Relationship between pore connectivity and mean pore size in modulated mesoporous vanado-phosphoro-aluminates and some similarities with the branching of trees

 
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Relationship between pore connectivity and mean pore size in modulated mesoporous vanado-phosphoro-aluminates and some similarities with the branching of trees (EN)

Pomonis, P. J. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Pomonis, P. J. (EN)

Sixteen mesoporous vanado-phosphoro-aluminate solids, of the general formula Al100PXVY (X, Y = 0, 5, 10, 20), have been prepared and characterized by their N-2 adsorption/desorption isotherms. The materials were truly mesoporous, and the addition of P and/or V affects in a very precise and profound way the corresponding specific surface areas SP (m(2) g(-1)), specific pore volumes (cm(3) g(-1)), the mean hydraulic pore diameter d(p) (4V(p)/S-p) (nm), the maximum of the pore size distribution (psd) d(max) (nm), and the full width at half-maximum (fwhm) (nm) of the psd. The pore connectivity c was also determined and the dimensionality D-cc of adsorption was estimated in the pressure range where capillary condensation of N-2 in the pores takes place. The dimensionality D-cc was found to be related to the d(max), reduced over the fwhm, via the relation D-cc approximate to 3.7(d(max)/fwhm). The two parameters, dimensionality D-cc and connectivity c, are also related to each other via the simple relation log proportional to -1.83 log D-cc, which in turn results in the relation log c proportional to -1.83 log(d(max)/fwhm). A parallelism is drawn between the connectivity of pores in solids and its relation to the pore size, on one hand, and the degree of branching b of trees and its relation with the branch diameter d(k), on the other. Using allometric relations already established for such hierarchically developed natural systems, that is, trees, we reach a relation between b and d(k) of the form log b proportional to -2.34 log(d(k,max)/2d(mean)) where d(k,max) is the average diameter of the higher order (thinner) branches in a typical tree and d(mean) is the arithmetic mean diameter of all branches of that tree. The reasons for these similarities are discussed. (EN)

nitrogen sorption measurements (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Langmuir (EN)

Αγγλική γλώσσα

2001

<Go to ISI>://000172956200069

American Chemical Society (EN)



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