Effect of catalytic condition on the properties of carbon nanotubes/calcium aluminate cement and its synthesis mechanism

Carbon nanotubes/calcium aluminate cement (CNTs/CAC) have endowed refractory castables with excellent performance. However, the properties of CNTs/CAC at varying catalytic conditions were significantly affected by the characteristics of carbon matters and the microstructure of cement, especially oxidation resistance and water dispersibility. The CNTs/CAC and the pyrolysis process of its precursors were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetry-Fourier transform. The optimum catalyst content of cement was determined to be 0.2 wt.% (Fe count), the optimal catalytic temperature was 700°C, and the optimal catalytic time was 3 h. The graphitization degree of carbon and the microstructure of cobweb-like carbon/cement particles were optimized within the optimal catalytic conditions, thereby improving the oxidation resistance and water dispersion of CNTs/CAC. In addition, the research of the CNTs/CAC pyrolysis process has also shown that bamboo-shaped carbon nanotubes were aggregated, interweaved, and embedded within the interstices of calcium aluminate particles to form a cobweb-like microstructure during the CNTs/CAC formation process.