Preparation and Properties of Metallic, Superhard Rhenium Diboride Crystals

• DOI: 10.1021/ja804989q
• Publication Date: 2008-12-01T21:46:48Z
• Authors: Jonathan B. Levine; Sandy L. Nguyen; Haider I. Rasool; Jeffrey A. Wright; Stuart E. Brown; Richard B. Kaner
• Keywords: Thermogravimetric analysis; Indentation; Vickers hardness test

Single crystals of ReB(2) have been prepared from an aluminum flux under inert gas flow. The are typically 1-3 mm in diameter and 500 microm thick, growing along the [002] direction with a distinct hexagonal morphology. Vickers microhardness nanoindentation testing indicate that (002) plane possesses highest hardness measured values 40.5 36.4 GPa, respectively. elastic anisotropy was examined indentation moduli basal (hk0) unknown indices 675 510 Four-probe electrical resistivity measurements demonstrate is hardest material known to exhibit metallic behavior. Thermogravimetric analysis indicates stable air up 1000 degrees C due formation protective boron oxide coating.