Characterization and separation resistance of an in-situ 2D nanocarbon/calcium aluminate composite synthesized via a combustion method

In-situ 2D nanocarbon/calcium aluminate composite (NCAC) was synthesized via a combustion method designed based on aluminothermic reduction using calcium carbonate (CaCO3) as carbon source. The results demonstrate that compared with the pristine product, when the molar substitution rate of CaCO3 for CaO2 in the reactants was 25%, the contents of CaAl2O4 (CA), CaAl4O7 (CA2) and Ca12Al14O33 (C12A7) in the combusted product did not change substantially and were close to those of Secar71. When the molar substitution rate was increased to 50%, the contents of CA and CA2 decreased, and that of C12A7 increased substantially. Interestingly, the nanocarbons generated in-situ in the combusted composite were embedded in calcium aluminate and had a nanoflake morphology (2D) with a thickness of approximately 50 nm, few defects and high graphitization degree. The results of the suspension experiment demonstrate that the floating ratio of NCAC in the suspension after ultrasonic vibration for 10 min was approximately 5.5 wt.%, which is much lower than that (78.8 wt.%) of a carbon black/Secar71 composite powder; thus, the in-situ 2D nanocarbon/aluminate composite had strengthened interfacial bonds and satisfactory separation resistance. These would be favorable for the uniform dispersion of nanocarbons within the matrix, improving the performance of cement-based composites.