Journal of Hazardous Materials 192 (2011) 691–697 Contents lists available at ScienceDirect Journal of Hazardous Materials jou rn al h om epage: www.elsevier.com/loc ate/jhazmat Application of fly ash as a catalyst for synthesis of carbon nanotube ribbons Dilip C.D. Nath ∗ , Veena Sahajwalla Centre for Sustainable Materials Research and Technology, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia a r t i c l e i n f o Article history: Received 12 December 2010 Received in revised form 29 April 2011 Accepted 22 May 2011 Available online 27 May 2011 Keywords: Fly ash Carbon nanotube Poly (vinyl alocohol) Composite film and interface a b s t r a c t The larger diameter-based carbon nanotube (CNT) ropes and ribbons are currently synthesized by cat- alytic decomposition of hydrocarbons with transition metal-based catalysts e.g., Co, Ni, Fe and Mo at 1100–1200 ◦ C, using chemical vapour deposition (CVD) and electric arc methods. We produced CNT rib- bons by fly ash (FA) catalyzed pyrolysis of a composite film of poly (vinyl alcohol) (PVA) with FA at 500 ◦ C for 10 min under a nitrogen flow of 2 L/min. Different geometrical structures, e.g.; knotted and twisted, U- and spiral-shaped CNT ribbons were observed in the images of scanning and transmission electron microscopy. The widths of the CNT ribbons measured varied in the ranges 18–80 nm. X-ray photoelectron spectroscopy analysis showed five types of carbon binding peaks, C–C/C–H (∼77%), C–O–H (∼9%), –C–O–C (∼5%), C O (∼5%) and –O–C O (∼3%). The ratio of intensities of G and D bands, IG/ID was 1.61 analysed by Raman Spectroscopy. CNT ribbons grown on the surface of FA have potential for the fabrication of high-strength composite materials with polymer and metal. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. 1. Introduction CNT is a potential advanced material for wide ranges of appli- cations, e.g. composites, devices for energy storage and energy conversion, electrodes, catalyst supports and sensors [1]. The self-assembly of CNT fiber/ribbon is a big challenging task using one-step fabrication process. CNT tying knots and ribbons with high flexibility were assembled by post-processing method using the aqueous solution of sodium dodecyl sulphate (SDS) and PVA [2], or blended with PVA solution/gels [3]. The threads of CNTs have been assembled as a result of van der Waal interactions on silicon substrate. Another post-processing method for the fabrication of CNT films was reported using the dispersed gel/solution of CNT in oleum followed by drying [4]. The CVD of hexane and thiophene in the presence of ferrocene catalyst in a furnace has generated the isolated fiber strands [5]. The pyrolysis of benzene at 1000 ◦ C over Ni powder for 60 min also generated different types of carbon nanostructures materials [6]. Carbon nanocapsules with SiC nanoparticles were reported by ther- mal decomposition of PVA with SiC clusters at 500 ◦ C in argon [7]. Catalytic graphitization of amorphous carbon formed in the pyrol- ysis of PVA with Fe-containing catalyst has happened in the frame of CNT structure at 600–800 ◦ C in nitrogen flow for 2 h. The catalyst particles uniformly distributed on the surface and filled the hollow channel of CNT [8]. ∗ Corresponding author. Tel.: +61 2 9385 5130; fax: +61 2 9385 4292. E-mail address: dilip.nath@unsw.edu.au (D.C.D. Nath). Coal combustion in power station generates a huge amount of FA as a by-product. The managements of FA consequently made a global concern on the environmental and economic points of view [9]. FA is generally disposed as landfill in the fulfilment of dams and lagoons. It is typically consisted of crystalline aluminosilicate, mul- lite and -quartz along with trace amount of calcium, magnesium, potassium, sodium and titanium oxides, depending on the nature of coal burned. The particle size distribution patterns of the spherical- shaped FA are in the range of 1–100 m based on the processing condition [10]. In 2007, the beneficial application of FA is counted less than 20% on the amount of total production ∼14.5 million tons produced in Australia [11]. Research on recycling and reuse of FA as filler and catalyst/support has established an eco-friendly technology for value-added products and engineering composites. The successful beneficial applications of FA are agriculture and soil management, absorbents for heavy metals, waste stabilization, composite with polymer [10,12], cement and concrete [13], composite with metal [14] and catalyst/support [9,11]. Iron nitrate impregnated FA was recently used for the synthesis of multi-walled carbon nanotube (MWCNT) by CVD of the mixtures of gaseous precursors, ethylene, hydrogen and nitrogen at 700 ◦ C for 30 min [11]. This method consumed costly ethylene and highly flammable hydrogen gas as well as an additional impregnation step for FA. There is no published report to present where FA is used alone as catalyst for the synthesis of self-assembled CNT ribbon structures even with non-metal catalyst. We present a pyrolysis method using composite of PVA and FA in which FA acts as a catalyst for the growth of self-assembled CNT ribbons along with different geometrical CNT structures. 0304-3894/$ – see front matter. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2011.05.072