Diffusivities of gas mixtures in single-wall boron nitride nanotubes form MD Simulation

In recent years there has been a great deal of interest generated by the properties of a novel class of graphitic materials, carbon nanotubes (CNTs). These materials have shown great promise in such applications as membranes for gas separation and adsorptive storage of gases [1]. Especially most of them based on their ability to condition the diffusion of fluids. Diffusion is a fundamental mechanism of molecular transport through porous media. The diffusivities in CNTs are compared with diffusivities of the same gases in silicate, a common zeolite, under the same conditions [2]. Self-diffusion (Ds) of argon and neon in single wall CNT (SWCNT) have been considered by molecular simulation methods [2, 3] and results for diffusion of Ar show that tubes of larger size lead to higher diffusivity and helicity of SWCNT has no bearing on self diffusion and Ds data for different SWCNTs are all qualitatively similar. Values of Ds for Ar and Ne in all nanotubes decrease dramatically with increased loading, in other word; the most important parameter is the density of fluid. Also, the effect of the rigidity and flexibility of the tube on the diffusivities of argon has considered [3] and found that flexibility of the tubes such as helicity has almost no noticeable influences in diffusion of argon. So the effect of flexibility and helicity of the tubes is not investigated in this study.Boron nitride nanotube (BNNT) is similar to the CNT but its B–N bond length of 1.46 Å is larger than the C–C bond length of 1.42 Å in the CNT. Consequently, the BNNT is considered to have the faster rate for gas penetration through the wall. The interaction of hydrogen with single-walled boron nitride nanotubes (SWBNNTs) have been investigated from molecular dynamic (MD) simulation [4] and indicted that hydrogen atoms dissociated at the wall cannot bind to either boron or nitrogen atoms in the interior wall of the nanotube.In this paper, we determine whether the pristine BNNT might be good candidates for a practical gas diffusion material or not and in the next step, we simulate the diffusion of Ar/Ne, Ar/N2 and Ne/N2 mixtures in SWBNNTs at different temperatures to illustrate the effect of temperatures on diffusivities of gas mixtures