Magnesium Incorporation and Exfoliation of Lanthanum and Calcium Hexaboride

Metal borides are a type of high-performance materials with various stoichiometries that are known for their properties such as high thermal and oxidative stability, mechanical strength and notably high melting points (above 2000 °C). These unique features, however, are also what make the borides challenging to process for industrial applications where often thin films for coatings are required. Typically, methods such as physical and chemical vapor deposition are employed to form such films, but these techniques offer little control over the thickness and uniformity of the deposited layers. One approach to avoid this issue is converting the bulk borides to nanosheets, which commonly self-assemble and lay flat. Since nanosheets tend to stay suspended in various solvents, different techniques such as dip coating, spray deposition and even inkjet printing can be used to apply them instead. One big deterrence to this approach is that unlike van der Waals materials, whose layers are held together by van der Waals forces, the metal-boron framework is bonded by stronger ionic and covalent interactions. Thus, conventional methods such as the scotch tape method or simple sonication cannot be applied to produce metal boride nanosheets. Our research focuses on a novel top down approach, which involves the incorporation of a small metal ion into the bulk material followed by the boride exfoliation into nanosheets. Particularly, the nanostructuring of LaB₆ and CaB₆ will be disc​ussed.