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ABSTRACT
Mechanical exfoliation can generate graphene, but a consistent and scalable preparation of few-layer graphene (FLG) continues to be a challenge. We employed a mechanochemical milling technique to achieve maximum shear and frictional force by dual drive mode operation for preparation of FLG directly from beneficiated graphite ore. Low-grade graphite ore from Jharkhand, India, with a carbon content of 9%, was subjected to primary beneficiation by froth flotation technique using the naturally hydrophobic property of graphite as opposed to the associated impurities. The obtained graphite concentrates with an enriched carbon content above 90% after flotation was subjected to chemical treatment process including alkali roasting and acid leaching, which yielded an enriched graphite powder with fixed carbon of about 98.16%. A comparative study regarding the leaching efficiency was carried out between sulfuric acid and hydrochloric acid. The few-layered graphene was successfully prepared by mechanical milling of beneficiated graphite ore with oxalic acid at 20 hours with optimized critical speed. At various milling hours, the amplitude of the peak (002) decreased continuously, suggesting that the graphite size and thickness had decreased. Raman Spectroscopy confirmed the 20 h milled graphite is having single and few layered (<4 layers) graphene sheets.
Acknowledgments
We acknowledge the Ministry of Mines, New Delhi for financial support. Authors also would like to thank The Director of CSIR – National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum and CSIR – National Metallurgical Laboratory, Madras Centre, Chennai for their permission to publish this paper. We would also like to acknowledge Dr. Kaustabh Kumar Maiti, Peer Mohamed, and Harish Raj for their support in characterising the samples at CSIR-NIIST.