Engineering Commons^™

Evaluation Of Environmental Materials As Thermal Witness Materials, Shashank Vummidi Lakshman

Dissertations

New and complex energetic materials are under development for achieving tunable pyrotechnical events for applications such as neutralization of biological weapons, bunker busters and many others. To guide the development of hybrid materials, the pyrotechnical environment they produce requires higher degree of characterization i.e. good description of spatial and temporal temperature distribution.

Temperature measurements in pyrotechnical events are especially challenging, where the temperature of the environment rises more than 2000 K on microseconds to few milliseconds time scale. These environments produce high thermal stress where traditional sensors like thermocouples, optical pyrometers struggle to describe the dynamic changes in the environment. …

Novel Scrubbing Systems For Post-Combustion Co2 Capture And Recovery, Tripura Mulukutla

Dissertations

Power plant emissions of flue gas releases considerable CO₂ to the atmosphere; CO₂ is considered to be the main contributor to global warming. Several gas absorption techniques are being investigated to reduce the capital and operating costs for CO₂ capture from post-combustion flue gas. Conventional method of CO₂ capture by an aqueous solution of monoethanolamine (MEA) and its subsequent stripping in a separate tower with steam at 120°C, is a highly energy intensive process. The low partial pressure of CO₂ in the flue gas inhibits the application of CO₂-selective membranes unless methods are …

Ignition Mechanism In Nanocomposites Thermites, Rayon Williams

Dissertations

Nanocomposite thermites (n-thermites) have been actively investigated for a wide range of potential applications including propellants, explosives, and pyrotechnics. There have been several recent efforts aimed at understanding ignition mechanisms of nanocomposite reactive materials. Although significant progress has been made, ignition mechanisms remain elusive. At the same time, a robust ignition model is required to incorporate these materials in practical energetic formulations. A challenge of this effort is to describe the mechanisms of ignition of n-thermites prepared by Arrested Reactive Milling (ARM) with different stimuli, including heat, spark and impact and also develop a multi-step kinetic model describing different processes …

Synthesis And Characterization Of Metal-Based Reactive Powders, Yasmine Aly

Dissertations

Aluminum added to propellants, explosives, and pyrotechnics, boosts their energy density. Different approaches were investigated that could shorten aluminum ignition delays, increase combustion rates, and decrease the tendency of aluminum droplets to agglomerate. Here, Al-based reactive, mechanically milled materials are prepared and characterized.

For powders with Fe, Ni, or Zn additives, the particles consist of an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling times. Thermogravimetric analysis shows selective …

The Photophysics Properties Of Lanthanide Luminescent Probes, Ke Li

Theses

A detailed study of the luminescence quantum yield, lifetimes and the number of water molecules coordinated to lanthanide luminescent probes based on biphenylyl-7-amino-4- methyl-2(1H)-quinolinon (Bi-cs124) derivatives have been carried out using a time- resolved fluorescence assay (TRFA). Bi-cs124 was conbined with different chelating agents, specifically diethylene triamine pentaacetic acid (DTPA), ethylene diamine tetraacetic acid (EDTA), ethylene glycol tetraacetic acid (EGTA), and 3,6,9,12-Tetrakis carboxymethyl)-3,6,9,12-tetraazatetradecane-1,14-dioic acid (TTHA). The results indicate that Bi-cs 124-TTHA has a longest lifetime and smallest number of coordinated water molecules because TTHA has larger number of chelating groups. The dependence of the luminescence lifetimes on the probes concentrations …

Preparation And Characterization Of Fast Dissolving Pullulan Films Containing Griseofulvin Nanoparticles For Bioavailability Enhancement, Zhelun Ma

Theses

The aim of this study is to enhance the bioavailability of griseofulvin, a model poorly water-soluble drug, via increasing drug dissolution rate through preparation of drug nanoparticle-laden, pullulan-based strip films. The work entails (i) wet-milling griseofulvin in a stirred media mill using pullulan (polymer) along with sodium dodecyl sulfate (surfactant) as stabilizers, (i i) preparing strip films by casting-drying a precursor suspension consisting of the mixture of the milled drug suspension and a film-forming pul l ul an–xanthan gum-glycerin solution, (iii) characterizing the suspensions and the films, and (iv) exploring the effects of film thickness, drug and xanthan gum loadings, …

Synthesis Of Silver Nanoparticles Supported On Graphene Quantum Dots For Oxygen Reduction Reaction, Jian Ju, Wei Chen

Journal of Electrochemistry

Silver-based catalysts have been extensively investigated as the platinum substituted catalysts due to their high catalytic efficiency, low cost and long-term durability. In this study, the surfactant-free silver nanoparticles supported on graphene quantum dots were synthesized through a facile approach without addition of any other protecting ligands and reducing agents. The “surface-clean” silver nanoparticles had remarkable electrocatalytic performance towards oxygen reduction reaction (ORR) with the most efficient four-electron transfer process. Compared with commercial Pt/C catalyst, the hybrid nanoparticles showed comparable catalytic performance for ORR but much higher tolerance to methanol. Such silver nanoparticles supported on graphene quantum dots may have …

Electrochemical Catalysis: A Dft Study, Li Li, Zi-Dong Wei

Journal of Electrochemistry

In this review, we focus on achievements in electro-catalysis based on the density function theory study. The relationships among the electrode potential, electronic structure of catalysts and electro-catalytic activity are summarized in three parts: the adsorption and desorption of species, electron transfer, and stability of catalysts. The electrode potential and the electronic structure (d-band center or Fermi (HOMO) energy) of catalysts significantly influence the formation, adsorption and desorption of surface species on electrode. The electro-catalytic activity can be improved by modulating the electrode potential and electronic structure of catalysts.

Recent Progress In The Mechanistic Understanding Of Formic Acid Oxidation On Pt Electrode, Jie Xu, Dao-Chuan Jiang, Dong Mei, Zheng-Da He, Yan-Xia Chen

Journal of Electrochemistry

This article reviews the recent progress in understanding of the mechanisms for formic acid oxidation on Pt electrode. There are two pathways for formic acid oxidation on Pt electrode: (1) Indirect Pathway through which HCOOH is oxidized to CO₂ through CO_ad intermediate. This pathway contributes only 1% of the total current; (2) Direct Pathway where HCOOH is oxidized directly to CO₂. The results from IR Spectroscopy, single-crystal electrochemistry and DFT calculation all support that the bridge-bonded formate is neither the intermediate of direct pathway nor the precursor for CO_ad formation in indirect pathway. Possible mechanism …

Electrocatalytic Oxidation Of Formate On Pd-Cu/C - Effect Of Dealloying Pretreatment, Kun Jiang, Ye Wang, Tao Lin, Wen-Bin Cai

Journal of Electrochemistry

Carbon supported highly dispersed Pd-Cu nanoalloy catalyst toward formate electrooxidation is prepared via one-pot synthesis by using ethylene glycol as the reducing agent and sodium citrate as the stabilizer. The as-prepared catalyst is structurally characterized by TEM and XRD. The Cu dealloyment is carried out through repetitive potential cycling of the Pd-Cu/C catalyst in an acidic solution. The dealloying effect on the performance of the Pd-Cu/C is investigated by using cyclic voltammetry and chronoamperometry, and the surface structural change of Pd-Cu/C is probed by in situ ATR-IR measurement. The results show that the as-prepared Pd-Cu/C processes a better long-term stability …

Electrochemical Fabrication Of Two-Dimensional Flower-Like Pt Nanostructures For Methanol Electrocatalytic Oxidation, Xia Wang, Jun Hu, Yong-Jun Li

Journal of Electrochemistry

Two-dimensional flower-like Pt nanostructures (2D FPNs) were fabricated on glassy carbon substrates by galvanostatical electrochemical technique. The electrolyte was the HAuCl₄ + HClO₄ aqueous solution without addition of any structure-directing organic reagent, which made as-prepared Pt nanostructures cleaner, exhibiting much higher reactivity. Scanning electron microscopic images revealed that 2D FPNs were spherical Pt nano-flowers constructed by the smallest building blocks, nano-leaves. The number density of spherical Pt nano-flowers can be tuned by controlling the electrodeposition time. High resolution transmission electron microscopic images indicated that each nano-leaf was formed by growing along Pt(111) direction. Electrocatalytic activities of as-prepared 2D …

Preparation Of Pt-Tio2/Graphene Composites With High Catalytic Activity Towards Methanol Oxidation And Oxygen Reduction Reaction, Li Qi, Ying Yin, Wen-Guang Tu, Bing-Bing Wu, Zhao-Sheng Wang, Jian-Guo Liu, Jun Gu, Zhi-Gang Zou

Journal of Electrochemistry

A series of graphene-supported TiO₂ nanoparticles (TiO₂/G) with different TiO₂ contents were prepared by a facile hydrothermal method, and then the Pt-TiO₂/G catalysts were successfully prepared by reducing Pt-precursor with microwave technique. Compared with Pt-G catalysts, the catalytic performance toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) of Pt-TiO₂/G catalysts was improved due to the addition of TiO₂. However, the excessive TiO₂ would lead to a poor catalytic performance of Pt-TiO₂/G catalysts because of the low electrical conductivity of TiO₂.

Effecting Of Dissolved Oxygen On Microbial Fuel Cells Based On Pseudomonas Aeruginosa, Chang-Li Cao, Li-Xiang Chen, Ran-Ran Wu, Ken-Lin Chang, Feng Zhao

Journal of Electrochemistry

In this work, the reaction between the electron shuttle secreted by Pseudomonas aeruginosa and anode was studied by measuring cyclic voltammogram and open circuit potential. The effect of dissolved oxygen on the oxidation reaction of anode was explored. It was demonstrated that the reaction was a diffusion-controlled and reversible process. The anode was a little affected when the dissolved oxygen of inocula was low (0 ~ 1.6 mg·L^-1). The polarization curves showed that the current output of microbial fuel cells decreased 7% with the impact of dissolved oxygen.

An Economic Analysis Of Small-Scale Biodiesel Production: Implementation Of Ethyl Ester Production In A Job Shop Setting, Scott Haase, Benjamin Craig

Journal of Undergraduate Research at Minnesota State University, Mankato

Biodiesel is becoming a demanded consumer automotive alternative fuel used in diesel vehicles today. An emerging trend is toward small-scale biodiesel production performed by the final consumer. A limited source of commercially available production systems exists and has resulted in many systems being designed and built by the user. Preliminary research conducted by the authors has shown biodiesel to be the least-cost alternative to petroleum diesel after as few as 8 months of system use. This study examines the economic viability of building and producing biodiesel using a small-scale production system versus buying consumer petroleum diesel. During production, measurements were …

Humic Substances-Based Polymer System, Gerard R. Thiel

Patents (University of Northern Iowa)

A system for use in forming polymer compositions, including as a replacement for phenolic based resin systems, for instance, in preparing foundry molds. In a preferred embodiment, the system includes the use of a) a polyermizable hydroxyl-containing component comprising a humic substance (as can be provided by lignite), b) an isocyanate component, and c) a catalyst, and preferably amine catalyst, component adapted to catalyze the polymerization of a) and b). The system is optionally used as binder system in the presence of a filler, such as, in combination with a foundry aggregate such as sand. A polymer system of this …

Applying Accelerator Mass Spectrometry For Low-Level Detection Of Complex Engineered Nanoparticles In Biological Media, Binghui Wang, George S. Jackson, Robert A. Yokel, Eric A. Grulke

Pharmaceutical Sciences Faculty Publications

Complex engineered nanoparticles (CENPs), which have different core and surface components, are being developed for medicinal, pharmaceutical and industrial applications. One of the key challenges for environmental health and safety assessments of CENPs is to identify and quantity their transformations in biological environments. This study reports the effects of in vivo exposure of citrate-coated nanoalumina with different rare isotope labels on each component. This CENP was dosed to the rat and accelerator mass spectrometry (AMS) was used to quantify ²⁶Al, ¹⁴C, and their ratio in the dosing material and tissue samples. For CENPs detected in the liver, the …

Influence Of Crystal Structure On The Electrochemical Performance Of A-Site-Deficient Sr 1-Xnb 0.1 Co 0.9 O 3-Δ Perovskite Cathodes, Yinlong Zhu, Ye Lin, Xuan Shen, Jaka Sunarso, Wei Zhou, Shanshan Jiang, Dong Su, Fanglin Chen, Zongping Shao

Faculty Publications

The creation of A-site cation defects within a perovskite oxide can substantially alter the structure and properties of its stoichiometric analogue. In this work, we demonstrate that by vacating 2 and 5% of A-site cations from SrNb_0.1Co_0.9O_3−δ (SNC1.00) perovskites (Sr_1−sNb_0.1Co_0.9O_3−δ, s = 0.02 and 0.05; denoted as SNC0.98 and SNC0.95, respectively), a Jahn–Teller (JT) distortion with varying extents takes place, leading to the formation of a modified crystal lattice within a the perovskite framework. Electrical conductivity, electrochemical performance, chemical compatibility and microstructure of Sr …

Oxidation-Resistant, Solution-Processed Plasmonic Ni Nanochain-SioX (X < 2) Selective Solar Thermal Absorbers, Xiaobai Yu, Xiaoxin Wang, Qinglin Zhang, Juchuan Li, Jifeng Liu

Chemical and Materials Engineering Faculty Publications

Metal oxidation at high temperatures has long been a challenge in cermet solar thermal absorbers, which impedes the development of atmospherically stable, high-temperature, high-performance concentrated solar power (CSP) systems. In this work, we demonstrate solution-processed Ni nanochain-SiO_x (x < 2) and Ni nanochain-SiO₂ selective solar thermal absorbers that exhibit a strong anti-oxidation behavior up to 600 °C in air. The thermal stability is far superior to previously reported Ni nanoparticle-Al₂O₃ selective solar thermal absorbers, which readily oxidize at 450 °C. The SiO_x (x < 2) and SiO₂ matrices are derived from hydrogen silsesquioxane and tetraethyl orthosilicate precursors, respectively, which comprise Si-O cage-like …

Lipid Extraction From Scenedesmus Sp. Microalgae For Biodiesel Production Using Hot Compressed Hexane, Hee-Yong Shin, Jae-Hun Ryu, Seong-Youl Bae, Czarena L. Crofcheck, Mark Crocker

Center for Applied Energy Research Faculty and Staff Publications

Lipid extraction from Scenedesmus sp. microalgae using hot compressed hexane (HCH) was investigated. Extraction performance was evaluated near the critical point of hexane and was compared with that of hexane extraction performed at room temperature and pressure, and the Bligh and Dyer extraction method. Experimental data showed that HCH significantly improves the lipid yield and rate of lipid extraction compared to the use of hexane at ambient conditions. High yields of biodiesel-convertible lipid fractions were rapidly achieved at the critical point of hexane, at a level comparable to that of the Bligh and Dyer method.

Engineering Biosensors For Short-Chain Alcohols, Yu Xia

McKelvey School of Engineering Graduate Student Theses & Dissertations

Biofuel is a promising substitute for fossil fuel and the research of biofuel production has been extensively conducted during the recent years. Great efforts have been made to create many types of the fuel production hosts. However, effective approaches for high specificity and high throughput screening of the fuel production strains are still lacking. The cellular stress response is one universal defense mechanism when a microbial cell is exposed to an unfavorable substance or environment. It triggers a series of downstream responses when a cell senses certain chemicals. Transcriptional factors are widely used in living organisms to regulate gene expression. …

Theoretical Investigation Of Heterogeneous Catalysis At The Solid–Liquid Interface For The Conversion Of Lignocellulosic Biomass Model Molecules, Muhammad Faheem

Theses and Dissertations

Catalytic conversion of biomass-derived oxygenates to fuels and value-added chemicals is a promising strategy in the search for renewable and sustainable energy sources. Most relevant catalytic processes are carried out in an aqueous environment using supported transition metal catalysts. The reaction network consists of multiple series and parallel pathways leading to formation of hydrogen, alkanes, and lighter oxygenates. The final product distribution ultimately depends on the sequence and competition of C−C, C−O, C−H, and O−H bonds scissions. Ethylene glycol (EG) is the simplest model molecule of various biomass-derived polyols that has a C:O stoichiometry of 1:1 and contains all relevant …

A Non-Destructive Method For Measuring The Mechanical Properties Of Ultrathin Films Prepared By Atomic Layer Deposition, Qinglin Zhang, Xingcheng Xiao, Yang-Tse Cheng, Mark W. Verbrugge

Chemical and Materials Engineering Faculty Publications

The mechanical properties of ultrathin films synthesized by atomic layer deposition (ALD) are critical for the liability of their coated devices. However, it has been a challenge to reliably measure critical properties of ALD films due to the influence from the substrate. In this work, we use the laser acoustic wave (LAW) technique, a non-destructive method, to measure the elastic properties of ultrathin Al₂O₃ films by ALD. The measured properties are consistent with previous work using other approaches. The LAW method can be easily applied to measure the mechanical properties of various ALD thin films for multiple …

Gas-Phase, Catalytic Hydrodeoxygenation Of Propanoic Acid Over Supported Group Viii Noble Metals, Yuliana K. Lugo José

Theses and Dissertations

Recent advances for the deoxygenation of biomass, have demonstrated that hydrodeoxygenation (HDO) is one of the most promising route for the upgrading pyrolysis bio-oils. Catalytic hydrodeoxygenation of pyrolysis bio-oil have shown to be an efficient and economical process, since the raw materials consist mainly of waste. Propanoic Acid (PAc) is considered as one of the main constituents of pyrolysis bio-oils. However, these carboxylic acids are extremely corrosive and difficult to deoxygenate. Therefore, much effort have been given to the development of novel catalytic techniques, to improve the activity, stability and selectivity for the HDO of carboxylic acids.

This dissertation explores …

Synthesis, Characterization And Evaluation Of Ir-Based Bimetallic Catalysts, You Jung Song

Theses and Dissertations

This dissertation considers effective bimetallic preparation for supported Ir-based bimetallic catalysts and their catalytic activity. Since bimetallic catalysts exhibit significantly different catalytic and chemical properties than their corresponding monometallic components by providing enhanced selectivity, stability and /or activity, many monometallic catalysts in industrial processes have been replaced by bimetallic catalysts. However, conventional synthetic methods used to produce monometallic and bimetallic catalysts often result in wide particle size distributions and non-uniform materials which can be difficult to characterize on a fundamental level. Two alternate preparation methods, dendrimer templating and electroless deposition, are developed and compared with conventional incipient wetness method. In …

Ultrathin Graphene Oxide Membranes/Coatings For Separations, Hang Li

Theses and Dissertations

Graphene oxide (GO) was utilized as a novel material for making ultrathin membranes for gas separation and for making functional coatings for nano-/ultra-filtration in oil/water separation. Fundamental separation mechanisms by ultrathin GO membranes/coatings and potential applications were explored. This work can be divided into three parts. In the first part, ultrathin GO membranes supported on flat and smooth anodic aluminum oxide (AAO) substrates, with thickness down to 1.8 nm, were prepared by a facile vacuum filtration method. The as-prepared GO membranes were then studied for single-gas permeation and hydrogen mixture separation. It was revealed that the separation mechanism for the …

Synthesis Of Graphitic Carbon Nanostructures And Use As Electrocatalyst For Oxygen Reduction Reaction, Daniel A. Moniot

Theses and Dissertations

Graphitic carbon nanostructure (GCN) was synthesized by a simple procedure using cobalt(II) gluconate as a precursor and used as a catalyst support for polymer electrolyte membrane (PEM) fuel cell cathode. A novel stabilization procedure was developed to enhance the thermal stability of the GCN support. Support stabilization resulted in well-defined crystalline graphitic hollow structures as confirmed by highresolution transmission electron microscope (HRTEM). The prepared GCNs are used as support for depositing platinum nanoparticles (size) by modified polyol process. Rotating ring disk electrode (RRDE) and fuel cell studies were carried out to evaluate the catalyst performance. Cycling studies (0.6-1.0 V vs. …

Polymer Nano-Dielectrics For High Density Energy Storage, Sayful Islam Md

Theses and Dissertations

Military and commercial users require next-generation polymer dielectric materials for pulse power and power conditioning applications with rise times less than 1 ms and AC power at frequencies ranging from kHz to MHz. These power density and rate capability requirements necessitate the use of dielectric capacitors that store energy via polarization of electrons in molecular scale dipoles. Multiphase polymer composites and all-polymer dielectrics could be new kinds of materials to meet this acute need for capacitors with compact size and high rate capability.

The polymer nanocomposite (PNC) approach to achieve high energy density employed a “colossal” dielectric constant material, calcium …

Catalysis In Petroleum Coking, Robert Khakimov, Anya Heinimann, Enrico Martinez, Hyun-Tae Hwang

The Summer Undergraduate Research Fellowship (SURF) Symposium

The petroleum industry is challenged with the processing of present heavy crudes caused by high composition of sulfur and metals, which lead to a higher yield of unfavorable bottom product as vacuum residue. Vacuum residue is the least valuable fraction of four, such as saturates, aromatics, resins and asphaltenes. However, it can be upgraded to recover more valuable products such as light hydrocarbons. The Delayed Coking process is going to be used to transform the vacuum residue at different experimental conditions. First of all, the behavior of the vacuum residue needs to be analyzed with no additions in feedstock. Secondly, …

Flow Regime Transition In Trickle Bed Reactors, Eric P. Lehmann, Gregory Honda, Arvind Varma

The Summer Undergraduate Research Fellowship (SURF) Symposium

In industry, trickle bed reactors – fixed beds in which gas and liquid reactants flow concurrently downward through catalyst - are often operated at gas and liquid superficial velocities near the transition boundaries between flow regimes, especially the transition between trickle to pulse flow. Previous studies have characterized flow regime transitions as sharp transitions that occur at single superficial liquid velocities for a fixed superficial gas velocity. In reality, transitions evolve gradually over a range of superficial liquid velocities. Experiments were conducted in a fixed bed with air and water flowing concurrently downward using two different packing media. The transitions …

Polymer-Based Thermoelectric Devices, Stuart W. Hilsmier, Edward P. Tomlinson, Bryan Boudouris

The Summer Undergraduate Research Fellowship (SURF) Symposium

Currently, over 50% of all energy generated in the US is lost as waste heat, and thermoelectric generators offer a promising means to recoup some of this energy, if their efficiency is improved. While organic thermoelectric materials lack the efficiency of their inorganic counterparts, they are composed of highly abundant resources and have low temperature processing conditions. Recently, a new class of redox-active polymers, radical polymers, has exhibited high electrical conductivity in an entirely amorphous medium. In addition, these radical polymers have a simple synthetic scheme and can be highly tunable to provide desired electrical properties. In this study, the …