Are we using the right sintering models: new insights from in situ experiments?
Monday, January 31, 2022; 2:00 – 3:00 p.m. Eastern US time
The ACerS Basic Science Division is hosting the webinar Are we using the right sintering models: new insights from in situ experiments? presented by Dr. Shen J. Dillon (University of California, Irvine).
Densification during sintering is almost universally interpreted in context of diffusional models first developed by Coble. The models assume that grain boundaries act as an infinite vacancy sink (or interstitial source), the surface acts as an infinite vacancy source (or interstitial sink), and atomic diffusion limits the overall kinetics at a rate proportional to the instantaneous sintering stress. A variety of technologically important sintering phenomena are challenging to rationalize in context of these classical models, such as the effects of high heating rates on sintering trajectory, the efficacy of 2-step sintering, the role of shear stresses in enhancing densification, and certain aspects of residual stress development. Our group has begun utilizing ultrahigh temperature in situ transmission electron microscopy-based model bicrystal tensile creep, bicrystal sintering, and multiparticle sintering experiments to better quantify the thermodynamics and kinetics of sintering. These experiments suggest that the nucleation rate of grain boundary line defects (e.g. disconnections), that act as vacancy sinks and mediate densification through climb, is the rate limiting step. These observations are also supported by recent large scale molecular dynamics simulations. The stresses necessary to nucleate these disconnections is large relative to the average sintering stresses, which necessitates the dissipation of surface energy to drive the system into activated states. A new thermo-kinetic sintering model is proposed to account for this mechanism. It is shown that the model fits traditional isothermal sintering data well. It also makes useful predictions about processes such as high heating rate sintering methods, 2-step sintering, sinterability of different types or materials, and residual stress evolution. These issues will be discussed in the context of opportunities for new scientific and engineering development.
Shen J. Dillon is a Professor in the Department of Materials Science and Engineering at the University of California Irvine. He received his B.S. and Ph.D in Materials Science and Engineering from Lehigh University in 2007. He began as an Assistant Professor at the University of Illinois at Urbana-Champaign in 2009 and joined the faculty at UC Irvine in 2021. His scientific interests relate to understanding the key role played by inorganic interfacial structure-property relationships in affecting the performance of systems in extreme environments. Much of his recent work relates to developing and applying novel in situ characterization techniques that can be applied to understanding the dynamic properties of materials and their interfaces. He is the author of over 100 articles, and was a recipient of the 2011 Department of Energy Early Career Award, the 2013 National Science Foundation CAREER Award, and the 2015 American Ceramic Society’s Robert L. Coble Award for Young Scholars.
ACerS member: no cost
ACerS GGRN and Material Advantage student member: no cost
Non-member student: $15
If you have any questions, please contact Erica Zimmerman.
This webinar is brought to you by ACerS Basic Science Division.
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