Growth mechanisms and selectivity for graphene or carbon nanotube formation on SiC ( 0 0 0 1 ¯ ): A density-functional tight-binding molecular dynamics study
Abstract We have performed density-functional tight-binding simulations mimicking the thermal decomposition of the SiC ( 0 0 0 1 ¯ ) surface to reproduce the experimentally observed growth of either graphene or carbon nanotubes. A graphene-like network was obtained from a layer-by-layer decomposition of the SiC surface. The interaction between graphene and SiC was found to be relatively weak. Meanwhile, carbon nanotubes grew when a five-membered ring was initially formed together with a carbon chain. The simulation results suggest that growth selectivity depends on the overall carbon network connectivity and carbon aggregation speed at the very initial stage of the decomposition process.
A controllable impregnation of glass fibre structures used in high performance fibre reinforced cement composites can nowadays only be obtained by hand lay-up means, constraining possible structural applications of this promising composite. This paper discusses an innovative manufacturing process designed for the mechanical impregnation of textile reinforcements by a suitable cement matrix. The basic principles of this self-compacting impregnator (SCI) as well as the manufacturing of the cement based laminates will be explained. For comparison, uniaxial tensile strength and interlaminar shear strength were measured on specimens obtained by both production techniques, hand lay-up and SCI. The quality obtained with the laboratory prototype SCI is comparable with the quality obtained by hand lay-up.