Ceramic materials often exhibit novel physical and chemical properties as their sizes approach nanometer dimensions. These new properties have inspired a variety of new applications in several fields, ranging from nanosensors to cathode materials for fuel cells and lithium batteries. As well, the possibility is opened for the development of new materials in response to the current energy problems such as the U.S. increasing demand for energy, dependence on foreign oils, and climate change. However, the optimization of nanoceramic processing is still a challenge, and understanding the fundamental concepts requires further research. Within this project, Prof. Castro focuses on the larger volume fraction of interfaces present in nanoceramics to improve processing control. He hypothesizes that manipulation of the interface composition can be used to change processing and product properties on a thermodynamic basis. In particular, Prof. Castro works on improving densification and phase transformation, two fundamental parts of processing, by controllably changing interface energies by tuning composition, enabling faster, less expensive, and more controlled processing and products. This unique thermodynamic approach is carried out by providing unprecedented data on interface energetics (rarely found in the literature) on technologically important materials, bringing those significant advances closer to industrial manufacturing. The project also has an important educational component that focuses on the promotion of engineering in middle and high-schools. The program, Materials&You, involves demonstrations of interesting processing and properties at school events to expose students to basic materials' concepts. Two high-schools with significant Latin American students and the underlying goal of getting all students to graduate have been selected.
TECHNICAL DETAILS: This project uses unique calorimetric techniques to measure interface energies of nanoceramics and use them to improve the control of sintering and phase transformation by monitoring and manipulating driving forces. The aim is to quantify the effects of dopants on the interface energies and correlate them with processing parameters and kinetics. The effect of dopants in processing is typically considered exclusively on a kinetic basis, but with the advent of high-resolution calorimetry available at the University of California at Davis laboratories (recently developed by the Prof. Castro and collaborators), Prof. Castro's group is capable of quantifying the effect of composition change on the energetics of the system, opening a new avenue for processing control. Within this project, high-temperature drop solution calorimetry is used to measure the interface energies (both surface and grain boundary) of three technologically relevant oxides: tin dioxide, zinc oxide, and zirconia, and those data correlated with sintering and polymorphic stability. The better understanding of the role of interface energetics and dopants in nanoceramic processing enables improvement of composition design in industries, enabling more energy and cost efficient products, with predictable phases/sizes/densities. From the educational perspective, students participating in the project are mentored and work with strategic materials and processes, providing training for their future careers as materials' professionals.
