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Articles 31 - 47 of 47
Full-Text Articles in Membrane Science
Elevated Test Pressure Significantly Reduces Dynamic Accumulation Oxygen Transmission Rate (Astm F3136) Measurement Time For Barrier Packaging Films, Bruce A. Welt
Journal of Applied Packaging Research
Measurement of gas transmission rates of materials is important for successful package design. The dynamic accumulation (DA) method (ASTM F3136) is becoming increasingly popular for measuring oxygen transmission rate (OTR) due to its simplicity and low cost. However, measurement time increases with barrier properties of materials, limiting measurement throughput. A dynamic accumulation measurement prototype capable of operating up to 1,000 psig was developed in order to accelerate gas transfer by boosting concentration gradients via elevated absolute pressures. Results show that measurement results were independent of test pressure while measurement times were substantially reduced. These results also suggest that gas transmission …
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 …
Nanofiltration Membranes From Oriented Mesoporous Silica Thin Films, Mary K. Wooten
Nanofiltration Membranes From Oriented Mesoporous Silica Thin Films, Mary K. Wooten
Theses and Dissertations--Chemical and Materials Engineering
The synthesis of mesoporous silica thin films using surfactant templating typically leads to an inaccessible pore orientation, making these films not suitable for membrane applications. Recent advances in thin film synthesis provide for the alignment of hexagonal pores in a direction orthogonal to the surface when templated on chemically neutral surfaces. In this work, orthogonal thin film silica membranes are synthesized on alumina supports using block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) as the template. The orthogonal pore structure is achieved by sandwiching membranes between two chemically neutral surfaces, resulting in 90 nm thick films. Solvent flux of ethanol through …
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 …
Performance Evaluation On Vanadium Transport Through Supported Liquid Membrane By Tomac As Carrier, Somayyeh Nosrati Dr, N S. Jayakumar Dr, Mohd Ali Hashim Dr, Soumyadeep Mukhopadhyay Dr
Performance Evaluation On Vanadium Transport Through Supported Liquid Membrane By Tomac As Carrier, Somayyeh Nosrati Dr, N S. Jayakumar Dr, Mohd Ali Hashim Dr, Soumyadeep Mukhopadhyay Dr
Soumyadeep Mukhopadhyay Dr
Many industries use vanadium increasingly and as a consequence, the toxic effluents cause environmental concern. Here, we study the extraction of vanadium in supported ionic liquid membrane was studied. The effect of operational conditions on the process performance such as initial feed phase concentration, pH of the feed solution, pore size of the membrane support, type of ionic liquid charged on the support and stripping agent solution was investigated. Vanadium was effectively transported from the feed phase to the stripping phase of ammonia solution using the room temperature ionic liquid, tri-n-octyl methyl ammonium chloride (TOMAC) embedded in the support membrane. …
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 …
Behavior Of Hydrophobic Ionic Liquids As Liquid Membranes On Phenol Removal: Experimental Study And Optimization, Yee Sern Ng, Jayakumar Natesan Subramaniam, Mohd Ali Hashim
Behavior Of Hydrophobic Ionic Liquids As Liquid Membranes On Phenol Removal: Experimental Study And Optimization, Yee Sern Ng, Jayakumar Natesan Subramaniam, Mohd Ali Hashim
Ng Yee-Sern
Room temperature ionic liquids show potential as an alternative to conventional organic membrane solvents mainly due to their properties of low vapor pressure, low volatility and they are often stable. In the present work, the technical feasibilities of room temperature ionic liquids as bulk liquid membranes for phenol removal were investigated experimentally. Three ionic liquids with high hydrophobicity were used and their phenol removal efficiency, membrane stability and membrane loss were studied. Besides that, the effects of several parameters, namely feed phase pH, feed concentration, NaOH concentration and stirring speeds on the performance of best ionic liquid membrane were also …
Performance Evaluation Of Organic Emulsion Liquid Membrane On Phenol Removal, Yee Sern Ng, Jayakumar Natesan Subramaniam, Mohd Ali Hashim
Performance Evaluation Of Organic Emulsion Liquid Membrane On Phenol Removal, Yee Sern Ng, Jayakumar Natesan Subramaniam, Mohd Ali Hashim
Ng Yee-Sern
The percentage removal of phenol from aqueous solution by emulsion liquid membrane and emulsion leakage was investigated experimentally for various parameters such as membrane:internal phase ratio, membrane:external phase ratio, emulsification speed, emulsification time, carrier concentration, surfactant concentration and internal agent concentration. These parameters strongly influence the percentage removal of phenol and emulsion leakage. Under optimum membrane properties, the percentage removal of phenol was as high as 98.33%, with emulsion leakage of 1.25%. It was also found that the necessity of carrier for enhancing phenol removal was strongly dependent on the internal agent concentration.
Dynamics Of Individual Molecules Of Linear Polyethylene Liquids Under Shear: Atomistic Simulation And Comparison With A Free-Draining Bead-Rod Chain, David Keffer, J. M. Kim, B. J. Edwards, B. Khomami
Dynamics Of Individual Molecules Of Linear Polyethylene Liquids Under Shear: Atomistic Simulation And Comparison With A Free-Draining Bead-Rod Chain, David Keffer, J. M. Kim, B. J. Edwards, B. Khomami
David Keffer
Nonequilibrium molecular dynamics (NEMD) simulations of a dense liquid composed of linear polyethylene chains were performed to investigate the chain dynamics under shear. Brownian dynamics (BD) simulations of a freely jointed chain with equivalent contour length were also performed in the case of a dilute solution. This allowed for a close comparison of the chain dynamics of similar molecules for two very different types of liquids. Both simulations exhibited a distribution of the end-to-end vector, |Rete|, with Gaussian behavior at low Weissenberg number (Wi). At high Wi, the NEMD distribution was bimodal, with two peaks …
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 …
Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, David Keffer
Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, David Keffer
David Keffer
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 …
Atomistic Simulation Of Energetic And Entropic Elasticity In Short-Chain Polyethylenes, David Keffer, T. C. Ionescu, V. G. Mavrantzas, B. J. Edwards
Atomistic Simulation Of Energetic And Entropic Elasticity In Short-Chain Polyethylenes, David Keffer, T. C. Ionescu, V. G. Mavrantzas, B. J. Edwards
David Keffer
The thermodynamical aspects of polymeric liquids subjected to uniaxial elongational flow are examined using atomistically detailed nonequilibrium Monte Carlo simulations. In particular, attention is paid to the energetic effects, in addition to the entropic ones, which occur under conditions of extreme deformation. Atomistic nonequilibrium Monte Carlo simulations of linear polyethylene systems, ranging in molecular length from C24 to C78 and for temperatures from 300 to 450 K, demonstrate clear contributions of energetic effects to the elasticity of the system. These are manifested in a conformationally dependent heat capacity, which is significant under large deformations. Violations of the hypothesis …
Energetic And Entropic Elasticity Of Nonisothermal Flowing Polymers: Experiment, Theory, And Simulation, David Keffer, T. C. Ionescu, B. J. Edwards, V. G. Mavrantzas
Energetic And Entropic Elasticity Of Nonisothermal Flowing Polymers: Experiment, Theory, And Simulation, David Keffer, T. C. Ionescu, B. J. Edwards, V. G. Mavrantzas
David Keffer
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 …
Transport Analysis And Model For The Performance Of An Ultrasonically Enhanced Filtration Process, Michael T. Grossner, Joanne M. Belovich, Donald L. Feke
Transport Analysis And Model For The Performance Of An Ultrasonically Enhanced Filtration Process, Michael T. Grossner, Joanne M. Belovich, Donald L. Feke
Chemical & Biomedical Engineering Faculty Publications
This paper presents an analysis of a filtration technique that uses ultrasound to aid the collection of small particles (tens of microns in diameter) from suspension. In this method, particles are retained within a porous mesh that is subjected to a resonant ultrasonic field, even though the pore size of the mesh is two orders of magnitude greater than the particle diameter. The role of acoustic forces in driving the retention phenomena has previously been studied on a micro-scale, which included modeling and experimental verification of particle motion and trapping near a single element of the mesh. Here, we build …
Diffusivities Of N-Alkanes In Silicalite By Steady-State Single-Crystal Membrane Technique, Orhan Talu, Matthew S. Sun, Dhananjai B. Shah
Diffusivities Of N-Alkanes In Silicalite By Steady-State Single-Crystal Membrane Technique, Orhan Talu, Matthew S. Sun, Dhananjai B. Shah
Chemical & Biomedical Engineering Faculty Publications
A novel experimental technique that measures the diffusive flux through a single-crystal membrane (SCM) was developed and tested. Unlike all other macroscopic techniques that depend on a transient response, SCM is used under steady-state conditions, which results in a wide range of applicability from 10−2 to 10−11 cm2/s. Phenomenological equations for the steady-state data analysis were developed. The variation of driving force over the diffusion path is included in the model. As required by thermodynamics, the micropore concentration is given as a function of surface-excess amount adsorbed and gas density. The membrane configuration measures diffusivity in …