Strong and Tough Alumina Ceramic from the Particle-Stabilized Foam

Strength and toughness are two vital and contradictory properties, especially in alumina structural ceramics. This mutual exclusion limits the widespread application of advanced alumina ceramics in harsh environments. To deal with this issue, self-toughening alumina bulk ceramics without any ductile phase and with a unique combination of excellent toughness and reliable strength by combining the foam ceramics with hot-pressing sintering are prepared. Foam ceramics with honeycomb cellular structures are prepared by particle-stabilized foaming. Then, the foam ceramics is directly hot pressed sintered, in which the cellular structure is fractured into fragments and completely dense under pressure. Equiaxed grains that constituting the fragments grow anisotropically into plate-like grains with a large diameter-thickness ratio during hot-pressing sintering. Plate-like grains improve the material's fracture toughness by exerting a toughening mechanism similar to that of fibers. The self-toughening alumina ceramics exhibit a unique combination of high flexural strength (874 +/- 31 MPa) and high fracture toughness (6.2 +/- 0.1 MPa m(1/2)). The Vickers hardness also can reach 21 GPa. Herein, a new strategy with relatively simple processing to fabricate high-performance ceramics based on the widespread ceramic processing techniques are provided.