Bioinspired Nacre‐Like Alumina with a Metallic Nickel Compliant Phase Fabricated by Spark‐Plasma Sintering

Many natural materials present an ideal “recipe” for the development of future damage‐tolerant lightweight structural materials. One notable example is the brick‐and‐mortar structure of nacre, found in mollusk shells, which produces high‐toughness, bioinspired ceramics using polymeric mortars as a compliant phase. Theoretical modeling has predicted that use of metallic mortars could lead to even higher damage‐tolerance in these materials, although it is difficult to melt‐infiltrate metals into ceramic scaffolds as they cannot readily wet ceramics. To avoid this problem, an alternative (“bottom‐up”) approach to synthesize “nacre‐like” ceramics containing a small fraction of nickel mortar is developed. These materials are fabricated using nickel‐coated alumina platelets that are aligned using slip‐casting and rapidly sintered using spark‐plasma sintering. Dewetting of the nickel mortar during sintering is prevented by using NiO‐coated as well as Ni‐coated platelets. As a result, a “nacre‐like” alumina ceramic displaying a resistance‐curve toughness up to ≈16 MPa m ½ with a flexural strength of ≈300 MPa is produced.