Exploring properties of silicon-carbide nanotubes and their composites with polymers

2017-04-23We have utilized atomistic modeling and extensive molecular dynamics (MD) simulation to study and explore various properties of fluids in silicon‐carbide nanotubes (SiCNTs), and in their composites with a polymer. ❧ First, we show that pressure‐induced flow of water in the SiCNTs of various sizes is more efficient than the same phenomenon in carbon nanotubes (CNTs), requiring a pressure drop (and hence energy) that is at least one order of magnitude less than that in the CNTs. ❧ Next, we study the dynamics of low‐temperature water in SiCNTs, demonstrating that the cage‐cage correlation function, a measure of the water molecules’ motion in the nanotubes, follows the Kohlrausch‐Williams‐Watts stretched exponential law with an exponent that is in excellent agreement with the theoretical prediction by J.C. Phillips. ❧ Third, using extensive MD simulations, we compute the various correlation functions for water in SiCNTs and CNTs over the temperature range 100 K - 298 K, demonstrating that, in agreement with our calculation of the cage‐cage correlation function, due to spatial limitations and steric hindrance inside small enough nanotubes, water inside such nanotubes does not freeze. This has significant scientific and biological implications, potentially providing a method for preserving microorganisms for very long time for advanced research and studies. ❧ Finally, we develop an atomistic model of mixed‐matric polymeric composite made of polyetherimide (PEI) and SiCNTs and study, (i) the mechanical properties of the composite and compare them with those of pure PEI, and (ii) diffusion and sorption of several light gases in the composite in order to test its potential use as a membrane for gas separation. The results indicate that such a membrane has excellent properties for separation of hydrogen from a gaseous mixture