The Quest for Superhard Materials

WHY SUPERHARD?

For over 10 years, Dr. Richard Kaner and researchers at UCLA’s Kaner Laboratory, have been on a quest to develop cost-effective, superhard materials to meet the growing demand for next-generation cutting and polishing tools. Their work, mixing various transition metals, went through four stages until they achieved the best combination of properties in Tetrideᵀᴹ, which rivals diamond in incompressibility, scores high in fracture toughness, and can be synthesized without the use of high-pressure/high temperature. At the UCLA Faculty Research Lecture, in February, 2014, Dr. Kaner described the process and the promise of his work with superhard materials. But first, he answers a basic question.

PASSING THE DIAMOND SCRATCH TEST

In 2005, Dr. Kaner’s team combined the relatively soft element osmium, the most incompressible metal known, with small covalent-bond forming atoms to make a material that is almost as incompressible as diamond, yet is so hard that it scratches sapphire, which is ranked 9 on a hardness scale of 1 to 10. “We found that if we combine boron with osmium, we push the osmium atoms apart by only 10 percent from where they were in osmium metal, which is very good; you want to push them apart as little as possible,” said Dr. Kaner. “Then we searched through the transition metals to see if we could do better than osmium.” That led them to rhenium, a fairly dense, soft metal. “We formed short covalent bonds, pushing the rheniums apart by just 5 percent from where they were in rhenium metal, making it both incompressible and very hard. Rhenium diboride is as incompressible as diamond in one direction, and in the other direction, just slightly more compressible.” At low applied forces, the hardness of rhenium diboride is equivalent to cubic boron nitride, the second-hardest material known. At higher applied forces, rhenium diboride is a little bit below that. “Our material is hard enough to scratch diamond, and much harder than osmium diboride,” he said.

PATENTS AND PUBLICATIONS

We have a number of patents issued / papers published; additionally, we have a number of pending patent applications. Please find a few select publications related to research activity at SuperMetalix.
A.T. Lech, C.L. Turner, J. Lei, R. Mohammadi, S.H. Tolbert, R.B. Kaner. “Superhard Rhenium/Tungsten Diboride Solid Solutions”, J. Am. Chem. Soc. 138 (43), 14398-14408 (2016).

M.T .Yeung, J. Lei, R. Mohammadi, C.L Turner, Y. Wang, S.H. Tolbert, and R.B. Kaner. “Superhard Monoborides: Hardness Enhancement through Alloying in W1− xTaxB”, Advanced Materials 28 (32), 6993-6998 (2016).

M. Xie, B. Winkler, R.B. Kaner, A. Kavner and S.H. Tolbert,”Raman scattering from superhard rhenium diboride under high pressure“, Appl. Phys. Lett., 104, 011904 (2014).

A. Kavner, M.B. Weinberger, A. Shahar, R.W. Cumberland, J.B. Levine, R.B. Kaner, and S.H. Tolbert, “Lattice strain of osmium diboride under high pressure and nonhydrostatic stress”, J. Appl. Phys., 112, 013526 (2012).

R. Mohammadi and R.B. Kaner, “Superhard materials”, in Encyclopedia of Inorganic and Bioinorganic Chemistry (R.A. Scott ed., John Wiley and Sons, Inc. 2012).

A. Kavner, M. Armentrout, E. Rainey, M. Xie, S.H. Tolbert and R.B. Kaner, “Thermoelastic properties of ReB2 at high pressures and temperatures and comparison with Pt, Os and Re”, J. Appl. Phys., 110, 93518 (2012).

J.B. Levine, J.B. Betts, J.D. Garrett, J.D. Eng, S. Guo, R.B. Kaner and A. Migliori, “Full elastic tensor of a monocrystal of the superhard compound ReB2”, Acta Materialia, 58, 1530 (2010).

J.B. Levine, S.H. Tolbert and R.B. Kaner, “Advancements in the search for superhard, ultra-incompressible metal borides”, Adv. Funct. Mater., 19, 3519 (2009).

H.Y. Chung, M.B. Weinberger, J.-M. Yang, S.H. Tolbert and R.B. Kaner, “Correlation between hardness and elastic moduli of the ultra-incompressible transition metal diborides RuB2, OsB2 and ReB2”, Appl. Phys. Lett., 92, 261904 (2008).

H.Y. Chung, J.M. Yang, S.H. Tolbert and R.B. Kaner, “Anisotropic mechanical properties of ultra-incompressible osmium diboride”, J. Mater. Res., 23, 1797 (2008).

H.Y. Chung, M.B. Weinberger, J.B. Levine, R.W. Cumberland, A. Kavner, J.-M. Yang, S.H. Tolbert and R.B. Kaner, “Response to comment on synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure“, Science, 318, 1550d (2007).

H.Y. Chung, M.B. Weinberger, J.B. Levine, R.W. Cumberland, A. Kavner, J.-M. Yang, S.H. Tolbert and R.B. Kaner, “Synthesis of ultra-incompressible superhard rhenium diboride at ambient pressure“, Science, 316, 436 (2007). Featured in Chemical & Engineering News, April 23, 2007, p. 39 and Business Week, May 7, 2007, page 79.

Gilman, J. J.; Cumberland, R. W.; Kaner, R.B. “Design of hard crystals” International Journal of Refractory Metals & Hard Materials, 24, 1 (2006).

R.W. Cumberland, M.B. Weinberger, J.J. Gilman, S.M. Clark, S.H. Tolbert and R.B. Kaner, “Osmium diboride, an ultra-incompressible, hard material“, J. Am. Chem. Soc., 127, 7264 (2005). Featured in Chemical & Engineering News, May 16, 2005, p. 33.

R.B. Kaner, J.J. Gilman and S.H. Tolbert, “Materials Science: Designing superhard materials,” Science, 308, 1268 (2005).