Abstract:
The properties of ceramics are governed by a combination of intrinsic crystallographic and extrinsic microstructural characteristics. Microstructural characteristics, such as grain size/morphology/orientation, the amount and distribution of porosity and grain boundary phases, have pronounced effects on mechanical and non-mechanical properties. The advent of seeding and templated grain growth (TGG) processes has enabled access to a variety of unique bulk textured ceramics.
TGG allows us to mimic the microstructural characteristics of fracture resistant composites found in nature such as mollusk shells, bone and teeth. Nature uses combinations of inorganic and organic phases to achieve unique structural characteristics like high fracture toughness and large stain to failure. We demonstrate how different microstructural elements of differing connectivities (2:2, 1:3 and 0:3) can be processed in situ by TGG in a single phase material to yield flaw tolerant ceramic microstructure composites that are similar in fracture behavior to natural occurring composites. Alumina composites with high strength (~425 MPa) and high load retention (up to 0.5 mm deflection in 4-point bending in a 1.5 mm thick x 2 mm wide x 25 mm alumina composite) were designed in 2:2 composites. This non-catastrophic failure behavior is directly tied to crack deflection and bifurcation along basal surfaces of templated textured layers. I discuss how properties of the textured layers can be modified to enhance the load to failure in alumina microstructure composites and about how this approach can be applied to other systems. Evidence of flaw tolerance will be discussed in terms of indentation-strength measurements and the occurrence of multiple crack initiation and crack arrest.
In the second part of the presentation I will discuss recent efforts to achieve enhanced piezoelectric properties of K0.5Na0.5NbO3 and PMN-PZ-PT by the TGG process. Sintering and texture evolution will be presented as a function of template particles never reported before. Piezoelectric properties will be discussed as a function of microstructure and texture quality. I will conclude with challenges to the community for obtaining better and more unique properties through increased microstructure regulation during the processing of bulk ceramics.
Curriculum Vitae-Gary L. Messing
Dr. Gary L. Messing is Distinguished Professor of Ceramic Science and Engineering and Head of the Department of Materials Science and Engineering at the Pennsylvania State University. He served as Director of the Materials Research Laboratory at Penn State, and was Founding Director of the NSF Industry/University Cooperative Research Center on Particulate Materials at Penn State.
Dr. Messing received his B.S. degree in Ceramic Engineering at the New York State College of Ceramics at Alfred University in 1973 and his Ph.D. in Materials Science and Engineering at the University of Florida in 1977.
He has published over 250 papers and co-edited 13 books on various aspects of ceramic processing including solution synthesis, phase transformations, processing-microstructure relations, sintering and templated grain growth. He has co-organized the International Ceramic Processing Science Conference with Professor Shin-ichi Hirano of Nagoya University since 1986. He was co-editor of the Journal of the American Ceramic Society from 1993-98, Editor in Chief of Ceramics International and Principal Editor of Materials Letters from 2003-2009. In 2009 he was appointed Editor-in-Chief of the Journal of Materials Research.
Professor Messing has received numerous awards for his research and leadership in the field of ceramics including the Richard M. Fulrath Pacific Award and he gave the Robert M. Sosman Memorial Lecture of the American Ceramic Society. He was elected Fellow of the American Ceramic Society in 1990 and served on the Board of Directors for many years and was then elected President of the American Ceramic Society. In 1999 he was elected to the World Academy of Ceramics In 2003 he was recognized as one of the most “Highly Cited Researchers” in Materials, and was honored with the International Award of the European Ceramic Society for his international collaborations. In 2005 in received the Outstanding Educator Award of the Ceramic Education Council of ACerS. In 2005-2006 he served as Chairman of the University Materials Council and was elected President-elect of the International Ceramics Federation in 2008.
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