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

Abstract

In-situ 2D nanocarbon/calcium aluminate composite (NCAC) was synthesized via a combustion method designed based on aluminothermic reduction using calcium carbonate (CaCO 3 ) as carbon source. The results demonstrate that compared with the pristine product, when the molar substitution rate of CaCO 3 for CaO 2 in the reactants was 25%, the contents of CaAl 2 O 4 (CA), CaAl 4 O 7 (CA 2 ) and Ca 12 Al 14 O 33 (C 12 A 7 ) 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 CA 2 decreased, and that of C 12 A 7 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.

Synthesis of h‐BN composite powders via aluminothermic reduction combustion route

“…[9][10][11] However, the high cost and difficulty in dispersing the nanocarbon limited its industrial application. 12,13 In addition to introducing nanocarbon, substitutions possessing an analogous structure with graphite are also attractive. h-BN is an ideal substitution due to its similar crystal structure to graphite, superior thermal shock resistance, and corrosion resistance to molten slag.…”

“…The introduction of the nanocarbon could obtain comparable performance of the low carbon‐containing refractories to conventional counterparts 9–11 . However, the high cost and difficulty in dispersing the nanocarbon limited its industrial application 12,13 …”