Characterization of alumina/silicon carbide ceramic nanocomposites

Ceramics of an alumina matrix containing SiC reinforcements of approximately 100-300 nm diameter have been reported to have considerably higher strengths than monolithic polycrystalline aluminas. Niihara1 has reported strength increases from 320 MPa to 1050 MPa and an increase in fracture toughness from 3.1 MPa√m to 4.7 MPa√m. Although strength and possibly toughness increases over those of similar grain size alumina have been reported by a number of workers2,3,4, maximum strengths of only about 800 MPa have been achieved. In all cases the increase in strength is accompanied by a change in fracture mode from inter granular failure in the monolithic alumina to transgranular failure in the composite.