• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.42-45
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• 2003

Nondestructive damage sensing and mechanical properties for acid-treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electro-micromechanical technique and acoustic emission (AE). Carbon black (CB) was used to compare to CNT and CNF. The results were compared to the untreated case. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity under double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. For surface treatment case, the damage sensitivity and reinforcing effect were higher than those of the untreated case. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.117-120
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• 2003

Electro-micromechanical techniques were applied using four-probe method for carbon nanotube (CNT) or nanofiber (CNF)/epoxy composites with their content. Carbon black (CB) was used to compare with CNT and CNF. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity for double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites, and in CB case they were the lowest compared with CNT and CNF. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• 한국전기화학회:학술대회논문집
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• 2003.04a
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• pp.65-65
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• 2003

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.239-246
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• 2015

The hybridization of carbon nano-materials enhances the efficiency of each function of the resulting structure or composites. Also, the addition of non-carbon elements to nanomaterials modifies the electrochemical properties. Electrodes combining porous carbon nanofibers (CNFs) and metal oxides benefit from the combination of the double-layer capacitance of the CNFs and the pseudocapacitive character associated with the surface redox-type reactions. Consequently, they demonstrate superior supercapacitor performance in terms of high capacitance, high energy/power efficiency and high rate capability. This paper presents a comprehensive review of the latest advances made in the development and application of various metal oxide/CNF composites (CNFCs) to supercapacitor electrodes.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2369-2376
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• 2011

Effect of heat treatment of carbon nanofibers (CNF) on electrical properties and crystallization behavior of polypropylene was reported. Two types of CNFs (untreated and heat treated at 2300 $^{\circ}C$) were incorporated into polypropylene (PP) using intensive mixing. A significant drop in volume resistivity was observed with composites containing untreated 5 wt % and heat treated 3 wt % CNF. In non-isothermal crystallization studies, both untreated and heat treated CNFs acted as nucleating agents. Composites with heat treated CNFs showed a higher crystallization temperature than composites with untreated CNFs did. TEM results of CNF revealed that an irregular structure of CNFs can be converted into the continuous graphitic structure after heat treatment. Furthermore, STM showed that the higher carbonization temperature leads to the higher graphite degree which presents the larger carbon network size, suggesting that a more graphitic structure of CNFs led to a higher crystallization temperature of PP.

• Carbon letters
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• v.8 no.1
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• pp.37-42
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• 2007

Carbon nanofiber (CNF) grown catalytically was chemically activated with KOH to attain structural change of CNF. The structural changes of CNF through KOH activation were investigated by using BET and SEM. From the results of BET, it was found that KOH activation was effective to develop particular sizes of pores on the CNF surface, increasing the surface area of CNF. Activated CNF was applied as an anode catalyst support of fuel cell. The effects of different activation conditions including the activation temperature and the activation time on the specific surface area of the CNF activated with KOH were investigated to obtain appropriate structure as a catalyst support. The 60 wt% Pt-Ru catalyst prepared was observed by using TEM and XRD.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.139-144
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• 2023

In this study, carbon-coated porous nanofibers were prepared via electrospinning and the performance of Li[Ni_0.93Co_0.07]O₂ (NC) synthesized by electrospinning (E-NC) and co-precipitation (C-NC) was compared. E-NC had a discharge capacity of 206 mAh g^-1 at 0.1C (17 mA/g), which is 10% higher than that of C-NC (189.2 mAh g^-1). E-NC shows a high-rate performance of 118.32 mAh g^-1 (61.7%) at 5C (850 mA/g), which is 50% higher than that of C-NC (78.22 mAh g^-1 = 45.7%). Charge transfer of the carbon-coated porous nanofiber E-NC decreased by 35% compared to C-NC after 20 cycles as observed using electrochemical impedance spectroscopy. The results of this study show that the nanofiber structure with carbon coating shortens the Li-ion diffusion path, improves electrical conductivity, resulting in excellent rate performance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.125-128
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• 2005

The dispersion of carbon nanofiber (CNF) was carried out by solution blending, mechanical mixing, and sonication. CNFs at levels of 5-50% fiber weight content were mixed with polypropylene (PP) powder, and then were melt-mixed using a twin-screw extruder. For the further alignment of fibers, extruded rods were stacked uni-directionally in the mold cavity for the compression molding. For the evaluation of mechanical properties of nanocomposites, tension, in-plane shear, and flexural tests were conducted. CNF/PP composites clearly showed reinforcing effect in the longitudinal direction. The tensile modulus and strength have improved by 100% and 40%, respectively for 50 % fiber weight content, and the flexural modulus and strength have increased by 120% and 25%, respectively for the same fiber weight content. The shear modulus showed 65% increase, but the strength dropped sharply by 40%. However, the property enhancement was not significant due to the poor adhesion between fiber and matrix. In the transverse direction, the tensile, flexural, and shear strength decreased as more fibers were added.

• Journal of Powder Materials
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• v.22 no.5
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• pp.350-355
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• 2015

Perforated polygonal cobalt oxide ($Co_3O_4$) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal $Co_3O_4$, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal $Co_3O_4$ with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round $Co_3O_4$ and destroyed $Co_3O_4$ powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal $Co_3O_4$. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal $Co_3O_4$. Thus, perforated polygonal $Co_3O_4$ can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.142-147
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• 2009

The influence of graphitization of carbon support on the electrochemical corrosion of carbon and sintering of Pt particles are investigated by measuring $CO_2$ emission at a constant potential of 1.4 V for 30 min using on-line mass spectrometry and cyclic voltammogram. In comparison to commercial Pt/C (from Johnson Matthey), highly graphitized carbon nanofiber (CNF) supported Pt catalyst exhibits lower performance degradation and $CO_2$ emission. As the more carbon corrosion occurred, the more prominent changes were detected in electrochemical characteristics of fuel cell. This indicates that the carbon corrosion affects significantly the fuel cell durability. From the observed results, CNF is considered to be more corrosion resistant material as a catalyst support. However, CNF shows higher aggregation of Pt particles under repeated cyclic voltammetry between 0 and 0.8 V where the carbon corrosion is not initiated.