Speaker: Dr. Erica L. Corral
Materials Science and Engineering Department
The University of Arizona, Tucson
Conventional ceramic matrix composites use one-dimensional fiber reinforcements in order to enhance toughness to brittle ceramics. Carbon materials such as carbon fiber, carbon nanotubes have already been shown to enhance toughness to ceramics. However, graphene, a two dimensional sheet of carbon shows tremendous promise for use as a reinforcement material in ceramic matrix composite systems due its two exceptional mechanical, electrical and thermal properties and unique structure. Our recent work shows that small graphene additions to silicon nitride enhance the toughness of monolithic ceramic by 235%. Our approach uses graphene platelets (GPL) that are homogeneously dispersed with silicon nitride particles and densified using spark plasma sintering at a densification temperature that enables the GPL to survive the harsh processing environment, as confirmed by Raman spectroscopy. We find that the 100 % alpha-silicon nitride fracture toughness increases from ~2.8 to ~6.6 MPa-m1/2 using ~1.5% GPL volume fraction while maintaining high hardness. Most interestingly novel toughening mechanisms were observed that show GPL wrapping and anchoring themselves around individual ceramic grains to resist sheet-pullout. The resulting cage-like graphene structures that encapsulate the individual grains were observed to deflect propagating cracks in not just two- but three-dimensions. Previous work using carbon nanotubes in silicon nitride will also be discussed in order to compare observed toughening behaviors in one- versus two-dimensional reinforcements in ceramics.
Dr. Erica L. Corral initiated her academic career in, August 2008, as an Assistant Professor of Materials Science and Engineering, at The University of Arizona, Tucson, Arizona. Her research programs are focused on advancing the fundamental understanding of high-temperature materials for use in extreme environmental applications. Her area of expertise focuses around the processing science and fundamental thermal and mechanical properties of ceramics and ceramic composites. Specifically, her research efforts investigate ultra-high temperature ceramics and coatings, carbon nanostructured reinforced ceramic matrix composites, and joining of ceramics for use in aerospace applications. Her postdoctoral training was conducted at Sandia National Laboratories, in the Ceramic Processing and Inorganic Materials Department, Albuquerque, NM. Her Doctor of Philosophy Degree is in Materials Science and her Bachelors of Science degree is in Metallurgical and Materials Engineering from William Marsh Rice University, and The University of Texas at El Paso, respectively. Her scholarly and teaching efforts have been recognized as the recipient of a National Science Foundation Early Faculty CAREER Award, and the Air Force Office of Scientific Research Young Investigator Program Award, the Hispanic Engineer National Achievement Award for the “Most Promising Engineer,” and the ASM International Bradley Stoughton Award for Young Teachers.