Microwave Sintering of Alumina at 2.45 GHz (original) (raw)
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Microwave energy can be advantageously used for materials processing as it provides high heating rates and homogeneous temperature field distribution. These features are partly due to the large microwave penetration depth into dielectric materials which is, at room temperature, a few centimeters in most dielectric materials. However, up to now, this technology is not widely spread for high-temperature material processing applications (>1200 • C), because its reproducibly and ability to sinter large size samples (>30 cm 3) still needs to be improved. In this context, this paper describes both an empirically designed 915 MHz single-mode cavity made from SiC susceptors and refractory thermal insulation, and the 3D modeling of the process in order to improve our understanding of it. Different susceptors geometries and coupling slit position were numerically tested in order to better understand how these parameters impact the field homogeneity and the process stability. It was found that positioning the largest surface of the susceptors parallel to the electrical field allows a very uniform and hybrid heating of the material, while avoiding plasma or thermal instabilities. This was correlated to the 3D modeling results. Finally, thanks to a fully-automatized system this apparatus was used to sinter large size (~30 cm 3) low-loss dielectric alumina samples. The sintered materials were subsequently characterized in terms of density, grain size distribution, and homogeneity. The reproducibility was also discussed, demonstrating the process efficiency and reliability.
Microwave Processing of Liquid Phase Sintered Alumina
Microwave processing of ceramics has recently received a growing interest, because of the following research achievements: rapid volumetric heating, high densification rate, decreased sintering activation energy, improved microstructure and low energy consumption. The purpose of this study is to produce spherical mill grinding alumina media by microwave processing and to compare the resulting properties with those of conventionally produced samples. Liquidphase-sintering (LPS) of alumina was carried out in a pilot plant assisted by microwaves. The obtained samples were characterized by density measurements, microstructure analysis, mechanical properties and standard wear tests. Results on pilot scale microwave apparatus open the way to the production of microwave sinter alumina mill grinding media in a competitive industrial process.
Microwave sintering of transparent alumina
Materials Letters, 2002
Transparent alumina samples have been successfully prepared by microwave sintering processing. In comparison to the conventional sintering processing, microwave sintering to transparent alumina can be achieved at lower sintering temperature and shorter sintering time. It was also found that the microwave heating could substantially increase the conversion rate of polycrystalline alumina to single crystalline sapphire, to improve the transparency and other properties of the transparent alumina samples. D