Influence of zircon particle size on conventional and microwave assisted reaction sintering of in-situ mullite-zirconia composites

Mullite-zirconia composites were fabricated by reaction sintering of ZrSiO4 and alpha-Al2O3 using conventional heating and microwave processing. The powder mixtures were prepared from sub-micron zircon powders with three different particle sizes and CIPed as coin shaped samples. The samples sintered both in a muffle furnace and microwave furnace. The open porosities, bulk and true densities were measured. Phase transformations were characterized by X-ray diffraction and microstructures were evaluated by scanning electron microscopy. The effects of zircon particle size on the in-situ transformation system and mullitization was evaluated for both methods. As a result, decreasing zircon particle size decreases the in-situ transformation temperature for 25 degrees C (1575 degrees C) in conventional heating. Microwave assisted sintering (MAS) lowers the transformation temperature at least 50 degrees C by lowering the activation energy more efficiently and gives better densification than conventional sintering. Furthermore, milling also produces structures having finer mullite grains. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved