Ultrasmall diamond nanoparticles with unusual incompressibility

M Popov and V Churkin and D Ovsyannikov and A Khabibrakhmanov and A Kirichenko and E Skryleva and Y Parkhomenko and M Kuznetsov and S Nosulchin and P Sorokin and S Terentiev and V Blank, DIAMOND AND RELATED MATERIALS, 96, 52-57 (2019).

DOI: 10.1016/j.diamond.2019.04.033

Based on experimental and theoretical studies, the 607 GPa bulk modulus of nanodiamond 2-5 nm was determined, which significantly exceeds the bulk modulus of diamond crystal (443 GPa) and approaches the values typical of ultrahard fullerite (600-1000 GPa). Bulk modulus of nanodiamond 2-5 nm was experimentally measured by piezospectroscopy using a diamond anvil cell with anvils made of synthetic diamond with a high (similar to 60%) C-13 isotope content. The Raman frequency in such diamond is at 1306 cm(-1) and does not interfere with the recording of a peak at 1325 cm(-1) of nanodiamond 2-5 nm. The bulk compression modulus was calculated from the dependence of the displacement of two Raman bands at 1325 cm(-1) and 1600 cm(-1) (the latter does not apply to sp(2) bonds) of nanodiamond 2-5 nm on pressure up to 68 GPa. Simulation of nanodiamond 1.2-5.9 nm confirms experimental results and also predicts the rise of bulk modulus with a decrease of nanoparticles size. Analysis of simulated structures suggests a possible explanation of observed effect due to increasing contribution of surficial compressed bonds when nanoparticles size reduces.

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