15 min at 170oC, whereas FAPO-5 synthesis is completed in 6 h by conventional electric heating, confirming the acceleration about 20 times by microwave technique. There are no appreciable differences between two FAPO-5s in surface area and coordination state of iron. The FAPO-5 synthesized by microwave irradiation shows higher epoxide selectivity in the styrene epoxidation, which may be explained by the higher hydrophobicity of the catalyst.

Synthesis of Al-Doped ZnO by Microwave Assisted Hydrothermal Method and its Optical Property (마이크로파 수열합성법을 이용한 알루미늄이 도핑된 산화아연 합성 및 그 광학적 특성)

  • Hyun, Mi-Ho;Kang, Kuk-Hyoun;Lee, Dong-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.2
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    • pp.1555-1562
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    • 2015
  • Metal oxide semiconductors have been applied in several areas, such as solar cells, sensor, optical elements and displays, due to the high surface area, unique electrical and optical characteristics. Zinc oxide among the metal oxide has excellent physicochemical properties. Zinc oxide is a n-type semiconductor with a wide direct transition band gap of 3.37 eV at room temperature and large exciton binding energy of 60 meV. Cation-doped zinc oxide studies were conducted to complement the electrical and optical characteristics. In this paper, Al-doped ZnO was synthesized by hydrothermal synthesis using microwaves. ZnO was synthesized by adjusting the precursor ratio and using different dopants. The optimal ZnO synthesis conditions for crystal shape and optical properties were determined. The optical properties of aluminum doped zinc oxide were then examined by SEM, XRD, PL, UV-vis absorbance spectrum, and EDS.

α-Pinene Sensing Properties of Rhombohedral In2O3 Nanoparticles Prepared using the Microwave-assisted Hydrothermal Method (마이크로파 보조 수열 합성법으로 제조한 Rhombohedral In2O3 나노입자의 α-pinene 감지 특성)

  • Byeong-Hun, Yu;Hyo Jung, Lee;Joo Ho, Hwang;Ji-Wook, Yoon
    • Journal of Sensor Science and Technology
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    • v.31 no.6
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    • pp.418-422
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    • 2022
  • α-pinene is a natural volatile organic compound secreted by coniferous trees to protect themselves from attacks by insects, microorganisms, and viruses. Recently, studies have reported that α-pinene possesses pharmacological effects on various biological reactions such as anxiolytic, sleep-enhancing, anti-nociceptive, and inflammatory activity. Thus, forest bathing has recently received great attention as a novel therapy for treating severe diseases as well as psychological issues. However, appropriate places and timings for effective therapies are still veiled, because on-site monitoring of α-pinene gas in forests is barely possible. Although portable chemosensors could allow real-time analysis of α-pinene gas in forests, the α-pinene sensing properties of chemosensors have never been reported thus far. Herein, we report for the first time, the α-pinene sensing properties of an oxide semiconductor gas sensor based on rhombohedral In2O3 (h-In2O3) nanoparticles prepared by a microwave-assisted hydrothermal reaction. The h-In2O3 nanoparticle sensor showed a high response to α-pinene gas at ppm levels, even under humid conditions (for example, relative humidity of 50 %). The purpose of this research is to identify the potential of oxide semiconductor gas sensors for implementing portable devices that can detect α-pinene gas in forests in real-time.

Hydrated Vanadium Pentoxide/Graphene Oxide Nanobelts for Enhanced Electrochemical Performance

  • Hyegyeong Hwang;Jinsung Kwak
    • Korean Journal of Materials Research
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    • v.34 no.8
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    • pp.387-394
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    • 2024
  • Transition metal oxide-based materials have mainly been studied as electrodes for energy storage devices designed to meet essential energy demands. Among transition metal oxide-based materials, hydrated vanadium pentoxide (V2O5·nH2O), a vanadium oxide material, has demonstrated great electrochemical performance in the electrodes of energy storage devices. Graphene oxide (GO), a carbon-based material with high surface area and high electrical conductivity, has been added to V2O5·nH2O to compensate for its low electrical conductivity and structural instability. Here, V2O5·nH2O/GO nanobelts are manufactured with water without adding acid to ensure that the GO is uniformly dispersed, using a microwave-assisted hydrothermal synthesis. The resulting V2O5·nH2O/GO nanobelts exhibited a high specific capacitance of 206 F/g and more stable cycling performance than V2O5·nH2O without GO. The drying conditions of the carbon paper electrodes also resulted in more stable cycling performance when conducted at high vacuum and high temperature, compared with low vacuum and room temperature conditions. The improvement in electrochemical performance due to the addition of GO and the drying conditions of carbon paper electrodes indicate their great potential value as electrodes in energy storage devices.

Effect of Precursor Concentration on the Structural, Morphological, and Optical Properties of TiO2 Nano-Flowers

  • Anwar, M.S.;Danish, Rehan;Park, Keun Young;Koo, Bon Heun
    • Korean Journal of Materials Research
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    • v.25 no.5
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    • pp.247-252
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    • 2015
  • The effect of precursor concentration on the structural, morphological, and optical properties of $TiO_2$nano-flowers was investigated in this study. An increase in crystallite size was observed with an increase in the concentration of the precursor (titanium butoxide). The FE-SEM micrographs of the as-prepared samples show a three-dimensional flower-like morphology. The flowers consist of several nanorods coming out of a single core and have very sharp edges. Also, the variation in the aspect ratio of the nanostructure was observed with the concentration of the precursor. The photocatalytic properties of the samples show that the sample that has a high aspect ratio (AR~9) has a much better photocatalytic activity compared to the nano-crystal with a low aspect ratio (AR~6.1). It is believed that the excellent photocatalytic performance and short time synthesis of $TiO_2$nano-flowers using the microwave hydrothermal method can have potential applications in the field of photocatalysis.

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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    • 2011.05a
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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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The Mineralogical and Chemical Characteristics of Fe Impurities and the Efficiency of their Removal Using Microwave Heating and Magnetic Separation in the Pyrophyllite Ore (엽납석광석에 존재하는 Fe 불순물의 광물학적/화학적 특성과 마이크로웨이브 가열 및 자력분리에 의한 제거효과)

  • Cho, Kang-Hee;Kim, Bong-Ju;Choi, Nag-Choul;Park, Cheon-Young
    • Journal of the Mineralogical Society of Korea
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    • v.29 no.2
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    • pp.47-58
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    • 2016
  • The Fe-component of pyrophyllite is an impurity that reduces its grade in the final product. In order to identify the amount of impurity in pyrophyllite and to remove the Fe from the ore using a dry method, microwave heating and magnetic separation were carried out. Pyrite and hematite were identified to contain pyrophyllite by microscopy, XRD, XRF, SEM/EDS and EPMA analysis. It is suggested that the euhedral pyrite in the pyrophyllite is formed by hydrothermal solution, and then the dissolution cavity structure is formed with a partial remainder of the pyrite which dissolved in acidic water. And the $Fe^{3+}$ ion contained in the acidic water precipitated out in the concentric structure of hematite as the origin of sedimentary structure. As a result of the microwave heating and magnetic separation experiments, the Fe removal rates obtained were 96% and 93% from pyrophyllite ore from the Sunsan mine and Wando mine, respectively. It is confirmed that the microwave heating and magnetic separation method was an environmentally friendly method to upgrade the low-grade pyrophyllite.

Effect of Working Temperature on Sensitivity of Au/SnO2 Core-Shell Structure Nanoparticles for CO Gas (Au/SnO2 core-shell 나노구조 센서의 구동온도가 CO 감동에 미치는 영향)

  • Yu, Yeon-Tae
    • Journal of Sensor Science and Technology
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    • v.21 no.6
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    • pp.456-460
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    • 2012
  • Au/$SnO_2$ core-shell structure nanoparticles (NPs) were synthesized by microwave hydrothermal method, and the effect of working temperature on sensitivity of Au/$SnO_2$ core-shell NPs for CO gas was investigated. The $SnO_2$ shell layer was consisted of $SnO_2$ primary particles with 4.5 nm diameter. The response of Au/$SnO_2$ core-shell NPs for CO gas was maximized at the working temperature of $350^{\circ}C$ while the sensitivity increased with decreasing the working temperature due to the low grain size effect of $SnO_2$ NPs on the response of CO gas.

Properties, Preparation, and Energy Storage Applications of Two-dimensional Molybdenum Disulfide (2차원 이황화몰리브덴의 성질, 제조 및 에너지 저장 소자 응용)

  • Choi, Bong Gill
    • Applied Chemistry for Engineering
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    • v.30 no.2
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    • pp.133-140
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    • 2019
  • Two-dimensional (2D) ultrathin molybdenum dichalcogenides $MoS_2$ has gained a great deal of attention in energy conversion and storage applications because of its unique morphology and property. The 2D $MoS_2$ nanosheets provide a high specific surface area, 2D charge channel, sub-nanometer thickness, and high conductivity, which lead to high electrochemical performances for energy storage devices. In this paper, an overview of properties and synthetic methods of $MoS_2$ nanosheets for applications of supercapacitors and rechargeable batteries is introduced. Different phases triangle prismatic 2H and metallic octahedral 1T structured $MoS_2$ were characterized using various analytical techniques. Preparation methods were focused on top-down and bottom-up approaches, including mechanical exfoliation, chemical intercalation and exfoliation, liquid phase exfoliation by the direct sonication, electrochemical intercalation exfoliation, microwave-assisted exfoliation, mechanical ball-milling, and hydrothermal synthesis. In addition, recent applications of supercapacitors and rechargeable batteries using $MoS_2$ electrode materials are discussed.

Synthesis and spectroscopic characterization of zinc ferrite nanoparticles

  • Arora, Shefali;Nandy, Subhajit;Latwal, Mamta;Pandey, Ganesh;Singh, Jitendra P.;Chae, Keun H.
    • Advances in nano research
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    • v.13 no.5
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    • pp.437-451
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    • 2022
  • Synthesis approaches usually affect the physical and chemical properties of ferrites. This helps ferrite materials to design them for desired applications. Some of these methods are mechanical milling, ultrasonic method, micro-emulsion, co-precipitation, thermal decomposition, hydrothermal, microwave-assisted, sol-gel, etc. These methods are extensively reviewed by taking example of ZnFe2O4. These methods also affect the microstructure and local structure of ferrite which ultimately affect the physical and chemical properties of ferrites. Various spectroscopic techniques such as Raman spectroscopy, Fourier Transform Infrared spectroscopy, Ultra Violet-Visible spectroscopy, Mossbauer spectroscopy, extended x-ray absorption fine structure, and electron paramagnetic resonance are found helpful to reveal this information. Hence, the basic principle and the usefulness of these techniques to find out appropriate information in ZnFe2O4 nanoparticles is elaborated in this review.