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Experimental Characterization of Multifunctional Shape Memory Polymers With Carbon-Based Nanofillers
Description
This paper focuses on the fabrication and characterization of shape memory polymer (SMP) with interspersed carbon-based nanofillers which showed significant improvements in quasi-static and dynamic mechanical properties. These composite shape memory polymers have been fabricated using a specialized acetone solvent mixing technique to achieve high dispersion. The effect of individual and hybrid additions of graphene oxide (GO) and carbon nanotubes (CNT) with a total nanofiller content of 2 wt.% was investigated. These high dispersion SMPs showed significant improvements in tensile moduli (up to 25% over baseline), tensile strength (up to 15% over baseline), and strain to failure (up to 75% over baseline), owing to crack propagation hindrance induced by the carbon nanofillers. Further, dynamic mechanical analysis (DMA) showed a minimal reduction in polymer chain mobility and improvements in storage modulus. Dispersion is characterized by micrograph acquisition and subsequent binary image processing.
ContributorsRoman, Jose (Author, Co-author) / Chattopadhyay, Aditi (Thesis director) / Venkatesan, Karthik (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2022-05
Description
This paper focuses on the sample preparation and material characterization of a carbon fiber-reinforced silicon carbonitride (C/SiNC) ceramic matrix composite (CMC) system. C/SiNC CMC systems have desirable mechanical and thermal properties which makes them suitable for a wide variety of applications ranging from aerospace to power generation. CMCs are highly susceptible to manufacturing-induced defects, and the effect of these defects on the microscale damage behavior of the microstructure of these CMCs has not been researched. In order to perform the material characterization study, samples of the C/SiNC CMC system had to be prepared through a meticulous polishing process. After the samples were prepared, micrographs of the intratow region of the samples were captured using a confocal microscope. Feature extraction were subsequently performed on the micrographs that were captured. Different image processing techniques were applied to the captured micrographs to quantify the features that were identified.
ContributorsRanade, Rayva (Author) / Chattopadhyay, Aditi (Thesis director) / Khafagy, Khaled (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor)
Created2022-05
Description
Statistical process control (SPC) is an important quality application that is used throughout industry and is composed of control charts. Most often, it is applied in the final stages of product manufacturing. However it would be beneficial to apply SPC throughout all stages of the manufacturing process such as the beginning stages. This report explores the fundamentals of SPC, applicable programs, important aspects of implementation, and specific examples of where SPC was beneficial. Important programs for SPC are general statistical software such as JMP and Minitab, and some programs are made specifically for SPC such as SPACE: statistical process and control environment. Advanced programs like SPACE are beneficial because they can easily assist with creating control charts and setting up rules, alarms and notifications, and reaction mechanisms. After the charts are set up it is important to apply rules to the charts to see when a system is running off target which indicates the need to troubleshoot and investigate. This makes the notification part an integral aspect as well because attention and awareness must be brought to out of control situations. The next important aspect is ensuring there is a reaction mechanism or plan on what to do in the event of an out of control situation and what to do to get the system running back on target. Setting up an SPC system takes time and practice and requires a lot of collaboration with experts who know more about the system or the quality side. Some of the more difficult parts of implementation is getting everyone on board and creating trainings and getting the appropriate personnel trained.
ContributorsSennavongsa, Christy (Author) / Raupp, Gregory (Thesis director) / Dai, Lenore (Committee member) / Materials Science and Engineering Program (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The two central goals of this project were 1) to develop a testing method utilizing coatings on ultra-thin stainless steel to measure the thermal conductivity (k) of battery electrode materials and composites, and 2) to measure and compare the thermal conductivities of lithium iron phosphate (LiFePO4, "LFP") in industry-standard graphite/LFP mixtures as well as graphene/LFP mixtures and a synthesized graphene/LFP nanocomposite. Graphene synthesis was attempted before purchasing graphene materials, and further exploration of graphene synthesis is recommended due to limitations in purchased product quality. While it was determined after extensive experimentation that the graphene/LFP nanocomposite could not be successfully synthesized according to current literature information, a mixed composite of graphene/LFP was successfully tested and found to have k = 0.23 W/m*K. This result provides a starting point for further thermal testing method development and k optimization in Li-ion battery electrode nanocomposites.
ContributorsStehlik, Daniel Wesley (Author) / Chan, Candace K. (Thesis director) / Dai, Lenore (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05
Description
Asymmetric polystyrene-gold composite particles are successfully synthesized alongside core-shell composite particles via a one-step Pickering emulsion polymerization method. Unlike core-shell particles which form in the droplet phase of a stabilized Pickering emulsion, asymmetric particles form via a seeded growth mechanism. These composite particles act as catalysts with higher recyclability than pure gold nanoparticles due to reduced agglomeration. With the addition of N-isopropylacrylamide (NIPAAM) monomers, temperature-responsive asymmetric and core-shell polystyrene/poly(N-isopropylacrylamide)-gold composite particles are also synthesized via Pickering emulsion polymerization. The asymmetric particles have a greater thermo-responsiveness than the core-shell particles due to the increased presence of NIPAAM monomers in the seeded-growth formation. Poly(N-isopropylacrylamide) (PNIPAM)-containing asymmetric particles have tunable rheological and optical properties due to their significant size decrease above the lower critical solution temperature (LCST).
ContributorsRabiah, Noelle Ibrahim (Author) / Dai, Lenore (Thesis director) / Torres, Cesar (Committee member) / Zhang, Mingmeng (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05
Description
Recently, a number of publications have suggested that ionic liquids (ILs) can absorb solid particles. This development may have implications in fields like oil sand processing, oil spill beach cleanup, and water treatment. In this Honors Thesis, computational investigation of this phenomenon is provided via molecular dynamics simulations. Two particle surface chemistries were investigated: (1) hydrocarbon-saturated and (2) silanol-saturated, representing hydrophobic and hydrophilic particles, respectively. Employing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]-[PF6]) as a model IL, these nanoparticles were allowed to equilibrate at the IL/water and IL/hexane interfaces to observe the interfacial self-assembled structures. At the IL/water interface, the hydrocarbon-based nanoparticles were nearly completely absorbed by the IL, while the silica nanoparticles maintained equal volume in both phases. At the IL/hexane interface, the hydrocarbon nanoparticles maintained minimal interactions with the IL, whereas the silica nanoparticles were nearly completely absorbed by it. Studies of these two types of nanoparticles immersed in the bulk IL indicate that the surface chemistry has a great effect on the corresponding IL liquid structure. These effects include layering of the ions, hydrogen bonding, and irreversible absorption of some ions to the silica nanoparticle surface. These effects are quantified with respect to each nanoparticle. The results suggest that ILs likely exhibit this absorption capability because they can form solvation layers with reduced dynamics around the nanoparticles.
ContributorsMachas, Michael Stafford (Author) / Dai, Lenore (Thesis director) / Lind, Mary Laura (Committee member) / Frost, Denzil (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
"The Wedding Dress" is a creative project investigating the history of wedding dress design that led to the design and construction of a wedding dress with historical inspiration. The project details the process of creating the wedding dress, in addition to the historical study of wedding dresses, and the designer/author's inspiration.
ContributorsAlbasha, Heba (Author) / Facinelli, Diane (Thesis director) / Dai, Lenore (Committee member) / Raad, Nada (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
This project is part of a larger project involving making membranes for the separation of potable water from urine solutions for applications in space travel. This project deals specifically with testing LTA nanozeolites that will be used in the membrane under a variety of acidic conditions, specifically in solutions of sulfuric acid, chromium trioxide, and potassium phosphate of pHs ranging from .5 to 5, in order to investigate the effects of pH, acid type, and time. They were analyzed using SEM, FTIR, and XRD, in order to analyze how much the zeolite was degraded under the conditions of each solution. It was determined that, for high pH values (4-5), potassium phosphate had the strongest effect, as it degraded the zeolite to the point of destroying the crystal structure completely. Because of the solubility limit of potassium phosphate in water, it could not be analyzed at low pH, so only sulfuric acid and chromium trioxide were analyzed at low pH (.5-3). They both had severe effects, sulfuric acid being slightly more severe, with both of them completely dissolving the zeolite at pH values of 1 and lower. Decreasing pH increased degradation for all of the acids, with pH values above 2 for sulfuric acid and chromium trioxide showing only minor degradation, and pH 5 potassium phosphate showing only minor degradation.
ContributorsWaller, Aaron Christopher (Author) / Lind, Mary Laura (Thesis director) / Dai, Lenore (Committee member) / Lin, Jerry (Committee member) / Barrett, The Honors College (Contributor)
Created2013-05
Description
The goal of this research is to couple a physics-based model with adaptive algorithms to develop a more accurate and robust technique for structural health monitoring (SHM) in composite structures. The purpose of SHM is to localize and detect damage in structures, which has broad applications to improvements in aerospace technology. This technique employs PZT transducers to actuate and collect guided Lamb wave signals. Matching pursuit decomposition (MPD) is used to decompose the signal into a cross-term free time-frequency relation. This decoupling of time and frequency facilitates the calculation of a signal's time-of-flight along a path between an actuator and sensor. Using the time-of-flights, comparisons can be made between similar composite structures to find damaged regions by examining differences in the time of flight for each path between PZTs, with respect to direction. Relatively large differences in time-of-flight indicate the presence of new or more significant damage, which can be verified using a physics-based approach. Wave propagation modeling is used to implement a physics based approach to this method, which is coupled with adaptive algorithms that take into account currently existing damage to a composite structure. Previous SHM techniques for composite structures rely on the assumption that the composite is initially free of all damage on both a macro and micro-scale, which is never the case due to the inherent introduction of material defects in its fabrication. This method provides a novel technique for investigating the presence and nature of damage in composite structures. Further investigation into the technique can be done by testing structures with different sizes of damage and investigating the effects of different operating temperatures on this SHM system.
ContributorsBarnes, Zachary Stephen (Author) / Chattopadhyay, Aditi (Thesis director) / Neerukatti, Rajesh Kumar (Committee member) / Barrett, The Honors College (Contributor) / Department of English (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
Poly(ionic liquid)s (PILs) with an intrinsically conducting pyrrole polymer (ICP) backbone were synthesized and utilized as novel dispersants of carbon nanotubes (CNTs) in various polar and nonpolar solvents. This is due to their highly tunable nature, in which the anions can be easily exchanged to form PILs of varying polarity but with the same polycation. These CNT dispersions were exceedingly stable over many months, and with the addition of hexane, Pickering emulsions with the PIL-stabilized CNTs at the droplet interfaces were formed. Depending on the hydrophobicity of the PIL, hexane-in-water and hexane-in-acetonitrile emulsions were formed, the latter marking the first non-aqueous stabilized-CNT emulsions and corresponding CNT-in-acetonitrile dispersion, further advancing the processability of CNTs. The PIL-stabilized CNT Pickering emulsion droplets generated hollow conductive particles by subsequent drying of the emulsions. With the emulsion templating, the hollow shells can be used as a payload carrier, depending on the solubility of the payload in the droplet phase of the emulsion. This was demonstrated with silicon nanoparticles, which have limited solubility in aqueous environments, but great scientific interest due to their potential electrochemical applications. Overall, this work explored a new class of efficient PIL-ICP hybrid stabilizers with tunable hydrophobicity, offering extended stability of carbon nanotube dispersions with novel applications in hollow particle formation via Pickering emulsion templating and in placing payloads into the shells.
ContributorsHom, Conrad Oliver (Co-author) / Chatterjee, Prithwish (Co-author) / Nofen, Elizabeth (Co-author, Committee member) / Xu, Wenwen (Co-author) / Jiang, Hanqing (Co-author) / Dai, Lenore (Co-author, Thesis director) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12