التفاصيل البيبلوغرافية
| العنوان: |
Adsorption of supercritical CO2 in aerogels as studied by small-angle neutron scattering and neutron transmission techniques. |
| المؤلفون: |
Melnichenko, Y. B., Wignall, G. D., Cole, D. R., Frielinghaus, H. |
| المصدر: |
Journal of Chemical Physics; 5/28/2006, Vol. 124 Issue 20, p204711, 11p, 16 Graphs |
| مصطلحات موضوعية: |
NEUTRON scattering, AEROGELS, ADSORPTION (Chemistry), POROUS materials, GLASS, SILICA, SUPERCRITICAL fluids, CARBON dioxide |
| مستخلص: |
Small-angle neutron scattering (SANS) has been used to study the adsorption behavior of supercritical carbon dioxide (CO2) in porous Vycor glass and silica aerogels. Measurements were performed along two isotherms (T=35 and 80 °C) as a function of pressure (P) ranging from atmospheric up to 25 MPa, which corresponds to the bulk fluid densities ranging from ρCO2∼0 to 0.9 g/cm3. The intensity of scattering from CO2-saturated Vycor porous glass can be described by a two-phase model which suggests that CO2 does not adsorb on the pore walls and fills the pore space uniformly. In CO2-saturated aerogels an adsorbed phase is formed with a density substantially higher that of the bulk fluid, and neutron transmission data were used to monitor the excess adsorption at different pressures. The results indicate that adsorption of CO2 is significantly stronger in aerogels than in activated carbons, zeolites, and xerogels due to the extremely high porosity and optimum pore size of these materials. SANS data revealed the existence of a compressed adsorbed phase with the average density ∼1.07 g/cm3, close to the density corresponding to closely packed van der Waals volume of CO2. A three-phase model [W. L. Wu, Polymer 23, 1907 (1982)] was used to estimate the volume fraction [lowercase_phi_synonym]3 of the adsorbed phase as a function of the fluid density, and gave [lowercase_phi_synonym]3∼0.78 in the maximum adsorption regime around ρCO2∼0.374 g/cm3. The results presented in this work demonstrate the utility of SANS combined with the transmission measurements to study the adsorption of supercritical fluids in porous materials. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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