Rapid synthesis of mullite powders
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This study covers the synthesis of high purity mullite powders using ultrasonic spray pyrolysis and the microstructural evaluation of bulk materials prepared by using this powder. Tetraethylorthosilicate and aluminum nitrate nanohydrate chemicals were used to prepare an aqueous solution and this solution was turned into aerosol droplets using an ultrasonic nebulizer with a resonance frequency of 1.63 MHz. These aerosol droplets were carried to the vertical tube furnace the temperature of which was set beforehand by using a gas with a flow rate of 1.5 L minute. Spherically shaped mullite powders were successfully synthesized at 1075 C according to the results of XRD and FTIR. Bulk materials were obtained by sintering the pressed mullite powders at different temperatures (1500, 1550, 1600 and 1650 C) with a soaking time of 5 hours. SEM images show that the particle shape changes wth the sintering temperature of the bulk ceramic. For low temperature sintering, the particles are still quite spherical whereas they tend to form a rod-like structure with an increase in the sintering temperature.