Flash sintering of metal-like ceramics: A short overview

Flash sintering was officially discovered about fifteen years ago as a ground-breaking method to consolidate ceramics in very short time at furnace temperature much lower than that used for conventional sintering. Since then, it has been applied to several ceramics and composites with the common feature of being characterized by a negative temperature coefficient for resistivity while few attempts have been made on materials with metal-like electronic conduction. In the present overview the results of the investigation carried out in the last years aiming at consolidating tungsten carbide and zirconium diboride by flash sintering are reported and the conditions for inducing a thermal runaway phenomenon like in other ceramics and understand the physical mechanisms behind the flash effect are analysed. The investigation allows to point out the importance of the fundamental processing variables like the applied pressure and voltage for obtain high density material. The key role of the starting particles' surface chemistry is identified to generate specific microstructures and determine peculiar physical and mechanical properties in the flash sintered ceramic.