| Abstract Scope |
Nanomaterials are considered metastable structures due to the excess energy coming from the interfacial regions. These energies include surfaces and grain boundaries, and can significantly increase the overall energy of the system due to the unsatisfied bonds and ionic coordination. A fair description of nanoscale thermodynamics must thus include interfacial energies in addition to bulk energies used in conventional phase diagrams. Not surprisingly, similarly to bulk thermodynamics, interfacial energies also vary with composition and crystallographic structures. As a result, the thermodynamics of nano-oxides is not simple to assess, and determining the ‘meta’ stable phase requires a combination of interfacial energies and microstructure (particularly surface and grain boundary areas). Here we present a series of microcalorimetric data which reveal polymorphic energetic trends in nano-oxides. Zirconium based oxides are initially used as the foundation for the analyses, but we further introduce new data for other functional oxides, including TiO2 and LiMn2O4. |