Facile 1D graphene fiber synthesis from an agricultural by-product: A silicon-mediated graphenization route

K Fujisawa and Y Lei and C de Tomas and I Suarez-Martinez and CJ Zhou and YC Lin and S Subramanian and AL Elias and M Fujishige and K Takeuchi and JA Robinson and NA Marks and M Endo and M Terrones, CARBON, 142, 78-88 (2019).

DOI: 10.1016/j.carbon.2018.10.032

A one-dimensional (1D) graphene fiber with a novel structure has been prepared by a heat treatment of rice husk, a natural by-product that contains high amounts of silica. A step-by-step heat treatment of rice husk revealed that (i) carbonization yields porous carbon and silica, (ii) 1D beta-SiC nanowires are formed by the carbothermic reduction of silica, (iii) finally 1D graphene fibers are created by silicon sublimation from 1D beta-SiC nanowires. Raman spectroscopy and electron microscopy studies revealed that the graphene fiber is composed of a turbostratic multilayer structure. The SiC-derived material exhibits a large crystalline size and turbostratic stacking making each layer as quasi-free-standing graphene, which is confirmed by the 3.9 times higher Raman G'-band intensity over the G-band intensity. Molecular dynamics simulations revealed a high diffusion rate of Si atoms and a volume reduction of the SiC structure at the sublimation temperature. Since the silicon sublimation occurred from multiple points of the SiC nanowire, this led to radially-collapsed fibers and faceted structures with thick- graphitic-layer that are inter-connected (deflated-balloons and inter- connected balloon-like fibers). This facile synthesis route opens up a new avenue to the cost-effective and etching-free production of self- standing graphene for its bulk usage. (C)2018 Elsevier Ltd. All rights reserved.

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