2015 Beckman Symposium   

Avalon Dismukes

Presentation Date:

Avalon Dismukes

43 - Molybdenum Di- and Tri-Boride Systems: Synthesis and Analysis

University of California, Los Angeles

Chemistry and Materials Science

Refractory metal borides have recently generated intense interest in materials chemistry. These compounds have been shown to possess many advantageous properties, such as exceptionally high hardness, electrical conductivity, and even superconductivity. Previous research was directed at tungsten tetraboride in conjunction with Chris Turner€s (current graduate student) project but new research has been directed at molybdenum-boride systems. Higher molybdenum borides (i.e. MoB2, MoB3, Mo0.91B3, and MoB4) are currently under exploration as compounds of interest in this category of materials. However, the complex phase relationships in the molybdenum-boron system complicate the preparation of phase-pure samples. Here we expand upon the phase relationships in arc melted MoB2 and MoB3. Systematically varying the ratio of boron to molybdenum in sub- to super-stoichiometric amounts has yielded samples approaching phase purity. System compositions are examined by X-ray diffraction (XRD) and their grain structure analyzed by scanning electron microscopy (SEM). We also demonstrate preferential phase formation of the MoB2 structure in both binary and ternary solid solutions despite wide stoichiometric variation, as suspected from previous reports (and literature). This work enables further exploration of the properties of molybdenum borides such as through hardness measurements, thermogravimetric stability testing, and crystallographic phase design.

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