Matching Items (13)
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- All Subjects: Polymers
- All Subjects: Materials
- Creators: Chemical Engineering Program
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
Solid oxide fuel cells have become a promising candidate in the development of high-density clean energy sources for the rapidly increasing demands in energy and global sustainability. In order to understand more about solid oxide fuel cells, the important step is to understand how to model heterogeneous materials. Heterogeneous materials are abundant in nature and also created in various processes. The diverse properties exhibited by these materials result from their complex microstructures, which also make it hard to model the material. Microstructure modeling and reconstruction on a meso-scale level is needed in order to produce heterogeneous models without having to shave and image every slice of the physical material, which is a destructive and irreversible process. Yeong and Torquato [1] introduced a stochastic optimization technique that enables the generation of a model of the material with the use of correlation functions. Spatial correlation functions of each of the various phases within the heterogeneous structure are collected from a two-dimensional micrograph representing a slice of a solid oxide fuel cell through computational means. The assumption is that two-dimensional images contain key structural information representative of the associated full three-dimensional microstructure. The collected spatial correlation functions, a combination of one-point and two-point correlation functions are then outputted and are representative of the material. In the reconstruction process, the characteristic two-point correlation functions is then inputted through a series of computational modeling codes and software to generate a three-dimensional visual model that is statistically similar to that of the original two-dimensional micrograph. Furthermore, parameters of temperature cooling stages and number of pixel exchanges per temperature stage are utilized and altered accordingly to observe which parameters has a higher impact on the reconstruction results. Stochastic optimization techniques to produce three-dimensional visual models from two-dimensional micrographs are therefore a statistically reliable method to understanding heterogeneous materials.
ContributorsPhan, Richard Dylan (Author) / Jiao, Yang (Thesis director) / Ren, Yi (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Within recent years, metal-organic frameworks, or MOF’s, have gained a lot of attention in the materials research community. These micro-porous materials are constructed of a metal oxide core and organic linkers, and have a wide-variety of applications due to their extensive material characteristic possibilities. The focus of this study is the MOF-5 material, specifically its chemical stability in air. The MOF-5 material has a large pore size of 8 Å, and aperture sizes of 15 and 12 Å. The pore size, pore functionality, and physically stable structure makes MOF-5 a desirable material. MOF-5 holds applications in gas/liquid separation, catalysis, and gas storage. The main problem with the MOF-5 material, however, is its instability in atmospheric air. This inherent instability is due to the water in air binding to the zinc-oxide core, effectively changing the material and its structure. Because of this material weakness, the MOF-5 material is difficult to be utilized in industrial applications. Through the research efforts proposed by this study, the stability of the MOF-5 powder and membrane were studied. MOF-5 powder and a MOF-5 membrane were synthesized and characterized using XRD analysis. In an attempt to improve the stability of MOF-5 in air, methyl groups were added to the organic linker in order to hinder the interaction of water with the Zn4O core. This was done by replacing the terepthalic acid organic linker with 2,5-dimethyl terephthalic acid in the powder and membrane synthesis steps. The methyl-modified MOF-5 powder was found to be stable after several days of exposure to air while the MOF-5 powder exhibited significant crystalline change. The methyl-modified membrane was found to be unstable when synthesized using the same procedure as the MOF-5 membrane.
ContributorsAnderson, Anthony David (Author) / Lin, Jerry Y.S. (Thesis director) / Ibrahim, Amr (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Based on theoretical calculations, a material that is highly transmissive below 3000 nm and opaque above 3000 nm is desired to replace glass covers for flat plate solar thermal systems. Additionally, a suitable replacement material needs to have a sufficiently high operating temperature in order to prevent the glazing from melting and warping in a solar system. Traditional solar thermal applications use conventional soda lime glass or low iron content glass to accomplish this; however, this project aims to investigate acrylic, polycarbonate, and FEP film as suitable alternatives for conventional solar glazings. While UV-Vis and FT-IR spectroscopy indicate that these polymer substitutes may not be ideal when used alone, when used in combination with coatings and additives, these materials may present an opportunity for a glazing replacement. A model representing a flat plate solar collector was developed to qualitatively analyze the various materials and their performance. Using gathered spectroscopy data, the model was developed for a multi-glazing system and it was found that polymer substitutes could perform better in certain system configurations. To complete the model, the model must be verified using empirical data and coatings and additives investigated for the purposes of achieving the desired materials optical specifications.
ContributorsBessant, Justin Zachary (Author) / Friesen, Cody (Thesis director) / Lorzel, Heath (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Increased investigation into the development of macromolecular fluorophores has resulted in the synthesis and discovery of several potential candidates. These include modified and polymeric based dendritic structures, hyperbranched polymers and linear polymers. Strong inherent blue photoluminescence has been recently described in linear polyamine polymers in the absence of any chemical modifications. Here we describe the screening of amine/polyamine compounds for inherent photoluminescence. Several compounds that exhibited strong inherent blue photoluminescence following excitation with UV light were identified. Furthermore we demonstrated successful synthesis of poly(amino ether) polymers as well as chemically cross-linked poly(amino ether) thermosets with the lead Pentaethylenehexamine which was found to have strong inherent blue photoluminescence. The polymers and thermosets were found to retain the photoluminescent properties of the original lead compound. The polymers and thermosets were investigated for their ability to sequester heavy metals from aqueous solutions. An increased decrease in initial photoluminescence was observed as the materials were incubated with increasing metal salt concentration as a result of metal binding sequestration. The poly(amino ether) polymers were found to have higher sensitivity for metal sequestration when compared to equivalent amount of linear 25 kDa polyethylenimine. The strong inherent blue photoluminescence and the ease of synthesis of the poly(amino ether) polymers and thermosets give these materials strong potential for future applications as sensors.
ContributorsVu, Jeffrey (Co-author) / Ramos, James (Co-author) / Rege, Kaushal (Thesis director) / Godeshala, Sudakhar (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
This study aims to provide a foundation for future work on photo-responsive polymer composite materials to be utilized in additive manufacturing processes. The curing rate of 2,2-dimethoxy-2-phenyl-acetophenone (DMPA) in thin (<20 µm) and thick (>2 mm) layers of DMPA and poly(ethylene glycol) diacrylate (PEG-DA) mixtures was assessed for 5.0 w/v% (grams per 100 mL) concentrations of DMPA dissolved in PEG-DA. The polymerization rate and quality of curing was found to decrease as the concentration of DMPA increased beyond 1.0 w/v%; thus, confirming the existence of an optimum photo-initiator concentration for a specific sheet thickness. The optimum photo-initiator concentration for a 3-3.1 mm thick sheet of PEG-DA microstructure was determined to be between 0.3 and 0.38 w/v% DMPA. The addition of 1,6-hexanediol or 1,3-butanediol to the optimum photo-initiator concentrated solution of DMPA and PEG-DA was found to increase the Tg of the samples; however, the samples could not fully cure within 40-50 s, which suggested a decrease in polymerization rate. Lastly, the DMPA photo-initiator does not produce gaseous byproducts and is translucent when fully cured, which makes it attractive for infusion with strengthening materials because quality light penetration is paramount to quick polymerization rates. It is recommended that more trials be conducted to evaluate the mechanical properties of the optimum curing rate for DMPA and PEG-DA microstructures as well as a mechanical property comparison following the addition of either of the two alcohols.
ContributorsPiper, Tyler Irvin (Author) / Green, Green (Thesis director) / Lind, Mary Laura (Committee member) / School of Sustainability (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This study details the construction and operation of a dry-jet wet spinning apparatus for extruding hollow fiber membranes (HFMs). The main components of the apparatus are a spinneret, a coagulation bath, and an automatic collection reel. Continuous fiber formation was achieved using two syringe pumps simultaneously delivering polymer dope and bore fluid to the spinneret. Based on apparatus runs performed with Polysulfone (PSF) dopes dissolved in N,N-Dimethylacetamide and supporting rheological analysis, the entanglement concentration, ce, was identified as a minimum processing threshold for creating HFMs. Similarly, significant increases in the ultimate tensile strength, fracture strain, and Young's modulus for extruded HFMs were observed as polymer dope concentration was increased at levels near ce. Beyond this initial increase, subsequent tests at higher PSF concentrations yielded diminishing changes in mechanical properties, suggesting an asymptotic approach to a point where the trend would cease. Without further research, it is theorized that this point falls on a transition from the semidiute entangled to concentrated concentration regimes. SEM imaging of samples revealed the formation of grooved structures on the inner surface of samples, which was determined to be a result of the low flowrate and polymer dope concentrations used in processing the HFMs during apparatus runs. Based on continued operation of the preliminary apparatus design, many areas of improvement were noted. Namely, these consisted of controlling the collector speed, eliminating rubbing of nascent fibers against the edge of the coagulation bath by installing an elevated roller, and replacing tygon tubing for the polymer line with a luer lock adapter for direct syringe attachment to the spinneret.
ContributorsBridge, Alexander Thomas (Author) / Green, Matthew D. (Thesis director) / Lin, Jerry Y. S. (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Polymer-nanoparticle composites (PNCs) show improved chemical and physical properties compared to pure polymers. However, nanoparticles dispersed in a polymer matrix tend to aggregate due to strong interparticle interactions. Electrospun nanofibers impregnated with nanoparticles have shown improved dispersion of nanoparticles. Currently, there are few models for quantifying dispersion in a PNC, and none for electrospun PNC fibers. A simulation model was developed to quantify the effects of nanoparticle volume loading and fiber to particle diameter ratios on the dispersion in a nanofiber. The dispersion was characterized using the interparticle distance along the fiber. Distributions of the interparticle distance were fit to Weibull distributions and a two-parameter empirical equation for the mean and standard deviation was found. A dispersion factor was defined to quantify the dispersion along the polymer fiber. This model serves as a standard for comparison for future experimental studies through its comparability with microscopy techniques, and as way to quantify and predict dispersion in polymer-nanoparticle electrospinning systems with a single performance metric.
ContributorsBalzer, Christopher James (Author) / Mu, Bin (Thesis director) / Armstrong, Mitchell (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The problem of catastrophic damage purveys in any material application, and minimizing its occurrence is paramount for general health and safety. We have successfully synthesized, characterized, and applied dimeric 9-anthracene carboxylic acid (Di-AC)-based mechanophores particles to form stress sensing epoxy matrix composites. As Di-AC had never been previously applied as a mechanophore and thermosets are rarely studied in mechanochemistry, this created an alternative avenue for study in the field. Under an applied stress, the cyclooctane-rings in the Di-AC particles reverted back to their fluorescent anthracene form, which linearly enhanced the overall fluorescence of the composite in response to the applied strain. The fluorescent signal further allowed for stress sensing in the elastic region of the stress\u2014strain curve, which is considered to be a form of damage precursor detection. Overall, the incorporation of Di-AC to the epoxy matrix added much desired stress sensing and damage precursor detection capabilities with good retention of the material properties.
ContributorsWickham, Jason Alexander (Co-author) / Nofen, Elizabeth (Co-author, Committee member) / Koo, Bonsung (Co-author) / Chattopadhyay, Aditi (Co-author) / Dai, Lenore (Co-author, Thesis director) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Lithium ion batteries are quintessential components of modern life. They are used to power smart devices — phones, tablets, laptops, and are rapidly becoming major elements in the automotive industry. Demand projections for lithium are skyrocketing with production struggling to keep up pace. This drive is due mostly to the rapid adoption of electric vehicles; sales of electric vehicles in 2020 are more than double what they were only a year prior. With such staggering growth it is important to understand how lithium is sourced and what that means for the environment. Will production even be capable of meeting the demand as more industries make use of this valuable element? How will the environmental impact of lithium affect growth? This thesis attempts to answer these questions as the world looks to a decade of rapid growth for lithium ion batteries.
ContributorsMelton, John (Author) / Brian, Jennifer (Thesis director) / Karwat, Darshawn (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Ionic liquids boast a wide variety of application as modern electrolytes. Their unique collection of attributes, most notably insignificant vapor pressures, considerable ionic conductivity, and excellent thermal stability, prove ionic liquids excellent candidates for low-temperature electrolyte applications. This project focuses on the development of a low-temperature iodide-based ionic liquid electrolyte for a molecular electronic transducer (MET) seismometer. Based on ionic liquid 1-butyl-3-methylimidazolium iodide ([BMIM][I]), a functional electrolyte system is developed and optimized with addition of organic solvents, gamma-butyrolactone (GBL) and propylene carbonate (PC), and lithium iodide, showing the promise of operating at excessively low temperatures. The molecular interactions between [BMIM][I] and the organic solvents were classified using FTIR and 1H NMR spectroscopy. Specifically, the presence of hydrogen bonding between the carbonyl group on the organic solvents and the [BMIM]+ cation were captured. The effect of these interactions on several electrolyte properties were observed, including an extended glass transition temperature (Tg) of -120.2 °C and enhanced transport properties. When compared to the previous formulations, the optimized electrolyte exhibits a broader working temperature range, a higher fluidity over the temperature range from 25°C to -75 °C, and an enhanced ionic conductivity at temperatures below -70 °C as suggested by the Vogel–Fulcher–Tammann (VFT) model. Cyclic voltammetry (CV) confirmed the electrochemical stability of the electrolyte as well as the activity of the I3- / I- redox reaction for the MET sensing technology at room temperature. The presented works not only present a facile strategy of designing low-temperature electrolyte systems via design of molecular interactions, but also support future operations of MET seismometer.
ContributorsMacdonald, Shaun Michael (Author) / Dai, Dr. Lenore L. (Thesis director) / Lin, Wendy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05