Drying of alkoxide gels?Observation of an alternate phenomenology: Code: H6

摘要: The process of drying a porous material as per the current phenomenological theory can be divided into two stages. At first body shrinks by an amount equal to volume liquid that evaporates, and liquid-vapor interface remains at exterior surface body. second stage begins when becomes too stiff shrink recedes interior, leaving air filled pores near surface. We shall refer this phenomenology front model. In our investigation alkoxide silica gels less than 50 Angstroms pore radius, we have observed different pattern, in which even after gel stops shrinking, continues occur evaporation on body, causing spontaneous nucleation partially or fully dried opaque clusters, randomly distributed interior parts gel. These clusters increase number size till they coalesce form Upon further drying, returns its transparent form. postulate is possible only if rate fluid flow diffusion faster Darcy's flow, well cluster present results pin-hole experiments cylindrical showing for identical increased change from one exhibits both simultaneously finally phenomenology. also show effect distribution under conditions. Finally, will evidence successful large gels, conditions favoring desirable.