Journal of the American Ceramic Society, Vol.100, No.1, 443-450, 2017
Combined effects of boron carbide, silicon, and MWCNTs in alumina-carbon refractories on their microstructural evolution
The phase and microstructure evolutions of multiwalled carbon nanotubes (MWCNTs) in B4C- and Si-containing Al2O3-C specimens under elevated temperatures were investigated by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show that the incorporation of B4C decreases the partial pressure of SiO(g) in Al2O3-C specimens due to the oxidation of B4C prior to Si at lower temperature, which prevents the transformation of MWCNTs at 1000 degrees C and suspends the transformation under higher temperature. B2O3 vapor resulting from oxidation of B4C powder reacts with C sources to generate nanoscaled B4C droplets, which facilitate the catalytic formation of new MWCNTs and nano onion-like carbon. In addition, B-doped MWCNTs and BN tubes with the coexistence of B2O3, MWCNTs, and N-2 are obtained under evaluated temperatures.