Microwave sintering of nuclear ceramics

International audienceMicrowave sintering is a promising technique to bring innovative microstructures, while reducing temperature, processing time and energy consumption. This process could be used to improve nuclear ceramics sintering efficiency, reduce economic costs and to potentially improve fuels features. This paper describes the development of an instrumented and automated microwave setup, qualified on fuel surrogates, which will allow reproducible and reliable comparison between microwave and conventional sintering of nuclear fuels. Finite elements modeling were used to design the setup and a hybrid heating technique with a specific sintering cell (nature and geometry of insulator and susceptor) in a multimode furnace has been chosen to obtain uniform and controlled heating of the specimens. This setup allows heating under Ar/4%-H2 with a specific partial pressure of oxygen. The results will be used to evaluate the feasibility of nuclear ceramics microwave sintering and to look at the future development of an industrial furnace

Microwave sinter forging of alumina powder

International audienceMicrowave sintering under load is expected to be a promising technique to process ceramics with fine microstructure. This paper presents a new setup allowing sinter forging ceramic compacts in a 2.45 GHz single-mode microwave cavity. This setup has the following features: maximum temperature of 1600 degrees C, heating rate between 1 and 250 degrees C min(-1), maximum stress of 50 MPa applied upon an 8 mm diameter sample. A specific protocol has been defined to calibrate the pyrometer used to measure the sample temperature. Alpha-alumina compacts have been microwave sinter forged under various stresses in the range 0-30 MPa. The results are compared to those obtained in a conventional furnace under 0, 4 and 8 MPa. Final axial and radial shrinkages are identical with the two techniques. The final relative density of the material is not affected by load and is equal to 0.94 and 0.96 in microwave sinter forging and conventional sinter forging, respectively. Two assumptions are proposed to explain this difference: a microwave effect and a temperature discrepancy. Finally the load does not significantly affect grain growth