Efficient multiscale strategy for toughening HfB ₂ ceramics: A heterogeneous ceramic–metal layered architecture

Abstract

Abstract A multiscale structural design was innovatively adopted herein to increase the toughness of monolithic HfB 2 ceramics. SiC whiskers (SiC w ) and graphene oxide (GO) were used as fillers for the HfB 2 matrix, whereas a ductile W foil was introduced as an interlayer to synthesize laminated HfB 2 ‐SiC w ‐rGO/W ceramics. Monolithic HfB 2 ‐SiC p (particulate) and laminated HfB 2 ‐SiC p /W ceramics were prepared using the same routes and used as controls. Following tape casting and spark plasma sintering at 1800°C, the toughness of the prepared laminated HfB 2 ‐SiC w ‐rGO/W samples was increased to 14.2 ± 0.6 MPa·m 1/2 , with minimal sacrifice in flexural strength (421 ± 16 MPa). Morphological analysis of the fracture surface revealed the synergistic effects of micro‐toughening (including bridging and pullout of whiskers and rGO) and macro‐toughening (including crack deflection, bifurcation, and delamination) mechanisms responsible for improving the fracture toughness of the laminated HfB 2 ‐SiC w ‐rGO/W composites.