One-step synthesis of core–shell structured CNFs@CAC with excellent water wettability and oxidation resistance

Abstract

The core–shell structured calcium aluminate cement coated carbon nanofibers (CNFs@CAC) with the same phase composition as Secar71 cement were synthesized to improve the water dispersion and oxidation resistance of carbon nanofibers. The FTIR spectroscopy showed that catalyst ferric chloride can catalyze the polymerization of the maleate. Raman spectroscopy indicated that the graphitization degree of the CNFs was the highest when the amount of catalyst was 0.5 wt%. The CNFs@CAC were characterized by SEM and HRTEM, the results showed that the length and the diameter of the CNFs were ∼ 500 µm and tens of nm, respectively. Carbon nanofibers agglomerates were wrapped in a compact ∼ 3–5 μm thick shell of calcium aluminate forming a core–shell structure. The growth mechanism of carbon nanofibers and the formation process of core–shell structure were studied. The DFT calculation suggested that iron atoms donated d-state electrons to C and O atoms weakening the strength of C-H and C≡O bonds and promoting the growth of CNFs. Calcium aluminate coated carbon nanofibers agglomerates was closely related to the formation of liquid phase calcium aluminate. Moreover, the CNFs@CAC had better water wettability and oxidation resistance compared with S71CB mixed by the same carbon content carbon black and Secar71 cement.