Fibrous monoliths: non-brittle fracture from powder-processed ceramics

Fibrous monoliths are non-brittle ceramics, fabricated from conventional powders using new methods that create a fibrous mesostructure to obtain an in situ composite. Ceramic-BN fibrous monoliths fracture like wood, with graceful failure occurring by shear delamination. Examples are Si3N4-BN fibrous monoliths, which have flexural strengths around 460 MPa between room temperature and 1000 °C and retain about half of their load-bearing ability after failure initiates, which apparent fracture energies up to 4800 J m−2 (SiC-alloy)-BN fibrous monoliths have flexural strengths around 400 MPa and exhibit graceful failure between room temperature and 1200 °C. Ceramic-metal fibrous monoliths also have graceful failure. Results are presented for (yttria-zirconia)-Ni fibrous monoliths, which fail by tensile cracking, with crack bridging by ductile metal ligaments. About 25 vol.% Ni imparts a fracture energy of 2200 J m−2, with a strength of 574 MPa.