Chemical Engineering Commons^™

Preparation, Structure And Electrochemical Hydrogenation Of Carbon Nanotubes Supported Platinum Catalysts, Qing-Gang He, Xiao-Zi Yuan, Xian-Xia Yuan, Zi-Feng Ma

Journal of Electrochemistry

In this paper, Pt/CNTs catalyst was prepared and its electrocatalytic property was studied by obtaining cycling voltammetry curves (C-V) and Tafel curves. In addition, the XRD,XPS and TEM tests were carried out to determine the structure and composition of the catalysts. It can be found that the platinum loading has been increased significantly using a carbon nanotubes support. Dispersion of Platinum was better and gave more active sites. The electrochemical characteristic of Pt/CNTs was also more desirable than that of Pt/C catalys t(Johnson Matthey). In conclusion, carbon nanotubes can played a conspicuous role in "electrogenerative" processes of PEMFC hydrogenation reactor.

Electrochemical Synthesis Of Ferrate(Vi) By Anodic Oxidation, Jia-Ju Xu, Jian-Ming Wang, Wei-Hua Yang, Cheng Chen, Jian-Qing Zhang

Journal of Electrochemistry

The ferrate(Ⅵ) was synthesized by electrochemical anodic oxidation. The effects of preparation conditions on the current yield of ferrate(VI) synthesis have been studied in this work. The experimental results showed that grey cast iron as an anodic material is suitable for electrochemical synthesis and NaOH solution as an electrolyte results in a higher current yield than KOH solution. The highest current yield was obtained at a current density (4.54) mA·cm^-2, temperature 20 ℃ and 14 mol·dm^-3 NaOH. In this case, a current yield of 68.5% was obtained by electrolysis for 1 h.

Progress In Research For Biofuel Cell, Yue Bao, Xia-Qin Wu

Journal of Electrochemistry

In this article, research progresses of the biofuel cell in recent years were summarized. The operation principle and classification of the biofuel cells were described. The role of the mediator for promoting electron transfer in biofuel cells and the techniques for improving the electric properties of biofuel cells, such as output potential, were discussed with some attracting research instances. Finally, the choke points for research of biofuel cell were explored, and the application prospect of biofuel cells was forecasted.

Growth Dynamics Of Isotactic Polypropylene Single Crystals During Isothermal Crystallization From A Miscible Polymeric Solvent, Rujul Mehta, Wirunya Keawwattana, Thein Kyu

College of Polymer Science and Polymer Engineering

The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This …

Analyzing And Modeling Of Photobioreactors By Combining First Principles Of Physiology And Hydrodynamics, Hu Ping Luo, Muthanna H. Al-Dahhan

Chemical and Biochemical Engineering Faculty Research & Creative Works

Mixing in Photobioreactors is Known to Enhance Biomass Productivity Considerably, and Flow Dynamics Play a Significant Role in the Reactor's Performance, as They Determine the Mixing and the Cells' Movement. in This Work We Focus on Analyzing the Effects of Mixing and Flow Dynamics on the Photobioreactor Performance. based on Hydrodynamic Findings from the CARPT(Computer Automated Radioactive Particle Tracking) Technique, a Possible Mechanism for the Interaction between the Mixing and the Physiology of Photosynthesis is Presented, and the Effects of Flow Dynamics on Light Availability and Light Intensity Fluctuation Are Discussed and Quantitatively Characterized. Furthermore, a Dynamic Modeling Approach is …

Studies On Improved Integrated Membrane-Based Chromatographic Process For Bioseparation, Yanke Xu

Dissertations

To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process.

Interfacial polymerization was carried out to coat the bottom section of the …

Kinetics Of Ho2 Abstraction Of H Atoms From Hydrocarbons And Thermochemical Properties Of Urethane Monomers And Radicals, Rajul Shah

Theses

SECTION I: Kinetics of HO₂ Abstraction of H Atoms From Hydrocarbons

Structures, internal rotational barriers and ideal gas thermochemical properties, ΔH^°_f98 for representative series of transition states for abstraction of H atoms from primary, secondary and tertiary hydrocarbons by the HO₂ radical, TC-HOOH (1), TCC-HOOH (2), TC₂C-HOOH (3), TC₃C-HOOH (4), TC₂CC-HOOH (5), TC₂CC-HOOHC (6) and TC₃CCC-HOOH (7) are analyzed in this study. Molecular structures and vibrational frequencies are determined at the B3LYP/6-3111G(d,p) density functional level. The S°₂₉₈ and C_p(T) values (300≤T/K≤1500) from vibrational, …

Transcriptome-Based Determination Of Multiple Transcription Regulator Activities In Escherichia Coli By Using Network Component Analysis, Katy Kao, Young-Lyeol Yang, Riccardo Boscolo, Chiara Sabatti, Vwani Roychowdhury, James Liao

Faculty Publications

Cells adjust gene expression profiles in response to environmental and physiological changes through a series of signal transduction pathways. Upon activation or deactivation, the terminal regulators bind to or dissociate from DNA, respectively, and modulate transcriptional activities on particular promoters. Traditionally, individual reporter genes have been used to detect the activity of the transcription factors. This approach works well for simple, non-overlapping transcription pathways. For complex transcriptional networks, more sophisticated tools are required to deconvolute the contribution of each regulator. Here, we demonstrate the utility of network component analysis in determining multiple transcription factor activities based on transcriptome profiles and …

High-Resolution Touch Sensor Could Be Boon To Cancer Surgeons, Others

Department of Chemical and Biomolecular Engineering: News Releases

Lincoln, Neb., June 8, 2006 -- One of the trickiest decisions facing a cancer surgeon today is where to stop cutting. The surgeon doesn't want to stop too soon and leave cancer cells in the patient's body, but he or she also doesn't want to take too many cells and do unnecessary damage to organs. That decision could soon be made much easier, though, thanks to a high-resolution touch sensor developed by chemical engineers at the University of Nebraska-Lincoln that may allow surgeons to tell at the level of a single layer of cells whether or not they have excised …

Teaching Engineering Courses With Workbooks, Yaşar Demirel

Department of Chemical and Biomolecular Engineering: News Releases

Society expects that a modem college education will turn out students who are analytical. intellectually curious, culturally aware, employable, and capable of leadership. Some important skills needed for all degree programs are problem solving, communication (written and oral), team or group work, learning and information processing, and technology. Instructors feel rewarded and satisfied when they sense that they have made a difference in the life of a student.

Teaching Coupled Transport And Rate Processes, Yaşar Demirel

Department of Chemical and Biomolecular Engineering: News Releases

Coupling refers to a flux occurring without its primary thermodynamic driving force; for example, mass flux without a concentration gradient called the thermal diffusion is a well-known coupled process. Coupling also refers to a flux occurring in a direction opposite to the direction imposed by its driving force; for example, a mass flux can occur from a low to a high concentration region and is called the active transport or uphill transport, such as potassium and sodium pumps coupled to chemical energy released by the hydrolysis of adenosine triphosphate (ATP) in biological systems. Although the coupled processes seem to be …

Retention And Viability Characteristics Of Mammalian Cells In An Acoustically Driven Polymer Mesh, Zhaowei Wang, Paul Grabenstetter, Donald L. Feke, Joanne M. Belovich

Chemical & Biomedical Engineering Faculty Publications

A processing approach for the collection and retention of mammalian cells within a high porosity polyester mesh having millimeter-sized pores has been studied. Cell retention occurs via energizing the mesh with a low intensity, resonant acoustic field. The resulting acoustic field induces the interaction of cells with elements of the mesh or with each other and effectively prevents the entrainment of cells in the effluent stream. Experiments involving aqueous suspensions of polystyrene particles were used to provide benchmark data on the performance of the acoustic retention cell. Experiments using mouse hybridoma cells showed that retention densities of over 1.5 × …

Modeling The Direct Solar Conversion Of Co2 To Co And O2, Thomas H. Fletcher

Faculty Publications

At high temperatures (greater than 2300 K), CO₂ is known to dissociate to CO and O. A prototype solar collector was previously demonstrated to achieve such high temperatures, achieving 4-6 mol % CO in the product stream from an inlet stream of pure CO₂. This paper describes the results of computer modeling performed to determine the flow, temperature, and reactions occurring in the prototype device. Of particular interest are the heat-transfer and reaction mechanisms involved and how much photolysis occurs in the prototype. Predictions were performed with two different computational fluid dynamic codes (Fluent and PCGC-3). The …

Ignition Behavior Of Live California Chaparral Leaves, Joshua D. Engstrom, Jared K. Butler, Steven G. Smith, Larry L. Baxter, Thomas H. Fletcher, David R. Weise

Faculty Publications

Current forest fire models are largely empirical correlations based on data from beds of dead vegetation. Improvement in model capabilities is sought by developing models of the combustion of live fuels. A facility was developed to determine the combustion behavior of small samples of live fuels, consisting of a flat-flame burner on a moveable platform. Qualitative and quantitative combustion data are presented for representative samples of California chaparral: manzanita (Arctostaphylos parryana); oak (Quercus berberidifolia); ceanothus (Ceanothus crassifolius), and chamise (Adenostoma fasciculatum). Times to ignition were significantly influenced by shape effects, whereas ignition temperature was more dependent on chemical composition

Etching With Electron Beam Generated Plasmas, D. Leonhardt, Scott G. Walton, Christopher Muratore, Richard F. Fernsler, R. A. Meger

Chemical and Materials Engineering Faculty Publications

A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen–argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to 220 nm/min at 100 eV), with reasonable anisotropic pattern transfer above 50 eV. Little change in etch rate was …

Effect Of Plasma Flux Composition On The Nitriding Rate Of Stainless Steel, Christopher Muratore, Scott G. Walton, D. Leonhardt, Richard F. Fernsler, David D. Blackwell, R. A. Meger

Chemical and Materials Engineering Faculty Publications

The total ion flux and nitriding rate for stainless steel specimens exposed to a modulated electron beam generated argon-nitrogen plasma were measured as a function of distance from the electron beam axis. The total ion flux decreased linearly with distance, but the nitriding rate increased under certain conditions, contrary to other ion flux/nitriding rate comparisons published in the literature. Variation in ion flux composition with distance was explored with a mass spectrometer and energy analyzer as a possible explanation for the anomalous nitriding rate response to ion flux magnitude. A transition in ion flux composition from mostly N2 1 to …

Laboratory Automation Education, James D. Sterling

Business and Information Technology Faculty Research & Creative Works

No abstract provided.

Laboratory Automation Curriculum At Keck Graduate Institute, James D. Sterling

Business and Information Technology Faculty Research & Creative Works

A novel curriculum in laboratory automation and high-throughput technologies has been developed at the Keck Graduate Institute (KGI) over the past five years as part of the professional master's degree program in applied life sciences. The goal of this curriculum has been four-fold: (1) motivate study by describing the need for automation through several example problems in combinatorial biological discovery, (2) provide elements of fundamental engineering science that are required for the development of the technologies and tools that enable automation, (3) provide opportunities for the students to see and use state-of-the-art instruments, learn about existing industry standards, and to …

Effect Of Porosity On The Capacity Fade Of A Lithium-Ion Battery: Theory, Godfrey Sikha, Branko N. Popov, Ralph E. White

Faculty Publications

A mathematical model is presented to predict the performance of a lithium-ion battery. It includes the changes in the porosity of the material due to the reversible intercalation processes and the irreversible parasitic reaction. The model was also extended to predict the capacity fade in a lithium-ion battery based on the unwanted parasitic reaction that consumes Li⁺ along with the changes in the porosities of the electrodes with cycling due to the continuous parasitic side reaction. The model can be used to predict the drop in the voltage profile, change in the state of charge, and the effects of …

Closed Material Cycles And Organic Solvent Recovery, Tim De Jong

Theses

A survey was conducted of the pharmaceutical sector in Ireland to establish organic solvent usage, recovery and treatment practices. The eleven companies covered by the survey, which included several of the worlds largest multinational companies, consumed in the region of 122,000 tonnes of organic solvent in 2002. Approximately 53,000 tonnes was recovered on-site while 69,000 tonnes of virgin solvent was brought on-site to replace that which was lost through wastewater treatment, incineration, fugitive emissions and off-site treatment or reuse. The total quantity of virgin solvent consumed by the eleven companies accounted for 75.4 % of organic solvent imports to Ireland. …

The Dependence Of The Overall Drying Time And Product Quality Of A Lyophilization Process On The Relative Position Of Vials On A Tray With Tray Sides And Without Tray Sides For Different Heat Input Control Policies, Kian Hui Gan

Masters Theses

"The dynamic behavior of the primary and secondary drying stages of the lyophilization process were studied when (a) single vials located at different positions on the tray were individually being dried, and (b) the vials on the tray are arranged in clusters of square and hexagonal arrays and all the vials on the tray are simultaneously being dried. For both cases (a) and (b), fast drying times and relatively more uniform distributions of temperature and concentration of bound water at the end of the secondary drying stage are obtained by heat input control that runs the lyophilization process close to …

Electrodeposition Of Feconicu Quaternary System, Qiang Huang

LSU Doctoral Dissertations

Electrodeposition is a cost-effective method to produce thin film materials, which have been used widely in the microelectronic industry, and is advantageous to fabricate metal deposits into recessed and curved areas. In this dissertation, FeCoNiCu quaternary alloy system was investigated, both experimentally and theoretically, for fabrication of multilayers, grating structures, and nanowires. Multilayer structures are composed of alternating ferromagnetic and nonmagnetic nanometric layers, and are of interest due to the giant magnetoresistance (GMR) property it possesses, a change in electric resistance in the presence of an external magnetic field. In addition, the compositional modulation, or the composition contrast, in multilayer …

Exploration Of Artificial Multiferroic Thin-Film Heterostructures Using Composition Spreads, K.-S. Chang, M. A. Aronova, C.-L. Lin, M. Murakami, M.-H. Yu, Jason R. Hattrick-Simpers, O. O. Famodu, S. Y. Lee, R. Ramesh, M. Wuttig, I. Takeuchi, C. Gao, L. A. Bendersky

Faculty Publications

We have fabricated a series of composition spreads consisting of ferroelectric BaTiO₃ and piezomagnetic CoFe₂O₄ layers of varying thicknesses modulated at nanometer level in order to explore artificial magnetoelectricthin-film heterostructures. Scanning microwavemicroscopy and scanning superconducting quantum interference device microscopy were used to map the dielectric and magnetic properties as a function of continuously changing average composition across the spreads, respectively. Compositions in the middle of the spreads were found to exhibit ferromagnetism while displaying a dielectric constant as high as ≈120.

Series Solution To The Transient Convective Diffusion Equation For A Rotating Disk Electrode, Shiriram Santhanagopalan, Ralph E. White

Faculty Publications

A series solution to the transient convective diffusion equation for the rotating disc electrode system is presented and compared to previously reported solutions. The solution presented here is for the entire time domain and agrees well with both the short and long time solutions presented earlier in the literature.

Parameter Estimates For A Pemfc Cathode, Qingzhi Guo, Vijay A. Sethuraman, Ralph E. White

Faculty Publications

Five parameters of a model of a polymer electrolyte membrane fuel cell (PEMFC) cathode (the volume fraction of gas pores in the gas diffusion layer, the volume fraction of gas pores in the catalyst layer, the exchange current density of the oxygen reduction reaction, the effective ionic conductivity of the electrolyte, and the ratio of the effective diffusion coefficient of oxygen in a flooded spherical agglomerate particle to the square of that particle radius) were determined by least-squares fitting of experimental polarization curves. The values of parameters obtained in this work indicate that ionic conduction and gas-phase transport are two …

Analytical Solution For The Impedance Of A Porous Electrode, Sheba Devan, Venkat R. Subramanian, Ralph E. White

Faculty Publications

A macrohomogeneous model is presented for a porous electrode that includes coupled potential and concentration gradients with linear kinetics. The equations are solved to obtain an analytical expression for the impedance of a porous electrode. Complex plane plots are presented that illustrate two well-defined arcs: a kinetic arc and a diffusion arc with their time constants far apart. The effects of parameters such as exchange current density, porosity, diffusion coefficient, thickness, and interfacial area on the impedance spectra are presented. The usefulness of the analytical solution in investigating the effect of solution phase diffusion is also presented.

A Steady-State Impedance Model For A Pemfc Cathode, Qingzhi Guo, Ralph E. White

Faculty Publications

A model for the simulation of the steady-state impedance response of a polymer electrolyte membrane fuel cell (PEMFC) cathode is presented. The catalyst layer of the electrode is assumed to consist of many flooded spherical agglomerate particles surrounded by a small volume fraction of gas pores. Stefan-Maxwell equations are used to describe the multicomponent gas-phase transport occurring in both the gas diffusion layer and the catalyst layer of the electrode. Liquid-phase diffusion of O2 is assumed to take place in the flooded agglomerate particles. Newman’s porous electrode theory is applied to determine over-potential distributions. © 2004 The Electrochemical Society. All …

Cycle Life Modeling Of Lithium-Ion Batteries, Gang Ning, Branko N. Popov

Faculty Publications

A first-principles-based charge-discharge model was developed to simulate the capacity fade of Li-ion batteries. The model is based on the loss of active lithium ions due to solvent reduction reaction and on the rise of the anode film resistance. The effect of parameters such as exchange current density, depth of discharge (DOD), end of charge voltage, film resistance, and the overvoltage of parasitic reaction were studied quantitatively. The model controls the required DOD by controlling the discharge time and estimates the end of discharge voltages as a function of cycle number.

Development Of First Principles Capacity Fade Model For Li-Ion Cells, P. Ramadass, Bala Haran, Parthasarathy M. Gomadam, Ralph E. White, Branko N. Popov

Faculty Publications

A first principles-based model has been developed to simulate the capacity fade of Li-ion batteries. Incorporation of a continuous occurrence of the solvent reduction reaction during constant current and constant voltage (CC-CV) charging explains the capacity fade of the battery. The effect of parameters such as end of charge voltage and depth of discharge, the film resistance, the exchange current density, and the over voltage of the parasitic reaction on the capacity fade and battery performance were studied qualitatively. The parameters that were updated for every cycle as a result of the side reaction were state-of-charge of the electrode materials …

Development Of Novel Method For Preparation Of Pemfc Electrodes, Hansung Kim, Branko N. Popov

Faculty Publications

A method based on pulse electrodeposition technique was developed for preparation of membrane electrode assemblies (MEAs). In this approach, platinum is deposited directly on the surface of the carbon electrode. The method ensures most of the platinum to be in close contact with the membrane. Using this method it is possible to increase the Pt/C ratio up to 75 wt % near the surface of the electrode resulting in a 5 µm thick catalyst layer. The MEA prepared by pulse electrodeposition exhibits a current density of 0.33 A/cm² at 0.8 V with platinum loading of 0.25 mg of Pt/cm …