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Chemical Engineering

2009

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Articles 1 - 30 of 127

Full-Text Articles in Engineering

Preparation And Hydrogen Absorption/Desorption Of Nanoporous Palladium Thin Films, Wen-Chung Li, Thomas John Balk Dec 2009

Preparation And Hydrogen Absorption/Desorption Of Nanoporous Palladium Thin Films, Wen-Chung Li, Thomas John Balk

Chemical and Materials Engineering Faculty Publications

Nanoporous Pd (np-Pd) was prepared by co-sputtering Pd-Ni alloy films onto Si substrates, followed by chemical dealloying with sulfuric acid. X-ray diffractometry and chemical analysis were used to track the extent of dealloying. The np-Pd structure was changed from particle-like to sponge-like by diluting the sulfuric acid etchant. Using suitable precursor alloy composition and dealloying conditions, np-Pd films were prepared with uniform and open sponge-like structures, with interconnected ligaments and no cracks, yielding a large amount of surface area for reactions with hydrogen. Np-Pd films exhibited shorter response time for hydrogen absorption/desorption than dense Pd films, showing promise for hydrogen …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Exploring Stress Overshoot Phenomenon Upon Startup Deformation Of Entangled Linear Polymeric Liquids, Yangyang Wang, Shi-Qing Wang Dec 2009

Exploring Stress Overshoot Phenomenon Upon Startup Deformation Of Entangled Linear Polymeric Liquids, Yangyang Wang, Shi-Qing Wang

College of Polymer Science and Polymer Engineering

This work explores the picture associated with stress overshoot during sudden continual (i.e., startup) external deformation of entangled polymeric liquids and proposes a specific scaling form to depict the intermolecular interactions responsible for chain deformation. Following a previously proposed idea that the stress overshoot in startup deformation is a signature of yielding, we search for ingredients that should go into the description of the force imbalance at the yield point and show that the expression for the intermolecular locking force f(iml), derived from the characteristics associated with the yield point, can be tested against experiment. New rate-switching experiments support the …

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Nature Of Steady Flow In Entangled Fluids Revealed By Superimposed Small Amplitude Oscillatory Shear, Pouyan E. Boukany, Shi-Qing Wang Dec 2009

Nature Of Steady Flow In Entangled Fluids Revealed By Superimposed Small Amplitude Oscillatory Shear, Pouyan E. Boukany, Shi-Qing Wang

College of Polymer Science and Polymer Engineering

We carry out a systematic investigation into steady-state shear behavior of six entangled solutions based on a superposition of continuous shear and small amplitude oscillatory shear (SAOS). During steady shear in the shear thinning regime, the superimposed SAOS frequency sweep measurements reveal characteristics of viscous liquids, e. g., terminal dynamics, on the experimental time scale of the reciprocal shear rate. The residual entanglement network retains the same level of elastic stiffness as the equilibrium system does. Consistent with the convective constraint release idea, chains in the network are forced to pass around each other as they must do so to …

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Energy Efficiency Of Hydrogen Sulfide Decomposition In A Pulsed Corona Discharge Reactor, Morris D. Argyle, Sanil John, Jerry C. Hamann, Suresh S. Muknahallipatna, Stanislaw Legowski, John F. Ackerman Dec 2009

Energy Efficiency Of Hydrogen Sulfide Decomposition In A Pulsed Corona Discharge Reactor, Morris D. Argyle, Sanil John, Jerry C. Hamann, Suresh S. Muknahallipatna, Stanislaw Legowski, John F. Ackerman

Faculty Publications

A novel pulsed corona wire-in-tube reactor with quartz view-ports allowed visual observation of the effect of charge voltage and gas composition on the corona distribution. The H2S conversion and energy efficiency of H2S decomposition in this pulsed corona discharge reactor varied at constant power due to the selected values of the electrical parameters of pulse forming capacitance, charge voltage, and pulse frequency. Low pulse forming capacitance, low charge voltage, and high pulse frequency operation produce the highest energy efficiency of H2S conversion at constant power. H2S conversion is more efficient in Ar-N2 gas mixtures than in Ar or N2. these …

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Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, Ruichang Xiong, Rebecca L. Empting, Ian C. Morris, David J. Keffer Nov 2009

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 …

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Improved Implementation Of Kirkwood-Buff Solution Theory In Periodic Molecular Simulations, Joseph W. Nichols, Stan G. Moore, Dean R. Wheeler Nov 2009

Improved Implementation Of Kirkwood-Buff Solution Theory In Periodic Molecular Simulations, Joseph W. Nichols, Stan G. Moore, Dean R. Wheeler

Faculty Publications

Kirkwood-Buff (KB) solution theory is a means to obtain certain thermodynamic derivatives from knowledge of molecular distributions. In actual practice the required integrals over radial distribution functions suffer inaccuracies due to finite-distance truncation effects and their use in closed systems. In this work we discuss how best to minimize these inaccuracies under traditional KB theory. In addition we implement a method for calculating KB quantities in molecular simulations with periodic boundary conditions and particularly within the canonical ensemble. The method is based on a finite-Fourier-series expansion of molecular concentration fluctuations and leads to more reliable results for a given computational …

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Quantifying And Resolving Multiple Vector Transformants In S. Cerevisiae Plasmid Libraries, Thomas C. Scanlon, Elizabeth C. Gray, Karl E. Griswold Nov 2009

Quantifying And Resolving Multiple Vector Transformants In S. Cerevisiae Plasmid Libraries, Thomas C. Scanlon, Elizabeth C. Gray, Karl E. Griswold

Dartmouth Scholarship

In addition to providing the molecular machinery for transcription and translation, recombinant microbial expression hosts maintain the critical genotype-phenotype link that is essential for high throughput screening and recovery of proteins encoded by plasmid libraries. It is known that Escherichia coli cells can be simultaneously transformed with multiple unique plasmids and thusly complicate recombinant library screening experiments. As a result of their potential to yield misleading results, bacterial multiple vector transformants have been thoroughly characterized in previous model studies. In contrast to bacterial systems, there is little quantitative information available regarding multiple vector transformants in yeast. Saccharomyces cerevisiae is the …

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Aligned Nanotubule Membranes, Bruce J. Hinds Iii Nov 2009

Aligned Nanotubule Membranes, Bruce J. Hinds Iii

Chemical and Materials Engineering Faculty Patents

A method is provided for producing a permeable membrane, comprising the steps of aligning a plurality of hollow nanotubules to form a mat, coating the mat with a continuous polymer matrix to form a membrane. The membrane is etched (a) to open the plurality of hollow nanotubules and form pores and (b) to oxidize the carboxyl groups to carboxylate groups. At least one additional functional unit having at least one available amine group to bind the at least one additional functional unit to the nanotubule end carboxylate group may be provided. Membranes fabricated in accordance with the method of the …

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Characterisation And Mechanical Testing Of Hydrothermally Treated Ha/Zro2 Composites, D. J. Curran, T. J. Fleming, G. Kawachi, C. Ohtsuki, Mark R. Towler Nov 2009

Characterisation And Mechanical Testing Of Hydrothermally Treated Ha/Zro2 Composites, D. J. Curran, T. J. Fleming, G. Kawachi, C. Ohtsuki, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

Hydrothermal treatment is traditionally employed to improve the sinterability of powder compacts by reducing porosity and increasing apparent density. The effect of hydrothermal treatment on green powder compacts has been assessed in order to better understand how treatment may affect the sinter ability of the bodies. Laboratory synthesized nano sized hydroxyapatite (HA) and a commercial zirconia (ZrO2) powder have been ball milled together to create composite mixtures containing 0-5 wt% ZrO2 loadings. Disc shaped bodies have been formed using uniaxial and subsequent isostatic pressure. The resultant coherent samples were subjected to hydrothermal treatment at either 120 or …

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Fabrication Of Spherical Cao-Sro-Zno-Sio2 Particles By Sol-Gel Processing, Ill Yong Kim, Mark R. Towler, Anthony Wren, Chikara Ohtsuki Nov 2009

Fabrication Of Spherical Cao-Sro-Zno-Sio2 Particles By Sol-Gel Processing, Ill Yong Kim, Mark R. Towler, Anthony Wren, Chikara Ohtsuki

Chemical and Biochemical Engineering Faculty Research & Creative Works

This study was concerned with the fabrication of ceramic CaO-SrO-ZnO-SiO2 spherical particles, which are novel candidates for the glass phase in glass polyalkenoate cements (GPCs). GPCs made from these glasses have potential as bone cements because, unlike conventional GPCs, they do not contain aluminum ions, which inhibit the calcification of hydroxyapatite in the body. The glass phase of GPCs require a controllable glass morphology and particle size distribution. Sol-gel processing can potentially be used to fabricate homogenous ceramic particles with controlled morphology. However, a thorough study on preparation conditions of spherical CaO-SrO-ZnO-SiO2 particles by sol-gel processing has, to …

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Analysis Of Γ-Irradiated Synthetic Bone Grafts By ²⁹Si Mas-Nmr Spectroscopy, Calorimetry And Xrd, D. Boyd, S. Murphy, Mark R. Towler, A. W. Wren, S. Hayakawa Nov 2009

Analysis Of Γ-Irradiated Synthetic Bone Grafts By ²⁹Si Mas-Nmr Spectroscopy, Calorimetry And Xrd, D. Boyd, S. Murphy, Mark R. Towler, A. W. Wren, S. Hayakawa

Chemical and Biochemical Engineering Faculty Research & Creative Works

Ca-Sr-Zn-Si glasses have demonstrated excellent biocompatibility both in vitro using the MTT assay with L929 mouse fibroblast cells, and in vivo using healthy and ovariectomized female Wistar rats. However, the biological evaluation of the materials was performed on glass granules that were autoclaved, rather than γ-irradiated; the sterilisation procedure required prior to implantation of these materials in the human body. Given the fact that when a glass is exposed to ionizing radiation changes in its physical properties can take place, it is imperative to determine whether the structure of such glasses will be altered as a result of exposure to …

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Nonlinearity In Large Amplitude Oscillatory Shear (Laos) Of Different Viscoelastic Materials, Xin Li, Shi-Qing Wang, Xiaorong Wang Oct 2009

Nonlinearity In Large Amplitude Oscillatory Shear (Laos) Of Different Viscoelastic Materials, Xin Li, Shi-Qing Wang, Xiaorong Wang

College of Polymer Science and Polymer Engineering

The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of four different polymeric materials using simultaneous conventional rheometric measurements and particle-tracking velocimetric observations. In contrast to most studies in the literature that treat nonlinearity in LAOS in steady state, we emphasize by the present four examples that nonlinearity in LAOS often arise in complex fluids due to time-dependent rearrangement of their microstructures in response to LAOS. Consequently, no correlation is obvious between strain dependence of the steady-state stress response and the time-dependent characteristics of the steady-state response. For instance, a highly viscoelastic material made of nano-sized polybutadiene …

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Computing Arrival Cost Parameters In Moving Horizon Estimation Using Sampling Based Filters, Sridhar Ungarala Oct 2009

Computing Arrival Cost Parameters In Moving Horizon Estimation Using Sampling Based Filters, Sridhar Ungarala

Chemical & Biomedical Engineering Faculty Publications

Moving horizon estimation (MHE) is a numerical optimization based approach to state estimation, where the joint probability density function (pdf) of a finite state trajectory is sought, which is conditioned on a moving horizon of measurements. The joint conditional pdf depends on the a priori state pdf at the start of the horizon, which is a prediction pdf based on historical data outside the horizon. When the joint pdf is maximized, the arrival cost is a penalty term based on the a priori pdf in the MHE objective function. Traditionally, the a priori pdf is assumed as …

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The Effect Of Glass Synthesis Route On Mechanical And Physical Properties Of Resultant Glass Ionomer Cements, A. Wren, O. M. Clarkin, F. R. Laffir, C. Ohtsuki, I. Y. Kim, Mark R. Towler Oct 2009

The Effect Of Glass Synthesis Route On Mechanical And Physical Properties Of Resultant Glass Ionomer Cements, A. Wren, O. M. Clarkin, F. R. Laffir, C. Ohtsuki, I. Y. Kim, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

Glass ionomer cements (GICs) have potential orthopaedic applications. Solgel processing is reported as having advantages over the traditional melt-quench route for synthesizing the glass phase of GICs, including far lower processing temperatures and higher levels of glass purity and homogeneity. This work investigates a novel glass formulation, BT 101 (0.48 SiO2-0.36 ZnO-0.12 CaO-0.04 SrO) produced by both the melt-quench and the solgel route. The glass phase was characterized by X-ray diffraction (XRD) to determine whether the material was amorphous and differential thermal analysis (DTA) to measure the glass transition temperature (Tg). Particle size analysis (PSA) was …

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Methods For Cancer Detection, Kimberly W. Anderson, Kimberly M.L. May, Leonidas G. Bachas Sep 2009

Methods For Cancer Detection, Kimberly W. Anderson, Kimberly M.L. May, Leonidas G. Bachas

Chemical and Materials Engineering Faculty Patents

A method is provided for detecting an analyte indicative of a cancer or a metastatic disease condition, which utilizes the ability of the analyte to induce permeability in a barrier. The method includes providing a biosensor having a barrier which is substantially impermeable to an ion, a permeable membrane which is selective for the ion, and a detector capable of detecting the ion. The biosensor is contacted with a sample including at least one of the ion and the analyte, wherein the analyte causes at least a portion of the ion to pass through the barrier and the membrane. Passage …

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Phage-Induced Alignment Of Membrane Proteins Enables The Measurement And Structural Analysis Of Residual Dipolar Couplings With Dipolar Waves And Lambda-Maps, Sang Ho Park, Woo Sung Son, Rishi Mukhopadhyay, Homayoun Valafar, Stanley J. Opella Sep 2009

Phage-Induced Alignment Of Membrane Proteins Enables The Measurement And Structural Analysis Of Residual Dipolar Couplings With Dipolar Waves And Lambda-Maps, Sang Ho Park, Woo Sung Son, Rishi Mukhopadhyay, Homayoun Valafar, Stanley J. Opella

Faculty Publications

At pH > 6 added filamentous bacteriophage fd is compatible with many of the detergents used to solubilize membrane proteins for solution NMR studies of membrane proteins and, therefore, serves as an alignment media. In combination with strained polyacrylamide gel alignment, Dipolar Waves can be used to directly assess the secondary structure and a λ-map extracts the order tensors for de novo structure calculation of membrane proteins without distance restraints.

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Chemical-Free Iron Removal And Disinfection Unit Of Drinking Water For Single House Application, Michael O'Hehir Sep 2009

Chemical-Free Iron Removal And Disinfection Unit Of Drinking Water For Single House Application, Michael O'Hehir

Masters

The supply of safe drinking water is a major worldwide problem. In the developed world the frequency of water related problems are increasing The shortage of fresh water supply is as a result of pollution from industrial, agricultural and natural disasters. To make water suitable for human consumption, it must first be treated. However, consumers do not always receive potable water even after public treatment. In some cases the consumer must treat the water being supplied to them, or have to source their own water from private wells and treat it prior to use. The purpose of this research was …

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Chameleon Coatings: Adaptive Surfaces To Reduce Friction And Wear In Extreme Environments, Christopher Muratore, Andrey A. Voevodin Aug 2009

Chameleon Coatings: Adaptive Surfaces To Reduce Friction And Wear In Extreme Environments, Christopher Muratore, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

Adaptive nanocomposite coating materials that automatically and reversibly adjust their surface composition and morphology via multiple mechanisms are a promising development for the reduction of friction and wear over broad ranges of ambient conditions encountered in aerospace applications, such as cycling of temperature and atmospheric composition. Materials selection for these composites is based on extensive study of interactions occurring between solid lubricants and their surroundings, especially with novel in situ surface characterization techniques used to identify adaptive behavior on size scales ranging from 10−10 to 10−4 m. Recent insights on operative solid-lubricant mechanisms and their dependency upon the ambient environment …

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Synthesis And Characterization Of Some Rhenium Complexes, Joseph Brian Scott Aug 2009

Synthesis And Characterization Of Some Rhenium Complexes, Joseph Brian Scott

Masters Theses & Specialist Projects

Plastics or polymers are thought to behave oppositely from metals. Ideally, polymers behave as insulators while metals conduct electricity. Shirakawa and coworkers discovered conductive polymers in 1977.1 These conductor polymers have been extensively studied, discovering that charge transfer oxidative doping of polyacteylene could increase its conductivity by 12 orders of magnitude. Polyacetylene, although showing promise as an organic conductor, because it is highly air-sensitive and oxidizes when exposed to molecular oxygen, therefore making this an unattractive use for commercial products. Attention has been focused on heterocylic aromatic polymers such as polythiophene and polypyrrole, in efforts to produce conductive polymers that …

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Comparison Of Failure Mechanisms For Cements Used In Skeletal Luting Applications, O. Clarkin, D. Boyd, Mark R. Towler Aug 2009

Comparison Of Failure Mechanisms For Cements Used In Skeletal Luting Applications, O. Clarkin, D. Boyd, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

Glass Polyalkenoate Cements (GPCs) based on strontium calcium zinc silicate (Sr-Ca-Zn-SiO2) glasses and low molecular weight poly (acrylic acid) (PAA) have been shown to exhibit suitable compressive strength (65 MPa) and flexural strength (14 MPa) for orthopaedic luting applications. In this study, two such GPC formulations, alongside two commercial cements (Simplex ® P and Hydroset™) were examined. Fracture toughness and tensile bond strength to sintered hydroxyapatite and a biomedical titanium alloy were examined. Fracture toughness of the commercial Poly(methyl methacrylate) cement, Simplex® P, (3.02 MPa m1/2) was superior to that of the novel GPC (0.36 MPa …

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Comparison Of An Experimental Bone Cement With A Commercial Control, Hydroset™, O. M. Clarkin, D. Boyd, S. Madigan, Mark R. Towler Jul 2009

Comparison Of An Experimental Bone Cement With A Commercial Control, Hydroset™, O. M. Clarkin, D. Boyd, S. Madigan, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

Glass polyalkenoate cements based on strontium calcium zinc silicate glasses (Zn-GPCs) and high molecular weight polyacrylic acids (PAA) (MW; 52,000-210,000) have been shown to exhibit mechanical properties and in vitro bioactivity suitable for arthroplasty applications. Unfortunately, these formulations exhibit working times and setting times which are too short for invasive surgical applications such as bone void filling and fracture fixation. In this study, Zn-GPCs were formulated using a low molecular weight PAA (MW; 12,700) and a modifying agent, trisodium citrate dihydrate (TSC), with the aim of improving the rheological properties of Zn-GPCs. These novel formulations were then compared with commercial …

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Electrospinning Route For The Fabrication Of P-N Junction Using Nanofiber Yarns, A. F. Lotus, S. Bhargava, E. T. Bender, E. A. Evans, R. D. Ramsier, Darrell Hyson Reneker, G. G. Chase Jul 2009

Electrospinning Route For The Fabrication Of P-N Junction Using Nanofiber Yarns, A. F. Lotus, S. Bhargava, E. T. Bender, E. A. Evans, R. D. Ramsier, Darrell Hyson Reneker, G. G. Chase

College of Polymer Science and Polymer Engineering

Electrospinning is a simple, versatile, and cost effective method for generating nanoscale fibers, wires, and tubes. Nanowires and nanotubes could be important building blocks for nanoscale electronics, optoelectronics, and sensors as they can function as miniaturized devices as well as electrical interconnects. We report on a simple method to fabricate free standing ceramic nanofiber heterostructures, which exhibit rectifying behavior of a p-n junction.

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Nonlinear-Optical Studies Of A Fluorinated Poled Polyimide Guest-Host System, S. F. Hubbard, K. D. Singer, F. Li, Stephen Z. D. Cheng, F. W. Harris Jun 2009

Nonlinear-Optical Studies Of A Fluorinated Poled Polyimide Guest-Host System, S. F. Hubbard, K. D. Singer, F. Li, Stephen Z. D. Cheng, F. W. Harris

College of Polymer Science and Polymer Engineering

We report on poling of a low dielectric constant preimidized fluorinated fully aromatic guest-host polyimide nonlinear optical material including thermal stability of optical nonlinearities and waveguiding properties. We measured a second-harmonic coefficient (d33 = 4.9 +/- 0.5 pm/V at 1217 nm fundamental wavelength) which is accurately predicted by a thermodynamic model of poled polymers. The optical nonlinearity of a poled sample was thermally stable at 80-degrees-C for over 300 h. Films were observed to have negative birefringence. Optical losses for slab waveguides in lowest order TE and TM modes were greater-than-or-equal-to 7.7 dB/cm for doped waveguides at 800 nm wavelength …

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Effects Of Ultramicroelectrode Dimensions On The Electropolymerization Of Polypyrrole, Benjamin J. Fletcher, Jared T. Fern, Kevin Rhodes, Timothy E. Mcknight, Jason D. Fowlkes, Scott T. Retterer, David J. Keffer, Michael L. Simpson, Mitchel J. Doktycz Jun 2009

Effects Of Ultramicroelectrode Dimensions On The Electropolymerization Of Polypyrrole, Benjamin J. Fletcher, Jared T. Fern, Kevin Rhodes, Timothy E. Mcknight, Jason D. Fowlkes, Scott T. Retterer, David J. Keffer, Michael L. Simpson, Mitchel J. Doktycz

Faculty Publications and Other Works -- Chemical and Biomolecular Engineering

Anode geometry can significantly affect the electrochemical synthesis of conductive polymers. Here, the effects of anode dimensions on the electropolymerization of pyrrole are investigated. Band microelectrodes were prepared with widths ranging from 2 to 500 μm. The anode dimension has a significant effect on the resulting thickness of polymer film. The electropolymerization process deviates significantly from that predicted by simple mass transfer considerations when electrode dimensions are less than ∼ 20 μm. Polymer film thickness is thinner than expected when electrode dimensions become less than ∼ 10 μm. A simple mathematical model was derived to explain the observed effects of …

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Universal Scaling Behavior In Startup Shear Of Entangled Linear Polymer Melts, Pouyan E. Boukany, Shi-Qing Wang, Xiaorong Wang Jun 2009

Universal Scaling Behavior In Startup Shear Of Entangled Linear Polymer Melts, Pouyan E. Boukany, Shi-Qing Wang, Xiaorong Wang

College of Polymer Science and Polymer Engineering

We have studied stress overshoot behavior in startup shear of four monodisperse polymer melts with a range of chain entanglement from Z = 24 to 160 entanglement points per chain. In the elastic deformation regime defined by (gamma)over dot tau(R) > 1 where tau(R) is the Rouse relaxation time, (i) the peak shear stress sigma(max) scales with the time t(max) at the peak to -1/2 power, in contrast to an exponent of -1/4 in the viscoelastic regime (for (gamma)over dot tau(R) < 1), (ii) sigma(max) changes linearly with the elapsed strain at the stress peak gamma(max), which scales with the applied shear rate as (gamma)over dot(1/3), (iii) a supermaster curve collapses time-dependent shear stress growth curves up to the stress maximum at all shear rates for all the four styrene-butadiene rubber samples. (C) 2009 The Society of Rheology. [DOI: 10.1122/1.3086872]

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Web Based Classes For Enhancement Of Prelaboratory Lectures, Tiffany Hesser, Michael Collura Jun 2009

Web Based Classes For Enhancement Of Prelaboratory Lectures, Tiffany Hesser, Michael Collura

Chemistry and Chemical Engineering Faculty Publications

The use of web classes, such as Tegrity Campus1, as a supplement to pre laboratory reading or a replacement for pre laboratory lectures could become a standard tool in laboratory education protocol. In classes with multiple lab sections and instructors, pre laboratory lectures can lack consistency and it can be difficult to gauge the students’ level of preparation. With the ever increasing exposure to technology, students generally prefer information in a digital and multimedia form, rather than textbook readings. Therefore, this method can prove to better prepare students prior to laboratory experiments, increasing the overall understanding of the chemical reactions …

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A Rapid Method For Flow-Ready Cylindrical Microchannel Fabrication, Kimberly H. Henthorn Jun 2009

A Rapid Method For Flow-Ready Cylindrical Microchannel Fabrication, Kimberly H. Henthorn

Chemical and Biochemical Engineering Faculty Research & Creative Works

Most current methods of microchannel fabrication are expensive and time consuming or result in noncylindrical channels, which is undesirable for many applications. A rapid inexpensive method for the fabrication of flow-ready cylindrical polymer microchannels from polydimethylsiloxane (PDMS) is presented here. In this method, cylindrical needles are used as molds for the channels and also function as flow delivery devices after fabrication. Validation of channel function and smoothness can be accomplished by comparing experimental data to theoretical models. One model was previously developed by the author to predict the incipient motion of a glass sphere in contact with a perfectly smooth …

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