EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Colloidal processing has been widely used in the manufacture of ceramics and composites because it allows the design of complex shaped parts and a suitable control of microstructure with cost-effective methods and increased reliability. Although ceramic oxides have been largely studied and produced from the basis of focused studies on colloidal stability and shaping performance of aqueous suspensions, the application to non-oxide ceramics has been much lower due to the problems associated to surface oxidation and the difficulties to find suitable deflocculants. The objective of this work was to demonstrate the suitability of using aqueous suspensions for the production of non-oxide ceramics with enhanced properties and better performance by improving the dispersion of the different phases including sintering aids and secondary phases. The feasibility of colloidal processing for the near-net shaping of superhard ceramics is studied focusing on the stability and rheological behavior of B4C aqueous suspensions containing intermetallic additives to promote sintering through a transient liquid phase. Furthermore, the effect of graphene on the suspension properties and the microstructure and properties of the sintered compacts is also discussed. Colloidal methods were used either to achieve a homogeneous dispersion of the components by freeze-drying or to produce near-net shaped parts by slip casting or tape casting with concentrated suspensions. In all cases uniform powders or bodies with high green densities are obtained that can be sintered to near to theoretical density and good microstructural uniformity by pressureless sintering or spark plasma sintering.

This work has been supported by a Spanish Project RTI2018-009033-B-C33 (MCIU/AEI/FEDER, UE).