Investigation on the role of Joule heating on flash sintering using a combined experimental and modeling approach

Abstract

Flash sintering is a novel technique of ultrafast densification. There is a continuous debate over the mechanisms that are responsible for such fast sintering. In this work, we have assessed the role of Joule heating and thermal runaway on densification using a combined experimental and modeling approach. First, flash sintering (FS) experiments have been carried out for three different oxides that have very different electrical and thermal conductivities, namely, 3-and 8-mol% yttria-stabilized zirconia and titania (TiO 2 ). Then, we modeled the densification during FS, for identical experimental conditions, using a novel combined finite element modeling and master sintering curve approach. The results obtained through experiment and modeling have been compared. Finally, our results show that ultrafast densification observed during FS cannot be replicated through Joule heating and thermal runaway alone at low current density (<100 mA/mm 2 ), suggesting that a contribution from other mechanisms is likely essential to explain the observed ultrafast densification. However, Joule heating and thermal runaway can account for the ultrafast densification at higher than 100 mA/mm 2 current density.

Experimental and Numerical Studies of Densification and Grain Growth of 8YSZ during Flash Sintering

“…Li et al [ 41 ] used FEM coupled with a phenomenological constitutive equation to simulate the densification of flash sintering of 3YSZ. Arya et al [ 42 ] used the master sintering curve (MSC) to include the influencing factor of the heating rate to predict the densification behavior of 3YSZ, 8YSZ, and TiO 2 . Their prediction of relative density (RD) matches closely with the experimental observation at a higher current density (100–150 mA mm − 2 ) while failing at a lower current density (<100 mA mm − 2 ).…”

Electric Current‐Assisted Sintering of 8YSZ: A Comparative Study of Ultrafast High‐Temperature Sintering and Flash Sintering

“…[25][26][27][28] However, other studies suggested that the effect of electric field in FS and the extremely high maximum temperature of the sample also play a role in the enhanced densification. [29,30] To study the temperature profile of the ceramic sample for investigating the densification mechanisms during ECAS, modeling efforts have been made both on FS [31][32][33][34] and UHS [8,9,26,35] in recent years. Mishra et al [26] adopted finite element methods (FEM) to simulate the temperature distribution in strontium titanite (STO) during UHS and found that the temperature required to densify the ceramic green body by UHS is comparable to that by conventional sintering (CS).…”