boron nitride transformations

High pressure phase transformations in turbostratic boron ...

Results of high pressure phase transformations in turbostratic boron nitride (tBN) using magnesium boron nitride as the catalyst-solvent are described. It was observed that turbostratic boron nitride undergoes various structural changes accompanied with the formation of hexagonal, cubic and wurtzitic modifications of boron nitride at high ...

Strain-induced disorder, phase transformations, and ...

Strain-induced disorder, phase transformations, and transformation-induced plasticity in hexagonal boron nitride under compression and shear in a rotational diamond anvil cell: In situ x-ray diffraction study and modeling Valery I. Levitas,a Yanzhang Ma, and Javad Hashemi

Turbostratic1 Boron Nitride, Thermal Transformation to ...

Well-orientated cubic boron nitride nanocrystals as studied by high-resolution transmission electron microscopy. Journal of Microscopy 2006, 223 (3), 205-207. DOI: 10.1111/j.1365-2818.2006.01620.x. Yong Jun Chen, Hong Zhou Zhang, Ying Chen. Pure boron nitride nanowires produced from boron …

Shear-induced phase transition of nanocrystalline ...

Nov 20, 2012· Disordered structures of boron nitride (BN), graphite, boron carbide (BC), and boron carbon nitride (BCN) systems are considered important precursor materials for synthesis of superhard phases in these systems. However, phase transformation of such materials can be achieved only at extreme pressure–temperature conditions, which is irrelevant to industrial applications.

Features of phase transformations in boron nitride ...

Since boron nitride polymorphs, unlike those of carbon, are not naturally available, their synthesis is a particularly important task. Phase transformations in solids under shock compression have been the subject of many reviews (for the most recent ones, see refs.,,, ).

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Boron Nitride powder is a white solid material which has low porosity.It can be easily machined into complex shapes using standard carbide tooling. The material is anisotropic for its electrical and mechanical properties due to the platy hexagonal crystals …

Mechanisms of martensitic transformations in boron nitride ...

Mechanisms of martensitic transformations in boron nitride and conditions of their development. V. F. BRITUN Institute for Materials Science Problems, National Academy of Sciences of Ukraine, 3 Krzhyzhanovsky Str., Kiev, 252680, ...

Boron nitride - Wikipedia

Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to …

STRUCTURE AND PROPERTIES MODIFICATIONS IN BORON …

Direct polymorphic transformations mechanisms in boron nitride 39 Fig.2. The P-T phase equilibrium diagram of boron nitride and the kinetic lines for the direct transformations between the BN polymorphs Among the transformations indicated in Fig.2 the most interesting one from a

Structural transformations in the formation of superhard ...

Apr 12, 2012· Abstract. Mechanisms of structural transformations, which occur in sintering materials produced on the basis of wurtzitic boron nitride at high pressures and …

Transformations of graphite and boron nitride in shock ...

Key words: Polymorphous transformations, Shock adiabats, Graphite, Boron nitride, Mechanism of transformation, Kinetics Received 11 March 1993 / Accepted 15 September 1993 This is a preview of subscription content, log in to check access.

Phase transformations of carbon and boron nitride at high ...

Phase transformations of carbon and boron nitride at high pressure and deformation under pressure. Pages 35 . Carbon with its unique physical and mechanical properties, as well as its structural analogue boron nitride, is of great interest for research. Suffice it to say that carbon is the most refractory and, in the crystal lattice of diamond ...

The geometry of hexagonal boron nitride clusters in the ...

To understand the nucleation process in the growth of hexagonal boron nitride (h-BN) on transition metal substrates by chemical vapor deposition (CVD), the energy of formation and stability of h-BN clusters of different geometries on a pristine Cu(111) surface were systematically investigated using density functional theory calculations.

In situ FTIR investigation on phase transformations in BN ...

Will, G., High pressure phase transformation of cubic boron nitride from amorphous boron nitride using magnesium boron nitride as the catalyst, J. Cryst. Growth, 1995, 152: …

Phase Transformation of Amorphous Boron Nitride under High ...

Jun 05, 2003· Amorphous boron nitride (BN) powder was prepared by mechanically milling hexagonal BN and used as a starting material for studying BN phase transformation behavior. Fabricated amorphous BN (aBN) powder was significantly reactive with humidity in the air. When it was kept under a dry nitrogen atmosphere without H2O or O2, the phase transformation from aBN to cubic BN (cBN) …

Transformation of Hexagonal Boron Nitride in Cubic Boron ...

Transformation of Hexagonal Boron Nitride in Cubic Boron Nitride with Catalytic Magnesium. ... To facilitate the transformation of hBN to cBN, there can be applied one or more catalytic, such as ...

Boron steel - Wikipedia

Boron is effective at very low concentrations - 30 ppm B can replace an equivalent 0.4% Cr, 0.5% C, or 0.12% V. 30 ppm B has also been shown to increase depth of hardening (~ +50%) in a low alloy steel - thought to be due to its retardation of the transformation …

Transformations of Cold-Compressed Multiwalled Boron ...

Multiwalled boron nitride nanotubes (BNNTs) were compressed at room temperature in diamond anvil cells up to 35 GPa, followed by decompression. For the first time, in situ infrared absorption spectroscopy was used to monitor BNNT structural transformations. These BNNTs were found to undergo pressure-induced transformations from a hexagonal to a more closely packed wurtzite structure at 11 GPa ...

High pressure phase transformations of cubic boron nitride ...

Results are described of high pressure phase transformations of amorphous boron nitride (aBN) to cubic boron nitride (cBN) using magnesium boron nitride (Mg 3 B 2 N 4) as a catalyst-solvent.It was observed that amorphous boron nitride undergoes various structural modifications under high pressures and high temperatures leading to the formation of hexagonal, cubic and wurtzitic phases of boron ...

Researchers Discover New Phase of Boron Nitride and a New ...

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 ...

Stone-Wales transformation in boron nitride nanotubes ...

A hybrid atomistic/continuum model is used to study the Stone-Wales transformation (90° rotation of an atomic bond) in boron nitride nanotubes (BNNTs) subjected to tension. The critical strain for Stone-Wales transformation is 11.47% for (5, 5) armchair and 14.23% for (10, 0) zigzag BNNTs, which agree well with the atomistic simulations.

Ab initio study of phase transition of boron nitride ...

Boron nitride has polymorphs such as zinc-blende (c-BN), wurtzite (w-BN), rhombohedral (r-BN), and graphite-like (h-BN) forms. We simulate the direct conversion of r-BN to c-BN through electronic excitation. In our calculation, the conversion is made possible by …

Structural transformations of carbon and boron nitride ...

The behavior of nanostructures under high strain-rate conditions has been the object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high-velocity impacts. However, the response of many 2018 PCCP HOT Articles

Ab initio study of phase transformations in boron nitride

The p-T phase diagrams of these four boron nitride phases are constructed with the quasiharmonic approximation. Direct compression simulations are then performed to find probable phase transformation paths among these polytypes, with additional energy calculations of …

Ion Beam Modifications of Boron Nitride By Ion …

boron nitride (aBN), (b) the rhombohedral boron nitride (rBN) modifications, (c) crys-talline and amorphous boron clusters, which are a result of the agglomeration of elemen-tary boron during and immediately after ion implantation. These transformations were observed at high energies. Unfortunately, the XRD measurements carried out could not

Ab initio study of phase transformations in boron nitride ...

Request PDF on ResearchGate | Ab initio study of phase transformations in boron nitride | The structural properties and phase stability of the four common polytypes of boron nitride, cubic zinc ...

Stone–Wales transformation in boron nitride nanotubes

study the Stone–Wales transformation in boron nitride nanotubes subject to tension. It is shown that the Stone–Wales transformation occurs and generates the 5775 defects when the tensile strain reaches 11.47% for (5,5) armchair and 14.23% for (10,0) zigzag BNNTs. The …

Probing the Transformation of Boron Nitride Catalysts ...

Hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs) were recently reported as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins in the gas phase. Previous studies revealed a substantial increase in surface oxygen content after exposure to ODH conditions (heating to ca. 500 °C under a flow of alkane and oxygen); however, the complexity of ...

Oxidative Unzipping and Transformation of High Aspect ...

Morphological and chemical transformations in boron nitride nanotubes under high temperature atmospheric conditions is probed in this study. We report atmospheric oxygen induced cleavage of boron nitride nanotubes at temperatures exceeding 750 °C for the first time. Unzipping is then followed by ...

PHASE TRANSFORMATIONS IN BORON NITRIDE CAUSED BY …

Citations consider compacting and sintering processes. Phase transformations, crystallization, and devitrification processes are considered. Aluminum nitride, boron nitride, silicon nitride, silicon oxynitride, and titanium nitride are among materials discussed. The use of hot isostatic pressing is considered in a separate bibliography.