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 approximate to 16 MPa m(1/2) with a flexural strength of approximate to 300 MPa is produced.