EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Nowadays, many industrial applications demand the use of components working under extreme conditions, particularly very high temperatures for long times. For this kind of applications properties such as low thermal conductivity, low thermal expansion coefficient and high chemical resistance are strongly required. Advanced ceramics, such as zircon and zirconia, have similar coefficient of thermal expansion, thermal conductivity and high chemical resistance. The main disadvantage of these materials is the high temperatures and holding times needed to obtain high densities, what means an elevated energy consumption and cost. Therefore, microwave sintering is a promising technique capable of reducing sintering and holding temperatures, resulting in energy savings and cost reductions in the order of 70% compared to conventional methods. The aim of this study is to evaluate the sinterability of zircon powders and mixtures of zircon-zirconia with 80/20 volume ratio prepared by a colloidal processing route and sintered through microwave technology at 1300 ºC-15 min (MW). Mechanical and microstructural properties were evaluated and compared with those obtained by conventional sintering (CS) at 1500 ºC-2 h.
Dense ceramics were obtained by microwave without any sintering additive at lower temperatures and shorter time than using CS. Values of HV of 9.1 and 11.6 GPa were obtained by CS at 1500 ºC-2h for zircon alone and zircon-zirconia, respectively. The composite obtained by microwave at 1300 ºC-15 min showed values of Hv: 10.8 GPa, 25% higher than zircon sintered by MW at the same conditions, thus evidencing that zirconia reinforcement is more efficient by the microwave radiation. These preliminary results demonstrate the viability of microwave technique for fast consolidation of zircon-zirconia composites.

The authors would like to thank to the Spanish Ministry of Science, Innovation and Universities (RTI2018-099033-B-C32 and C33, MCIU/AEI/FEDER, UE), and RYC-2016-20915.