Abstract
: Dense diamond-like BCN compounds are of interest due to their extreme hardness and predicted excellent thermal and chemical stability, which are superior to those of diamond and c-BN. Here, we report on the high-pressure high-temperature (HP-HT) behavior of amorphous BC2N and BC4N -as potential precursors for HP-HT synthesis of diamond-like BCN. Prepared via hydroboration reaction of piperazine borane and pyridine borane, respectively, amorphous BC2N and BC4N are characterized by well-mixed B-N, C-C and C-N bonds, confirmed by XPS analysis. These BCN compositions were subjected to pressures between 5-12 GPa and temperatures up to 1700 °C using multi-anvil apparatus and toroid-type press. In- and ex-situ X-ray diffraction reveals the decomposition of BC4N to graphite and h-BN between 5 and 12 GPa above 500 °C, in contrast to BC2N which remains amorphous up to 1600 °C.
Highlights
Dense B-C-N ternary phases have drawn considerable attention during last two decades due to their predicted properties, making them the best alternative to diamond and c-BN [1]: Super-hard BCN phase is believed to be harder than c-BN and to have better thermal and oxidation stability than diamond [1, 2]
In the present paper we report on the high-pressure high-temperature (HP-HT) behavior of amorphous BC2N and BC4N, which are synthesized via hydroboration reaction of piperazine borane and pyridine borane, respectively [1, 20, 21]
Precursor synthesis and characterization The precursors BC2N and BC4N were prepared by the hydroboration reaction of piperazine borane and pyridine borane, respectively [1, 20]
Summary
Dense B-C-N ternary phases have drawn considerable attention during last two decades due to their predicted properties, making them the best alternative to diamond and c-BN [1]: Super-hard BCN phase is believed to be harder than c-BN and to have better thermal and oxidation stability than diamond [1, 2]. Subsequent HP-HT studies can be roughly divided into two categories: i) Synthesis at 20 GPa and above, focusing on superhard cubic B-C-N phase; ii) synthesis below 20 GPa, focusing on crystalline graphitic ternary B-C-N. Later Solozhenko et al [11] studied graphite-like BC4N up to 1800 °C and 7 GPa using multi anvil press and showed its metastable behavior. Nicolich et al [12] reported the formation of ordered graphitic ternary crystals from turbostratic BCN around 3-5 GPa and 1200-1500 °C. Several recent papers reported formation of h-BCN [14], orthorhombic BC3.3N [15], solid solutions of c-BN in carbon [16], and even c-BCN below 20 GPa and 2000 °C [17,18,19]. The samples were characterized by in and ex–situ X-ray diffraction (XRD)
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