Oxidation resistance of multi-walled carbon nanotubes coated with polycarbosilane-derived SiCxOy ceramic

Multi-walled carbon nanotubes (MWCNTs) have been successfully coated with a thin SiCxOy coating when polycarbosilane (PCS) was used as precursor and pyrolyzed in a coke bed. Meanwhile, effect of PCS concentration on oxidation resistance of the coated MWCNTs is studied. The results showed that the pyrolysis products of PCS were composed of amorphous SiCxOy as the main phase, together with β-SiC and SiO2 as the minor phases whose amount increased a little with the increase of temperature from 1000 °C to 1500 °C. The thickness of SiCxOy coating on the surface of MWCNTs increased a little from 1 wt.% to 5 wt.%, but decreased dramatically with PCS concentration in the range of 10–30 wt.%. The oxidation resistance of the coated MWCNTs was greatly improved in comparison with as-received ones. The oxidation peak temperature of the coated MWCNTs reached 783.7 °C, much higher than 652.2 °C for as-received ones.