The Synthesis and Characterization of Ultra-Incompressible, Superhard Borides

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

This award to University of California-Los Angeles by the Solid State Materials Chemistry program in the Division of Materials Research is to grow single crystals of Rhenium diboride (ReB2) and to measure the physical properties of ReB2 as a function of crystallographic orientation. The hardness of ReB2 will then be enhanced by forming solid solutions and synthesizing dense nanocrystalline composites. In other studies, rhenium will be replaced completely with other transition metals such as Titanium while maintaining the ReB2 structure type. These approaches may enable to construct new ultra-incompressible, superhard materials using less expensive metals. The search for new ultra-incompressible, superhard materials holds both scientific and practical interest. The proposed design plan is to combine high valence electron density transition metals with small main group elements to replace the weak metallic bonds with strong covalent bonds. Using this approach, it is possible to convert relatively soft rhenium metal into an extremely hard Rhenium diboride, which has many exciting physical properties including low incompressibility, high hardness, and the ability to scratch diamond. Synthesis and testing of coatings will be carried out in conjunction with a local company that specializes in developing ultra-hard coatings. Hardness, fracture toughness and Young?s modulus will be determined by indentation techniques. Radial diffraction experiments will also be used to determine the mechanical properties of these materials. As part of this project, an outreach program be developed entitled ?It?s a Material World? that is suitable for both undergraduate students and general audiences. This course will be offered to UCLA undergraduates each year to enhance their interest in materials chemistry. In addition, materials developed for this course will be used for interactive seminars with both high school and middle school students. The main thrust of the proposal is to synthesize crystals of Rhenium Diboride and other structurally related borides of transition metals such as Titanium. Using this approach, it is possible to convert relatively soft metals into extremely hard materials, which are harder than diamond. The search for new ultra-incompressible, superhard materials holds both scientific and practical interest in a number of applications. An outreach program will be developed entitled ?It?s a Material World? that is suitable for both undergraduate students at the campus and general audiences. This program offered to non-science undergraduate students is to enhance their interest in science in general and materials science in particular. In addition, materials developed for this course will be used for interactive seminars with both high school and middle school students.