Flash sintering effect on fly ash microstructure

Abstract

In this study, densification of fly ash, (FA, industrial waste glass ceramic material) powder is carried out by electric field assisted flash sintering method. FA obtained from Tuncbilek Thermal Power Plant (Kutahya, Turkey). During the flash sintering experiment, 450 V/mm electric field is applied on sample with 0.85 amp current cutoff value. Flash sintering is accomplished in 70 sec at approximate to 1137 degrees C. According to XRD analysis, glassy phase, quartz, hematite, magnetite, magnesioferrite and mullite structures are in the structure. Based on the results of chemical analysis (XRF), reported in the literature, the sintering of ceramic materials formed by SiO2, Al2O3 and Fe2O3 individually or all together occurs at temperatures of 1500 degrees C and above. By electric field assisted flash sintering technique, the sintering temperature is decreased from 1500 to 1137 degrees C along with a decrement in sintering time from 3 hours to 70 seconds. The sintering process with this method was performed at a lower temperature and in a shorter time than traditional sintering methods. With the SEM micrographs, it has been proven that fly ash flash sintering processes have a denser structure compared to the conventional sintering.