Structural characterization of heat-treated activated carbon fibers

Abstract

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 T m ~ 1200 °C, which is well below the J H T 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.

Synthesis of nanoporous carbons from mixtures of coal tar pitch and furfural and their application as electrode materials

“…On the other hand, it is also known that heating at high temperature may favour internal rearrangements in the carbon structure, which depending on the carbon precursor can end up with an increase in the electrical conductivity if graphitic-like domains are created during the rearrangements. However, thermal treatment may also cause important modifications in the textural and structural properties of the carbon skeleton (annealing effects) [31,32] thus it becomes necessary to investigate the porosity of the samples after thermal treatment. The results show a decrease in the surface area and pore volumes of the treated carbons, which is more important in the case of F55H (treated at a highest temperature), and more precisely in the mesopore volume.…”

Improved phenol adsorption on carbons after mild temperature steam reactivation

“…This was further corroborated by the similar values of micropore volumes W 0,CO2 as compared to the as-received sample. Hence, minor modifications observed are attributed to a somewhat collapse of the pore walls as a consequence of the heat treatment (structural annealing) [5,21].…”

New solid polymer electrolytes based on PEO/PAN hybrids

“…PAN, which consists of a saturated carbon backbone with a nitrile group on alternate carbon atoms, is a wellknown precursor for conducting polymer 15 and carbon fiber. 16 Thermally treated PAN films show a rich evolution of structural as well as electronic properties. The polymer chains undergo cyclization at temperature above 200°C to form a conjugated-chain chemical structure, 17 which exhibits very good mechanical properties.…”