• 한국재료학회지
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• 제29권2호
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• pp.79-86
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• 2019

A heterogeneous photocatalytic system is attracting much interest for water and air purification because of its reusability and economical advantage. Electrospun nanofibers are also receiving immense attention for efficient photocatalysts due to their ultra-high specific surface areas and aspect ratios. In this study, ZnO nanofibers with average diameters of 71, 151 and 168 nm are successfully synthesized by facile electrospinning and a subsequent calcination process at $500^{\circ}C$ for 3 h. Their crystal structures, morphology features and optical properties are systematically characterized by X-ray diffraction, scanning electron microscopy, UV-Vis and photoluminescence spectroscopies. The photocatalytic activities of the ZnO nanofibers are evaluated by the photodegradation of a rhodamine B aqueous solution. The results reveal that the diameter of the nanofiber, controlled by changing the polymer content in the precursor solution, plays an important role in the photocatalytic activities of the synthesized ZnO nanofibers.

• Composites Research
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• 제18권3호
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• pp.31-37
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• 2005

본 연구에서는 나노섬유로 강인화된 복합재료를 만들기 위해 전기방사방법을 이용해서 폴리에틸렌옥사이드 (PEO) 나노섬유를 제조하였고, 제조된 복합재료와의 기계적 계면특성을 비교하기 위해 PEO 입자로 강인화된 복합재료를 제조하였다. PEO 나노섬유의 파이버 직경과 모폴로지는 주사전자현미경을 통해 관찰하였고, 복합재료의 기계적 계면특성은 파괴인성 $(K_{IC})$과 층간 전단 강도실험 (ILSS)을 통하여 알아보았다. 실험결과, 인가전압이 증가될수록 파이버의 직경은 감소하였고. 고전압에서 제트 불안정성의 증가로 인해서 최적의 섬유구조는 15 kV에서 얻을 수 있었다. PEO 나노섬유로 강인화된 에폭시 복합재료는 파괴인성인자 값인 $K_{IC}$와 ILSS가 PEO 입자로 강인화된 복합재료보다 향상된 값을 나타내었다. 이는 나노섬유가 입자에 비해 높은 비표면적과 aspect ratio를 가짐에 따라 복합재료의 기계적 계면특성을 향상시키는데 중요한 역할을 하는 것으로 판단된다.

• 마이크로전자및패키징학회지
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• 제23권2호
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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.

• Carbon letters
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• 제12권3호
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• pp.171-176
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• 2011

Polyacrylonitrile-based carbon nanofibers (CNFs) containing Ti and Mn were prepared by electrospinning. The effect of metal content on the hydrogen storage capacity of the nanofibers was evaluated. The nanofibers containing Ti and Mn exhibited maximum hydrogen adsorption capacities of 1.6 and 1.1 wt%, respectively, at 303 K and 9 MPa. Toward the development of an improved hydrogen storage system, the optimum conditions for the production of metalized CNFs were investigated by characterizing the specific surface areas, pore volumes, sizes, and shapes of the fibers. According to the results of Brunauer-Emmett-Teller analysis, the activation of the CNFs using potassium hydroxide resulted in a large pore volume and specific surface area in the samples. This is attributable to the optimized pore structure of the metal-containing polyacrylonitrile-based electrospun CNFs, which may provide better sites for hydrogen adsorption than do current adsorbates.

• 멤브레인
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• 제27권3호
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• pp.284-289
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• 2017

본 연구에서는 복합막의 물성향상을 위해 clay를 도입한 polysulfone 나노섬유 복합막을 제조하였다. Polysulfone/clay 복합막은 clay가 들어간 N,N-dimethyl acetamide와 acetone 혼합용매에 polysulfone을 첨가한 후 전기방사법을 이용하여 제조하였으며, 제조된 나노섬유 복합막은 적층수를 변화해 기공크기를 조절한 후 사용하였다. 전반적인 분리막의 특성은 SEM, contact angle, 기공특성, tensile strength, water flux 분석을 사용하여 고찰하였다. 특히 SEM image로 clay의 도입을 확인하였으며 contact angle 측정을 통해 표면이 개질된 결과를 확인할 수 있었다. 그리고 clay의 도입량에 따른 복합막의 기계적 물성을 확인하였다. 따라서 본 연구에서 제조된 분리막은 수처리용 분리막으로 충분히 활용 가능할 것으로 판단된다.

• 한국의류학회지
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• 제42권2호
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• pp.269-277
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• 2018

This study extracted Artemisia capillaris Thunberg with distilled water and ethanol to investigate its antioxidant effect. We then investigated the possibility of producing nanofibers by an electrospinning process by adding the extracts to polyvinyl alcohol (PVA). The electrospinning method used a PVA concentration of 12wt.%, an applied voltage of 10kV, and a tip-to-collector distance of 15cm. Total polyphenol and total flavonoid contents were measured to verify the antioxidant activity of Artemisia capillaris Thunberg extracts (ACEs). The total polyphenol content of the distilled water extract and the ethanol extract were measured as 218.47 and 271.26mg/g, respectively, and the total flavonoid content of the distilled water extract and the ethanol extract were measured as 141.68 and 34.98mg/g, respectively. As the content of the ACEs in the PVA nanofibers increased, the Diameters of the nanofibers and the uniformity of the diameters decreased. The electrospinning process was fabricated in a relatively uniform form without beads, and the diameters of the nanofibers that were produced ranged from 340 to 390nm. The results of FT-IR, XRD and DSC analyses confirmed that the ACEs were well mixed with the PVA molecules and were electrospun.

• 한국재료학회지
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• 제24권12호
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• pp.663-670
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• 2014

Diameter-controlled tin oxide nanofibers have been successfully prepared using electrospinning and a subsequent calcination process; their diameters, morphologies, and crystal structures have been characterized. The diameters of the as-spun nanofibers can be decreased by lowering the concentration of a polymer and a tin precursor in the electrospinning solution because of the decrease in the solution viscosity. The crystal structure of the nanofibers calcined at various temperatures from $200^{\circ}C$ to $800^{\circ}C$ has been proved to be the tetragonal rutile of tin oxide; crystallinity is improved by increasing the temperature. However, nanofibers with lower concentrations of tin precursor do not maintain their fibrous structures after calcination at high temperatures. In this study, the effect of the relationship between the precursor concentration and the calcination temperature on the diameter and the morphology of the tin oxide nanofiber has been systematically investigated and discussed.

• 한국응용과학기술학회지
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• 제25권3호
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• pp.341-346
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• 2008

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity ($X_c$) and molecular weight ($M_w$) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and $M_w$ of MFC by HBr hydrolysis considerably decreased, but $X_c$ showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

• 한국응용과학기술학회지
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• 제20권2호
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• pp.130-140
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• 2003

In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.

• 한국세라믹학회지
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• 제36권5호
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• pp.504-512
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• 1999

The high-quality carbon nanofibers were prepared by chemical vapor deposition of gas mixtures of CO-H2 and C3H8-H2 over Fe-Cu and Ni-Cu bimetallic catalysts. The yield and structure of carbon nanofiber produced were altered by the change of catalyst composition and reaction temperature. The high yields were obtained around 500$^{\circ}C$ with e-Cu catalyst and around 700-750$^{\circ}C$ with Ni-Cu catalyst and the relatively higher yields were obtained with the bimetallic catalyst containing 50-90% of Ni and Fe respectively in comparison with the pure metals. The carbon nanofibers produced over the Fe-Cu catalyst at around 500$^{\circ}C$ with the maximum yields had the highest surface ares of 160-200 m2/g around 650$^{\circ}C$ which was slightly lower than the temperature for maximum yields. In order to examine the characteristics of carbon nanofibers as catalyst support Ni and Co metals were supporte on the carbon nanofibers and CO hydrogenation reaction was performed with the catalysts. The particle size distribution of Ni and Co supported over the carbon nanofibers were 6-15 nm and the CO hydrogenation reaction rate with the carbon-nanofiber supported catalysts was much higher than that over the other supports.