• Title/Summary/Keyword: Double pore structures

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Fabrication and Pore Properties of SUS316L Membrane with Double-Layered Pore Structures by Wet Powder Spraying

  • Min-Jeong Lee;Hyeon-Ju Kim;Manho Park;Jung-Yeul Yun
    • Archives of Metallurgy and Materials
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    • v.67 no.4
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    • pp.1531-1534
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    • 2022
  • In this study, a SUS316L membrane having double layered pore structures was fabricated, and the pore characteristics were analyzed after coating with a spherical powder and a flake-shaped powder on a disk-shaped SUS316L support using a wet powder spraying process. The thickness of the coated layer was checked using an optical microscope, and air permeability was measured using a capillary flow porometer. When the coating amount was similar, the fine porous layer prepared using flake powder was thicker and showed higher porosity. In the case of a similar thickness, the case of using flake powder was half of the amount of spherical powder used. Therefore, it was confirmed that it is possible to manufacture a metal membrane having a high filter efficiency even with a small coating amount when using the flake powder.

Microstructure and Pore Characteristics of a SUS316L Gas Filter Fabricated by Wet Powder Spraying

  • Min-Jeong Lee;Yu-Jeong Yi;Hyeon-Ju Kim;Manho Park;Jungwoo Lee;Jung-Yeul Yun
    • Archives of Metallurgy and Materials
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    • v.67 no.4
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    • pp.1547-1550
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    • 2022
  • In this study, a flake-shaped metal powder was coated on a tube shaped pre-sintered 316L stainless steel support using a wet powder spraying process to fabricate a double pore structure, and the pore characteristics were analyzed according to coating time and tube rotation speed. The thickness of the coated layer was checked via optical microscopy, and porosity was measured using image analysis software. Air permeability was measured using a capillary flow porometer. As a result of the experiment, the optimal rotation speed of the support tube was established as 200 rpm. When the rotation speed was fixed, the coating thickness and the coating amount of the double pore structure increased as the coating time increased. The porosity of the double pore structure was increased due to the irregular arrangement of the flake-shaped powder. The air permeability of the double pore structure decreased with increasing fine pore layer thickness.

An Overview of the Activated Carbon Fibers for Electrochemical Applications

  • Lee Gyoung-Ja;Pyun Su-Il
    • Journal of the Korean Electrochemical Society
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    • v.9 no.1
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    • pp.10-18
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    • 2006
  • This article is concerned with the overview of the activated carbon fibers. Firstly, this review provides a comprehensive survey of the overall processes for the synthesis of the activated carbon fibers from the carbonaceous materials. Subsequently, the physicochemical properties such as pore structures and surface oxygen functional groups of the activated carbon fibers were discussed in detail. Finally, as electrochemical applications of the activated carbon fibers to electrode materials for electric double-layer capacitor (EDLC), the electrochemical characteristics of the activated carbon fiber electrodes and the various methods to improve the capacitance and rate capability were introduced. In particular, the effect of pore length distribution (PLD) on kinetics of double-layer charging/discharging was discussed based upon the experimental and theoretical results in our work. And then we discussed in detail the applications of the activated carbon fibers to adsorbent materials for purification of liquid and gas.

Behaviour of Nak-dong River Sand on Cyclic Stress History (낙동강 모래의 반복응력이력에 의한 거동)

  • 김영수;박명렬;김병탁;이상복
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.295-302
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    • 2000
  • Earthquakes not only produce additional load on the structures and underlying soil, but also change the strength characteristics of the soil. Therefore, in order to analyze soil structures for stability, the behaviour after earthquake must be considered. In this paper, a series of cyclic triaxial tests and monotonic triaxial tests were carried out to investigate the undrained shear strength and liquefaction strength characteristics of Nak-Dong River sand soils which were subjected to cyclic loading. The sample was consolidated in the first stage and then subjected to stress controlled cyclic loading with 0.1Hz. After the cyclic loading, the cyclic-induced excess pore water pressure was dissipated by opening the drainage valve and the sample was reconsolidated to the initial effective mean principal stress(p/sub c/'). After reconsolidation, the monotonic loading or cyclic loading were applied to the specimen. In the results, the undrained shear strength and liquefaction strength characteristics depended on the pore pressure ratio(Ur=U/p/sub c/'). The volume change following reconsolidation can be a function of cyclic-induced excess pore water pressure and the maximum double amplitude of axial strain.

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Effects of pore structures on electrochemical behaviors of polyacrylonitrile-based activated carbon nanofibers by carbon dioxide activation

  • Lee, Hye-Min;Kim, Hong-Gun;An, Kay-Hyeok;Kim, Byung-Joo
    • Carbon letters
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    • v.15 no.1
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    • pp.71-76
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    • 2014
  • Activated carbon nanofibers (ACNF) were prepared from polyacrylonitrile (PAN)-based nanofibers using $CO_2$ activation methods with varying activation process times. The surface and structural characteristics of the ACNF were observed by scanning electron microscopy and X-ray diffraction, respectively. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. As experimental results, many holes or cavernous structures were found on the fiber surfaces after the $CO_2$ activation as confirmed by scanning electron microscopy analysis. Specific surface areas and pore volumes of the prepared ACNFs were enhanced within a range of 10 to 30 min of activation times. Performance of the porous PAN-based nanofibers as an electrode for electrical double layer capacitors was evaluated in terms of the activation conditions.

Mesoporous Control Effect of Porous Carbon Nanofibers for Electrical Double-Layer Capacitors (전기 이중층 커패시터를 위한 다공성 탄소나노섬유의 메조 기공 제어 효과)

  • Jo, Hyun-Gi;Shin, Dong-Yo;Ahn, Hyo-Jin
    • Korean Journal of Materials Research
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    • v.29 no.3
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    • pp.167-174
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    • 2019
  • To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of $696m^2g^{-1}$, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of $110.1F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$ and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of $0.1A\;g^{-1}$. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.

Fabrication of Mesoporous Carbon Nanofibers for Electrical Double-Layer Capacitors (전기 이중층 커패시터용 메조 다공성 탄소 나노섬유의 제조)

  • Lee, Do-Young;An, Geon-Hyoung;Ahn, Hyo-Jin
    • Korean Journal of Materials Research
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    • v.27 no.11
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    • pp.617-623
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    • 2017
  • Mesoporous carbon nanofibers as electrode material for electrical double-layer capacitors(EDLCs) are fabricated using the electrospinning method and carbonization. Their morphologies, structures, chemical bonding states, porous structure, and electrochemical performance are investigated. The optimized mesoporous carbon nanofiber has a high sepecific surface area of $667m^2\;g^{-1}$, high average pore size of 6.3 nm, and high mesopore volume fraction of 80 %, as well as a unifom network structure consiting of a 1-D nanofiber stucture. The optimized mesoporous carbon nanofiber shows outstanding electrochemical performance with high specific capacitance of $87F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$, high-rate performance ($72F\;g^{-1}$ at a current density of $20.0A\;g^{-1}$), and good cycling stability ($92F\;g^{-1}$ after 100 cycles). The improvement of the electrochemical performance via the combined effects of high specific surface area are due to the high mesopore volume fraction of the carbon nanofibers.

Synthesis of Core-Shell Silica Nanoparticles with Hierarchically Bimodal Pore Structures

  • Yun, Seok-Bon;Park, Dae-Geun;Yun, Wan-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.467-467
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    • 2011
  • Reflecting the growing importance of nanomaterials in science and technology, controlling the porosity combined with well-defined structural properties has been an ever-demanding pursuit in the related fields of frontier researches. A number of reports have focused on the synthesis of various nanoporous materials so far and, recently, the nanomaterials with multimodal porosity are getting an emerging importance due to their improved material properties compared with the mono porous materials. However, most of those materials are obtained in bulk phases while the spherical nanoparticles are one of the most practical platforms in a great number of applications. Here, we report on the synthesis of the core-shell silica nanoparticles with double mesoporous shells (DMSs). The DMS nsnoparticles are spherical and monodispersive and have two different mesoporous shells, i.e., the bimodal porosity. It is the first example of the core-shell silica nanoparticles with the different mesopores coexisting in the individual nanoparticles. Furthermore, the carbon and silica hollow capsules were also fabricated via a serial replication process.

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Improving Physical Fouling Tolerance of PES Filtration Membranes by Using Double-layer Casting Methods (PES 여과막의 물리적 막오염 개선을 위한 기공 구조 개선 연구)

  • Chang-Hun Kim;Youngmin Yoo;In-Chul Kim;Seung-Eun Nam;Jung-Hyun Lee;Youngbin Baek;Young Hoon Cho
    • Membrane Journal
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    • v.33 no.4
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    • pp.191-200
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    • 2023
  • Polyethersulfone (PES) is a widely employed membrane material for water and industrial purification applications owing to its hydrophilicity and ease of phase separation. However, PES membranes and filters prepared using the nonsolvent induced phase separation method often encounter significant flux decline due to pore clogging and cake layer formation on the dense membrane surfaces. Our investigation revealed that tight microfiltration or loose ultrafiltration membranes can be subject to physical fouling due to the formation of a dense skin layer on the bottom side caused by water intrusion to the gap between the shrank membrane and the substrate. To investigate the effect of the bottom surface porosity on membrane fouling, two membranes with the same selective layers but different sub-layer structures were prepared using single and double layer casting methods, respectively. The double layered PES membrane with highly porous bottom surface showed high flux and physical fouling tolerance compared to the pristine single layer membrane. This study highlights the importance of physical optimization of the membrane structure to prevent membrane fouling.

Preparation and Electrochemical Characterization of Activated Carbon Electrode by Amino-fluorination (아미노불소화 반응에 의한 활성탄소전극 제조 및 전기화학적 특성)

  • Lim, Jae Won;Jeong, Euigyung;Jung, Min Jung;Lee, Sang Ick;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.22 no.4
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    • pp.405-410
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    • 2011
  • High-performance of an electric double layer capacitance (EDLC) electrode was prepared by the amino-fluorination of activated carbon by using $NF_3$ gas. The pore structure and surface chemistry were investigated based on the specific capacitance of EDLC. The amino-fluorination of activated carbon introduced functional groups of nitrogen and fluorine which are beneficial for the specific capacitance of EDLC without the change of pore structures. The E-NF100AC electrode, which has nitrogen and fluorine functional groups less than 1 at%, showed the highly improved specific capacitance of 528 (${\pm}9$) F/g at 2 mV/s showing 122% improved value when comparing with that of non-functionalized E-RAC electrodes. Whereas, the E-NF200AC electrode, which has nitrogen and fluorine functional groups over 1 at%, showed the decreased specific capacitance because of perfluorinated introduction. So, it is concluded that the proper contents of nitrogen and fluorine groups improved the specific capacitance of EDLC.