Synthesis and High Pressure Mechanical Properties of Superhard Rhenium/Tungsten Diborides Nanocrystals

Rhenium diboride is an established superhard compound that can scratch diamond and can be readily synthesized under ambient pressure. Here, we demonstrate two synergistic ways to further enhance the already high yield strength of ReB2. The first approach builds on previous reports where tungsten is doped into ReB2 at concentrations up to 48 at.%, forming a rhenium/tungsten diboride solid solution (Re0.52W0.48B2). In the second approach, the composition of both materials is maintained, but the particle size is reduced to the nanoscale (40~150 nm). Bulk samples were synthesized by arc melting above 2500 oC and salt flux growth at ~850 oC was used to create nanoscale materials. In situ radial X-ray diffraction was then performed under high pressures up to ~60 GPa in a diamond anvil cell to study mechanical properties including bulk modulus, lattice strain, and strength anisotropy. The differential stress for both Re0.52W0.48B2 and nano ReB2 (n-ReB2) was increased compared to bulk ReB2. In addition, the latti...