Exploration of Structural and Mechanical Properties of Superhard Metal Borides under High Pressure
- Author(s): Lei, Jialin
- Advisor(s): Tolbert, Sarah H
- Kaner, Richard B
- et al.
Superhard materials have many technological applications including cutting, polishing and drilling. The design strategy to create superhard compounds involves two important parameters: high valence electron density and short covalent bonds. We have demonstrated this concept in compounds such as OsB2, ReB2, and WB4. In the course of our studies involving WB4 and its solid solutions, we have found that the monoborides should not be neglected as they still offer a hardness advantage over commonly used materials (such as tungsten/titanium carbides), while having the added desirable qualities of being more thermodynamically stable and requiring less boron than WB4. In this thesis, a complete discussion is made for WB in two different phases and its solid solutions aiming to study their deformation behavior in a lattice specific manner and hardening mechanisms. In addition, dodecaborides (ZrB12, YB12 and ZrYB12) were investigated to understand the role that boron cages play in its mechanical properties. More importantly, the synthesis of nano-scale ReB2 and its lattice preferred orientation are discussed as well as the dominant mechanism for its plasticity.