These results showed that the CNFs produced at 700°C had the highest quantity of graphitic carbon and were similar to those reported in previous studies where Fe-supported catalysts were used [42]. Figure 3 Raman spectra and I D / I G ratios. (a) Laser Raman spectra of as-received coal fly ash and the products from fly ash exposed to acetylene at various temperatures. (b) I D/I G ratios of the CNFs synthesized in acetylene. The D and G band peaks confirmed the formation of CNFs that were identified by TEM. CNFs at 500°C displayed the highest degree of disorder. Figure 4 The first-order weight derivatives of as-received and acetylene-treated

coal fly ash at varying temperatures. CNFs at 700°C displayed the highest oxidation temperature, but CNFs at 500°C displayed CFTRinh-172 a bimodal oxidation PI3K inhibitor profile. Thermogravimetric studies Thermogravimetric analyses were carried out to investigate the thermal degradation behaviour of as-received and acetylene-treated fly ash. It has been reported that the graphitic nature of CNMs is directly proportional to their

thermal stability [43]. Hence, the first-order weight derivatives of the data so obtained typically gives an indication of the type of carbon present (Figure 4). Typically, highly crystalline nanofibers have been found to be resistant to oxidation when compared to other forms of carbon [44]. Additionally, the diameters and the amount of CYT387 purchase defects

in such materials have also been known to influence their oxidation temperatures [36]. From the TGA thermograms, it was observed that all of the CNMs produced had final oxidation temperatures that were greater than 550°C. However, as previously stated, at least two different forms of carbon were synthesized when the reaction temperature was 500°C. These may have Thiamet G arisen due to the poor carbonization of acetylene, leading to impurities such as amorphous carbon and hence the formation of a higher degree of non-graphitic carbonaceous materials, as confirmed by the laser Raman results (Figure 3a). However, CNFs synthesized at 700°C had the highest oxidation temperature (c.a. 690°C). These results concurred with the laser Raman data, where CNFs formed at 700°C displayed the lowest I D/I G ratio, i.e. they were the most graphitic. Particle size and surface area measurements The particle sizes and surface areas of the as-received and acetylene-treated coal fly ash which reacted at temperatures between 400°C and 700°C are depicted in Figures 5,6,7. As-received coal fly ash, when analysed in water, had a particle size of 160 μm. After exposure to acetylene at 700°C, this size was reduced to 130 μm. A small reduction in the particle size was anticipated, as the fly ash particles were entrained in the CNFs, hence reducing their agglomeration.