Nanostructured cementitious sol gel coating on graphite for application in monolithic refractory composites

A nanostructured sol gel coating of calcium aluminate (CaAl2O4) over flaky graphite has been prepared by a hybrid set of precursors. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), differential thermal analysis (DTA), particle size distribution and microstructural studies have been performed to understand the phase evolution of calcium aluminate and its related characteristics. The topography and microstructural aspects of coated and uncoated graphites have been differentiated by atomic force microscopy (AFM) and scanning electron microscopy (SEM) with energy dispersive spectral (EDS) analysis. FTIR and XRD patterns of both graphites have also been investigated to substantiate the evolution of a thin extended hydrophilic film of calcium aluminate over coated ones. The better oxidation resistance of coated graphite has been confirmed by thermogravimetric analysis (TGA). Improved water-wettability of coated graphites has been examined by the ‘ball-in-hand’ test for moisture requirement during installation of a high alumina based refractory castable composite containing that graphite. Green bulk density of castable cubes has been determined to corroborate the better performance of the graphite coated with calcium aluminate.