Effects of flake-shape and content of nano-mullite on mechanical properties and fracture process of corundum composite ceramics

Abstract

Coal gangue is used to prepare flake nano-mullite with a molten salt method. In order to increase the utilization value, corundum composite ceramics were prepared from the nanomullite and alumina. The effect of particle size of the raw material size and the content of mullite on mechanical properties of the corundum composite ceramics was studied. It is found that the mullite with appropriate sizes can be filled in between the corundum grains, thus increasing the density of the samples. The mechanical properties were enhanced due to the variation in the crack propagation mode. The optimized sample exhibited flexural strength and fracture toughness of 263.7 MPa and 5.0 MPa·m1/2, respectively. Griffith fracture theory analysis results indicated that the critical crack size reached 173.9 μm and the fracture energy was 127.6 J/m2. Coal gangue has realized deep resource utilization, and the mechanical properties of composite ceramics are higher than alumina ceramics prepared under the same conditions. Flake nanomullite contributes to mechanical properties.

Keywords

• corundum composite ceramics
• mechanical properties
• gangue