One of the main characteristics closely related to the performance of a polycrystalline abrasive grain is its microstructure. This has a very particular influence on the physical and mechanical properties of the grain (hardness, toughness, wear resistance). Moreover, one of the major actors in the "Abrasive" world being corundum thanks to its properties in temperature, the ceramic composites based on corundum elaborated by Sol-Gel chemistry have then aroused a very great interest since several decades [1-2].

Microwave sintering has emerged in recent years as a promising technology for faster, cheaper and more environment-friendly processing of a wide variety of materials, giving it a significant advantage over conventional sintering processes [3-4]. Moreover, hybrid sintering with the help of a susceptor has been generally developed until now for their densification by radiative contribution [5].

In this context, a sintering process by direct heating in dynamic mode has been considered with two project partners: ITACA and INNCEINNMAT. A lab prototype furnace was hence manufactured and is currently operating at Imerys Technology Center in Austria. Thereby, the present work firstly focuses on the direct interaction Microwave-Matter by measuring the dielectric properties of some alumina-based sol-gel composites using a specific equipment developed by ITACA [6]. The sintering tests carried out on the lab prototype have then shown promising results notably in terms of reduced energy consumption compared to conventional techniques. Therefore, the challenging development of a pilot unit involving a 915 MHz industrial microwave generator is explored.

1. T. E. Wood et al., (2016) “Sol–Gel Abrasive Grains: History, Precursor Properties, and Microstructural Control”.  In: Klein L., Aparicio M., Jitianu A. (eds) Handbook of Sol-Gel Science and Technology. Springer, Cham

2. G. L. Messing et al., “Enhanced Densification of Boehmite Sol-Gels by α-Alumina Seeding”, Journal of the American Ceramic Society 67 (11), 230-231 (1984).

3. A. Borell et al., “Microwave Technique: A Powerful Tool for Sintering Ceramic Materials”, Current Nanoscience, 10, 32-35 (2014).

4. J. Croquesel et al., “Direct microwave sintering of pure alumina in a single mode cavity: Grain size and phase transformation effects”, Acta Materialia, 116, 53-62 (2016).

5. R. Benavente et al., “Mechanical properties and microstructural evolution of alumina-zirconia nanocomposites by microwave sintering”, Ceramics International, 40, 11291-11297 (2014).

6. J.M. Catala-Civera et al., “Dynamic measurement of dielectric properties of materials at high temperature during Microwave heating in a Dual-Mode Cylindrical Cavity”, IEEE Transactions on Microwave Theory and Techniques, 63, 2905-2914 (2015).