One‐step synthesis of in situ nanocarbon‐containing calcium aluminate cement in reducing atmosphere

Abstract

AbstractIn order to overcome the problems caused by poor water wettability/dispersion and oxidation resistance of carbons for improving properties of carbon‐containing refractory castables, we prepare in situ nanocarbon‐containing cement through the carbon‐bed sintering method with calcium citrate tetrahydrate (CCT, C12H10Ca3O14·4H2O) and Al2O3 as raw materials, and FeCl3 as a catalyst. In this paper, the carbonization process of CCT was analyzed by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetric analysis coupled with a FTIR. In addition, the synthesized cement was characterized through XRD, Raman spectroscopy, field‐emission scanning electron microscopy, and high‐resolution transmission electron microscopy. The results show that the in situ carbon was generated through carbonization of calcium aconitic acid which was generated by pyrolysis of CCT, accompanying with overflowing of H2O, CO2, CO, and CH4. Interestingly, as the sintering temperature increases, the freshly generated carbons were transformed into nanofiber and nanoflake carbons under the action of Fe catalyst. After sintering at 1500°C for 4 hours, the phase compositions of the synthesized product approached to that of the commercial cement Secar71, and the in situ carbons with nanofiber and nanoflake morphologies dispersed in calcium aluminate grains.