Figure 8 EDS of CNFs synthesized at 700°C. Berrylium, carbon, aluminium, silica and iron were the elements identified after synthesis. Figure 9 XRD of as-received coal fly ash and acetylene-treated coal fly ash at 700°C. As-received coal fly ash contained mullite, quartz and hematite as major phases. After synthesis, peak shifting selleck screening library occurred, the crystallinity changed, and the formation of silicates and Fe phases were more evident. The major phases in the as-received Fosbretabulin coal fly ash were quartz (SiO2), hematite (α-Fe2O3) and mullite (3Al2O3 · 2SiO2).

After exposure to acetylene, it was noted that peak shifting and broadening had occurred, as was most evident in quartz at 26.5° (2θ). This may have been caused by amorphous glassy phases, found in the as-received fly ash, which when exposed to acetylene and hydrogen became more crystalline [12]. The iron content with the presence of silicates also became more apparent after CNF formation. However, SCH772984 order the new phase of iron could not

be identified by XRD (which is a bulk technique). Previous studies have shown that when iron is in low quantities and high dispersions, some of its phases cannot be identified using XRD [47]. Likewise for iron, it has been shown that in such cases, the exact phase identification by XRD is difficult as it tends to form a large variety of carbides [47]. In one study, cementite (Fe3C), which could not be identified by XRD, was observed by Mössbauer spectroscopy during the formation of CNTs over iron catalysts from acetylene decomposition [47]. Hence, 57Fe Mössbauer spectroscopy, which is able to identify all forms of iron, was employed in this study. In order to obtain the chemical and structural information check details of iron-containing materials, three main hyperfine parameters, namely the isomer shift, quadrupole splitting and magnetic splitting, need to be investigated. Figure 10a,b shows the fitted spectra obtained for the as-received coal fly ash sample and the sample after being exposed to acetylene.

The spectra were characterized by broadened six-line patterns, and the central region was dominated by a distribution of quadrupole split doublets. The magnetic feature for the as-received coal fly ash sample (not subjected to acetylene) was fitted with three sextets (SX1_U, SX2_U and SX3_U), while the spectrum for the acetylene-treated sample was analysed with one sextet (SX1_T). For each spectrum, two doublets were required in the central region to give good fits. Table 2 gives a summary of the hyperfine parameters obtained from the fits to the data for both the as-received and acetylene-treated samples. Isomer shifts and velocities were given relative to the centre of the spectrum of alpha-Fe at room temperature (RT). For the as-received fly ash sample, the hyperfine parameters extracted for SX1_U and SX3_U were as follows: B hf = 49.0 T, δ = 0.40 mm/s; ΔE Q = −0.02 mm/s and B hf = 44.2 T, δ = 0.