• Macromolecular Research
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• v.12 no.4
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• pp.374-378
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• 2004

The biodegradable and biocompatible poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a copolymer of microbial polyester, was fabricated as nanofibrous mats by electrospinning. Image analysis of the electrospun nanofibers fabricated from a 2 wt% 2,2,2-trifluoroethanol solution revealed a unimodal distribution pattern of fiber diameters with an observed average diameter of ca. 185 nm. The fiber diameter of electrospun fabrics could be controlled by adjusting the electro spinning parameters, including the solvent composition, concentration, applied voltage, and tip-to-collector distance. Chondrocytes derived from rabbit ear were cultured on a PHBV cast film and an electrospun PHBV nano-fibrous mat. After incubation for 2 h, the percentages of attached chondrocytes on the surfaces of the flat PHBV film and the PHBV nanofibrous mat were 19.0 and 30.1 %, respectively. On the surface of the electrospun PHBV fabric, more chondrocytes were attached and appeared to have a much greater spreaded morphology than did that of the flat PHBV cast film in the early culture stage. The electro spun PHBV nanofabric provides an attractive structure for the attachment and growth of chondrocytes as cell culture surfaces for tissue engineering.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.113-118
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• 2015

To improve the methanol electro-oxidation in direct methanol fuel cells(DMFCs), Pt electrocatalysts embedded on porous carbon nanofibers(CNFs) were synthesized by electrospinning followed by a reduction method. To fabricate the porous CNFs, we prepared three types of porous CNFs using three different amount of a styrene-co-acrylonitrile(SAN) polymer: 0.2 wt%, 0.5 wt%, and 1 wt%, respectively. A SAN polymer, which provides vacant spaces in porous CNFs, was decomposed and burn out during the carbonization. The structure and morphology of the samples were examined using field emission scanning electron microscopy and transmission electron microscopy and their surface area were measured using the Brunauer-Emmett-Teller(BET). The crystallinities and chemical compositions of the samples were examined using X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties on the methanol electro-oxidation were characterized using cyclic voltammetry and chronoamperometry. Pt electrocatalysts embedded on porous CNFs containing 0.5 wt% SAN polymer exhibited the improved methanol oxidation and electrocatalytic stability compared to Pt/conventional CNFs and commercial Pt/C(40 wt% Pt on Vulcan carbon, E-TEK).

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.47-52
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• 2012

Porous carbon nanofibers were prepared as a gas sensor electrode to study the $CO_2$ sensing property based on effects of porosity and introduced amine functional groups. Electrospun fibers were obtained by using electrospinning method with polyacrylonitrile precursor and they were treated by the thermal treatment and chemical activation. Amine functional groups were introduced by the liquid state treatment using diethylenetriamine. The specific surface area increased up to $2000m^2/g$ by the chemical activation. The Introduced amine functional group was identified using FT-IR spectroscopy. $CO_2$ gas sensing property was improved as four folds via introduced amine functional groups on the activated carbon nanofiber. In conclusion, the gas sensing property was improved based on the developed porosity by the chemical activation and the chemical attraction of $CO_2$ gas by introduced functional groups.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.148-155
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• 2015

Electrospun $LaCoO_3$ perovskite nanofibers were produced for the air electrode in Zn-air rechargeable batteries using electrospinning technique with sequential calcination. The final calcination temperature was varied from 500 to $800^{\circ}C$ in order to determine its effect on the physical and electrochemical properties of the prepared $LaCoO_3$ perovskite nanofibers. The surface area of the electrospun $LaCoO_3$ perovskite nanofibers were observed to decrease with increasing final calcination temperature. Electrospun $LaCoO_3$ perovskite nanofibers calcined with final calcination temperature of $700^{\circ}C$ had the best electrocatalytic activity among the prepared perovskite nanofibers.

• Journal of Environmental Impact Assessment
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• v.29 no.3
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• pp.198-209
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• 2020

In this study, electrospun nanofibers made of PAN (polyacrylonitrile) were activated through a physical method to obtain an optimized pore structure. In particular, to enhance the surface alkalinity, the activated carbon fibers (ANFs) were impregnated with tetraethylenepentamine (TEPA) with the aid of HNO₃. Then, the low level (3,000 ppm) CO₂ adsorption capacity for each ANF sample was evaluated. The specific surface area of ANFs increased from 308.4 ㎡/g to 839.4 ㎡/g and the total pore volume increased from 7.882 ㎤/g to 27.50 ㎤/g. Although the TEPA impregnation reduced the specific surface area and pore volume of the ANFs due to blocking of micropores, the HNO₃ pre-oxidation enhanced the amino groups tethered, increasing the amine content from 6.42% to 17.19%, and finally, increased the adsorption capacity of CO₂. This study showed that the sample 60-ANF-HNO₃-TEPA, which was activated for 60 minutes and was impregnated with HNO₃ and TEPA, had the best adsorption capacity for low level (0.3%) CO₂ (in a binary mixture with N₂).

• Journal of Powder Materials
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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.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.94-98
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• 2021

In this study, pure and Co3O4/CoFe2O4-loaded Indium oxide (In2O3) nanofibers were synthesized by the electrospinning of an Indium/Polyvinylpyrrolidone precursor solution containing cobalt and iron bimetallic zeolitic imidazolate frameworks and subsequent heat treatment. The ethanol, toluene, p-xylene, benzene, carbon monodxide, and hydrogen gas sensing characteristics of the solution were measured at 250-400 ℃. 0.5 at%-Co3O4/CoFe2O4-loaded In2O3 nanofibers exhibited extreme response (resistance ratio - 1) to 5 ppm of ethanol (210.5) at 250 ℃ and excellent selectivity over the interfering gases. In contrast, pure In2O3 nanofibers exhibited relatively low responses to all the analyte gases and low selectivity above 250-400 ℃. The superior response and selectivity toward ethanol is explained by the catalytic roles of Co3O4 and CoFe2O4 in gas sensing reaction and the electronic sensitization induced by the formation of p (Co3O4/CoFe2O4)-n (In2O3) junctions.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.250-257
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• 2016

Octahedral $Co_3O_4$/carbon nanofiber (CNF) composites are fabricated using electrospinning and hydrothermal methods. Their morphological characteristics, chemical bonding states, and electrochemical properties are used to demonstrate the improved photovoltaic properties of the samples. Octahedral $Co_3O_4$ grown on CNFs is based on metallic Co nanoparticles acting as seeds in the CNFs, which seeds are directly related to the high performance of DSSCs. The octahedral $Co_3O_4$/CNFs composites exhibit high photocurrent density ($12.73mA/m^2$), superb fill factor (62.1 %), and excellent power conversion efficiency (5.61 %) compared to those characteristics of commercial $Co_3O_4$, conventional CNFs, and metallic Co-seed/CNFs. These results can be described as stemmnig from the synergistic effect of the porous and graphitized matrix formed by catalytic graphitization using the metal cobalt catalyst on CNFs, which leads to an increase in the catalytic activity for the reduction of triiodide ions. Therefore, octahedral $Co_3O_4$/CNFs composites can be used as a counter electrode for Pt-free dye-sensitized solar cells.

• Carbon letters
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• v.15 no.4
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• pp.290-294
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• 2014

New precursors, poly(acrylonitrile-co-crotonic acid) (poly(AN-CA)) and poly(acrylonitrile-co-itaconic acid-co-crotonic acid) (poly(AN-IA-CA)) copolymers, for the preparation of carbon fibers, were explored in this study. The effects of comonomers with acidic groups, such as crotonic acid (CA) and/or itaconic acid (IA), on the stabilization of nanofibrous polyacrylonitrile (PAN) copolymers were studied. The extent of stabilization, evaluated by Fourier transform infrared spectroscopy, revealed that the CA comonomer could retard/control the stabilization rate of PAN, in contrast to the IA comonomer, which accelerated the stabilization process. Moreover, the synthesized PAN copolymers containing CA possessed higher Mv than those of the IA copolymers and also showed outstanding dimension stability of nanofibers during the stabilization, which may be a useful property for improving the dimensional stability of polymer composites during manufacturing.

• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.1-7
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• 2011

Undoped and Sb-doped $SnO_2$ nanofibers were prepared by electrospinning and their responses to $H_2$, CO, $CH_4$, $C_3H_8$, and $C_2H_5OH$ were measured. In the undoped $SnO_2$ nanofibers, the gas response ($R_a/R_g$, $R_a$: resistance in air, $R_g$: resistance in gas) to 100 ppm $C_2H_5OH$ was very high(33.9), while that to the other gases ranged from 1.6 to 2.2. By doping with 2.65 wt% Sb, the response to 100 ppm $C_2H_5OH$ was decreased to 4.5, whereas the response to $H_2$ was increased to 3.0. This demonstrates the possibility of detecting a high $H_2$ concentration with minimum interference from $C_2H_5OH$ and the potential to control the gas selectivity by Sb doping.