Effects of oxidative treatments with air and CO2 on vapour grown carbon nanofibres (VGCNFs) produced at industrial scale

Vapour grown carbon nanofibres (VGCNFs) produced at industrial scale were subjected to different treatments in N2, air and CO2 atmospheres. The effect of these treatments on the homogeneity of the industrial product was investigated by means of TG analysis. Temperature programmed oxidation (TPO) experiments were performed to obtain DTG profiles. The DTG curves were deconvoluted into a mixture of Gaussian–Lorentzian curves, so that the contribution of each peak could be evaluated and assigned to phases of different reactivity. It was found that treatments in air are more selective in removing the most reactive phase (which has a higher content of amorphous carbon) at low burn-off, while at an elevated burn-off degree CO2 treatments result in a greater enrichment of the product in the less reactive phase (which has a higher content of fibre). This behaviour is attributed to the presence of a certain amount of iron in the industrially produced materials and its catalytic effect on the oxidative reactions. The effect of the treatments on the porous texture, surface chemistry and graphite-like character of the samples was also investigated.