No abstract

No abstract

Using non-equilibrium molecular dynamics simulations, we investigate the effect of wall roughness on the transport resistance of water molecules inside modified carbon nanotubes. The effective shear stress, which characterizes the strong interaction between liquid molecules and solid wall, is a quantity that dominates the nanofluidic transport resistance. Both the effective shear stress and nominal viscosity arise with the increase of the amplitude or the decrease of the wavelength of roughness. The effect of roughness is also relatively more prominent in smaller nanotubes. The molecular mechanism is elucidated through the study of the radial density profile, hydrogen bonding, and velocity field of the confined water molecules.

In a system containing nanoporous materials and liquids, the well-known thermo-capillary effect can be amplified by the ultralarge specific surface area of the nanopores. With appropriate temperature change, the relative wetting-dewetting transition can cause the liquid to flow in or out of the nanopores, and part of the thermal energy is converted to significant mechanical output. A conceptual design of such a thermal actuation/energy conversion/storage system is investigated in this paper, whose working mechanism, i.e. the thermally dependent infiltration behaviors of liquids into nanopores, is analyzed using molecular dynamics simulations. The fundamental molecular characteristics, including the density profile, contact angle, and surface tension of the confined liquid molecules, are examined in considerable detail. The influences of pore size, solid phase and liquid species are elucidated, which couple with the thermal effect. The energy density, power density, and efficiency of the thermal actuation system are evaluated. An infiltration experiment on a zeolite/water system is performed to qualitatively validate these findings.

No abstract