Stress capillary

Drying without the occurrence of large capillary stresses was obtained with supercritical drying in an autoclave. In this case a mean pore size was obtained which was twice that obtained under normal drying conditions and with a broad pore size distribution in accordance with the expectation for a noncompressed, random packing of particles. 

Finally, we note the value of rinsing the water-deposited film with methanol. As methanol is more volatile and has a lower surface tension, film cracking due to the capillary stresses exerted by the meniscus of the drying solvent on the walls of nanosized pores is reduced. Similar results have been reported by Goh.22 Films thicker than a few hundred nm exhibit cracks due to stresses that result during drying of the film, even after methanol treatment. Eliminating these cracks will require other modifications of the drying process. 

The total stress on the ceramic green body can be estimated from the temperature stress, pressure stress, and the capillary stress. The total radial and tangential stress at radius r in a spherical green body of radius R is given by [27]... 

The enhancement of the surface area of ccria-based materials related to the surfactant effect that reduces the surface tension inside the pores by decreasing capillary stress during drying and calcination processes. Better thermal stability is related to the structural arrangement and the morphology of the inorganic-organic... 

This capillary stress (see Eq. (8.3)) is related to, and usually smaller than, the developing drying stress (see below). The larger the capillary stress the larger the drying stress which reaches its maximum at or just after the critical point (see Eq. (8.7). 

With mild drying conditions the presence of capillary stresses might contribute to interparticle "bonds", at harsh drying conditions (20% RH, 90°C) this is not the case. 

If the surface tension coefficient is not constant along the interface between two nonmixing fluids, then there arise additional tangential stresses on the interface they are referred to as capillary stresses and can substantially affect the motion of the fluid or even solely determine it in the absence of gravitational and... 

These results, are rather general. They cover all cases in which the capillary stresses on the drop surface are stationary and do not depend on the motion of the fluid. Formulas (5.10.8) and (5.10.9), which were derived for Pe = 0, can be obtained from (5.10.11) and (5.10.12) for specific functions a. 

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