Theory of pore formation in glass under tensile stress: Generalized Gibbs approach

A theoretical analysis is performed of the process of nucleation of a pore in small samples of an under-cooled diopside liquid, enclosed by a solid crystalline surface layer growing from the melt. Due to the density misfit of the crystal and liquid phases the growth of the crystalline layer leads to a uniform stretching of the encapsulated liquid. After reaching some critical values, the resulting tensile stress results in nucleation of a single pore. Nucleation of the pore is followed by its rapid growth, which decreases considerably the magnitude of elastic stresses and therefore eliminates the pre-condition for nucleation. This process has been analyzed earlier in terms of classical nucleation theory leading to a qualitatively correct interpretation. However, quantitatively, theoretical estimates performed in the framework of classical nucleation theory and experimental data differ. It is shown here that the generalized Gibbs approach results in a more adequate quantitatively correct description of the process of pore nucleation.