Top priority current path between SiC particles during ultra-high temperature flash sintering: Presence of PyC “bridges”

Flash sintering (FS) is a novel technique for rapidly densifying silicon carbide (SiC) ceramics. This work achieved a rapid sintering of SiC ceramics by the utilization of ultra-high temperature flash sintering within 60 s. Pyrolysis carbon (PyC) “bridges” were constructed between SiC particles through the carbonisation of phenolic resin, providing a large number of current channels. The incubation time of the flash sintering process was significantly reduced, and the sintering difference between the centre and the edge regions of the ceramics was minimized, with an average particle size of the centre region and edge region being 12.31 and 9.02 μm, respectively. The results showed that the porosity of the SiC ceramics after the flash sintering was reduced to 14.79% with PyC “bridges” introduced, and the Vickers hardness reached 19.62 GPa. PyC “bridges” gradually evolved from amorphous eddy current carbon to oriented graphite carbon, indicating that the ultra-high temperature environment in which the sample was located during the flash sintering was successfully constructed. Ultra-high temperature flash sintering of SiC is expected to be applied to the local repair of matrix damage in SiC ceramic matrix composites.