Search

Context: The incorporation of functionalized carbon nanotubes can enhance the mechanical properties of cement-based materials. However, the types of functional groups and their roles in composite materials are not yet clear. In this study, molecular dynamics (MD) simulation methods were employed to investigate the mechanical performance of hybridized calcium silicate hydrate gel reinforced with pure carbon nanotubes, epoxy-coated carbon nanotubes, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes. The results indicate that the addition of all four types of nanotubes can enhance the mechanical properties of hydrated calcium silicate gel compared to pure C–S–H. Tensile loading results show that carbon nanotubes can act as bridges for microcracks in the composite material, and functionalized nanotubes exhibit a better reinforcing effect than pure carbon nanotubes. Under tensile stress, hydroxylated nanotubes are more effective in increasing the toughness of the composite material, while carboxylated nanotubes tend to enhance the strength of the composite material. The compressive loading results indicate that the compressive strength of cement-based materials is higher than their tensile strength. Overall, carboxylated nanotubes show particularly remarkable performance in enhancing the mechanical properties of cement-based materials. Compared to pure C–S–H gel, the tensile and compressive elastic moduli of carboxylated nanotube/C–S–H composite material increased by 18.13% and 34.78%, respectively. Its tensile and compressive strengths also increased by 30.40% and 40.23%, respectively. Method: All molecular dynamics simulations were performed on the classical computational simulation platform LAMMPS. In this paper, the parameters in the ClayFF force field are chosen to simulate calcium hydrated silicate (/C–S–H), and the ClayFF-CVFF combined force field is used to simulate the mechanical properties of the CNT/C–S–H molecular model structure. [ABSTRACT FROM AUTHOR]

Abstract SiC-graphene nanosheets (GNSs) core-shell nanoparticles were incorporated into alumina matrix composites. The composites showed refined grain sizes, increased toughness and hardness. Ball-on-disk wear tests were conducted and the results demonstrated that the coefficient of friction was reduced by 29.4%, and the wear rate was reduced by 90.1% for the composite containing 5 vol % SiC and 1 vol % GNSs at 90 N in comparison to monolithic alumina. These results are superior to Al 2 O 3 -graphene composites documented in the literature. The microstructure and topography of the wear scars were examined to understand the wear behaviour. GNSs-rich tribofilms were observed on the wear scar. The contributing mechanism of the self-lubricating and wear-resistance performance was explored. Highlights • The composites showed excellent wear-resistant and self-lubricating performance. • The reduction effect of the nanofiller on friction tends to be more significant under higher loads. • The enhancement is attributed to the improved microstructure, mechanical properties and GNSs-rich tribofilms. [ABSTRACT FROM AUTHOR]