A facile preparation of multi-scale BN/SiC ceramic with high toughness by vacuum-assisted filtration

Multi-scale BN/SiC ceramic with high toughness was successfully prepared by vacuum-assisted filtration. The BN/SiC ceramic bulk is composed of macroscopic laminated structure and microscopic brick–mortar structures in layer. In this ceramic, improving toughness relies on the design of multi-scale structure. The ordered arrangement of BN sheets and SiC form a ceramic layer with a structure similar to brick and mortar. At the same time, the SiC layer and BN/SiC layer are alternately arranged by layer-by-layer deposition method to form the macro-layer structure. The thickness of SiC layer and BN/SiC layer is only about 74 μm and 7.6 μm, respectively. The mode of crack propagation changed with the change in the structure and variation of BN content in the BN/SiC layer. The delamination cracks occurred inside the BN/SiC layer or at the interface between SiC and BN/SiC layers. The BN/SiC laminated ceramic possesses high toughness (9.37 MPa m^1/2) when the BN content is 20wt.%, which is much higher than that of pure SiC bulk (3.45 MPa·m^1/2).