Thermochemistry of Nanoceramics: Understanding and Controlling Densification and Grain Growth

University Of California-Davis, Davis CA

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Ceramic materials can exhibit unique physical and chemical properties when their feature size approaches nanometer dimensions. These properties have inspired a variety of applications in several fields and opened the development of solutions in response to current U.S. challenges such as the increasing demand for energy and national security. However, design and fabrication of optimal and durable ceramics at the nanoscale still face significant difficulties, and more understanding at the fundamental level of these processes is required. Within this project, Prof. Castro focuses on the larger volume fraction of interfaces present in nanoscaled ceramics to improve processing control by targeting modifications on their intrinsic thermodynamic properties. This approach challenges old paradigms in the field that infer thermodynamics is irrelevant on processing optimization, and offers opportunities for unprecedented breakthroughs. Prof. Castro works on the science behind products, i.e. the consolidation of powders. The goals are to enable faster, less expensive, and more controlled processing, and more durable materials. This research investigates a technologically-important material (magnesium aluminate). The project also has important education components that focus on the promotion of engineering in middle and high-schools; and training of undergraduate and graduate students in research and development. The K-12 program involves demonstrations of interesting processing and properties at school events to expose students to basic materials' concepts. The undergraduate program involves competitions and hands-on research opportunities in contemporary technologies, while the graduate students are directly involved in cutting-edge research. TECHNICAL DETAILS: This project uses highly-sensitive calorimetric techniques to measure interface energies of nanoscaled ceramics with the goal of improving the control of sintering and grain growth 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 University of California-Davis, 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 on a thermodynamic basis. Within this project, differential scanning calorimetry, oxide melt drop-solution calorimetry and water adsorption microcalorimetry are used to thermodynamically characterize magnesium aluminate properties ? a material of strategic interest for armor, laser, and refractory applications. The data is then correlated with sintering and grain growth behavior. A better understanding of the role of interface energetics and dopants in processing fosters improvement of composition design in industries, enabling more energy and cost efficient products, with more stable grain sizes (a key element on the control of ceramics? properties). From an education perspective, students participating in the project are being mentored, are working with strategic materials and processes, and are receiving training for their future careers as materials? professionals.