Atomic-Scale Structural Investigations on the Nucleation of Cubic Boron Nitride from Amorphous Boron Nitride under High Pressures and Temperatures

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Detail(s)

Original languageEnglish
Pages (from-to)1873-1878
Journal / PublicationChemistry of Materials
Volume14
Issue number4
Online published6 Mar 2002
Publication statusPublished - 1 Apr 2002
Externally publishedYes

Abstract

By controlling the microstructure of the starting materials, i.e., by ball-milling a commercial hexagonal boron nitride (h-BN) to an amorphous boron nitride (a-BN), the subsequent high-pressure and high-temperature (HP-HT) induced phase transformation has been significantly facilitated. Namely, cubic boron nitride (c-BN) forms at 900°C and achieves accomplishment at 1350°C under 7.7 GPa, which are significantly less-extreme conditions than that of crystalline h-BN under similar HP-HT treatments. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) clarified the nucleation mechanism at an atomic scale. It demonstrated that the c-BN phase nucleates directly from the sp3-hybridized amorphous matrix, which is originally induced by ball-milling and is therefore responsible for the reduced HP-HT conditions. This c-BN nucleation mechanism is completely different from the so-called diffusionless "puckering" mechanism involved in the HP-HT experiments starting from crystalline h-BN but very similar to one of the proposed mechanisms involved in the chemical vapor deposition (CVD) of diamond and c-BN. It turns out that the present experimental results provide not only a less-extreme way to synthesize nanocrystalline c-BN material but also key clues to the understanding of the nucleation mechanisms involved in the CVD diamond or c-BN, which are still under controversy.