Reduction of carbon byproducts for high-purity carbon nanocoil growth by suppressing catalyst collision

Abstract

Carbon nanocoils (CNC) are promising nanocarbon materials for application as functional composites such as electromagnetic wave absorbers. However, the suppression of carbon byproducts during CNC growth is necessary to obtain high purity CNCs with high yield. Here, we demonstrate a simple but efficient method for the reduction of carbon byproducts using a patterned thin film catalyst. Results show that the collision of tip catalysts of growing CNCs to the substrate or other CNCs inhibits the smooth growth of CNCs because of the deactivation of the catalyst. The collision also stimulates the formation of a carbon byproduct layer underneath the CNC layer. The well-controlled thin film catalyst with checkerboard pattern brings us four-times-higher efficiency of the catalyst and suppresses the carbon byproduct layer to ~1/3.

Growth of Carbon Nanocoils by Porous α-Fe2O3/SnO2 Catalyst and Its Buckypaper for High Efficient Adsorption

“…4a. It is found that the height of CNC layer continuously increased with growth time, and the maximum thickness of the CNC layer reaches 306 μm after the reaction for 6 h. This is the highest value compared with those reported recently [34][35][36][40][41][42]. It is noted that both curves of the yield and thickness versus time are well matched, suggesting that the carbon deposits are almost CNCs.…”

“…1 f. The enlarged image of the area indicated by the box in Fig. 1 f shows the morphology of by-product layer, which is mainly composed of carbon-containing catalytic metal particles [ 42 ].

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“…Although some improvements were made in raising the purity and yield of CNCs using different systems of catalysts, the low CNC purity is still a challenging issue. The main problem is that the high-purity CNCs are mainly present on the surface of carbon deposits, and there is always an amorphous carbon layer with a thickness ranging from several to tens of microns between the CNC layer and substrate [40][41][42]. This amorphous carbon layer mixed in the products seriously reduces the purity of CNCs and introduces additional problems of purification.…”

“…In order to overcome this problem, some valuable work has been performed, Hirahara et al successfully improved the growth efficiency of CNCs by introducing an extra SnO 2 buffer layer between the catalyst layer and substrate, the thickness of by-product carbon layer was reduced by 50%, and the growth rate was improved 200% compared with the substrate without coating SnO 2 [ 41 ]. Takehiro et al reduced the thickness of by-product carbon layer to 1/3 by designing a patterned catalyst thin film based on the principle of suppressing catalyst collision [ 42 ]. However, the use of lithography or magnetron sputtering technology does not make it possible for large-scale industrial production of CNCs.…”