The measurement of a potential difference between two surfaces of zirconia is reported, when a normal stress is applied to one surface, leaving the other surface stress free. The potential difference ...is proportional to the applied stress over a wide range. The proportionality constant represents a new thermodynamic measurement of the interfacial state because the measurement is reversible and independent of temperature. In zirconia, the proportionality constant is related to the volume and the charge on the oxygen ion by considering thermodynamic equilibrium among the electrochemical potentials of the oxygen ion at the stressed and unstressed interfaces. The agreement with theory is within 10% for specimens made of polycrystalline zirconia, or single crystal cubic zirconia of (100) orientation. The proportionality constant changes by up to 20% for other orientations of the single crystal; this change is attributed to differences in the effective charge on the oxygen ion on different surface orientations. The kinetics of the voltage response was also investigated in detail; it is consistent with the diffusion of the oxygen ion along the interface formed between the metal electrode and the zirconia surface. The present measurements provide the first experimental confirmation of the fundamental relationship between the chemical potential, the normal traction, and the atomic volume of species at interfaces of crystalline materials. The measurement has implications in further understanding of diffusional creep, creep cavitation and sintering in ionic (or partially ionic) solids.
Many important systems feature strongly curved interfaces with low surface tension. Four examples are micelles, emulsions, giant bilayer vesicles, and biological membranes. A fifth is the microbubble ...nuclei that initiate cavitation in aqueous media. A model describing these nuclei and how they respond to changes in ambient pressure attributes their remarkable resiliency to a surrounding film of surface-active molecules. An independent derivation of this model is obtained in this paper by applying thermodynamic methods formulated recently to describe strongly curved amphiphilic interfaces. This illuminates previous models for microbubble nuclei and provides additional information on the mechanical and thermodynamic properties of interfaces in general.
The effect of capillarity on the chemical potential in interfaces Rabkin, E.; Estrin, Y.; Gust, W.
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
06/1998, Letnik:
249, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
A theory of the effect of curvature on the chemical potential of atoms inside an interface, e.g. a grain boundary, is developed under the assumption that the interface is an ideal source or sink for ...vacancies. Three simple geometries are considered to illustrate the theory. Corrections to the chemical potential appear already in the first order in curvature. The magnitude of the correction term depends on the elastic properties of the phases forming the interface, its intrinsic structure and the relative size of the grains it separates. For migrating interfaces between dissimilar phases, the correction depends on the diffusivities and the molar volumes of the two phases, rather than on their elastic moduli. The implications of the theory for fine-grained materials are discussed.
PDF