Electronic structure hexagonal boron nitride

The traditional method for the preparation of boron nitride is by the fusion of urea with boric acid in an atmosphere of ammonia at 750 °C.54 The product from these reactions is hexagonal boron nitride with a layer structure like that of graphite. Unlike graphite, it is colorless and is not an electronic conductor. Conversion of the hexagonal form to a cubic modification requires heating at 1,800 °C at 85,000 atmospheres pressure. 

The crystal structure of boron nitride resembles that of graphite. The boron and nitrogen atoms form plane regular hexagonal nets which are arranged parallel to one another at a distance of 3.33 A. An essential difference between graphite and boron nitride is that in the latter there are no free electrons. Pure boron nitride is white and does not conduct electricity. 

In this work, we investigate the formation of hexagonal boron nitride (h-BN) fiom the tribochemical reaction between a borated additive and a nitrogenous compound. We developed a multitechnique approach including X-Ray Photoelectron Spectroscopy (XPS), X-ray Absorption Near Edge Structure Spectroscopy (XANES), Electron Energy Loss Spectroscopy (EELS) and high resolution TEM (HRTEM). 

Boron nitride is a white slippery solid. One B atom and one N atom together have the same number of valency electrons as two C atoms. Thus boron nitride has almost the same structure as graphite, with sheets made up of hexagonal rings of alternate B and N atoms joined together. 

Boron compounds with nonmetals, i.e., boron hydrides, carbides, nitrides, oxides, silicides, and arsenides, show simple atomic structures. For example, boron nitride (BN) can be found in layered hexagonal, rhombohedral, and turbostratic or denser cubic and wurtzite-like structures, as well as in the form of nanotubes and fullerenes. Boron compounds with metalloids also differ from borides by electronic properties being semiconductors or wide-gap insulators. 

Boron nitride, for instance, having electronic properties that resemble carbon can exist in a hexagonal structure h-BN similar to the graphite layered geometry. Much like graphene sheets, BN sheets can be grown on more or less lattice-matched transition metal surfaces (Corso et al. 2004 Huda and Kleinman 2006). A model BN sheet is shown in O Fig. 27-14. 

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