Characterization of activated carbon fibers using argon adsorption

Nguyen, Thanh X.; Bhatia, Suresh K.

doi:10.1016/j.carbon.2004.11.004

Cited by 34 publications

(45 citation statements)

References 37 publications

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“…Recent studies have also stressed the importance of fluctuations in pore wall thickness on the adsorption potential [22,1]. Regardless of wall thickness, though, narrow pores tend to have deeper potential wells.…”

Section: Discussionmentioning

confidence: 99%

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Purewal¹,

Kabbour²,

Vajo³

et al. 2009

Nanotechnology

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Pore size distributions (PSD) and supercritical H 2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H 2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H 2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference.

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Section: Discussionmentioning

confidence: 99%

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Purewal¹,

Kabbour²,

Vajo³

et al. 2009

Nanotechnology

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“…Consequently, for systems similar to that investigated in this work adsorption equilibrium of argon at 87 K but not nitrogen at 77 K may be reached at practical time scales. In order to experimentally illustrate this case, we compare pore size distribution (PSD) extracted from experimental nitrogen and argon adsorption isotherms at 77 K and 87 K in a glassy carbon, reported by Pérez-Mendoza et al (2006), and activated carbon fiber ACF15, reported in our previous work (Nguyen and Bhatia 2005). From Figs.…”

Section: Determination Of Pore Connectivity In Structural Model Of Samentioning

confidence: 99%

“…A glassy carbon (P3M), reported by Pérez-Mendoza et al (2006), and activated carbon fiber ACF15, reported in our previous work (Nguyen and Bhatia 2005), were degassed at 300 • C overnight prior to nitrogen and argon adsorptions at 77 K and 87 K. A Micromeritics ASAP 2010 volumetric adsorption analyzer was used to obtain nitrogen and argon adsorption data at 77 K and 87 K in these carbons.…”

Section: Experimental Studymentioning

confidence: 99%

Pore accessibility of N2 and Ar in disordered nanoporous solids: theory and experiment

Nguyen

Bhatia

2007

Adsorption

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Recently (Nguyen and Bhatia, J. Phys. Chem. C 111:2212-2222, 2007 we have proposed a new algorithm utilising cluster analysis principles to determine pore network accessibility of a disordered material. The algorithm was applied to determine pore accessibility of the reconstructed molecular structure of a saccharose char, obtained in our recent work using hybrid reverse Monte Carlo simulation (Nguyen et al., Mol. Simul. 32:567-577, 2006). The method also identifies kinetically closed pores not accessed by adsorbate molecules at low temperature, when their low kinetic energy cannot overcome the potential barrier at the mouths of pores that can otherwise accommodate them.In the current work, the results are validated by transition state theory calculations for N 2 and Ar adsorption, showing that N 2 can equilibrate in narrow micropores at practical time scales at 300 K, but not at 77 K. Large differences between time scales for micropore entry and exit are predicted at low temperature for N 2 , the latter being smaller by over three orders of magnitude. For N 2 at 77 K the time constant for pore entry exceeds 3 hr., while for exit it is 134 days. At 300 K these values are smaller than 1 µs, indicating good accessibility at this temperature. These results are verified by molecular dynamics simulations, which reveal that while N 2 molecules enter and leave all pores frequently at 300 K, entry and exit events for apparently inaccessible pores are absent at 77 K. For Ar at 87 K better accessibility is evident for the saccharose char compared to N 2 at 77 K. This finding is now experimentally shown in this work by comparison of pore size distributions obtained from experimental nitrogen adsorption isotherms of nitrogen and argon at 77 K and 87 K.

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“…Further, the simulation-based PSDs of the HRMC constructed models obtained from FWT-DFT seem to follow the trends of SANS and helium-probed geometric PSDs which do not possess the very strong peak at 4.4 Å, as opposed to the experiment-based PSD from DFT. This peak is repeatedly detected in PSDs obtained from DFT based on interpretation of experimental argon adsorption for similar materials [25,36,37,45,[48][49][50][51]. However, our simulation-based PSDs from FWT-DFT suggest that this strong first peak is an artifact of inaccessibility to argon at 87 K. Thus, an exaggerated first peak at ~4.5 Å is observed in the experimental Ar isotherm-based PSD, and this occurs when smaller ultra-micropores that are inaccessible at low pressures on the experimental time scale are rapidly filled at higher than true equilibrium pressures.…”

Section: Structural Characterization Of the Hrmc Constructed Modelsmentioning

confidence: 99%

Hybrid Reverse Monte Carlo simulation of amorphous carbon: Distinguishing between competing structures obtained using different modeling protocols

Farmahini

Bhatia

2015

Carbon

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Please cite this article as: Farmahini, A.H., Bhatia, S.K., Hybrid reverse monte carlo simulation of amorphous carbon: Distinguishing between competing structures obtained using different modelling protocols, Carbon (2014), doi: http://dx.doi.org/10.1016/j.carbon. 2014.11.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ABSTRACTWe explore different multi-stage and multi-constraint modelling strategies using the Hybrid Reverse Monte Carlo (HRMC) technique to develop realistic models for the amorphous structure of silicon carbide derived-carbon, and investigate the effect of modelling parameters on the development of nano-structural features of the constructed models. It is shown that application of long simulations with slow thermal quench rate is essential for modelling of amorphous structures. Nevertheless, very slow quenching rates are shown to lead to the formation of configurations with large fraction of sp 2 carbon, lacking the level of disorder required to match structure-related experimental data. The predicted gas adsorption isotherms are very sensitive to the pore size distribution (PSD), thus the final structure must reasonably reproduce the total pore volume and pore size distribution of the experimental sample. The frequently-observed strong first peak of the DFT-based PSD obtained from argon adsorption is shown to be an artifact of argon inaccessibility. Pore accessibility analysis of the constructed models, as well as MD simulations of gas transport demonstrate that the HRMC constructed structures contain short-range structural anisotropy, however the models are successful in capturing the long range internal energy barriers of amorphous carbon for methane.

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Characterization of activated carbon fibers using argon adsorption

Cited by 34 publications

References 37 publications

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Pore accessibility of N2 and Ar in disordered nanoporous solids: theory and experiment

Hybrid Reverse Monte Carlo simulation of amorphous carbon: Distinguishing between competing structures obtained using different modeling protocols

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