Analysis of adsorption isotherms of water vapor for nonporous and porous adsorbents

Naono, Hiromitu; Hakuman, Masako

doi:10.1016/0021-9797(91)90371-e

Cited by 63 publications

(47 citation statements)

References 10 publications

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“…While most authors have observed a decrease in the porosity accessible to water [1] [2], this result can not explain the increase in the gas permeability observed by some authors [1] [3]. Some investigators believe that the water molecule, because of its small radius of 0.1 nm [4], can penetrate not only into meso and macro pores (radius larger than 2 nm) but also into nano-and micropores [5]. Hence, the water porosity decreases after carbonation means that the totality of pores decreases, but no specific information about the meso and macro pores, the porous domains which influence the gas permeability, can be drawn.…”

Section: Introductioncontrasting

confidence: 41%

“…The increase in the volume of the solid phase can be explained by the formation of CaCO 3 during carbonation. Because the carbonation of one mole of portlandite leads to an increase in volume of 4 cm 3 [13] [14], and the carbonation of one mole of C-S-H leads to an increase in volume of 12 cm 3 [15] or 39 cm 3 /mol [4], the CaCO 3 clogs the pores, thereby decreasing the porosity.…”

Section: Solid Phase Volume Determined By Helium Pycnometrymentioning

confidence: 99%

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Influence of Microstructural Changes on Some Macro Physical Properties of Cement Mortar during Accelerated Carbonation

Phạm¹

2014

OJCE

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The objective of this work was to examine the changes in the microstructure and macro physical properties caused by the carbonation of normalised CEM II mortar. Samples were prepared and subjected to accelerated carbonation at 20˚C, 65% relative humidity and 20% CO2 concentration. On the microstructure scale, the evolutions of the cumulative pore volume, pore size distribution, and specific surface area during carbonation were calculated from the adsorption desorption isotherms of nitrogen. We also examined the evolution of macro physical properties such as the solid phase volume using helium pycnometry, porosity accessible to water, gas permeability, and thermal conductivity. The conflict between nitrogen porosity and water porosity results indicated that the porous domains explored using these two techniques are different and help to complementarily evaluate the effects of carbonation. This is a multi-scale study where results on microstructural changes can help to explain the evolution of macro physical properties.

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Section: Introductioncontrasting

confidence: 41%

Section: Solid Phase Volume Determined By Helium Pycnometrymentioning

confidence: 99%

Influence of Microstructural Changes on Some Macro Physical Properties of Cement Mortar during Accelerated Carbonation

Phạm¹

2014

OJCE

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“…Eq. [16]). In our adsorption apparatus, the reliable CCl 4 isotherms at temperatures close to ambient can be measured in the pressure range of P/P 0 = 0.8-0.97 without difficulty (cf.…”

Section: Introductionmentioning

confidence: 93%

A New Method of Calculating Pore Size Distribution: Analysis of Adsorption Isotherms of N2 and CCl4 for a Series of MCM-41 Mesoporous Silicas

Hakuman

Naono

2001

Journal of Colloid and Interface Science

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“…The n mon is the number of adsorbed molecules in one full monolayer per unit area, r A is the cross-sectional area, and m is the diameter of the adsorbate molecule (for water, r A is 0.77 nm 2 and m is approximately 2.75 Å ) [14,15]. The typical values of C and n mon for different materials have been measured and it was shown that the film thickness is strongly dependent on the hydrophilicity of the adsorbent [16]. The C values used further for non-porous a-alumina and silica are 28 and 11 and the corresponding n mon values are 6.5 and 3.6 molecules per nm 2 , respectively [9,16].…”

Section: Theoretical Modelmentioning

confidence: 99%

“…The typical values of C and n mon for different materials have been measured and it was shown that the film thickness is strongly dependent on the hydrophilicity of the adsorbent [16]. The C values used further for non-porous a-alumina and silica are 28 and 11 and the corresponding n mon values are 6.5 and 3.6 molecules per nm 2 , respectively [9,16]. The BET isotherm for silica is shown in Fig.…”

Section: Theoretical Modelmentioning

confidence: 99%

On the Transition from Bulk to Ordered Form of Water: A Theoretical Model to Calculate Adhesion Force Due to Capillary and van der Waals Interaction

2013

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The adhesion force due to capillary interaction between two hydrophilic surfaces is strongly dependent on the partial pressure of water and is often calculated using the Kelvin equation. The validity of the Kelvin equation is questionable at low relative humidity (RH) of water, like in high vacuum and dry nitrogen environments, where water is only present as layers of several molecules thick at the surfaces. A model from ordered to bulk form of water has been developed using the Brunauer, Emmett, and Teller adsorption model. The results show that the adhesion force calculated using the Young-Laplace and Kelvin equations at low (5-30 %) RH is underestimated. The total adhesion force shows changes when the RH is changed from 0 to 100 %. In dry conditions, at RH below 10 %, the total adhesion force is contributed by the van der Waals interaction due to solid-solid contact. The total adhesion force then increases and remains constant being equal to the superposition of van der Waals interaction due to solidsolid contact and van der Waals interaction due to adsorbed water layers on the surfaces. The total adhesion force further increases slowly with the increase in RH incorporating capillary forces and then decreases at very high RH due to screening of van der Waals forces. This change in adhesion force occurs from solid-solid interaction to ordered form of water at low RH and from ordered form to bulk form of water at high RH along with the screening effect of van der Waals interaction. The results have been compared with the experiments and it has been seen that at small length scales, the model is in agreement with the existing experimental data. However, at large length scales roughness of the surfaces should be taken into account.

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Analysis of adsorption isotherms of water vapor for nonporous and porous adsorbents

Cited by 63 publications

References 10 publications

Influence of Microstructural Changes on Some Macro Physical Properties of Cement Mortar during Accelerated Carbonation

Influence of Microstructural Changes on Some Macro Physical Properties of Cement Mortar during Accelerated Carbonation

A New Method of Calculating Pore Size Distribution: Analysis of Adsorption Isotherms of N2 and CCl4 for a Series of MCM-41 Mesoporous Silicas

On the Transition from Bulk to Ordered Form of Water: A Theoretical Model to Calculate Adhesion Force Due to Capillary and van der Waals Interaction

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