(227b) Confinement-Induced Compression and High Pressure Phases in Nanopores
AIChE Annual Meeting
Monday, October 29, 2018 - 3:48pm to 4:06pm
For simple fluids in pores that are up to a few nanometers in width, molecular simulations show that both the normal and tangential pressures can be locally very high (thousands or tens of thousands of bars) in the pore, even though the bulk phase in equilibrium with the pore is at a pressure of one bar or less. The cause of these high in-pore pressures will be discussed.
When the molecules in the confined nanophase react with each other chemically it may be possible to achieve even higher tangential pressures, in the megabar range. Thus, Kaneko et al.3 have shown that when sulfur atoms are confined within a narrow carbon nanotube they covalently bond to form a one-dimensional phase that is metallic. In the bulk phase sulfur forms a metallic phase only at pressures above 95 GPa. In our recent molecular dynamics simulations of this system we find that the sulfur atoms are covalently bonded in the pore and that they experience tangential pressures in excess of 100 GPa as a result of the strong confinement4. Recently, Medeiros et al.5 have reported experiments in which they observe a similar covalently bonded one-dimensional phase, and an insulator-metal transition, for tellurium in single-walled carbon nanotubes.
- Yun Long, Jeremy C. Palmer, Benoit Coasne, MaÅgorzata Åliwinska-Bartkowiak and Keith E. Gubbins, MACROBUTTON MTEditEquationSection2 Equation Chapter 1 Section 1 SEQ MTEqn \r \h \* MERGEFORMAT SEQ MTSec \r 1 \h \* MERGEFORMAT SEQ MTChap \r 1 \h \* MERGEFORMAT âPressure enhancement in carbon nanopores: A major confinement effectâ, Physical Chemistry Chemical Physics, 13, 17163-17170 (2011).
- Yun Long, Jeremy C. Palmer, Benoit Coasne, MaÅgorzata Åliwinska-Bartkowiak, George Jackson, Erich A. MÃ¼ller and Keith E. Gubbins, âOn the Molecular Origin of High Pressure Effects in Nanoconfinement: Effects of Surface Chemistry and Roughnessâ, Journal of Chemical Physics, 139, 144701 (2013)
- Y. Fujimori, A. Morelos-GÃ³mez, Z. Zhu, et al., âConducting Linear Chains of Sulphur Inside Carbon Nanotubesâ, Nature Comm., 4, 2162 (2013).
- K.E. Gubbins, C.A Addington and J.M. Mansell, âComputer Simulation of Conductive Linear Sulfur Chains Confined in Carbon Nanotubesâ, Molecular Simulation, 43, 519-525 (2017).
- P. V. C. Medeiros et al., âSingle-Atom Scale Structural Selectivity in Te Nanowires Encapsulated Inside Ultranarrow, Single-Walled Carbon Nanotubes,â ACS Nano, 11, 6178â6185 (2017).