Energetics of Nanomaterials
This project, ''Energetics of Nanomaterials'', represents a three-year collaboration among Alexandra Navrotsky (University of California at Davis), Brian Woodfield and Juliana Boerio-Goates (Brigham Young University) and Frances Hellman (University of California at San Diego). Its purpose has been to explore the differences between bulk materials, nanoparticles, and thin films in terms of their thermodynamic properties, with an emphasis on heat capacities and entropies, as well as enthalpies. We used our combined experimental techniques to address the following questions: How does energy and entropy depend on particle size and crystal structure? Do entropic differences have their origins in changes in vibrational densities of states or configurational (including surface configuration) effects? Do material preparation and sample geometry, i.e., nanoparticles versus thin films, change these quantities? How do the thermodynamics of magnetic and structural transitions change in nanoparticles and thin films? Are different crystal structures stabilized for a given composition at the nanoscale, and are the responsible factors energetic, entropic, or both? How do adsorption energies (for water and other gases) depend on particle size and crystal structure in the nanoregime? What are the energetics of formation and strain energies in artificially layered thin films? Do the differing structures of grain boundaries in films and nanocomposites alter the energetics of nanoscale materials? Of the several directions we first proposed, we initially concentrated on a few systems: TiO(sub 2), CoO, and CoO-MgO. In these systems, we were able to clearly identify particle size-dependent effects on energy and vibrational entropy, and to separate out the effect of particle size and water content on the enthalpy of formation of the various TiO(sub 2) polymorphs. With CoO, we were able to directly compare nanoparticle films and bulk materials; this comparison is important because films can be either 2 dimensional structures, limited by thickness, or can be dominated by nanoparticle granular behavior. These materials represent good model systems which are relevant to technological and geochemical applications as well as to the fundamental underlying science. The collaboration was both congenial and fruitful. We exchanged both samples and scholars among the laboratories. We met several times a year, rotating these meetings among the three institutions. We had frequent conference calls and were in constant email contact. We learned an immense amount from each other because we brought not just different methodologies but different disciplines to the project. In particular, the interplay of physics (Hellman), chemistry (Woodfield, Boerio-Goates, Navrotsky) and geochemistry (Navrotsky) viewpoints has been very enriching. The result has been a number of publications already in print, and several more in preparation, graduate student PhD and MS degrees, and undergraduate research students supported, as well as a well-developed collaboration that will lead to even more fruitful and important science in the coming years.
- Research Organization:
- Regents of the University of California, San Diego, CA
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- FG03-01ER15236
- OSTI ID:
- 898911
- Report Number(s):
- DOE/ER/15236-3; TRN: US200709%%489
- Country of Publication:
- United States
- Language:
- English
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