ESR study of activated carbon fibers: preliminary results

1993 ◽  
Vol 8 (9) ◽  
pp. 2282-2287 ◽  
Author(s):  
S.L. di Vittorio ◽  
A. Nakayama ◽  
T. Enoki ◽  
M.S. Dresselhaus ◽  
M. Endo ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Carbon Fibers ◽  
Room Temperature ◽  
Broad Peak ◽  
Activated Carbon Fibers ◽  
Temperature Peak ◽  
Dangling Bond ◽  
Surface Areas ◽  
Spin Resonance

We have carried out Electron Spin Resonance (ESR) measurements on activated carbon fibers (ACF) with specific surface areas (SSA) of 3000 and 2000 m2/g. The ESR spectrum of ACF fibers in air is extremely broad (500 to 1000 Gauss), and the spin susceptibility decreases rapidly with decreasing specific surface area. Also measured was the ESR signal of the desorbed fibers in vacuum. As a result of desorption, the broad peak decreases slightly in intensity, and a narrow (≍65 Gauss at room temperature) peak appears. We report results on the temperature dependence of both peaks. The narrow peak is interpreted as due to spins associated with dangling bonds, whereas we attribute the broad peak to the conduction carrier spins which is broadened by the boundary scattering process (T1 contribution) and the dipolar broadening process (T2 contribution) associated with the dangling bond spins.

Modified polyacrylonitrile-based activated carbon fibers applied in supercapacitor

2016 ◽  
Vol 45 (3) ◽  
pp. 164-171 ◽  
Author(s):  
Linjie Su ◽  
Bohong Li ◽  
Dongyu Zhao ◽  
Chuanli Qin ◽  
Zheng Jin
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Specific Capacitance ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Fibers ◽  
Electrode Material ◽  
High Specific Capacitance ◽  
Activated Carbon Fibers ◽  
Content Type

Purpose The purpose of this paper is to prepare a new modified activated carbon fibers (ACFs) of high specific capacitance used for electrode material of supercapacitor. Design/methodology/approach In this study, the specific capacitance of ACF was significantly increased by using the phenolic resin microspheres and melamine as modifiers to prepare modified PAN-based activated carbon fibers (MACFs) via electrospinning, pre-oxidation and carbonization. The symmetrical supercapacitor (using MACF as electrode) and hybrid supercapacitor (using MACF and activated carbon as electrodes) were tested in term of electrochemical properties by cyclic voltammetry, AC impedance and cycle stability test. Findings It was found that the specific capacitance value of the modified fibers were increased to 167 Fg-1 by adding modifiers (i.e. 20 wt.% microspheres and 15 wt.% melamine) compared to that of unmodified fibers (86.17 Fg-1). Specific capacitance of modified electrode material had little degradation over 10,000 cycles. This result can be attributed to that the modifiers embedded into the fibers changed the original morphology and enhanced the specific surface area of the fibers. Originality/value The modified ACFs in our study had high specific surface area and significantly high specific capacitance, which can be applied as efficient and environmental absorbent, and advanced electrode material of supercapacitor.

scholarly journals Photoconductivity of activated carbon fibers

1991 ◽  
Vol 6 (5) ◽  
pp. 1040-1047 ◽  
Author(s):  
K. Kuriyama ◽  
M.S. Dresselhaus
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Carbon Fibers ◽  
Low Temperatures ◽  
Room Temperature ◽  
High Surface ◽  
Localized States ◽  
Activated Carbon Fibers ◽  
Disordered Carbon ◽  
Increasing Temperature

The conductivity and photoconductivity are measured on a high-surface-area disordered carbon material, i.e., activated carbon fibers, to investigate their electronic properties. This material is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000–2000 m2/g. Our preliminary thermopower measurements show that the dominant carriers are holes at room temperature. The x-ray diffraction pattern reveals that the microstructure is amorphous-like with Lc ≃ 10 Å. The intrinsic electrical conductivity, on the order of 20 S/cm at room temperature, increases by a factor of several with increasing temperature in the range 30–290 K. In contrast, the photoconductivity in vacuum decreases with increasing temperature. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The recombination kinetics changes from a monomolecular process at room temperature to a bimolecular process at low temperatures, indicative of an increase in the photocarrier density at low temperatures. The high density of localized states, which limits the motion of carriers and results in a slow recombination process, is responsible for the observed photoconductivity.

scholarly journals Activated carbon fibers loaded with MnO2 for removing NO at room temperature

2014 ◽  
Vol 256 ◽  
pp. 101-106 ◽  
Author(s):  
Mingxi Wang ◽  
Henian Liu ◽  
Zheng-Hong Huang ◽  
Feiyu Kang
Keyword(s):  
Activated Carbon ◽  
Carbon Fibers ◽  
Room Temperature ◽  
Activated Carbon Fibers

Fabrication of Activated Carbon Fibers from Stabilized PAN-Based Fibers by KOH

2004 ◽  
Vol 449-452 ◽  
pp. 217-220 ◽  
Author(s):  
Young Jae Lee ◽  
Jae Hyung Kim ◽  
Jang Soon Kim ◽  
Dong Bok Lee ◽  
Jae Chun Lee ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Fibers ◽  
Potassium Hydroxide ◽  
Chemical Activation ◽  
Activated Carbon Fibers ◽  
High Concentration

Activated carbon fibers were prepared from stabilized PAN-based fibers by chemical activation using potassium hydroxide at different concentration. The experimental data showed variations in specific surface area, microstructure by the activated carbon fibers. Specific surface area of about 2545 m2/g was obtained in the KOH/stabilized PAN-based fiber ratio of 1:1 at 800°. An abrupt reduction of specific surface area was observed in the experiments with the ratio of 3:1 of OH/stabilized PAN-based fiber, being dissimilar with the result of KOH/fiber ratios of 1:1 and 2:1 in the similar experiments. The high concentration of KOH led to the destruction of micropore walls instead of forming mesopores.

Analysis of pore structure of activated carbon fibers using high resolution transmission electron microscopy and image processing

1995 ◽  
Vol 10 (10) ◽  
pp. 2507-2517 ◽  
Author(s):  
K. Oshida ◽  
K. Kogiso ◽  
K. Matsubayashi ◽  
K. Takeuchi ◽  
S. Kobayashi ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Pore Structure ◽  
Carbon Fibers ◽  
Electronic Materials ◽  
Low Frequency ◽  
Quantitative Information ◽  
Activated Carbon Fibers ◽  
Surface Areas ◽  
Three Samples ◽  
Specific Frequency

Activated carbon fibers (ACF's), already used widely as absorbent materials, are now expected to be useful as new electrical and electronic materials, for their very large specific surface areas (SSA). Chemical adsorption as well as x-ray diffraction have been mainly used for characterizing the ACF structure. While TEM observations reveal the texture of ACF's, such observations have not yet yielded quantitative information about the microstructure. To promote the quantitative interpretation of the TEM images, computer image analysis is used in this work to clarify the pore structure of ACF's. The microstructures of three samples, which are all isotropic pitch-based ACF's but with different SSA values, have been investigated. Operations such as noise reduction, low frequency cut-off filtering, and binary image formation are used to clarify the pore images of the ACF's. The distribution of the ACF porosity size is clearly shown by a frequency analysis of the two-dimensional fast Fourier transform (FFT). The results suggest that TEM images include contributions from many different pore sizes. Pores in different size ranges are extracted by the inverse FFT (IFFT) operation by selecting the specific frequency range, and by-this analysis the pore structure is shown to have fractal characteristics.

scholarly journals Coconut-based activated carbon fibers for efficient adsorption of various organic dyes

RSC Advances ◽  
2018 ◽  
Vol 8 (74) ◽  
pp. 42280-42291 ◽  
Author(s):  
Ling Zhang ◽  
Ling-yu Tu ◽  
Yan Liang ◽  
Qi Chen ◽  
Ze-sheng Li ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Fibers ◽  
Organic Dyes ◽  
Low Cost ◽  
Micropore Volume ◽  
Activated Carbon Fibers ◽  
Large Specific Surface Area

Activated carbon fibers with high micropore volume and large specific surface area were prepared from abundant and low-cost coconut fibers, which show excellent adsorption performances towards various dyes.

Negative Magnetoresistance in Activated Carbon Fibers Heat-Treated Above 2000°C

1993 ◽  
Vol 328 ◽  
Author(s):  
A. W. P. Fung ◽  
Z. H. Wang ◽  
M. S. Dresselhaus ◽  
G. Dresselhaus ◽  
M. Endo
Keyword(s):  
Activated Carbon ◽  
Carbon Fibers ◽  
Room Temperature ◽  
Weak Localization ◽  
Quantum Mechanical ◽  
Activated Carbon Fibers ◽  
Two Dimensional ◽  
Measurement Temperature ◽  
Heat Treated ◽  
Different Temperatures

ABSTRACTActivated carbon fibers (ACFs) were heat-treated at temperatures above 2000°C to study both the effect of heat treatment on the order development in ACFs and the effect of granularity on the transport properties of granular materials in general. The electrical conductivity σ(T) and Magnetoresistance (MR) were measured as a function of temperature for ACFs Made of two different precursors and heat-treated at different temperatures. While the field dependence of the observed negative MR could be fit to the two-dimensional weak localization (2D WL) theory at each measurement temperature, σ(T) showed only a weak temperature dependence, inconsistent with the ln (T) dependence predicted by the same theory. Even More interesting is the observation of a negative MR, which is a quantum-Mechanical phenomenon, near room temperature. It is thought that the grain boundaries might be responsible for such deviations from the standard 2D WL theory.

Novel Structure of Microporous Activated Carbon Fibers and Their Gas Adsorption

1994 ◽  
Vol 349 ◽  
Author(s):  
Toshiaki Enoki ◽  
Norikazu Kobayashi ◽  
Atsuko Nakayama ◽  
Kazuya Suzuki ◽  
Chiaki Ishii ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Activated Carbon ◽  
Carbon Fibers ◽  
Gas Adsorption ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Activated Carbon Fibers ◽  
Dangling Bond ◽  
Spin Lattice ◽  
Helium Gas

ABSTRACTActivated carbon fibers are a kind of microporous carbon. Using dangling bond spins attached to the peripheries of the micropores, we investigated the microporous structures in relation to the heat-treatment and gas adsorption effects. Functional groups weakly bonded to the graphitic backbone are removed by the heat-treatment at moderate temperatures 200-400°C, resulting in the generation of a variety of dangling bond spins. The heattreatment above 500°C brings about homogenization of the dangling bond spins. For gas adsorption, the introduction of helium gas strongly enhances the spin-lattice relaxation rate for the dangling bond spins. In addition to a remarkably large condensation of helium gas in the microporous region, the enhancement proves the presence of ultra-micropores which can accommodate only the smallest diameter helium atoms.

Preparation and Characterization of Nano-Scaled Ag Plated Activated Carbon Fibers for NO Removal

2005 ◽  
Vol 23 ◽  
pp. 215-218
Author(s):  
Soo Jin Park ◽  
Byung Joo Kim
Keyword(s):  
Activated Carbon ◽  
Carbon Fibers ◽  
Catalytic Reduction ◽  
Silver Content ◽  
Adsorption Properties ◽  
Activated Carbon Fibers ◽  
No Removal ◽  
Surface Areas ◽  
Silver Metal

In this work, the catalytic reduction of NO over activated carbon fibers (ACFs)/Ag prepared by nanoscaled Ag electroplating has been studied. It is observed that silver content on ACF surfaces increases with increasing the plating time. However, a decrease of adsorption properties, including BET’s specific surface areas and total pore volumes, in increasing the plating time is observed within the range of well-developed micropore structures. As the experimental results, the net heat of adsorption of the ACFs/Ag samples is largely influenced on the amount of silver metal, and the catalytic ability for NO removal over ACFs/Ag samples is improved in the presence of silver on the ACFs. However, the adsorption properties of the excessively silver loaded samples are significantly reduced, resulting in the decrease of the removal efficiency. Therefore, the NO removal is largely depended on silver content on ACFs, together with the results of adsorption properties of the ACFs.

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