Matching Items (311)
Description
This thesis investigates an interpenetrating network of polyacrylamide and poly acrylic acid for use in a dynamic tactile display, which presents traditionally two-dimensional electronic screens as three-dimensional topographical models that can be experienced through touch. This kind of display would allow for greater access to traditionally visual information for the visually impaired. This hydrogel demonstrates Upper Critical Solution Temperature (UCST) near room temperature which facilitates a swelling transition, characterized by a sharp increase in swelling as this temperature is surpassed. Through the utilization of light responsive additives, light can trigger this shift, as the additives harness visible light, convert it into heat to raise the gel’s temperature, and increase the volume of the gel. Light-responsive additives explored include chlorophyllin, gold nanoparticles, and carbon black. Each of these additives required unique synthesis planning and strategies in order to optimize the performance of the gels. Synthesized gels were characterized using thermal swelling tests, light response tests and compression tests to determine the material strength. The best performing additive was chlorophyllin and allowed for a 20.8%±4.5% percent weight increase upon exposure to light for 10 minutes. In addition to investigating light-responsive additives, modifications were pursued to alter the overall UCST behavior, such as the addition of sodium chloride. By adding sodium chloride into the hydrogel, the gel was found to have a wider transition. Overall, light-responsive behavior was developed, and further work can be done in improving the response time and degree of swelling in order to make this material more viable for use in a dynamic tactile display.
ContributorsSitterle, Philip Kerry (Author) / Dai, Lenore (Thesis director) / Xu, Yifei (Committee member) / School of Music (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
In the development of personalized medicine and many other clinical studies, biospecimen integrity serves as the prerequisite for not only the accurate derivation of patient- and disease-specific molecular data from biological specimens but the meaningful downstream validation of biomarkers. However, a large number of preanalytical variables may influence the quality of biospecimens in an undesired way and ultimately render the samples unsuitable for molecular analysis. The limited ability to directly reduce discrepancies caused by preanalytical variables gives rise to the need for development and retrospective application of appropriate tests for assessment of biospecimen integrity. Nevertheless, the most standard approaches to assessing biospecimen integrity involve nontrivial procedures. Thus, the need for quality control tools or tests that are readily applicable and can produce results in a straightforward way becomes critical. As one of the major ex vivo biomolecular degradation mechanisms, oxidation that occurs when blood plasma and serum samples are exposed to thawed states during storage and processing is hard to forestall and detect. In an attempt to easily detect and monitor the degree of oxidation, the technique of Fluorescence Resonance Energy Transfer (FRET) was examined to determine whether this concept could be employed to monitor exposure of samples to thawed conditions when controlled by spontaneous oxidative disulfide bonding. The intended mode of usage was envisioned as a fluorescence liquid being stored in a separate compartment but within the same test tube as archived plasma and serum samples. This would allow the assessment of sample integrity by direct visualization of fluorescence under a hand-held black light. The fluorescent dynamic range as well as kinetic control of the reaction were studied. While the addition of Cu(II) proved to facilitate excellent dynamic range with regard to fluorescence quenching, the kinetics of the reaction were too rapid for practical use. Further investigation revealed that the fluorescence quenching mechanism might have actually occurred via Intramolecular Charge Transfer (ICT) rather than FRET mediated by oxidative disulfide bond formation. Introduction of Cu(II) via copper metal slowed fluorescence quenching to the point of practical utility; facilitating demonstration that storing at room temperature, refrigerating or freezing the samples delayed fluorescence quenching to different extents. To establish better kinetic control, future works will focus on establishing controlled, thoroughly understood kinetic release of Cu(II) from copper metal.
ContributorsZhang, Zihan (Author) / Borges, Chad (Thesis director) / Emady, Heather (Committee member) / Williams, Peter (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
When it comes to the topic of chemical engineering, the general public has a set of neutral, if slightly uninformed perceptions that are largely tempered by the initial emotional responses to the field and its associated topics. These topics include the differentiation between chemical engineers and chemists, the importance and potential danger of the products they produce, as well as the association of the subject matter with less than favorable secondary education experiences. This thesis consists of first assessing the opinions of a population meant to represent the general public regarding these subjects, then exploring the potential improvements of opinion and understanding that may be yielded from presenting the subject matter by way of a concise learning tool, such as a video. The results of this effort showed that factual understanding can be at least incrementally improved for 18% of participants through this method, while the effect on opinions can range from being improved to maintaining an enduring indifference, with an average of 17% of participants seeing improvement. Further iteration of this methodology with more consistent, impartial survey methods and refined questions could potentially yield more noteworthy improvements within the subjective domain, with the resultant learning tool of that iteration being applicable as not only an instrument of educating the general public, but also as a means to recruit potential students to the ASU chemical engineering degree program.
ContributorsJanovsky, Trey Patrick (Author) / Taylor, David (Thesis director) / Martin, Thomas (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The purpose of this project is to investigate the swelling ratio exhibited due to photothermal effects of double network polyacrylamide poly(acrylic acid) hydrogels synthesized with carbon black as a light-sensitive chromophore. Optimal carbon black dispersion was achieved in solutions through sonication, using V9A32 carbon black, where dynamic light scattering recorded particle diameters in the range of 195.0-375.8 nanometers for water/carbon black mixtures, 242.4-262.6 nanometers for monomer/carbon black mixtures without initiator, and 1109.3-1783.9 nanometers for monomer/carbon black mixtures including initiator. The double network polyacrylamide poly(acrylic acid) hydrogels with carbon black yielded weight increases of 0.126% and 6.043%, respectively, after 2 minutes and 10 minutes of being exposed to a light stimulus; compared to previous work which showed a double network polyacrylamide poly(acrylic acid) hydrogel with chlorophyllin yielded weight increases of 18.3% and 20.8%, respectively, after 2 minutes and 10 minutes of being exposed to a light stimulus, the carbon black resulted in a less robust response. Future work for application of the light-responsive hydrogels includes the development of a screen covering that will be made of the hydrogels. This covering is intended for use on LED screen displays, where a light change will result in a protrusion from the screen. The purpose behind this application is that technology users who are visually impaired can still determine what their LED device is trying to communicate with them.
ContributorsReimann, Morgan Elizabeth (Co-author) / Yifei, Xu (Co-author) / Dai, Lenore (Co-author, Thesis director) / Xu, Yifei (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The inability of a single strain of bacteria to simultaneously and completely consume multiple sugars, such as glucose and xylose, hinder industrial microbial processes for ethanol and lactate production. To overcome this limitation, I am engineering an E. coli co-culture system consisting of two ‘specialists'. One has the ability to only consume xylose and the other only glucose. This allows for co-utilization of lignocellulose-derived sugars so both sugars are completely consumed, residence time is reduced and lactate and ethanol titers are maximized.
ContributorsAyla, Zeynep Ece (Author) / Nielsen, David (Thesis director) / Flores, Andrew (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are extensively used as precursors for the preparation of (photo-)catalysts, electrodes, magnetic materials, sorbents, etc. The synthesis typically involves the transformation to the corresponding mixed metal oxide via calcination, resulting in atomically dispersed mixed metal oxides (MMOs). This process alters the porosity of the materials, with crucial implications for the performance in many applications. Yet, the mechanisms of pore formation and collapse are poorly understood. Combining an integrated in situ and ex situ characterization approach, here we follow the evolution of porosity changes during the thermal decomposition of LDHs integrating different divalent (Mg, Ni) and trivalent (Al, Ga) metals. Variations in porous properties determined by high-resolution argon sorption are linked to the morphological and compositional changes in the samples by in situ transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which is facilitated by the synthesis of well crystallized LDHs of large crystal size. The observations are correlated with the phase changes identified by X-ray diffraction, the mass losses evidenced by thermogravimetric analysis, the structural changes determined by infrared and nuclear magnetic resonance spectroscopy, and the pore connectivity analyzed by positron annihilation spectroscopy. The findings show that the multimetallic nature of the LDH governs the size and distribution (geometry, location, and connectivity) of the mesopores developed, which is controlled by the crystallization of the MMO phase, providing key insights for the improved design of porous mixed metal oxides.
ContributorsMurty, Rohan Aditya (Author) / Deng, Shuguang (Thesis director) / Nielsen, David R. (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
As global population and demand for electrical power increase, humanity is faced with the growing challenge of harnessing and distributing enough energy to sustain the developing world. Currently, fossil fuels (coal
atural gas) are our main sources of electricity. However, their cost is increasing, they are nonrenewable, and they are very harmful to the environment. Thus, capacity expansion in the renewable energy sector must be realized to offset higher energy demand and reduce dependence on fossil fuels. Solar energy represents a practical solution, as installed global solar capacity has been increasing exponentially over the past 2 decades. However, even with government incentives, solar energy price ($/kWh) continues to be highly dependent on political climate and raw material (silicon and silver) cost. To realistically and cost effectively meet the projected expansions within the solar industry, silver must be replaced with less costly and more abundant metals (such as copper) in the front-grid metallization process of photovoltaic cells. Copper, while offering both higher achievable efficiencies and a raw material cost nearly 100 times cheaper than silver, has inherent disadvantages. Specifically, copper diffuses rapidly into the silicon substrate, requires more complex and error-prone processing steps, and tends to have less adhesive strength, reducing panel robustness. In this study, nickel deposition via sputtering was analyzed, as well as overall potential of nickel as a seed layer for copper plating, which also provides a barrier layer to copper diffusion in silicon. Thermally-formed nickel silicide also reduces contact resistivity, increasing cell efficiency. It was found that at 400 \u00B0C, ideal nickel silicide formation occurred. By computer modeling, contact resistivity was found to have a significant impact on cell efficiency (up to 1.8%). Finally, sputtering proved useful to analyze nickel silicide formation, but costs and time requirements prevent it from being a practical industrial-scale metallization method.
atural gas) are our main sources of electricity. However, their cost is increasing, they are nonrenewable, and they are very harmful to the environment. Thus, capacity expansion in the renewable energy sector must be realized to offset higher energy demand and reduce dependence on fossil fuels. Solar energy represents a practical solution, as installed global solar capacity has been increasing exponentially over the past 2 decades. However, even with government incentives, solar energy price ($/kWh) continues to be highly dependent on political climate and raw material (silicon and silver) cost. To realistically and cost effectively meet the projected expansions within the solar industry, silver must be replaced with less costly and more abundant metals (such as copper) in the front-grid metallization process of photovoltaic cells. Copper, while offering both higher achievable efficiencies and a raw material cost nearly 100 times cheaper than silver, has inherent disadvantages. Specifically, copper diffuses rapidly into the silicon substrate, requires more complex and error-prone processing steps, and tends to have less adhesive strength, reducing panel robustness. In this study, nickel deposition via sputtering was analyzed, as well as overall potential of nickel as a seed layer for copper plating, which also provides a barrier layer to copper diffusion in silicon. Thermally-formed nickel silicide also reduces contact resistivity, increasing cell efficiency. It was found that at 400 \u00B0C, ideal nickel silicide formation occurred. By computer modeling, contact resistivity was found to have a significant impact on cell efficiency (up to 1.8%). Finally, sputtering proved useful to analyze nickel silicide formation, but costs and time requirements prevent it from being a practical industrial-scale metallization method.
ContributorsBliss, Lyle Brewster (Author) / Bowden, Stuart (Thesis director) / Karas, Joseph (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Anaerobic digestion (AD), a common process in wastewater treatment plants, is traditionally assessed with Biochemical Methane Potential (BMP) tests. Hydrolysis is considered its rate-limiting step. During my research, I assessed the impact of pretreatment on BMPs and microbial electrochemical cells (MECs). In the first set of experiments, BMP tests were performed using alkaline and thermal pretreated waste activated sludge (WAS), a control group, and a negative control group as samples and AD sludge (ADS) as inoculum. The data obtained suggested that BMPs do not necessarily require ADS, since samples without inoculum produced 5-20% more CH4. However, ADS appears to reduce the initial methanogenesis lag in BMPs, as no pH inhibition and immediate CH4 production were observed. Consumption rate constants, which are related to hydrolysis, were calculated using three methods based on CH4 production, SSCOD concentration, and the sum of both, called the lumped parameter. All the values observed were within literature values, yet each provide a different picture of what is happening in the system. For the second set of experiments, the current production of 3 H-type MECs were compared to the CH4 production of BMPs to assess WAS solids' biodegradability and consumption rates relative to the pretreatment methods employed for their substrate. BMPs fed with pretreated and control WAS solids were performed at 0.42 and 1.42 WAS-to-ADS ratios. An initial CH4 production lag of about 12 days was observed in the BMP assays, but MECs immediately began producing current. When compared in terms of COD, MECs produced more current than the BMPs produced CH4, indicating that the MEC may be capable of consuming different types of substrate and potentially overestimating CH4 production in anaerobic digesters. I also observed 2 to 3 different consumption events in MECs versus 3 for BMP assays, but these had similar magnitudes, durations, and starting times in the control and thermal pretreated WAS-fed assays and not in alkaline assays. This might indicate that MECs identified the differences of alkaline pretreatment, but not between control WAS and thermal pretreated WAS. Furthermore, HPLC results suggest at least one hydrolysis event, as valerate, butyrate, and traces of acetate are observed in the reactors' effluents. Moreover, a possible inhibition of valerate-fixing microbial communities due to pretreatment and the impossibility of valerate consumption by ARB might explain its presence in the reactors' effluents.
ContributorsBrown Munoz, Francisco (Author) / Torres, Cesar (Thesis director) / Rittmann, Bruce E. (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
A scheme has been developed for finding the gas and temperature profiles in an environmental transmission electron microscope (ETEM), using COMSOL Multiphysics and the finite element method (FEM). This model should permit better correlation between catalyst structure and activity, by providing a more accurate understanding of gas composition than the assumption of homogeneity typically used. While more data is needed to complete the model, current progress has identified several details about the system and its ideal modeling approach.
It is found that at the low pressures and flowrates of catalysis in ETEM, natural and forced convection are negligible forms of heat transfer. Up to 250 °C, radiation is also negligible. Gas conduction, being enhanced at low pressures, dominates.
Similarly, mass transport is dominated by diffusion, which is most accurately described by the Maxwell-Stefan model. Bulk fluid flow is highly laminar, and in fact borders the line between continuum and molecular flow. The no-slip boundary condition does not apply here, and both viscous slip and thermal creep must be considered. In the porous catalyst pellet considered in this work, Knudsen diffusion dominates, with bulk flow being best described by the Darcy-Brinkman equation.
With these physics modelled, it appears as though the gas homogeneity assumption is not completely accurate, breaking down in the porous pellet where reactions occur. While these results are not yet quantitative, this trend is likely to remain in future model iterations. It is not yet clear how significant this deviation is, though methods are proposed to minimize it if necessary.
Some model-experiment mismatch has been found which must be further explored. Experimental data shows a pressure dependence on the furnace temperature at constant power, a trend as-yet unresolvable by the model. It is proposed that this relates to the breakdown of the assumption of fluid continuity at low pressures and small dimensions, though no compelling mathematical formulation has been found. This issue may have significant ramifications on ETEM and ETEM experiment design.
It is found that at the low pressures and flowrates of catalysis in ETEM, natural and forced convection are negligible forms of heat transfer. Up to 250 °C, radiation is also negligible. Gas conduction, being enhanced at low pressures, dominates.
Similarly, mass transport is dominated by diffusion, which is most accurately described by the Maxwell-Stefan model. Bulk fluid flow is highly laminar, and in fact borders the line between continuum and molecular flow. The no-slip boundary condition does not apply here, and both viscous slip and thermal creep must be considered. In the porous catalyst pellet considered in this work, Knudsen diffusion dominates, with bulk flow being best described by the Darcy-Brinkman equation.
With these physics modelled, it appears as though the gas homogeneity assumption is not completely accurate, breaking down in the porous pellet where reactions occur. While these results are not yet quantitative, this trend is likely to remain in future model iterations. It is not yet clear how significant this deviation is, though methods are proposed to minimize it if necessary.
Some model-experiment mismatch has been found which must be further explored. Experimental data shows a pressure dependence on the furnace temperature at constant power, a trend as-yet unresolvable by the model. It is proposed that this relates to the breakdown of the assumption of fluid continuity at low pressures and small dimensions, though no compelling mathematical formulation has been found. This issue may have significant ramifications on ETEM and ETEM experiment design.
ContributorsLangdon, Jayse Tanner (Author) / Crozier, Peter (Thesis director) / Hildreth, Owen (Committee member) / Chemical Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The United States and most of the world is pushing to significantly reduce carbon emissions, with many countries intent on fostering carbon negative energy processes to offset ozone depletion and climate changes. 30% of the U.S. greenhouse gas emissions are generated from the combustion of fossil fuels to generate electricity1. Current commercial IGCC carbon capture processes employ a capital and operating cost intensive water-gas shift reaction facilitated by a high temperature reactor followed by a low temperature reactor and an amine absorber to separate the hydrogen and carbon dioxide streams to capture the carbon. Dr. Jerry Y.S. and his laboratory at Arizona State have developed a hydrogen permselective MFI type ZSM-5 zeolite membrane reactor that effectively facilities the water gas shift reaction with high conversion and separates the CO2 and H2 streams during reaction to generate ultrapure retentate and permeate streams. The membrane, formed by secondary free growth, is synthesized on an ultrapure a-alumina membrane support currently purchased from an outside vendor. The purpose of this study was to design an α-alumina support processing plant with capability to supply one full-scale commercial reactor annually with membranes. The design yielded a DCFRoR of 71% for a 20-year project life. A zeolite membrane processing material balance was conducted using alumina support as the raw material. The study showed very low material costs and consumption rates for all materials except a gas used to refine the membrane after processing. The results of both studies were favorable enough to suggest further study.
ContributorsNorman, Taylor Cristine (Author) / Lin, Jerry Y.S. (Thesis director) / Meng, Lie (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05