Influence of multiwall carbon nanotubes on the structural and morphological features of Si–C–O ceramics derived from a hybrid polymeric precursor

Abstract

This study describes the effect of multiwall carbon nanotubes, MWCNT, as an additional C-source, on the structural and morphological features of silicon oxycarbide ceramics obtained by different heat treatment times of a hybrid polymeric precursor at 1500 °C under an Ar atmosphere. The precursor was prepared by a hydrosilylation reaction from poly(methylsiloxane) and divinylbenzene. The presence of MWCNT promoted a more effective crystallization of the SiC and c-SiO 2 phases in the resulting ceramics, in comparison with those without MWCNT. The heat treatment time at 1500 °C also affects the crystallization of the ceramic product. In addition, an increase of the defect density in the Csp 2 sheets of the C free dispersed phase, together with higher disordering of this phase, were observed in the ceramics obtained from MWCNT-containing precursor. The presence of MWCNT resulted in a ceramic matrix with a different morphology, in relation to that observed in the absence of MWCNT, with lower resistance to oxidation. Moreover, the extra C-source present in the ceramic matrix, introduced as MWCNT, reduced the solubility of SiO 2 in this matrix, promoting the early segregation of SiO 4-rich sites. Consequently, a more effective crystallization of SiO 2, with relatively large c-SiO 2 crystals, and of β-SiC occurred in the material with the increase of the heat treatment time.