Self-catalyzed growth of nonstoichiometric single-crystal mullite nanocolumns

A large-scale synthesis of single-crystal mullite nanocolumns has been successfully realized by a simple sol-gel method through the self-catalyzed growth process. The growth of this novel structure was induced by the self-catalyzed process due to the presence of surface excess Aluminum adlayers on mullite surfaces. X-ray diffraction (XRD) pattern observation concluded that the product consists of nonstoichiometric Al5.65 Si 0.35 O9.175 nanocolumns. The formation of such nanostructures is understood in terms of the formation energies of different faces and the diffusivity of adatoms on different surface planes. The SEM image shows that the overall surface of the substrate is covered by uniformly distributed nanocolumns. The SEM image at a higher magnification clearly indicates that the nanocolumns have square-framed and rectangularly framed cross-sections, and their surfaces are smooth and clean.