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Full-Text Articles in Nanoscience and Nanotechnology

Mobility Of Nano-Particles In Rock Based Micro-Models, Jagannath Upadhyay Apr 2018

Mobility Of Nano-Particles In Rock Based Micro-Models, Jagannath Upadhyay

LSU Doctoral Dissertations

A confocal micro-particle image velocimetry (C-μPIV) technique along with associated post-processing algorithms is detailed for obtaining three dimensional distributions of nano-particle velocity and concentrations at select locations of the 2.5D (pseudo 3D) Poly(methyl methacrylate) (PMMA) and ceramic micro-model. The designed and fabricated 2.5D micro-model incorporates microchannel networks with 3D wall structures with one at observation wall which resembles fourteen morphological and flow parameters to those of fully 3D actual reservoir rock (Boise Sandstone) at resolutions of 5 and 10 μm in depth and 5 and 25 μm on plane. In addition, an in-situ, non-destructive method for measuring ...


Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha Dec 2017

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 ...


Modal Phonon Transport Across Interfaces By Non-Equilibrium Molecular Dynamics Simulation, Yang Zhong, Tianli Feng, Xiulin Ruan Aug 2017

Modal Phonon Transport Across Interfaces By Non-Equilibrium Molecular Dynamics Simulation, Yang Zhong, Tianli Feng, Xiulin Ruan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Phonons represent the quantization of lattice vibration, responsible for heat transfer in semiconductors and dielectrics. Phonon heat conduction across interfaces is crucially important for the thermal management of real-life devices such as smartphones, electric vehicles, and satellites. Although recent studies have broadly investigated spectral phonon contribution to lattice thermal conductivity, the mechanism of phonon modal transport across interfaces is still not well-understood. Previous models, including the acoustic mismatch model (AMM) and diffuse mismatch model (DMM), only consider elastic process while neglecting inelastic phonon contributions. Herein, we employ spectral Non-Equilibrium Molecular Dynamics Simulation (NEMD) to probe the temperature and heat flux ...


Modeling Of Nanoscale Transport In Mesoporous Membranes, Ashutosh Rathi Jan 2017

Modeling Of Nanoscale Transport In Mesoporous Membranes, Ashutosh Rathi

Doctoral Dissertations

Mesoporous membranes with pore sizes in the range 2-50 nm provide an energy efficient alternative for separation of mixtures such as CO2 from stack effluents and volatile organic compounds (VOC) from air. Transport mechanisms such as capillary condensation, Knudsen diffusion and surface adsorption help in enrichment of a more condensable component based on the bulk mixture thermodynamics, surface chemistry and geometry of the mesopores. Despite the progress in synthesis techniques, design of better mesoporous materials for targeted separations is still a challenge due to the absence of clear design rules. Modeling techniques can be used to quantify the relevant ...


Low Molecular Weight Glucosamine/L-Lactide Copolymers As Potential Carriers For The Development Of A Sustained Rifampicin Release System: Mycobacterium Smegmatis As A Tuberculosis Model, Jorge Ragusa Dec 2014

Low Molecular Weight Glucosamine/L-Lactide Copolymers As Potential Carriers For The Development Of A Sustained Rifampicin Release System: Mycobacterium Smegmatis As A Tuberculosis Model, Jorge Ragusa

Chemical & Biomolecular Engineering Theses, Dissertations, & Student Research

Tuberculosis, a highly contagious disease, ranks as the second leading cause of death from an infectious disease, and remains a major global health problem. In 2013, 9 million new cases were diagnosed and 1.5 million people died worldwide from tuberculosis. This dissertation aims at developing a new, ultrafine particle-based efficient antibiotic delivery system for the treatment of tuberculosis. The carrier material to make the rifampicin (RIF)-loaded particles is a low molecular weight star-shaped polymer produced from glucosamine (molecular core building unit) and L-lactide (GluN-LLA). Stable particles with a very high 50% drug loading capacity were made via electrohydrodynamic ...


Multi-Scale Models For Sulfonated Cross-Linked Poly (1, 3-Cyclohexadiene) Polymer, Qifei Wang, David Keffer, Suxiang Deng, Jimmy Mays May 2013

Multi-Scale Models For Sulfonated Cross-Linked Poly (1, 3-Cyclohexadiene) Polymer, Qifei Wang, David Keffer, Suxiang Deng, Jimmy Mays

Jimmy W. Mays

Atomistic and coarse-grained (CG) models of cross-linked sulfonated Poly (1, 3-cyclohexadiene) (xsPCHD) were developed and implemented in Molecular Dynamics (MD) simulations of PCHD chains with different architectures. In the atomistic model, PCHD chains are cross linked by a sulfur–sulfur bond. Sulfonic acid groups are evenly distributed along the chain. The architecture is specifically aimed for application as a proton exchange membrane used in fuel cells. An atomistic force field for this architecture was tested and applied in the atomistic MD simulation of xsPCHD for the first time. The atomistic simulations generate the density and cross-linker separation distribution. To further ...


The Critical Role Of Mechanism-Based Models For Understanding And Predicting Liposomal Drug Loading, Binding And Release Kinetics, Sweta Modi Jan 2013

The Critical Role Of Mechanism-Based Models For Understanding And Predicting Liposomal Drug Loading, Binding And Release Kinetics, Sweta Modi

Theses and Dissertations--Pharmacy

Liposomal delivery systems hold considerable promise for improvement of cancer therapy provided that critical formulation design criteria can be met. The main objective of the current project was to enable quality by design in the formulation of liposomal delivery systems by developing comprehensive, mechanism-based mathematical models of drug loading, binding and release kinetics that take into account not only the therapeutic requirement but the physicochemical properties of the drug, the bilayer membrane, and the intraliposomal microenvironment.

Membrane binding of the drug affects both drug loading and release from liposomes. The influence of bilayer composition and phase structure on the partitioning ...


Molecular Dynamic Simulations Of The Effect On The Hydration Of Nafion In The Presence Of A Platinum Nanoparticle, Myvizhi Esai Selvan, Qianping He, Elisa Calvo-Muñoz, David Keffer Apr 2012

Molecular Dynamic Simulations Of The Effect On The Hydration Of Nafion In The Presence Of A Platinum Nanoparticle, Myvizhi Esai Selvan, Qianping He, Elisa Calvo-Muñoz, David Keffer

David Keffer

Platinum catalysts play a critical role in fuel cell technology. Current optimization efforts focus on reducing the amount of Pt in the system and optimizing the utilization of that which remains. The effect of the presence of Pt nanoparticles on the local structure and morphology of the polymer electrolyte membrane, water, and hydronium ions has been studied at molecular level in this work. Classical molecular dynamics simulation has been used to examine a system containing a 4 nm fcc cubic ({100} face) platinum nanoparticle at the center surrounded by Nafion polymer, water molecules, and hydronium ions at λ = 3, 6 ...


Multi-Scale Models For Sulfonated Cross-Linked Poly (1, 3-Cyclohexadiene) Polymer, Qifei Wang, David Keffer, Suxiang Deng, Jimmy Mays Feb 2012

Multi-Scale Models For Sulfonated Cross-Linked Poly (1, 3-Cyclohexadiene) Polymer, Qifei Wang, David Keffer, Suxiang Deng, Jimmy Mays

David Keffer

Atomistic and coarse-grained (CG) models of cross-linked sulfonated Poly (1, 3-cyclohexadiene) (xsPCHD) were developed and implemented in Molecular Dynamics (MD) simulations of PCHD chains with different architectures. In the atomistic model, PCHD chains are cross linked by a sulfur–sulfur bond. Sulfonic acid groups are evenly distributed along the chain. The architecture is specifically aimed for application as a proton exchange membrane used in fuel cells. An atomistic force field for this architecture was tested and applied in the atomistic MD simulation of xsPCHD for the first time. The atomistic simulations generate the density and cross-linker separation distribution. To further ...


Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman Jan 2012

Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

The impacts of the two-beam interference heating on the number of core-shell and embedded nanoparticles and on nanostructure coarsening are studied numerically based on the non-linear dynamical model for dewetting of the pulsed-laser irradiated, thin (< 20 nm) metallic bilayers. The model incorporates thermocapillary forces and disjoining pressures, and assumes dewetting from the optically transparent substrate atop of the reflective support layer, which results in the complicated dependence of light reflectivity and absorption on the thicknesses of the layers. Stabilizing thermocapillary effect is due to the local thickness-dependent, steady- state temperature profile in the liquid, which is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Linear stability analysis of the model equations set for Ag/Co bilayer predicts the dewetting length scales in the qualitative agreement with experiment.


Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman Dec 2011

Controlling Nanoparticles Formation In Molten Metallic Bilayers By Pulsed-Laser Interference Heating, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mikhail Khenner

The impacts of the two-beam interference heating on the number of core-shell and embedded nanoparticles and on nanostructure coarsening are studied numerically based on the non-linear dynamical model for dewetting of the pulsed-laser irradiated, thin (< 20 nm) metallic bilayers. The model incorporates thermocapillary forces and disjoining pressures, and assumes dewetting from the optically transparent substrate atop of the reflective support layer, which results in the complicated dependence of light reflectivity and absorption on the thicknesses of the layers. Stabilizing thermocapillary effect is due to the local thickness-dependent, steady- state temperature profile in the liquid, which is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Linear stability analysis of the model equations set for Ag/Co bilayer predicts the dewetting length scales in the qualitative agreement with experiment.


Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman Dec 2011

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.


Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman Dec 2011

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mikhail Khenner

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.


A Coarse-Grained Model For Polyethylene Glycol (Peg) Polymer, Qifei Wang, David Keffer, Donald Nicholson Nov 2011

A Coarse-Grained Model For Polyethylene Glycol (Peg) Polymer, Qifei Wang, David Keffer, Donald Nicholson

David Keffer

A coarse-grained (CG) model of polyethylene glycol (PEG) was developed and implemented in CG molecular dynamics (MD) simulations of PEG chains with degree of polymerization (DP) 20 and 40. In the model, two repeat units of PEG are grouped as one CG bead. Atomistic MD simulation of PEG chains with DP = 20 was first conducted to obtain the bonded structural probability distribution functions (PDFs) and nonbonded pair correlation function (PCF) of the CG beads. The bonded CG potentials are obtained by simple inversion of the corresponding PDFs. The CG nonbonded potential is parameterized to the PCF using both an inversion ...


Reactive Molecular Dynamics Study Of Proton Transport In Polymer Electrolyte Membranes, Myvizhi Esai Selvan, David Keffer, Shengting Cui Jul 2011

Reactive Molecular Dynamics Study Of Proton Transport In Polymer Electrolyte Membranes, Myvizhi Esai Selvan, David Keffer, Shengting Cui

David Keffer

Dynamical properties of water and protons in Nafion with an equivalent weight of 1144 are studied using the recently developed reactive molecular dynamics (RMD) algorithm at various water contents. The structural diffusion of a proton along the aqueous domains is modeled via a mechanism similar to that observed in bulk aqueous systems. The algorithm implements reactivity in classical MD simulations by three steps: (i) satisfaction of the trigger, (ii) instantaneous reaction, and (iii) local equilibration. Two different schemes (Method 1 and Method 2) of execution of the algorithm are investigated, which differ in terms of the range of the local ...


Toward A Predictive Understanding Of Water And Charge Transport In Proton Exchange Membranes, Myvizhi Esai Selvan, Elisa Calvo-Muñoz, David Keffer Feb 2011

Toward A Predictive Understanding Of Water And Charge Transport In Proton Exchange Membranes, Myvizhi Esai Selvan, Elisa Calvo-Muñoz, David Keffer

David Keffer

An analytical model for water and charge transport in highly acidic and highly confined systems such as proton exchange membranes of fuel cells is developed and compared to available experimental data. The model is based on observations from both experiment and multiscale simulation. The model accounts for three factors in the system including acidity, confinement, and connectivity. This model has its basis in the molecular-level mechanisms of water transport but has been coarse-grained to the extent that it can be expressed in an analytical form. The model uses the concentration of H3O+ ion to characterize acidity, interfacial surface area per ...


Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu Tekalign, Margo Levine Jan 2011

Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu Tekalign, Margo Levine

Mathematics Faculty Publications

The linear dispersion relation for longwave surface perturbations, as derived by Levine et al. Phys. Rev. B 75, 205312 (2007) is extended to include a smooth surface energy anisotropy function with a variable anisotropy strength (from weak to strong, such that sharp corners and slightly curved facets occur on the corresponding Wulff shape). Through detailed parametric studies it is shown that a combination of a wetting interaction and strong anisotropy, and even a wetting interaction alone results in complicated linear stability characteristics of strained and unstrained films.


Modeling Diverse Physics Of Nanoparticle Self-Assembly In Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Jan 2011

Modeling Diverse Physics Of Nanoparticle Self-Assembly In Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

Presents physics behind dewetting of thin liquid films and mathematical/computational modeling tools (Educational/Research presentation for senior physics majors).


Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu T. Tekalign, Margo S. Levine Jan 2011

Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu T. Tekalign, Margo S. Levine

Mathematics Faculty Publications

The linear dispersion relation for longwave surface perturbations, as derived by Levine et al. Phys. Rev. B 75, 205312 (2007) is extended to include a smooth surface energy anisotropy function with a variable anisotropy strength (from weak to strong, such that sharp corners and slightly curved facets occur on the corresponding Wulff shape). Through detailed parametric studies it is shown that a combination of a wetting interaction and strong anisotropy, and even a wetting interaction alone results in complicated linear stability characteristics of strained and unstrained films.


Applications Of A General Random Walk Theory For Confined Diffusion, Elisa Calvo-Muñoz, Myvizhi Esai Selvan, Ruichang Xiong, Madhusudan Ojha, David Keffer, Donald Nicholson, Takeshi Egami Dec 2010

Applications Of A General Random Walk Theory For Confined Diffusion, Elisa Calvo-Muñoz, Myvizhi Esai Selvan, Ruichang Xiong, Madhusudan Ojha, David Keffer, Donald Nicholson, Takeshi Egami

David Keffer

A general random walk theory for diffusion in the presence of nanoscale confinement is developed and applied. The random-walk theory contains two parameters describing confinement: a cage size and a cage-to-cage hopping probability. The theory captures the correct nonlinear dependence of the mean square displacement (MSD) on observation time for intermediate times. Because of its simplicity, the theory also requires modest computational requirements and is thus able to simulate systems with very low diffusivities for sufficiently long time to reach the infinite-time-limit regime where the Einstein relation can be used to extract the self-diffusivity. The theory is applied to three ...


On The Relationship Between The Structure Of Metal-Organic Frameworks And The Adsorption And Diffusion Of Hydrogen, Nethika Suraweera, Ruichang Xiong, J. P. Luna, Donald Nicholson, David Keffer Dec 2010

On The Relationship Between The Structure Of Metal-Organic Frameworks And The Adsorption And Diffusion Of Hydrogen, Nethika Suraweera, Ruichang Xiong, J. P. Luna, Donald Nicholson, David Keffer

David Keffer

In this work, the adsorptive and diffusive behaviours of molecular hydrogen in 10 different isoreticular metal–organic frameworks (IRMOFs) are studied using molecular-level simulation. Hydrogen adsorption isotherms and heats of adsorption at 77 and 300 K were generated for 10 MOFs at low-pressure conditions (up to 10 bar) using Path Integral Grand Canonical Monte Carlo simulations. Self-diffusivities and activation energies for diffusion were generated using molecular dynamics simulation. Density distributions showing the location and the shape of the adsorption sites are also provided. Statistical correlations for all of the properties as a function of surface area (SA), accessible volume (AV ...


Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu T. Tekalign, Margo S. Levine Dec 2010

Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu T. Tekalign, Margo S. Levine

Mikhail Khenner

The linear dispersion relation for longwave surface perturbations, as derived by Levine et al. Phys. Rev. B 75, 205312 (2007) is extended to include a smooth surface energy anisotropy function with a variable anisotropy strength (from weak to strong, such that sharp corners and slightly curved facets occur on the corresponding Wulff shape). Through detailed parametric studies it is shown that a combination of a wetting interaction and strong anisotropy, and even a wetting interaction alone results in complicated linear stability characteristics of strained and unstrained films.


Modeling Diverse Physics Of Nanoparticle Self-Assembly In Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2010

Modeling Diverse Physics Of Nanoparticle Self-Assembly In Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mikhail Khenner

Presents physics behind dewetting of thin liquid films and mathematical/computational modeling tools (Educational/Research presentation for senior physics majors).


Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner Mar 2010

Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner

Mathematics Faculty Publications

An introduction to mathematical modeling of ultrathin solid films and the role of such modeling in nanotechnologies: Educational presentation for senior physics majors


Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner Mar 2010

Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner

Mathematics Faculty Publications

An introduction to mathematical modeling of ultrathin solid films and the role of such modeling in nanotechnologies: Educational/Research presentation for senior physics majors


Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner Mar 2010

Morphological Evolution Of Single-Crystal Ultrathin Solid Films, Mikhail Khenner

Mikhail Khenner

An introduction to mathematical modeling of ultrathin solid films and the role of such modeling in nanotechnologies: Educational/Research presentation for senior physics majors


Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2010

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=OBi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev Jan 2010

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=OBi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Molecular Dynamics Simulation Of Poly(Ethylene Terephthalate) Oligomers, David Keffer, Qifei Wang, Simioan Petrovan, J. Thomas Dec 2009

Molecular Dynamics Simulation Of Poly(Ethylene Terephthalate) Oligomers, David Keffer, Qifei Wang, Simioan Petrovan, J. Thomas

David Keffer

Molecular dynamics simulations of poly(ethylene terephthalate) (PET) oligomers are performed in the isobaric−isothermal (NpT) ensemble at a state point typical of a finishing reactor. The oligomer size ranges from 1 to 10 repeat units. We report thermodynamic properties (density, potential energy, enthalpy, heat capacity, isothermal compressibility, and thermal expansivity), transport properties (self-diffusivity, zero-shear-rate viscosity, thermal conductivity), and structural properties (pair correlation functions, hydrogen bonding network, chain radius of gyration, chain end-to-end distance) as a function of oligomer size. We compare the results with existing molecular-level theories and experimental data. Scaling exponents as a function of degree of polymerization ...


Molecular Simulations Of H2 Adsorption In Metal-Porphyrin Frameworks (Mpfs): A Potential New Material Evaluation, Ruichang Xiong, David Keffer Dec 2009

Molecular Simulations Of H2 Adsorption In Metal-Porphyrin Frameworks (Mpfs): A Potential New Material Evaluation, Ruichang Xiong, David Keffer

David Keffer

Path integral grand canonical Monte Carlo (PI-GCMC) simulations using standard force fields are carried out to calculate the adsorption of H2 in five metal-porphyrin frameworks (MPFs), a new class of metal organic framework (MOF)-type materials. These simulations are performed at 77 K and room temperature (300 K). The adsorption isotherms of H2 in IRMOF-1 and IRMOF-10 are also calculated as a comparison. All calculations indicate that all MPFs adsorbed a higher weight fraction of H2 than both IRMOF-1 and IRMOF-10, with one exception (MPF-2). The gravimetric hydrogen capacities are still well short of practical goals. The MPFs provide additional ...