Liquid-Film Assisted Mechanism of Reactive Flash Sintering in Oxide Systems

Abstract

Reactive flash sintering in oxide systems is analyzed assuming the formation of a liquid film at the particle contacts at the flash onset temperature. Formation of intermediate phases, as well as phase assemblage, are predicted upon optimal conditions of the electric field and current density. In single-phase impure oxides, the solidus and the solubility limit determine the flash onset temperature. In reacting binary systems, the composition of the liquidus determines primarily the reaction products during the cooling. In multicomponent systems, the oxide with the lowest flash temperature forms the interfacial liquid film, and the solid phase assemblage follows the equilibrium phase diagram. Examples from literature are consistent with reactive flash sintering and flash sintering assisted by a transient liquid film.

Modelling the particle contact influence on the Joule heating and temperature distribution during FLASH sintering

“…Despite the lack of thermal gradients observation on the simulated scenarios, liquid phase formation on grain boundaries of FLASH sintering ceramics has been observed [18], [27], [34], [35]. A plausible explanation for such observations is that the fast heating upon grain boundaries allows the formation of low melting point phases that contribute for grain boundary amorphization and particle sliding, as previously proposed [27].…”

“…In these conditions, the proposed simulations allow the conclusion that thermal gradients from Joule heating generation should not be observed during FLASH sintering. However, previously reported observations and theoretical descriptions of amorphized grain boundaries in FLASH sintered ceramics and liquid phase formation during FLASH [18], [27], [34], [35] suggest, at least, two possibilities:…”

Flash sintering produces eutectic microstructures in Al2O3–LaPO4 versus conventional microstructures in 8YSZ–LaPO4

“…Furthermore, the area of the channeled region on the cross‐section in Figure 9, corresponding to the high current pathway, is significantly smaller than the gauge section – concentrating the heating further. It is also possible that a small amount of eutectic liquid can form at the interfaces which would enhance sintering as well as the local current 49,50 …”

Flash Sintering Research Perspective: A Bibliometric Analysis

“…As shown in the inset of Figure 5c, the documents come from six different countries: The USA, China, Brazil, Spain, India, and Israel. All authors internationally collaborate, besides authors from Israel with two single-country publications [124,125]. More details about author clusters and institutions are shown in Figure 5c.…”