The Mechanical Property Of Graphene-like And Diamond-like Nanomaterials And Its Application In Improving The Performance Of Cement-based Materials

The atomic-scale finite element method is an atomistic simulation method that is developed by some researchers in recent years. It needs less time consuming and has the same accuracy with molecular mechanics simulations. Besides, AFEM has exactly the same formal structure as continuum finite methods, and therefore can seamlessly be combined with them in multiscale computations. In this paper, the elastic properties of both graphene-like nanomaterials(e.g graphene, boron nitride and silicon carbide nanotubes) and nanomaterials with the diamond cubic lattice structure(e.g silicon nanomaterials) are studied based on the atomic-scale finite element method in which the Tersoff-Brenner potential is adopted to describe the interaction between atoms. Graphene is synthesized in recent years, both experimental studies and theoretical researches have proved that it has superior mechanical and optoelectronic properties. Graphene oxide is the product of chemical exfoliation of graphite that has good dispersibility in water. This paper use graphene oxide as nano-reinforcements in cement-based materials and use the nanoindentation tester to survey the mechanical properties and microstructure of a graphene oxide–cement composite. The main research conclusions are as follows:(1) The elastic properties of boron nitride and silicon carbide single-walled nanotubes are studied based on the atomic-scale finite element method. The Young’s modulus is evaluated for these nanotubes, and their buckling behavior are analyzed. It is shown that these nanotubes have similar elastic properties, that is, the diameter has an obvious influence on the Young’s modulus, and the buckling is little related to the length of the nanotubes.(2) For nanomaterials with the diamond cubic lattice structure, the AFEM element contains 17 atoms is given. Then, the atomic-scale finite element method(AFEM) is used to investigate the elastic properties of silicon nanomaterials. Young’s modulus and Poisson ratio of SiNWs with various diameters and crystallographic orientations were calculated. The results show that, with the same radius, the nanowire along the [100] direction possesses the lowest Young’s modulus, while the [110] wire has the highest value.(3) Young’s modulus of zigzag and armchair graphene is also calculated in this paper. All the simulation results prove that nanotubes(BNNTs, SiCNTs) and graphene with the hexagonal lattice structure possess superb elastic properties than the conventional metal materials.(4) In experimental section, Graphene oxide is used to enhance the mechanical properties of ordinary Portland cement paste. The results obtained in this investigation suggest that the introduction of 0.03 wt% and 0.05wt% GO can largely increase the proportion of high density and ultra high density calcium silicate hydrate.