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Articles 1 - 8 of 8
Full-Text Articles in Membrane Science
Characterization Techniques And Cation Exchange Membrane For Non-Aqueous Redox Flow Battery, Kun Lou
Characterization Techniques And Cation Exchange Membrane For Non-Aqueous Redox Flow Battery, Kun Lou
Doctoral Dissertations
The motivation of this work comes from one of the major problems of emerging non-aqueous flow battery (NAFB) that a separator or membrane which facilitates conductivity and blocks redox species crossover does not exist. Although many aspects of principles can be mirrored from mature fuel cell and aqueous flow battery, it is found that some well-defined membrane properties in aqueous systems such as swelling, transport and interactions are different in non-aqueous solvents to some extent. However, the approach of this work does follow the way perfluorosulfonate ion exchange membrane (PFSA) facilitated development of fuel cell and aqueous flow battery in …
Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha
Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha
Doctoral Dissertations
The narrow hydrophobic interior of a carbon nanotube (CNT) poses a barrier to the transport of water and ions, and yet, unexpectedly, numerous experimental and simulation studies have confirmed fast water transport rates comparable to those seen in biological aquaporin channels. These outstanding features of high water permeability and high solute rejection of even dissolved ions that would typically require a lot of energy for separation in commercial processes makes carbon nanotubes an exciting candidate for desalination membranes. Extending ion exclusion beyond simple mechanical sieving by the inclusion of electrostatics via added functionality to the nanotube bears promise to not …
A Study Of Diblock Copolymer/Charged Particle Nanoporous Membranes; Morphology, Design And Transport Property Modeling, Bo Zhang
Doctoral Dissertations
A combination of self-consistent field theory and density functional theory was used to examine the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a neutral or charged nanoparticle attached either between the two blocks or at the end of copolymer. Particle size was varied between one and four tenths of the radius of gyration of the copolymer. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the molecular-level self-assembly processes with the aim of determining the appropriate morphologies used as nanoporous membranes, (i.e. the periodic, hexagonal arrays of cylinders wherein the particles would primarily be …
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark
Doctoral Dissertations
A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …
Characterization Techniques And Electrolyte Separator Performance Investigation For All Vanadium Redox Flow Battery, Zhijiang Tang
Characterization Techniques And Electrolyte Separator Performance Investigation For All Vanadium Redox Flow Battery, Zhijiang Tang
Doctoral Dissertations
The all-vanadium redox flow battery (VRFB) is an excellent prospect for large scale energy storage in an electricity grid level application. High battery performance has lately been achieved by using a novel cell configuration with advanced materials. However, more work is still required to better understand the reaction kinetics and transport behaviors in the battery to guide battery system optimization and new battery material development. The first part of my work is the characterization of the battery systems with flow-through or flow-by cell configurations. The configuration difference between two cell structures exhibit significantly different polarization behavior. The battery output can …
Modeling Chemical Degradation And Proton Transport In Perfluorosulfonic Acid Ionomers, Milan Kumar
Modeling Chemical Degradation And Proton Transport In Perfluorosulfonic Acid Ionomers, Milan Kumar
Doctoral Dissertations
The ionomer-membrane interface in a membrane electrode assembly connects the catalyst and membrane and allows hydrated protons to move between the catalyst and membrane. The continuous operation of the polymer membrane electrolyte fuel cell at high temperature and/or in frequent freeze/thaw cycles leads to membrane degradation and delamination of the interface, which lower the proton conductivity. In this dissertation, we modeled the chemical degradation and proton conductivity of perfluorosulfonic acid (PFSA) ionomers by ab initio calculations and macroscopic modeling. All ab initio calculations were performed using Gaussian 03 suites of program by employing B3LYP/6-311++G** method/basis set. The macroscopic modeling involves …
Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, Ruichang Xiong, Rebecca L. Empting, Ian C. Morris, David J. Keffer
Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, Ruichang Xiong, Rebecca L. Empting, Ian C. Morris, David J. Keffer
Faculty Publications and Other Works -- Chemical and Biomolecular Engineering
Molecular dynamics (MD) simulations of a Lennard–Jones fluid in an inhomogeneous external field generate steady-state profiles of density and pressure with nanoscopic heterogeneities. The continuum level of mass, momentum, and energy transport balances is capable of reproducing the MD profiles only when the equation of state for pressure as a function of density is extracted directly from the molecular level of description. We show that the density profile resulting from simulation is consistent with both a molecular-level theoretical prediction from statistical mechanics as well as the solution of the continuum-level set of differential equations describing the conservation of mass and …
Energetic And Entropic Elasticity Of Nonisothermal Flowing Polymers: Experiment, Theory, And Simulation, T. C. Ionescu, B. J. Edwards, David Keffer, V. G. Mavrantzas
Energetic And Entropic Elasticity Of Nonisothermal Flowing Polymers: Experiment, Theory, And Simulation, T. C. Ionescu, B. J. Edwards, David Keffer, V. G. Mavrantzas
Faculty Publications and Other Works -- Chemical and Biomolecular Engineering
The thermodynamical aspects of polymeric liquids subjected to nonisothermal flow are examined from the complementary perspectives of theory, experiment, and simulation. In particular, attention is paid to the energetic effects, in addition to the entropic ones, that occur under conditions of extreme deformation. Comparisons of experimental measurements of the temperature rise generated under elongational flow at high strain rates with macroscopic finite element simulations offer clear evidence of the persistence and importance of energetic effects under severe deformation. The performance of various forms of the temperature equation are evaluated with regard to experiment, and it is concluded that the standard …