(257d) Motion of Carbon Nanotubes in Water Flowing Through a Silica Nano-Slit With a Dissipative Particle Dynamics Model

Carbon nanotubes (CNTs) are an interesting class of materials with a wide range of practical applications, because of their unique mechanical, thermal and electrical properties [1]. Depending on the interaction of the surrounding fluid with CNTs, the mobility of a CNT in the flow can be affected significantly. The main focus of this work is on the hydrodynamic interactions of a CNT with the fluid flow, the interactions of a solid surface with a CNT, and their effect on the propagation of CNTs in microflows.

This study is a model of water flow between two parallel silica plates using dissipative particle dynamics (DPD) with no slip boundary conditions. This is representative of the case of a CNT traveling in a pore in the subsurface, for example in a sandstone pore. DPD is a coarse graining method that is quite promising for studying hydrodynamic behavior at mesoscopic scales [2]. A DPD model for each simulated case, however, requires the determination of physicochemical parameters that characterize the interaction between the fluids and the solids involved. In our case, the parameters for CNT-water and CNT-silica need to be determined. We use prior results from molecular dynamics simulations of flow around CNTs to validate the DPD parameters in simple cases, before applying them to the final simulations. We adopt these parameters in order to simulate clusters of molecules that allow the simulation of not only nanoflow but also microflows. Then, a cylindrical CNT is released at the center of the flow flied, after the flow reaches equilibrium. The criteria used to validate the DPD model parameters include the satisfaction of the no-slip boundary condition at the water-silica interface, the viscosity of the water, the drag force on a cylinder and the slip length on the water-CNT interface. Different sizes of CNTs are investigated in our simulation in order to examine the effect of the aspect ratio on the hydrodynamic forces and on the rotation of a CNT as it is moving in the flow. As the CNT moves close to the solid surface, its trajectory can provide a set of data to determine a model for the potential interactions between the CNT and silica. Such a model can be applied in macroscopic calculations to account for CNT adsorption on the solid surface.

ACKNOWLEDGEMENTS

The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.

REFERENCES

1. Ray H. Baughman, Anvar A. Zakhidov, Walt A. de Heer, “Carbon nanotubes – the route toward applications,” Science,297,787-792, 2002
2. Robert D. Groot, Patrick B. Warren, “Dissipative particle dynamics: Bridging the gap between atomistic and mesoscopic simulation,” J. Chem. Phys., 107(11), 4423-4435, 1997.