On the condensation/evaporation pressures and isosteric heats for argon adsorption in pores of different cross-sections

Wang, Yao; Do, D.D.; Herrera, Luis Fernando Castillo; Nicholson, D.

doi:10.1016/j.colsurfa.2012.12.033

Cited by 7 publications

(10 citation statements)

References 29 publications

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“…No other significant differences in adsorption are observed and the normalized loops exhibit essentially the same shape, considering the much enlarged scale of the graph and the simplicity of the normalization procedure. This conclusion agrees with recent computer simulations of Ar adsorption in the open pores of nanometer size (∼10 nm) and with circular or triangular cross sections . The basis chosen for a quantitative comparison between pores of different shape is that they have the same surface area per unit volume.…”

Section: Resultssupporting

confidence: 89%

“…This conclusion agrees with recent computer simulations of Ar adsorption in the open pores of nanometer size (∼10 nm) and with circular or triangular cross sections. 51 The basis chosen for a quantitative comparison between pores of different shape is that they have the same surface area per unit volume. At low pressures, the adsorption isotherms look different and the adsorbed mass on open triangular pores is larger than that on open circular pores.…”

Section: ■ Resultsmentioning

confidence: 99%

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Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography

et al. 2017

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Adsorption on nanoporous matrices is characterized by a pronounced hysteresis loop in the adsorption isotherm, when the substrate is loaded and unloaded with adsorbate, the origin of which is a matter of immense debate in the literature. In this work, we report a study of argon adsorption at 85 K on nonconnecting nanopores with one end closed to the surrounding where the effects of different pore cross sections fabricated by electron beam lithography (EBL) are investigated. A polymethylmethacrylate (PMMA) resist is deposited on the electrodes of a sensitive quartz crystal microbalance without degradation of the resonance quality factor or the long-term and short-term stabilities of the device even at cryogenic temperatures. Four different pores' cross sections: circular, square, rectangular, and triangular, are produced from EBL, and the isotherms for these pore shapes exhibit pronounced hysteresis loops whose adsorption and desorption branches are nearly vertical and have almost the same slopes. No difference is observed in the hysteresis loops of the isotherms for the pores with triangular and square cross sections, whereas the hysteresis loop for the pore with circular cross sections is much narrower, suggesting that they are more regular than the other pores. All of these observations suggest that the hysteresis behavior resulted mainly from microscopic geometric irregularities present in these porous matrices.

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Section: Resultssupporting

confidence: 89%

Section: ■ Resultsmentioning

confidence: 99%

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography

et al. 2017

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“…These results are consistent with the data reported by other researchers. 44,45 This can be attributed to the fact that at low adsorbed amount, the enthalpy change associated with adsorption mainly arises from the contribution of solid−fluid interaction as the fluid molecules are adsorbed at the solid substrate. On the other hand, at larger adsorbed amounts, the enthalpy change mainly arises from the fluid−fluid interaction.…”

Section: Langmuirmentioning

confidence: 99%

Molecular Simulation of Sorption-Induced Deformation in Atomistic Nanoporous Materials

et al. 2019

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HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…The GCMC method utilizes the general statistical mechanical relationship between the differential entropy and enthalpy and the fluctuations of the adsorbate density and energy in the course of simulation. The GCMC method has been employed widely to calculate the isosteric heat of adsorption of simple fluids on carbons, ,− zeolites, − and mesoporous materials. − Most of reported GCMC simulations are based on the idealized models of homogeneous surfaces and pore walls neglecting geometrical and energetic heterogeneity. This is why the simulation results agreed with the experimental only in the case of crystalline surfaces like graphite and highly graphitized carbons. , The importance of direct accounting of surface heterogeneity in GCMC simulations was recently shown by Kowalczyk et al drawing on the example of hybrid reverse MC structural models of highly graphitized and disordered carbon surfaces.…”

Section: Introductionmentioning

confidence: 99%

Determination of Isosteric Heat of Adsorption by Quenched Solid Density Functional Theory

et al. 2017

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The heat of adsorption is one of the most important parameters characterizing energetic heterogeneity of the adsorbent surface. Heats of adsorption are either determined directly by calorimetry or calculated from adsorption isotherms measured at different temperatures using the thermodynamic Clausius-Clapeyron equation. Here, we present a method for calculating the isosteric heat of adsorption that requires as input only a single adsorption isotherm measured at one temperature. The proposed method is implemented with either nonlocal (NLDFT) or quenched solid (QSDFT) density functional theory models of adsorption that are currently widely used for calculating pore size distributions in various micro- and mesoporous solids. The pore size distribution determined from the same experimental isotherm is used for predicting the isosteric heat. The QSDFT method has advantages of taking into account two factors contributing to the structural heterogeneity of adsorbents: the molecular level roughness of the surface and the pore size distribution. The method is illustrated with examples of low temperature nitrogen and argon adsorption on selected samples of carbons of different degree of graphitization and MCM-41 mesoporous silicas of different pore size. The isosteric heat predictions from the NLDFT and QSDFT methods are compared against relevant experiments and the results of Monte Carlo (MC) simulations, with good agreement found in the cases where the surface model adequately reflects the pore surface roughness. Analyses with the QSDFT method show that the isosteric heat of adsorption significantly depends of the molecular level roughness of the adsorbent surface, which is ignored in NLDFT and MC models. The proposed QSDFT method with further verification can be used for calculating the isosteric heat as an additional parameter characterizing the adsorbent surface in parallel with routine calculations of the pore size distribution from a single adsorption isotherm.

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On the condensation/evaporation pressures and isosteric heats for argon adsorption in pores of different cross-sections

Cited by 7 publications

References 29 publications

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography

Molecular Simulation of Sorption-Induced Deformation in Atomistic Nanoporous Materials

Determination of Isosteric Heat of Adsorption by Quenched Solid Density Functional Theory

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