Exploring Fundamental Responses and Limits of Precipitation Processes for the Synthesis of Nanopowders of Unique Morphologies
Olivia Graeve, Ph.D.
Associate Professor of Materials Science and Engineering, Kazuo Inamori School of Engineering at Alfred University
Abstract: This talk will present an overview of fundamental responses and limits of precipitation processes for the synthesis of nanostructured ceramic nanopowders, with special emphasis on reverse micelle synthesis for the preparation of oxides and co-precipitation for the preparation of metals. Application of the materials for IR windows and nanofluidics will also be described. We will present an analysis and systematic investigation of the structure and stability of reverse micelle systems with the addition of NH4OH, ZrOCl2, and Al(NO3)3 salts. The concept of an electrical double layer, as it applies to reverse micelles, will be considered for explaining features of destabilization, including the initial decrease in reverse micelle size, the destabilization concentration, and the effect of cation valence. We propose that the reduction in size prior to instability is caused by compression of the reverse micelle electrical double layers, as higher concentrations of salts are present. All these effects have important implications for the preparation of nanopowders by reverse micelle synthesis. If the reverse micelles are unstable before the precipitates are formed then the advantage of reverse micelle synthesis is immediately lost. We will also present an analysis of powder agglomeration and thermal conductivity in copper-based nanofluids. Our results show that the use of surfactants during synthesis of copper nanopowders has important consequences on the dispersion of the powders in a base fluid. The thermal conductivity enhancement in our nanofluids exhibit a linear relationship with powder loading for an average particle size of ~100 nm and similar particle size distributions that range from ~50 to 650 nm, but independent of crystallite size and with all other factors maintained constant (surface area, surface additives, levels of oxidation) such that a 0.55 vol.% loading results in a thermal conductivity enhancement of 22% over water and a 1.0 vol.% loading results in a thermal conductivity enhancement of 48% over water. This study is the first to propose a definite correlation between a carefully determined particle size distribution from dynamic light scattering and the thermal conductivity enhancement of a nanofluid with respect to nanopowder loading in the base fluid.
Biosketch: Prof. Graeve holds a Ph.D. in Materials Science and Engineering from the University of California, Davis, and a Bachelor’s degree in Structural Engineering from the University of California, San Diego. Her area of research focuses on fundamental studies of the synthesis and processing of nanostructured materials, including ceramic and metallic nanomaterials and amorphous/nanocrystalline composites for both structural and functional applications, with a special emphasis on electromagnetic multifunctional materials for sensors and energy applications. She has published over 50 papers, which include research contributions and pedagogy and curriculum development contributions, as well as two book chapters. She has been involved in many activities related to the recruitment and retention of women and Hispanic students in science and engineering and has received several prestigious awards including the National Science Foundation CAREER award, the 2006 Hispanic Educator of the Year award of the Society of Hispanic Professional Engineers, the 2010 Karl Schwartzwalder Professional Achievement in Ceramic Engineering Award by the American Ceramic Society, and the 2011 Society of Hispanic Professional Engineers “Jaime Oaxaca” Award.