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Adsorption of supercritical in aerogels as studied by small-angle neutron scattering and neutron transmission techniques
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10.1063/1.2202324
/content/aip/journal/jcp/124/20/10.1063/1.2202324
http://aip.metastore.ingenta.com/content/aip/journal/jcp/124/20/10.1063/1.2202324
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Coexistence curve of bulk calculated using NIST-12 software (Ref. 20). Lines show thermodynamic paths studied in this work.

Image of FIG. 2.
FIG. 2.

Density variation of from bulk at .

Image of FIG. 3.
FIG. 3.

Density variation of at two temperatures specified in the inset. Experimental and calculated via Eq. (9) transmissions of bulk at different fluid densities (sample thickness of ) are also shown.

Image of FIG. 4.
FIG. 4.

Density variation of the correlation length at two temperatures specified in the inset.

Image of FIG. 5.
FIG. 5.

Neutron cross section of empty aerogels. The lines are fits to Eq. (20).

Image of FIG. 6.
FIG. 6.

Neutron cross section of Vycor porous glass saturated with at . Fluid densities are shown in the inset.

Image of FIG. 7.
FIG. 7.

vs density of at two different temperatures specified in the inset.

Image of FIG. 8.
FIG. 8.

from saturated nonoxidized aerogel at as a function of density.

Image of FIG. 9.
FIG. 9.

(A) as a function of the pressure at . (B) vs at two temperatures specified in the inset ( saturated oxidized aerogel).

Image of FIG. 10.
FIG. 10.

(A) as a function of the pressure at . (B) vs at two temperatures specified in the inset ( saturated nonoxidized aerogel).

Image of FIG. 11.
FIG. 11.

Transmission of oxidized aerogel vs (A) fluid pressure and (B) density of saturating at two temperatures specified in the inset. As is pointed out in the text, the total transmission of blank oxidized aerogel is lower than that of silica in aerogel strands due to additional attenuation of neutron beam by hydrogen nuclei contained in adsorbed moisture and methoxy groups on the aerogel surface. Dashed line is transmission of the imaginary two-phase system (no adsorbed phase) calculated using Eq. (9). Arrows show calculated transmission of the three-phase system at maximal adsorption (see explanations in the text).

Image of FIG. 12.
FIG. 12.

Transmission of nonoxidized aerogel vs (A) fluid pressure and (B) density of saturating at two temperatures specified in the inset. As is pointed out in the text, the total transmission of blank nonoxidized aerogel is lower than that of silica in aerogel strands due to additional attenuation of neutron beam by hydrogen nuclei contained in adsorbed moisture and methoxy groups on the aerogel surface. The transmission of blank nonoxidized aerogel is lower than transmission of blank oxidized aerogel as oxidation removes a fraction of methoxy groups from the aerogel surface at high temperature. Dashed line is transmission of an imaginary two-phase system (zero adsorbed phase) calculated using Eq. (9). Arrows show calculated transmission of the three-phase system at maximal adsorption (see explanations in the text).

Image of FIG. 13.
FIG. 13.

Excess adsorption of in oxidized and nonoxidized aerogels as a function of the fluid density at two temperatures specified in the inset. Data for are not shown for reasons explained in the text.

Image of FIG. 14.
FIG. 14.

Typical Kratky plots for saturated oxidized aerogel at and different fluid densities specified in the inset.

Image of FIG. 15.
FIG. 15.

Scattering invariant of saturated oxidized aerogel as a function of the fluid density. Solid line is the scattering invariant of an imaginary two-phase system (zero adsorption) calculated using Eq. (15). Dashed line is extrapolation to at which scattering invariants of the two- and three-phase systems become identical.

Image of FIG. 16.
FIG. 16.

Variation of the volume fraction of the adsorbed phase in oxidized and nonoxidized aerogels as a function of . Calculations are made using Eqs. (17) and (18) under an assumption that the density of adsorbed phase is and does not depend on . Data for are not shown for reasons explained in the text.

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/content/aip/journal/jcp/124/20/10.1063/1.2202324
2006-05-26
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Adsorption of supercritical CO2 in aerogels as studied by small-angle neutron scattering and neutron transmission techniques
http://aip.metastore.ingenta.com/content/aip/journal/jcp/124/20/10.1063/1.2202324
10.1063/1.2202324
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