Synthesis, consolidation and characterization of monolithic and SiC whiskers reinforced HfB2 ceramics

Spark Plasma Sintering is used for the fabrication of highly dense HfB2 monolithic and HfB2-26 vol.% SiCw composite. Reactive SPS from elemental reactants is preferred for the preparation of bulk HfB2 instead of classical sintering. The desired phase is rapidly formed through a solid solid combustion synthesis mechanism, while full densification is achieved in 30 min at 1350 A when the applied pressure is switched from 20 to 50 MPa after the synthesis reaction. A 99.4% dense whiskers-reinforced HfB2 ceramic matrix composite is also obtained in 30 min by SPS (I= 1350 A, P = 20 MPa) using SHSed HfB2 powders and SiCw. Nevertheless, whiskers degradation into SiCp resulted under such conditions (temperature up to 1830 degrees C). On the other hand, the presence of whiskers is clearly evidenced in 96% dense products obtained when the applied current was decreased down to 1200 A (1700 degrees C) while P was increased to 60 MPa. (C) 2012 Elsevier Ltd. All rights reserved.