event
Thursday 16 Jan 2014: New Ceramics by Rapid Sintering
Professor Mike Reece - School of Engineering and Materials Science, Queen Mary University of London
HAR/170 (3D Visualisation Suite) 14:00-15:00
Ceramics are normally produced by the densification of fine powders at high temperatures by the mechanisms sintering. The time required for this process is usually measured in hours because of the slow rate of heating/cooling of the furnaces used. Using direct Joule heating of graphite dies the heating rate can be much higher (>500C/min), and the densification process can be completed in minutes. This opens up the possibility of making ceramics with new microstructures and properties. This will be illustrated by research on nanostructured, textured and non-equilibrium ceramics. Recent advances in the chemical synthesis of nano-powders and carbon nanotubes combined with rapid sintering has made it possible to investigate nano-scale size effects in structural and functional ceramics. These are limiting in the case of ferroelectric materials and advantageous in the case of thermoelectric materials. The talk will focus on two topics that illustrate the ability of rapid sintering to produce new materials that can not be made using conventional sintering routes. Rapid sintering has made it possible to solve a thirty year problem in materials science, the fabrication of dense, textured perovskitelike layered structured ferroelectric ceramics with super high Curie points (>1400C) that demonstrate piezoelectricity activity. This has opened the door to further studies of these materials and the possibility of a step change in the operating temperature and sensitivity of high temperature piezoelectric ceramics. Rapid sintering has also opened up the possibility of producing ceramic-CNT composites in which the CNTs are not degraded during the processing. The CNTs have a significant and interesting effect on the densification and grain growth of ceramics.
