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.

scholarly journals Structural characterization of heat-treated activated carbon fibers

1992 ◽  
Vol 7 (7) ◽  
pp. 1788-1794 ◽  
Author(s):  
A.M. Rao ◽  
A.W.P. Fung ◽  
M.S. Dresselhaus ◽  
M. Endo
Keyword(s):  
Heat Treatment ◽  
Activated Carbon ◽  
Raman Scattering ◽  
Carbon Fibers ◽  
Insulator Transition ◽  
Activated Carbon Fibers ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Sequence Of Events ◽  
Heat Treated

Raman scattering, x-ray diffraction, and BET measurements are used to study the effect of heat treatment on the microstructure of activated carbon fibers (ACFs) and to correlate the structural changes with the metal-insulator transition observed in the electronic transport properties of heat-treated ACFs. A sequence of events is identified, starting with desorption, followed by micropore collapse plus the stacking of basic structural units in the c-direction, and ending up with in-plane crystallization. The graphitization process closely resembles that depicted by Oberlin's model, except that the final material at high-temperature heat treatment remains turbostratic. Because the metal-insulator transition was observed to occur at heat-treatment temperature THT ≃ 1200 °C, which is well below the THT value (2000 °C) for in-plane crystallization, we conclude that this electronic transition is not due to in-plane ordering but rather to the collapse of the micropore structure in the ACFs. Raman scattering also provides strong evidence for the presence of local two-dimensional graphene structures, which is the basis for the transport phenomena observed in heat-treated ACFs.

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.

Anomalous Spin-Lattice Relaxation Induced by Helium Gas in Microporous Carbon

1995 ◽  
Vol 64 (7) ◽  
pp. 2614-2620 ◽  
Author(s):  
Ko Sugihara ◽  
Atsuko Nakayama ◽  
Toshiaki Enoki
Keyword(s):  
Lattice Relaxation ◽  
Microporous Carbon ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Helium Gas

Micro−Nano Hierarchal Web of Activated Carbon Fibers for Catalytic Gas Adsorption and Reaction

2008 ◽  
Vol 47 (10) ◽  
pp. 3700-3707 ◽  
Author(s):  
Riju Mohan Singhal ◽  
Ashutosh Sharma ◽  
Nishith Verma
Keyword(s):  
Activated Carbon ◽  
Carbon Fibers ◽  
Gas Adsorption ◽  
Activated Carbon Fibers

Anomalous helium-gas-induced spin-lattice relaxation and the evidence for ultra micropores in microporous carbon

1995 ◽  
Vol 93 (4) ◽  
pp. 323-326 ◽  
Author(s):  
Atsuko Nakayama ◽  
Kazuya Suzuki ◽  
Toshiaki Enoki ◽  
Chiaki Ishii ◽  
Katsumi Kaneko ◽  
...  
Keyword(s):  
Lattice Relaxation ◽  
Microporous Carbon ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Helium Gas

On the Nature of the Native Defect ESR in Thin Diamond Films

1994 ◽  
Vol 339 ◽  
Author(s):  
J. Shinar ◽  
H. Jia ◽  
D. P. Lang ◽  
M. Pruski
Keyword(s):  
Relaxation Rate ◽  
Diamond Films ◽  
Stacking Faults ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Native Defect ◽  
Paramagnetic Centers ◽  
Dangling Bond ◽  
Spin Lattice ◽  
X Band

ABSTRACTThe X-band ESR of thin diamond films deposited from 99.5% H2/0.5% CH4 is compared to that of films similarly prepared from D2CD4 and H2/13CH4. The main line and the satellites at ±7.2 G are unaffected by annealing at T <. 1100°C, but their intensity is reduced upon annealing at T ∼ 1200°C. As the satellites are absent from the deuterated films, they are attributed to newly identified dangling bond-H centers, either on internal microvoid surfaces or embedded in the tetrahedral network. This is consistent with the 13C spin-lattice relaxation rate, which indicates that the distribution of paramagnetic centers is homogeneous to within ∼0.04 μm. However, they may be nonuniformly distributed on a finer scale, consistent with the concentrations in m ulti vacancies or stacking faults recently suggested by Fanciulli and Moustakas.

Activated Carbon Fibers Prepared by One-Step Activation with CuCl2 for Highly Efficient Gas Adsorption

2020 ◽  
Vol 59 (44) ◽  
pp. 19793-19802
Author(s):  
Liang Wang ◽  
Ji Li ◽  
Guoqiang Gan ◽  
Shiying Fan ◽  
Xin Chen ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Carbon Fibers ◽  
Gas Adsorption ◽  
Activated Carbon Fibers ◽  
Highly Efficient ◽  
One Step
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