• Title, Summary, Keyword: magnetic nanofiber

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Development of (α-Amylase Coated Magnetic Nanofiber for the Hydrolysis of Starch. ((α-Amylase가 고정화된 Magnetic Nanofiber를 이용한 전분 분해공정 개발)

  • Kim, Hyun;Lee, Jung-Heon
    • Journal of Life Science
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    • v.17 no.9
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    • pp.1260-1265
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    • 2007
  • Magnetically separable enzyme-coated nanofibers were developed for the hydrolysis of starch. Stability of ${\alpha}-amylase-coated$ nanofiber was greatly improved and its residual activity was maintained over 92.7% after 32 days incubation at room temperature and under shaking conditions (200 rpm). The recovery of enzyme was high and enzyme activity after 10 recycle was 95.2% of its original activity. Developed enzyme-coated nanofibers were used for the hydrolysis of starch. When 0.5 mg of magnetically separable enzyme nanofibers was used, 40 g/l of starch (2 ml) was completely degraded within 40 min. The continuous enzyme reactor was developed and used for starch hydrolysis and 76% of starch (30 g/l) was hydrolyzed with 1 hr residence time.

Study on the Optimization of Reduction Conditions for Samarium-Cobalt Nanofiber Preparation (사마륨-코발트 자성 섬유 제조를 위한 환원 거동 연구 및 환원-확산 공정의 최적화)

  • Lee, Jimin;Kim, Jongryoul;Choa, Yong-Ho
    • Journal of Korean Powder Metallurgy Institute
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    • v.26 no.4
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    • pp.334-339
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    • 2019
  • To meet the current demand in the fields of permanent magnets for achieving a high energy density, it is imperative to prepare nano-to-microscale rare-earth-based magnets with well-defined microstructures, controlled homogeneity, and magnetic characteristics via a bottom-up approach. Here, on the basis of a microstructural study and qualitative magnetic measurements, optimized reduction conditions for the preparation of nanostructured Sm-Co magnets are proposed, and the elucidation of the reduction-diffusion behavior in the binary phase system is clearly manifested. In addition, we have investigated the microstructural, crystallographic, and magnetic properties of the Sm-Co magnets prepared under different reduction conditions, that is, $H_2$ gas, calcium, and calcium hydride. This work provides a potential approach to prepare high-quality Sm-Co-based nanofibers, and moreover, it can be extended to the experimental design of other magnetic alloys.

The Effects of Electron Beam Irradiation on Thermal and Mechanical Properties of Electrospun Nylon 66 Nano-web (전기방사된 나일론66 나노웹의 열적·기계적 특성에 전자선 조사가 미치는 영향)

  • Jeun, Joon Pyo;Kang, Hyo-Kyoung;Kang, Phil Hyun
    • Journal of Radiation Industry
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    • v.5 no.1
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    • pp.69-73
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    • 2011
  • Polyamide 66 (PA66) nanofibers with Triallyl cyanurate (TAC) were obtained by electrospinning of formic acid and chloroform solution. Electron beam irradiation of PA66 nanofiber with and without TAC was carried out over a range of absorbed doses (20~100 kGy) in nitrogen. The characterization of the irradiated PA66 nanofibers and PA66 nanofibers with TAC was done by scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and universal testing machine (UTM). The results of the SEM image analysis confirmed that the morphology of PA66 nanofibers was not altered by electron beam. The amount of TAC in PA66 nanofiber with TAC was identified by $^1H-NMR$ analysis. The degradation temperature of PA66 nanofibers with TAC at an absorbed dose of 20~100 kGy was higher than the irradiated PA66 nanofiber without TAC. On the other hand, the decreasing rate of modulus of irradiated PA66 nanofibers with TAC was less than PA66 nanofibers.

Electrospun Polyacrylonitrile-Based Carbon Nanofibers and Their Hydrogen Storages

  • Kim Dong-Kyu;Park Sun Ho;Kim Byung Chul;Chin Byung Doo;Jo Seong Mu;Kim Dong Young
    • Macromolecular research
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    • v.13 no.6
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    • pp.521-528
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    • 2005
  • Electrospun polyacrylonitrile (PAN) nanofibers were carbonized with or without iron (III) acetylacetonate to induce catalytic graphitization within the range of 900-1,500$^{circ}C$, resulting in ultrafine carbon fibers with a diameter of about 90-300 nm. Their structural properties and morphologies were investigated. The carbon nanofibers (CNF) prepared without a catalyst showed amorphous structures and very low surface areas of 22-31 $m^{2}$/g. The carbonization in the presence of the catalyst produced graphite nanofibers (GNF). The hydrogen storage capacities of these CNF and GNF materials were evaluated through the gravimetric method using magnetic suspension balance (MSB) at room temperature and 100 bar. The CNFs showed hydrogen storage capacities which increased in the range of 0.16-0.50 wt$\%$ with increasing carbonization temperature. The hydrogen storage capacities of the GNFs with low surface areas of 60-253 $m^{2}$/g were 0.14-1.01 wt$\%$. Micropore and mesopore, as calculated using the nitrogen gas adsorption-desorption isotherms, were not the effective pore for hydrogen storage.

Immobilization of Lactase onto Various Polymer Nanofibers for Enzyme Stabilization and Recycling

  • Jin, Lihua;Li, Ye;Ren, Xiang-Hao;Lee, Jung-Heon
    • Journal of Microbiology and Biotechnology
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    • v.25 no.8
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    • pp.1291-1298
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    • 2015
  • Five different polymer nanofibers, namely, polyaniline nanofiber (PANI), magnetically separable polyaniline nanofiber (PAMP), magnetically separable DEAE cellulose fiber (DEAE), magnetically separable CM cellulose fiber (CM), and polystyrene nanofiber (PSNF), have been used for the immobilization of lactase (E.C. 3.2.1.23). Except for CM and PSNF, three polymers showed great properties. The catalytic activities (kcat) of the free, PANI, PAMP, and magnetic DEAE-cellulose were determined to be 4.0, 2.05, 0.59, and 0.042 mM/min·mg protein, respectively. The lactase immobilized on DEAE, PANI, and PAMP showed improved stability and recyclability. PANI- and PAMP-lactase showed only a 0-3% decrease in activity after 3 months of vigorous shaking conditions (200 rpm) and at room temperature (25℃). PANI-, PAMP-, and DEAE-lactase showed a high percentage of conversion (100%, 47%, and 12%) after a 1 h lactose hydrolysis reaction. The residual activities of PANI-, PAMP-, and DEAE-lactase after 10 times of recycling were 98%, 96%, and 97%, respectively.

Use of Selective Ethanol Adsorption for Ethanol Concentration (선택적 에탄올 흡착을 활용한 에탄올 농축공정개발)

  • Jin, Li-Hua;Lee, Jung-Heon
    • KSBB Journal
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    • v.25 no.5
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    • pp.466-470
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    • 2010
  • In this study, we developed simple process for ethanol concentration. We developed magnetically separable polyanilline nanofiber (PAMP) for selective ethanol adsorption. PAMP can adsorbed 80% of ethanol in the solution. After adsorption, the ethanol was recovered with simple magnetic separation and centrifugation process. After 10 times recycle of PAMP, the ethanol adsorption maintained 92% of its initial adsorption capacity. Using ethanol concentration process, the ethanol concentration increased up to 197.6 g/L from 46 g/L which was 4.3 folds increase.

Poly(vinylidene fluoride)-based Porous Carbon Nanofibers (폴리비닐리덴 풀루오라이드로부터 제조된 다공성 탄소나노섬유)

  • Chung, H.J.;Jo, S.M.;Kim, D.Y.;Chin, B.D.;Lee, D.W.
    • Transactions of the Korean hydrogen and new energy society
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    • v.16 no.4
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    • pp.334-342
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    • 2005
  • 200-300 nm 직경을 지닌 폴리비닐리덴 플루오라이드 초극세 섬유를 전기방사법으로 제조하였다. 이들을 불응화시킨 후, $800-1800^{\circ}C$ 온도에서 탄화시켜 PVdF 계 탄소나노 섬유를 제조하여 구조 및 기공분석을 하였다. 이들은 20-30 nm 크기의 탄소입자로 이루어져 있으며 탄소나노입자는 1 nm이하의 슬릿형 나노기공을 지니고 있었다. 탄화온도가 증가함에 따라 비표면적은 $1500^{\circ}C$에서 $414\;m^2/g$로 감소하였으나, $1800^{\circ}C$에서는 $1300\;m^2/g$로 급격히 다시 증가하였으며 1 nm 이하의 나노기공만을 지닌 탄소섬유가 얻어졌다. 비표면적 및 기공특성과 수소저장특성을 관계를 조사하기 위하여 Magnetic Syspension Balance(MSB)를 사용한 중량법으로 평가한 이들의 수소저장능은 0.04-0.4wt%이었다.

Electrospun Magnetic Nanofiber as Multifunctional Flexible EMI-Shielding Layer and its Optimization on the Effectiveness

  • Yu, Jiwoo;Nam, Dae-Hyun;Lee, Young-Joo;Joo, Young-Chang
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.2
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    • pp.57-63
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    • 2016
  • We developed a flexible and micro-thick electromagnetic interference (EMI) shielding nanofabric layer that also functions as a water resisting and heat sinking material. Electrospinning followed by a simple heat treatment process was carried on to produce the EMI-shielding Ni/C hybrid nanofibers. The ambient oxygen partial pressure ($pO_2$ = 0.1, 0.7, 1.3 Torr) applied during the heat treatment was varied in order to optimize the effectiveness of EMI-shielding by modifying the size and crystallinity of the magnetic Ni nanoparticles distributed throughout the C nanofibers. Permittivity and permeability of the nanofibers under the electromagnetic (EM) wave frequency range of 300 MHz~1 GHz were measured, which implied the EMI-shielding effectiveness (SE) optimization at $pO_2$ = 0.7 Torr during the heat treatment. The materials' heat diffusivity for both in-plane direction and vertical direction was measured to confirm the anisotropic thermal diffusivity that can effectively deliver and sink the local heat produced during device operations. Also, the nanofibers were aged at room temperature in oxygen ambient for water resisting function.

Enhanced Electromagnetic Properties of Nickel Nanoparticles Dispersed Carbon Fiber via Electron Beam Irradiation (전자선 안정화에 의한 니켈 나노 입자가 분산된 탄소섬유의 전자기적 특성 향상)

  • Lee, Yeong Ju;Kim, Hyun Bin;Lee, Seung Jun;Kang, Phil Hyun
    • Journal of Radiation Industry
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    • v.9 no.1
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    • pp.15-20
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    • 2015
  • Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.

Magnetic Nanofiber with Shape Memory Properties by Coaxial Electrospinning of Core/Sheath Structure (동축 전기방사를 이용한 Core/Sheath 구조의 자성 나노섬유 제조 및 특성 평가)

  • Choi, Wonseok;Hong, Kyung Hwa;Kang, Tae Jin
    • Textile Science and Engineering
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    • v.50 no.1
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    • pp.35-39
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    • 2013
  • A magnetorheological fluid(MR fluid) is a type of smart fluid in a carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic solid. And, Shape-memory polyurethane(SMPU) is a kind of polymeric smart materials that have the ability to return from a deformed state to their original shape induced by an external stimulus, such as temperature change. In this study, the multi-functional fiber webs showing magnetorheological(MR) property under magnetic field and shape memory(SM) effect by heat were prepared by coaxial electrospinning process. The fibers were designed to consist of two part; core part, SMPU+MRF and sheath part, SMPU. Consequently, we found that ca. 10 wt% MRF+15 wt% SMPU solution is most suitable for core part dope solution, and 17 wt% SMPU solution is most suitable for sheath part dope solution. Through scanning electron microscope(SEM) and transmission electron microscope(TEM), we observed stable core/sheath structure in the fiber of the electrospun web. From the dynamic mechanical analyzer(DMA) result to investigate the shape recovery ability of the fibe webs by heat, we discovered reasonable shape recovery property from the electrospun fiber web. Also, they showed MR effect under magnetic field through universal testing machine(UTM) test.