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Laser Heating of Boron Nitride and Graphite in a Diamond Anvil Cell
Published online by Cambridge University Press: 10 February 2011
Abstract
Cubic, hexagonal BN, and graphite were heated with the aid of cw CO2 or pulsed YAG laser in a diamond anvil cell at pressures up to 35 GPa. The recovered samples were analyzed by high resolution and scanning electron microscopy, micro-Raman, and X-ray diffraction using synchrotron radiation. Melting of hBN and cBN was achieved. Microcrystals of hBN or cBN were grown from the fluid of BN in nitrogen or argon. Analysis of the hBN-cBN transitions in dependence on pressure showed that the hBN-cBN-liquid triple point is located at 9 GPa. In the transient region between the two phases in the same sample amorphous BN was found revealing the microscopic mechanism of diffusion-like first-order transitions. BN nanotubes growing from an amorphous state at the surface of the crystals were discovered. Under nanosecond pulse laser heating graphite transforms to a diamond-like structure. Spherical droplets and nanocrystals were condensed from the ablated carbon. A compound of nitrogen with carbon was found.
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- Copyright © Materials Research Society 1998
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