A Mechanism of Flash Sintering of Ionic Ceramics

非技术描述：传统的陶瓷粉末致密化成功能组件通常需要至少几个小时。2010年，一组科学家发现，当高电压或高电流通过陶瓷粉末时，某些陶瓷几乎可以瞬间（在5秒内）发生完全致密化。因此，这种快速致密化技术被命名为闪速烧结。从那时起，闪速烧结已成为最有前途的陶瓷加工技术之一。然而，这种快速烧结过程的机制尚不清楚；这个项目试图揭示潜在的原因。本研究的实验工作与计算模型相辅相成，使我们对陶瓷粉末闪速烧结的快速致密化机理有了更全面的认识。这一新的知识可以作为基本的指导，将闪烧技术扩展到更广泛的陶瓷材料中。研究生和本科生（包括少数民族和其他代表性不足的学生）正在接受机械工程、材料科学和工程方面的培训，以适应学术界或高科技制造业的职业发展。虚拟现实技术用于为材料科学主题提供身临其境的交互式教学环境，并有助于教育能够在快速变化的社会中使用适应性新技术的劳动力。技术细节：闪蒸烧结技术已经证明了快速致密陶瓷材料粉末的能力。在这种技术中，外加电场引发“闪光”事件，烧结在几秒钟内发生（在给定外加电场的阈值温度下）。虽然在多种陶瓷体系中已经观察到闪速烧结，但除了已知的热失控焦耳加热欧姆机制外，电场或电流对提高致密率和影响微观结构演变的确切影响仍然是难以捉摸的。为了弄清闪烧过程中电场的热因素和非热因素，对离子陶瓷体系进行了一系列的实验和理论建模研究。利用原位纳米成像技术观察了钇稳定氧化锆陶瓷体系的闪烧过程随外加电场的变化，为闪烧机理的研究提供了新的思路。此外，还采用多尺度原子-连续介质模型模拟了离子陶瓷在电场作用下的闪烧过程。该模型在原子水平上揭示了离子陶瓷闪烧的快速致密化机制。学生被教育成为陶瓷烧结技术实验和计算方面的实践专家。因此，毕业生将为复杂问题创造可持续的工程解决方案做好充分准备，从而为陶瓷加工和材料科学的前沿科技做出贡献。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.