A Mechanism of Flash Sintering of Ionic Ceramics

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NON-TECHNICAL DESCRIPTION: Traditional densification of ceramics powders into a functional component usually takes at least several hours. In 2010, a group of scientists discovered that nearly instantaneous full densification can occur (within five seconds) for certain ceramics when a high-level voltage or current pass through a compact of these ceramic powders. Thus, this rapid densification technique was named flash sintering. Since then, flash sintering has become one of the most promising techniques for ceramics processing. However, the mechanisms for this rapid sintering process are unclear; this project attempts to reveal the underlying reasons. The experimental work in this study is complemented by computational modeling, enabling a more comprehensive understanding on the rapid densification mechanisms of flash sintering of ceramic powders. This new knowledge then serves as fundamental guidance to extend the flash sintering technique into a wider range of ceramic materials. Graduate and undergraduate students (including minority and other underrepresented students) are being trained in mechanical engineering and materials science and engineering for careers in academia or high-technology manufacturing. Virtual reality technology is used to provide an immersive and interactive teaching and learning environment for materials sciences topics, and helps to educate a workforce capable of using adaptive new technologies in a rapidly changing society.TECHNICAL DETAILS: The technique, flash sintering, has demonstrated the ability to rapidly densify powder compacts of ceramic materials. In this technique, an applied electric field initiates a "flash" event and sintering occurs within a few seconds (at a threshold temperature for a given applied electric field). Although flash sintering has been observed in a variety of ceramic systems, the exact effects of electric field or current on enhancing the densification rate and influencing the microstructure evolution remain elusive, apart from the known thermal runaway Joule heating ohmic mechanisms. A series of experimental and theoretical modeling research activities are being carried out on ionic ceramic systems to clarify the thermal and non-thermal factors of electric field in the flash sintering process. In situ nanoscale imaging is used to observe the flash sintering process of yttrium-stabilized zirconia ceramic systems as a function of applied electric field, providing insights into the flash sintering mechanism. In addition, multiscale atom-to-continuum modeling is being used to simulate the flash sintering process of ionic ceramics in the presence of an electric field. The modeling is revealing the rapid densification mechanisms of flash sintering of ionic ceramics at the atomic level. Students are being educated to become experts in the practice of experimental and computational aspects of ceramic sintering technologies. As a result, graduates are being well prepared to create sustainable engineering solutions to complex problems, and thereby contributing to the cutting-edge of science and technology of ceramics processing and materials science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.