Ultra-rapid microwave sintering of ceramics and powder metals

摘要

1. Ultra-rapid microwave sintering of various oxide powder materials with the duration of the high-temperature stage on the order of or less than 1 minute, has been demonstrated. 2. The observed rapid sintering effect is associated with a thermal instability, exhibiting sharp increase in the effective conductivity of the material and modification of the grain boundary structure with transient liquid phase formation. 3. The estimated deposited power of microwave heating, per unit volume, is on the same order of magnitude as the power measured in the dc field-assisted flash sintering experiments. 4. An optical registration system has been developed for in-situ measurement of shrinkage and temperature distribution during ultra-rapid microwave sintering. 5. The shrinkage curves obtained for alumina exhibit an increase in the dilatation rale at the thermal instability onset, indicating a transition to a different sintering mechanism. 6. Ultra-rapid microwave sintering of metal powder compacts is possible due to resonance effects Fast automatic control over the microwave power and/or frequency is necessary to ensure rapid densification and compensate for the instabilities.