Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air

Abstract

We report a direct conversion of hexagonal boron nitride (h-BN) into pure cubic boron nitride (c-BN) by nanosecond laser melting at ambient temperatures and atmospheric pressure in air. According to the phase diagram, the transformation from h-BN into c-BN can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa. Using nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to formation of super undercooled BN (Q-BN). The c-BN phase is nucleated from Q-BN depending upon the time allowed for nucleation and growth.

Novel synthesis and properties of pure and NV-doped nanodiamonds and other nanostructures

“…The characterization of diamond phase was carried by using electron backscatter diffraction (EBSD), Raman spectroscopy (532 nm source) and photoluminescence (PL) with 325 nm source. Detailed atomic structure and bonding characterization of various diamond structures using transmission electron microscopy/scanning transmission electron microscopy and electron energy loss spectroscopy have been already reported [12][13][14]. Alfa300 R superior confocal Raman spectroscope with a lateral resolution less than 200 nm was employed to characterize the Raman active vibrational modes.…”

“…These nanodiamonds can be arranged periodically in a self-organized fashion, which is needed for quantum devices. The special emphasis is on N-doped (NV diamond) nanostructures with concentrations exceeding solubility limits, while comparing with our earlier results on undoped diamond nanostructures [12][13][14]. Since diamond growth occurs from a liquid phase under ultrarapid quenching and solidification with velocity of the order of 5 m s −1 , it is possible to trap NV defects beyond thermodynamic limits.…”

“…Earlier work focused on the discovery of Q-carbon, Q-BN and direct conversion of carbon into diamond and h-BN into c-BN [11][12][13][14]. Nanodiamonds are formed by homogeneous or heterogeneous nucleation from the undercooled melt, where the size is dictated by the melt lifetime.…”

“…The EPR spectrum of a single NV center can be detected and shifts of EPR spectra are measured from perturbations in electric and magnetic fields, temperature, spatial Figure 1. (a) Atomic structure of substitutional nitrogen and vacancy (NV) defect in < 110 > chain of diamond; and (b) NV defect in a diamond tetrahedron contained in (a/2,a/2,a/2) diamond unit cell, where one of the carbon can be replaced by magnetic isotope 13 C.…”

Electrodischarge Drilling of Microholes in c-BN

“…Even if recent developments in material science have introduced an efficient way to create c-BN, which makes the material more viable for applications such as high-power electronics, transistors, and solid-state devices, they have not resolved the problem of the inefficient machining of c-BN [3]. The most frequently used technology for manufacturing parts of c-BN is sintering [4,5].…”