Pore size distribution in porous glass: fractal dimension obtained by calorimetry
Laboratoire de Physique des Solides, Université Paris-Sud, 91405 Orsay Cedex, France
Corresponding author: a firstname.lastname@example.org
Revised: 16 February 2001
Published online: 15 May 2001
By differential Scanning Calorimetry (DSC), at low heating rate and using a technique of fractionation, we have measured the equilibrium DSC signal (heat flow) of two families of porous glass saturated with water. The shape of the DSC peak obtained by these techniques is dependent on the sizes distribution of the pores. For porous glass with large pore size distribution, obtained by sol-gel technology, we show that in the domain of ice melting, the heat flow Jq is related to the melting temperature depression of the solvent, , by the scaling law: . We suggest that the exponent D is of the order of the fractal dimension of the backbone of the pore network and we discuss the influence of the variation of the melting enthalpy with the temperature on the value of this exponent. Similar D values were obtained from small angle neutron scattering and electronic energy transfer measurements on similar porous glass. The proposed scaling law is explained if one assumes that the pore size distribution is self similar. In porous glass obtained from mesomorphic copolymers, the pore size distribution is very sharp and therefore this law is not observed. One concludes that DSC, at low heating rate (C/min) is the most rapid and less expensive method for determining the pore distribution and the fractal exponent of a porous material.
PACS: 81.05.Rm – Porous materials; granular materials / 61.43.Hv – Fractals; macroscopic aggregates (including diffusion-limited aggregates)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001