We synthesized pure polycrystalline cubic boron nitride

We synthesized pure polycrystalline cubic boron nitride (cBN) and wurtzite boron nitride (wBN) by the direct conversion method from hexagonal boron nitride. We measured their longitudinal-wave elastic constants CL between 20 and 300 K using picosecond ultrasound spectroscopy. Their room-temperature values are 945 ± 3 GPa and 930 ± 18 GPa for cBN and wBN, respectively. The shear modulus G of cBN was also determined by combining resonance ultrasound spectroscopy and micromechanics calculation as G

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Elastic constants of cubic and wurtzite boron nitrides

What is Wurtzite boron nitride?Wurtzite boron nitride is a metastable superhard material that is a high-pressure polymorph of BN. Clarifying how the metastable high pressure material can be stabilized at atmospheric pressure is a challenging issue of fundamental scientific importance. Here, we fabricate millimeter-size w-BN bulk crystals via the hexagonal-to-wurtzite phase transformation at high pressure and temperatures. By combining transmission electron microscopy and ab initio molecular dyna

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Can gallium carbide be formed

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