Size Scale and Defect Engineered Nanostructures for Optimal Strength and Toughness

Realistic combinations of ceramics and/or semiconductors have been developed that simultaneously achieve high hardness (>40 GPa) and toughness (>400 MPa*m1/2). To achieve this goal, there were three primary objectives: (1) the development of physically based dislocation models to understand the deformation of brittle materials, (2) the synthesis of model ceramic nanocomposites that demonstrate high hardness and toughness, and (3) the detailed understanding of the arrangements and types of dislocation structures in small volumes. This involved the uniaxial compression of Si nanovolumes (spheres and towers) using a combination of TEM in situ indentation and molecular dynamics simulations for objective (1), the deposition of Si-SiC core-shell nanotowers for objective (2), and the HR TEM analysis of deformed Si nanovolumes for objective (3).