Investigation of relaxation of nanodiamond surface in real and reciprocal spaces |
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Authors: | B. Palosz C. Pantea E. Grzanka S. Stelmakh Th. Proffen T.W. Zerda W. Palosz |
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Affiliation: | aInstitute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland;bLANSCE at LANL, Los Alamos, USA;cTCU, Physics Department, Forth Worth, Texas, USA;dBAE Systems, NASA/MSFC, Huntsville, Alabama, USA |
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Abstract: | The structure of a nanodiamond powder with an average grain size of 5 nm was investigated using large-Q neutron diffraction. Both Bragg scattering and PDF analysis were employed. The effect of annealing under vacuum at temperatures up to 1200 °C was studied. The studies lead to a tentative model of nanocrystalline diamond, where the core with a perfect diamond lattice is surrounded by a shell of compressed diamond lattice, and this core–shell structure is enveloped in a non-diamond carbon. The non-diamond envelope of nanograins, a “gas-like” carbon, is stable up to 1000 °C and transforms into a graphite phase (an onion-type structure) at about 1200 °C. The amount of non-crystalline carbon in the powder annealed below 1000 °C is about 10%. In the sample annealed at 1200 °C a graphite-type carbon, with a total of about 15% of sp2 bonds is formed. |
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Keywords: | Diamond Nanocrystals Structure neutron diffraction |
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