Symposium CP04: Interfacial Science and Engineering—Mechanics, Thermodynamics, Kinetics and Chemistry
Ricardo Castro, University of California-Davis
Nano-scale Effects on Grain Growth—Grain Boundary Energy and Velocity in Magnesium Aluminate
Written by Aashutosh Mistry
Most of the materials of engineering relevance are polycrystalline in nature. Desired properties of such materials strongly depend on the underlying grain structure, making the study of grain formation and growth scientifically important. With advances, it has become possible to create a grain structure with nanosized grains. Nanograins possess lucrative characteristics of increased grain boundary density, greater resistance to dislocation movement, and equivalently higher mechanical strength. At such small dimensions, interfacial effects are expected to play a crucial role; however, such effects remain poorly understood.
Ricardo Castro and his research group have been investigating the nanoscale effects on grain growth. The essential question is: do nanosized grains grow differently than the microsized ones? The researchers studied MgAl2O4 spinel as a model system. Since the grain growth is a thermally activated process, they carried out DSC (differential scanning calorimetry) measurements over different temperature ranges to obtain different average grain sizes. Over the course of such experiments, the heat release due to grain growth recorded which in turn gives a measure of surface energies for different grain sizes. Their experiments demonstrate higher surface energies for smaller grains and approaching to the nominal value for microsized grains. Their ongoing work deals with identifying the origins of such excess surface energy.