Interface and Surface Energetics of Nanocrystalline Oxides
Speaker: Dr. Ricardo Castro
Chemical Engineering and Materials Science Department
University of California, Davis
Surface and interface energies have postulated importance to several materials and chemical processes, such as catalysis, crystal growth, sintering, and polymorphism control. This importance is even more critical when dealing with nanostructured materials, where the interface-to-volume ratio is considerably higher and the interface term accounts for a much larger fraction of the total free energy. In this seminar we show how to assess the energetics of nanomaterials by using calorimetric approaches using techniques capable of generating unprecedented data for nanocrystalline oxides. In our research, we exploited these methods to provide a better understanding of the polymorphic stability of nanocrystalline titanium dioxide, and showed a critical thermodynamic dependence of the phase stability with the “aggregation state” of the nanoparticles. Moreover, we monitored the surface/interface energies differences induced by doping or processing conditions in different oxides, and showed the correlations between the energetic changes and observed properties, such as densification behavior or phase stability. Summarizing, we show that calorimetry is indeed a potential tool for the improvement of the nanoscale understanding and control on a thermodynamic basis.
Dr. Castrois an Assistant Professor at the Chemical Engineering and Materials Science Department at University of California, Davis. He has a degree in Molecular Sciences, and obtained his PhD in Metallurgical and Materials Engineering. From 2005 to 2009 he was a Professor at the Department of Materials Engineering at FEI University Center. He assumed the position at UC Davis in 2009 and coordinates now a laboratory dedicated to both science (thermochemistry) and technology of nanoceramics and nanocomposites. The interest of his research group is in the energetics of nanomaterials, radiation tolerant nanoceramics, and energy damping devices. He has received the NSF CAREER award for a research on the fundamental science of sintering, and the DOE Early Career Program award for a research on the correlation of interface energetic and the radiation tolerance of nanoceramics.