A new class of ultra-hard materials based on AlMgB14

Bonding and elastic properties of amorphous AlYB

“…Hardness values in the range of 30 GPa were measured for AlLiB 14 [4]. With the addition of TiB 2 to AlMgB 14 hardness values up to 46 GPa were reported [11]. These ternary borides are semimetallic (band gap 0.3 eV for ErAlB 14 [12]), implying good electrical conductivity and large Seebeck coefficient (6500 mV K −1 for MgAlB 14 [12]), which gives rise to a potential application in thermoelectric devices.…”

Fracture Strength ofAlLiB14

“…[1][2][3] The orthorhombic borides, formulated as XYB 14 where X and Y are metal atoms, have been of interest to scientists and engineers for the past decade due to a report [4,5] that AlMgB 14 prepared by mechanical milling can achieve a hardness between 32 and 46 GPa. The reason for the observed superhardness is not understood.…”

“…[13][14][15]20] This is in part because the system is known to accept a large number of metal species including Li, Be, Na, Mg, Al, as well as a variety of rare-earth elements, such as Tb, Dy, Ho, Er, Yb, and Lu. [4,18,19,[21][22][23][24] In addition the superhard Ames Lab specimen was synthesized by a mechanical alloying method, which introduces a wide variety of impurity species to the crystal including Ti, Si, Fe, O, and C. [5] In these theoretical studies the reported figure of merit for hardness is the bulk modulus because its computation is relatively simple. However, the bulk modulus alone only gives information about the average bond strength under an applied volume dilation and does not give any information about the strength of individual bonds in the crystal.…”

Nanocoatings for High-Efficiency Industrial Hydraulic and Tooling Systems

“…The primary focus of the project was on the development and commercialization of a family of nanoscale composites in which the hardness is derived from microstructural engineering of the constituent phases, referred to as extrinsic hardness [4] . Proof-of-concept studies leading up to this project had shown that the constituent phases, AlMgB 14 and TiB 2 , were capable of producing low-friction coatings by pulsed laser deposition.…”