Theoretical aspects of the drying process from lyogel to xerogel film

3 Theoretical Aspects of the Drying Process from Lyogel to Xerogel Film 

In the next section typical experimental results for ceramic membranes are discussed. For a detailed discussion of all theoretical aspects the reader is referred to the extensive treatment by Brinker and Scherer [1]. 

A useful summary of the dr3dng literature is given by Simpkins et al. [14] and Fortes and Okos [20]. The drying of gels is treated by, e.g., Zarzycki [21] and by Dwivedi [22]. 

Initially the network is compliant in alkoxide derived gels and the small compressive forces cause it to contract into the liquid. The radius of the meniscus is much larger than the pore radius (Fig. 8.7a). As drpng proceeds the network becomes increasingly stiff, because particles come into contact, the porosity decreases, and the radius of the meniscus decreases continuously with a related increase of the capillary (compressive) force. Finally the radius of the 

The drying rate decreases for several reasons. In the first place the vapour pressure Py above a concave liquid meniscus with radius Pp decreases during the process. According to the Gibbs-Thomson (or Kelvin) equation Py is given by Eq. (8.4)  

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