A novel Ca3(PO4)2–CaCO3 support mixture for the CVD synthesis of roughened MWCNT-carbon fibres

Abstract

Multiwalled carbon nanotubes (MWCNTs) with unusual rough surfaces (including pits) have been synthesised by the chemical vapour decomposition process of acetylene using a novel Ca3(PO4)2–CaCO3 support mixture. An Fe–Co bimetallic mixture (50 : 50, w/w) was impregnated (5 wt% loading) onto either Ca3(PO4)2 to give <1% MWCNTs or CaCO3 to give high yields of MWCNTs with smooth surfaces. Mixtures of Ca3(PO4)2–CaCO3 (0/100–100/0) yielded tubes with very rough surfaces (t = 30 min, 1 h) and the CNT yield increased with respect to the amount of CaCO3 in the support mixture. The inner walls of the CNTs possessed a regular orientation of crystalline graphite sheets (3–5 nm), while the outer surface of the CNTs had a thick, rough, compact layer (∼30 nm) of carbon with a random orientation of graphite sheets. These induced extremely rough surfaces of the CNTs could serve as ‘docking stations’ that can harbour a variety of metal catalyst particles for industrially important applications.