Formation of diamond nanostructures from graphite using 10 W fibre laser
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Bull Mater Sci (2020) 43:279 https://doi.org/10.1007/s12034-020-02255-8
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Formation of diamond nanostructures from graphite using 10 W fibre laser ASSIM VERMA, BHANU PRAKASH and DEEPIKA SHARMA* Institute of Nano Science and Technology, Mohali 160062, India *Author for correspondence ([email protected]) MS received 13 April 2020; accepted 11 August 2020 Abstract. The high activation energy required for graphite–diamond transition limits its applicability in novel areas. To exploit fully the multifunctional properties of diamond in diverse fields, there is a necessity to explore more efficient ways for its synthesis. In this study, we have demonstrated a new approach for nanodiamonds formation by employing a commercially available low power 10 W continuous-wave fibre laser. The laser system is modulated to generate the highpressure high temperature environment necessary for the phase conversion of graphite to diamond. The microsecond pulse duration combined with liquid confinement effect on plasma provide scope for a lower rate of supercooling, which restricts the epitaxial growth of the crystals. The sample is characterized by X-ray powder diffraction, transmission electron microscope and Raman spectroscopy, confirming the presence of different types of nanodiamonds including newly discovered n-diamond. The process offers many important advantages like scalable process, non-catalyst-based eco-friendly and cost-effective synthesis of metastable nanodiamonds. The results demonstrate the effectuality of inexpensive commercial lasers towards attaining the localized extreme environment necessary for direct phase conversion of diamond materials. Keywords.
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Nanodiamond; laser ablation; allotropes; phase conversion; green synthesis; fibre laser.
Introduction
Diamond is the special allotrope of carbon having closest atomic packing (176 atoms nm-3) and exist from nano to macro scale. The high atomic density combined with the maximum number of equidistant covalent bonds among carbon atoms (4) results in the enormous bond strength of 7.4 eV. This strong atomic bonding is responsible for its extreme physical, chemical, electronical and optical properties. The combination of these properties in a single allotrope of carbon makes it a wonder material, which finds its way in many emerging technologies like diamond batteries [1], fuel cells [2], quantum computing [3], quantum sensing [4], particle detector [5], theranostics [6], etc. After the discovery of nanodiamonds in the 1960s [7], various synthesis routes have been developed like highpressure high temperature carbon vapour deposition (HPHT CVD) [8], microwave plasma carbon vapour deposition (MPCVD) [9], ultrasonic cavitation method [10], detonation synthesis [11] and pulse laser ablation in liquid (PLAL) [12]. Each route has its advantage and disadvantage, which strongly influence the properties of nanodiamond [13]. Nevertheless, the requirement of very high activation energy for graphite to diamond phase transition
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