In-situ monitoring of ceramic microwave sintering using optical method.
Microwave sintering is known to be a promising sintering technology. Indeed, this method has advantages such as reducing the duration of heat treatment and a significant energy saving compared with conventional processes. Year after year, sintering in a microwave environment is studied by a growing number of researchers. However, the reasons for the beneficial effect of this type of sintering are not clearly identified.In this context, the objective of this work was to verify the influence of an electromagnetic field at a frequency of 2.45 GHz on the densification of ceramic materials. This objective therefore involves a comparative study of sintering in a microwave chamber and in a conventional oven. However, the presence of electromagnetic field in a microwave oven does not allow the use of conventional methods to monitor the sintering. Thus, to compare the results, an experimental system containing a high resolution contactless dilatometer has been specifically developed. This system also allows monitoring of the temperature distribution on the sample surface.For identical thermal cycles, obtained by conventional and microwave sintering, the densification evolution of materials with different properties was compared. These materials are: pure alumina and doped with 800ppm magnesium oxide, zinc oxide and silicon-substituted hydroxyapatite. For each material, the coupling with the microwaves and the temperature distribution on the surface sample are also discussed. A beneficial effect of microwaves on the evolution of densification has been identified for alumina with addition of MgO and more pronounced for zinc oxide.