• 한국재료학회지
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• 제19권10호
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• pp.544-549
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• 2009

Activated carbon (AC) with very large surface area has high capacitance per weight. However, such activation methods tend to suffer from low yields, below 50%, and are low in electrode density and capacitance per volume. Carbon NanoFibers (CNFs) had high surface area polarizability, high electrical conductivity and chemical stability, as well as extremely high mechanical strength and modulus, which make them an important material for electrochemical capacitors. The electrochemical properties of immobilized CNF electrodes were studied for use as in electrical double layer capacitor (EDLC) applications. Immobilized CNFs on Ni foam grown by thermal chemical vapor deposition (CVD) were successfully fabricated. CNFs had a uniform diameter range from 50 to 60 nm. Surface area was 56 m$^2$/g. CNF electrodes were compared with AC and multi wall carbon nanotube (MWNT) electrodes. The electrochemical performance of the various electrodes was examined with aqueous electrolyte of 2M KOH. Equivalent series resistance (ESR) of the CNF electrodes was lower than that of AC and MWNT electrodes. The specific capacitance of 47.5 F/g of the CNF electrodes was achieved with discharge current density of 1 mA/cm$^2$.

• 한국재료학회지
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• 제26권12호
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• pp.741-750
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• 2016

Nanofibers(NFs), because of their high surface area and nanosized grains, have appropriate morphologies for use in chemiresistive-type sensors for gas detection applications. In this study, a highly sensitive and selective CO gas sensing material based on Au-decorated $SnO_2$ NFs was fabricated by electrospinning. $SnO_2$ NFs were synthesized by electrospinning and subsequently decorated with various amounts of Au nanoparticles(NPs) by sputtering; this was followed by thermal annealing. Different characterizations showed the successful formation of Au-decorated $SnO_2$ NFs. Gas sensing tests were performed on the fabricated sensors, which showed bell-shaped sensing behavior with respect to the amount of Au decoration. The best CO sensing performance, with a response of ~20 for 10 ppm CO, was obtained at an optimized amount of Au (2.6 at.%). The interplay between Au and $SnO_2$ in terms of the electronic and chemical sensitization by Au NPs is responsible for the great improvement in the CO sensing capability of pure $SnO_2$ NFs, suggesting that Au-decorated $SnO_2$ NFs can be a promising material for fabricating highly sensitive and selective chemiresistive-type CO gas sensors.

• 전기화학회지
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• 제16권3호
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• pp.145-150
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• 2013

In this study, the electrochemical investigation of various electrodes for reverse electrodialysis using potassium ferrocyanide and potassium ferricyanide as a redox system was carried out. Cyclic voltammetry was the employed method for this electrochemical study. From the results of cyclic voltammograms for various electrode materials, i.e., Au, Vulcan supported Pt, activated carbon, carbon nanofiber, Vulcan, the Vulcan electrode showed the lowest overpotential, but the Pt electrode having slightly higher overpotential obtained slightly higher anodic and cathodic current densities for the $Fe(CN)_6{^{4-}}/Fe(CN)_6{^{3-}}$ redox couple. The cyclic voltammograms for the Vulcan electrode confirmed very good electrochemical reversibility and kinetic behavior. As a result, among the electrode materials, the Vulcan electrode is the most promising electrode material for reverse electrodialysis.

• Macromolecular Research
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• 제14권5호
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• pp.552-558
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• 2006

Biodegradable nanofibrous poly(L-lactic acid) (PLLA) scaffold was prepared by an electrospinning process for use in tissue regeneration. The nanofiber scaffold was treated with oxygen plasma and then simultaneously in situ grafted with hydrophilic acrylic acid (AA) to obtain PLLA-g-PAA. The fiber diameter, pore size, and porosity of the electrospun nanofibrous PLLA scaffold were estimated as $250\sim750nm,\;\sim30{\mu}m$, and 95%, respectively. The ultimate tensile strength was 1.7 MPa and the percent elongation at break was 120%. Although the physical and mechanical properties of the PLLA-g-PAA scaffold were comparable to those of the PLLA control, a significantly lower contact angle and significantly higher ratio of oxygen to carbon were notable on the PLLA-g-PAA surface. After the fibroblasts were cultured for up to 6 days, cell adhesion and proliferation were much improved on the nanofibrous PLLA-g-PAA scaffold than on either PLLA film or unmodified nanofibrous PLLA scaffold. The present work demonstrated that the applications of plasma treatment and hydrophilic AA grafting were effective to modify the surface of electrospun nanofibrous polymer scaffolds and that the altered surface characteristics significantly improved cell adhesion and proliferation.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.94-98
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• 2008

비정형 $MnO_2$의 초고용량 캐폐시턴스 특성을 향상시키기 위하여 망간산화물을 높은 전기전도를 갖는 나노탄소섬유(vapour-grown carbon nanofibers, VGCF)와 복합화하여 나노탄소섬유/망간 산화물(VGCF(40 wt%)/$MnO_2$) 복합 전극을 제조하여 cyclic voltammetry(CV), impedance spectroscopy 및 chronopotentiometric charge/discharge 기법을 사용하여 1.0M $Na_2SO_4$ 전해질에서 초고용량 캐폐시터 특성을 조사하였다. 40 wt% VGCF를 포함한 복합전극에서 $0.8mg/cm^2$ 망간산화물을 로딩한 $VGCF/MnO_2$ 복합전극은 주사속도 20 mV/s에서는 380 F/g, 500 mV/s에서는 230 F/g의 비용량 값을 나타냈다. 또한, $2.0mA/cm^2$의 일정전류로 충방전 실험을 수행한 결과 3,000회에서 97%의 초기용량을 유지하였다.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.769-774
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• 2011

NaOH 활성화법을 이용하여 다공성 탄소나노섬유(carbon nanofibers; 이하 CNF)를 온도 범위 700~$900^{\circ}C$에서 합성하였고, 상기 제조된 다공성 CNF를 담지체로 하여 직접메탄올 연료전지의 연료극용 촉매를 제조하고 평가하였다. NaOH 활성화에 의한 CNF 표면 특성의 변화를 비표면적 및 기공 크기 분포 자료를 통하여 조사하였고, 형상 및 구조의 변화를 전자현미경을 통하여 관찰하였다. 활성화 CNF에 담지된 촉매의 활성을 메탄올 산화 특성 및 단위전지를 통하여 평가하였다. 본 활성화 방법에 의한 기공의 형성과 이에 담지된 촉매의 활성과의 관계에 대한 고찰을 하였다.

• Composites Research
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• 제29권4호
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• pp.186-193
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• 2016

The development of electrospun nanofibers with improved mechanical properties is of great scientific and technological interest because of their wide-range of applications. Reinforcement of carbon nanotubes (CNTs) into the polymer matrix is considered as a promising strategy for substantially enhancing the mechanical properties of resulting CNTs/polymer composite mats on account of extraordinary mechanical properties of CNTs such as ultra-high Young's modulus and tensile strengths. This paper summarizes the recent developments on electrospun CNTs/polymer composite mats with an emphasis on their mechanical properties.

• Earthquakes and Structures
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• 제13권3호
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• pp.241-253
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• 2017

In this paper, dynamic response of the horizontal nanofiber reinforced polymer (NFRP) strengthened concrete beam subjected to seismic ground excitation is investigated. The concrete beam is modeled using hyperbolic shear deformation beam theory (HSDBT) and the mathematical formulation is applied to determine the governing equations of the structure. Distribution type and agglomeration effects of carbon nanofibers are considered by Mori-Tanaka model. Using the nonlinear strain-displacement relations, stress-strain relations and Hamilton's principle (virtual work method), the governing equations are derived. To obtain the dynamic response of the structure, harmonic differential quadrature method (HDQM) along with Newmark method is applied. The aim of this study is to investigate the effect of NFRP layer, geometrical parameters of beam, volume fraction and agglomeration of nanofibers and boundary conditions on the dynamic response of the structure. The results indicated that applied NFRP layer decreases the maximum dynamic displacement of the structure up to 91 percent. In addition, using nanofibers as reinforcement leads a 35 percent reduction in the maximum dynamic displacement of the structure.

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.191-202
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• 2019

In this study, performance (particle removal efficiency and breathing resistance) of several commercially available face masks (electrostatic filter masks (KF80 certified), a nanofiber filter mask (KF80 certified), and an uncertified mask) with their filter structure and composition were evaluated. Also, effects of relative humidity (RH) of incoming air, water and alcohol exposure, and reusability on performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except the uncertified mask filter, PM_2.5 removal efficiency was found to be higher than 90%, and the nanofiber filter mask had the highest quality factor due to the low pressure drop and high removal efficiency (nanofibers were arranged in a densely packed pore structure and contained a significant amount of fluorine in addition to carbon and oxygen). In the case of the KF80 certified mask, the removal efficiency was little affected when the RH of incoming air increased. When the mask filters were soaked in water, the removal efficiency of mask filters was degraded. In particular, the uncertified mask filter showed the highest removal efficiency degradation (26%). When the mask was soaked in alcohol, the removal efficiency also decreased with the greater degree than the water soaking case. The nanofiber mask filter showed the strongest resistance to alcohol exposure among tested mask filters. During evaluation of reusability of masks in real life, the removal efficiency of certified mask filter was less than 4% for 5 consecutive days (2 hours per day), while the removal efficiency of uncertified mask filter significantly decreased by 30% after 5 days.

• 공업화학
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• 제18권3호
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• pp.205-212
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• 2007

본 연구는 polyacrylonitrile (PAN)를 dimethyl formamide (DMF)에 용해시켜 전압조건을 8~20 kV, PAN 농도조건을 5~15 wt%, 그리고 tip-to-collector distance (TCD)를 15 cm로 다양한 조건에서 전기방사를 실시하였다. 나노섬유는 $250^{\circ}C$에서 1 h 동안 안정화시켰으며, $800{\sim}1000^{\circ}C$에서 1 h 동안 탄화시켰다. 안정화와 탄화 전후의 나노섬유의 구조 특성은 FT-IR 장비를 이용하여 연구하였으며 나노섬유의 직경분포와 모폴로지 특성을 알기 위해서 SEM 분석장비를 이용하였다. 나노섬유웹의 전기화학적 특성은 순환전류 전압곡선 특성 실험을 통해 고찰하였다. 실험 결과로부터 전기방사한 나노섬유의 직경의 크기는 일반적으로 방사용액의 농도와 인가전압에 영향을 받는다는 것을 확인할 수 있었으며 섬유의 평균 직경은 고분자의 농도 10 wt% 이상 증가함에 따라 감소하며 15 kV의 전압과 15 cm의 TCD 조건에서 섬유의 직경분포가 균일하고 평균직경이 작은 것으로 나타났다.