March 10-15, 2019
The recent liquid film capillary mechanism [1, 2] proposed for the rapid densification during the flash sintering was consistent energetically with the dissipated power during the process. Following this mechanism, melting of contacts with high electric resistance will induce high attractive capillary forces. Wetting of a solid substrate by its own melt is termed homologous wetting with zero wetting (dihedral) angle. Therefore, wetting and spreading of the melt on its own substrate is extremely fast. Here we will show that particle surface softening / melting and the following transient processes associated with it namely local melt wetting and spreading, particle rearrangement, melts solidification, are also kinetically compatible with the flash process and its duration.
We analyzed the liquid-assisted densification kinetics of ceramic nanoparticles during flash sintering in terms of wetting and melt spreading, from the nanoparticle contacts, affected by the local electric field and capillary forces. Homologous wetting and spreading of the melt from the particle contacts reveal wetting velocities of 0.3×10-6 m×s-1 and 1 m×s-1 induced by the electric field and the capillary forces, respectively. The ultrafast densification kinetics by particle rearrangement is consistent with the enhanced diffusion and calculated wetting velocities. Epitaxial solidification of the melt after particle rearrangement is energetically favorable, and its tendency depends on the melt viscosity.
1. R. Chaim, Materials 9 (2016) 280.
2. R. Chaim, C. Estournes, J. Mater. Sci. 53 (2018) 6378-6389.
Rachman Chaim, "Kinetics of liquid-assisted densification during flash sintering of ceramic nanoparticles" in "Electric Field Enhanced Processing of Advanced Materials II: Complexities and Opportunities", Rishi Raj, University of Colorado, USA Olivier Guillon, Forschungzentrum Jülich, Germany Hidehiro Yoshida, National Institute for Materials Science, Japan Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/efe_advancedmaterials_ii/76