Impact Of Chain Architecture On The Thickness Dependence Of Physical Aging Rate Of Thin Polystyrene Films, Gregory Brown, Elizabeth Lewis, Bryan D. Vogt
Williams Honors College, Honors Research Projects
The dynamics of polymer thin films have been demonstrated to be significantly altered from the bulk, but the origins of such differences are not well defined. In this work, we seek to understand the differences in the structural dynamics (or physical aging) of polystyrene (PS) through branching and other well defined architectures (comb and centipede). The aging dynamics of ultrathin films (< 30 nm) differ from relatively thick films (100-150nm) with linear PS thin films aging more rapidly than the relatively “bulk-like” thick films. Ellipsometric measurements are used to characterize the physical aging rate of the films. The change in film thickness and refractive index as the films are held below the glass transition temperature (Tg) provides a simple measure of the physical aging. In this study, four different architectures (linear, comb, 4 arm star, and centipede) will be investigated. For each PS architecture, the aging rate will be determined for film thickness ranging ...
Influence Of Mechanical Properties Of Paper Coating On The Crack At The Fold Problem, 2019 University of Maine
Influence Of Mechanical Properties Of Paper Coating On The Crack At The Fold Problem, Seyyed Mohammad Hashemi Najafi
Electronic Theses and Dissertations
Paper coating layers are subject to various stresses and deformations in many converting processes such as calendering, printing, slitting, and folding of the paper. In some cases, products may crack during folding to generate a defect called cracking at the fold (CAF). The parameters that influence these defects are not well understood. The overall goal of this thesis is to better understand the CAF behavior as related to material properties of the coating layer.
A method was developed to produce free-standing pigmented coating layers thick enough to be tested in bending as well as tension. The mechanical properties of these ...
Influence Of Linear Reciprocating And Multi-Directional Sliding On Peek Wear Performance And Transfer Film Formation, Kevin A. Laux, Christian J. Schwartz
Because of their light weight, chemical resistance, and self-lubricating properties, polymers are used in applications ranging from biomedical to aerospace. Some polymers exhibit significant differences in wear resistancebased on whether they are in unidirectional or multidirectional sliding. Shear induced polymer chain orientation is believed to be responsible for this behavior. Polyetheretherketone (PEEK) has excellent wear resistance, but its multidirectional sliding behavior has not been thoroughly investigated. A factorial multidirectional pin-on-plate wear study of PEEK was conducted with a focus on molecular weight and sliding path directionality. These factors were studied for their correlation to over all wear performance. Additionally ...
Surface Layer Plastic Deformation As A Mechanism For Uhmwpe Wear, And Its Role In Debris Size., 2019 Oklahoma Christian University
Surface Layer Plastic Deformation As A Mechanism For Uhmwpe Wear, And Its Role In Debris Size., Kevin G. Plumlee, Christian J. Schwartz
Ultra-high molecular weight polyethylene (UHMWPE) remains the primary bearing material for use in artificial joints, but the longevity of these implants is still hindered by an osteolytic immune system response initiated by sub-micron sized wear debris released from the UHMWPE bulk component. Studies have shown that the severity of the immune system response is linked to particle size. Current treatments for reducing this effect focus on reducing the total volume of wear, but do not directly address particle size due to a limited understanding of the mechanisms involved in producing such small debris. Directly observing these mechanisms is inherently challenging ...
Effects Of Contact Pressure, Molecular Weight, And Supplier On The Wear Behavior And Transfer Film Of Polyetheretherketone (Peek), Kevin A. Laux, Christian J. Schwartz
Polyetheretherketone (PEEK) is a designation given to materials of the polyaryletherketone family having a characteristic distribution of ether and ketone groups in the polymer backbone. PEEK materials have high strength and chemical resistance as well as very high melting points and glass transition temperatures. Because of this combination of properties, PEEK materials find use for wear application in extreme environments where they provide a light-weight and corrosion resistant bearing material that often does not require lubrication. This study focused on determining the effects of supplier and molecular weight on the wear of particular PEEK materials, in addition to the effect ...
Characterization And Optimization Of Parylene-C Deposition Process Using Scs Parylene Coater, 2019 Singh Center for Nanotechnology
Characterization And Optimization Of Parylene-C Deposition Process Using Scs Parylene Coater, Hannah Hastings, Eric D. Johnston, Gyuseok Kim
Parylene-C has been deposited on bare Si wafers by physical vapor deposition using the SCS Coating Systems. Results show a 12 µm thick Parylene-C ﬁlm with 10 g of dimer and negligible thickness variation across a wafer. We ﬁnd a positive linear relationship between ﬁlm thickness and mass of dimer at a range of 1 g to 18 g. However, the Al boat for dimer was burnt with 18 g of dimer, suggesting multiple depositions with 1 g to 10 g of dimer are recommended to achieve the Parylene-C ﬁlm thicker than 12 µm.
Ionic Electroactive Polymer Actuators As Active Microfluidic Mixers, 2018 Iowa State University
Ionic Electroactive Polymer Actuators As Active Microfluidic Mixers, Catherine Meis, Reza Montazami, Nicole Nastaran Hashemi
Nicole N. Hashemi
On-chip sample processing is integral to the continued development of lab-on-a-chip devices for various applications. An active microfluidic mixer prototype is proposed using ionic electroactive polymer actuators (IEAPAs) as artificial cilia. A proof-of-concept experiment was performed in which the actuators were shown to produce localized flow pattern disruptions in the laminar flow regime. Suggestions for further engineering and optimization of a scaled-down, complete device are provided. While the device in its current state of development necessitates further engineering, the use of IEAPAs addresses issues currently associated with the use of electromechanical actuators as active microfluidic mixers and may prove to ...
Fluid‐Induced Alignment Of Carbon Nanofibers In Polymer Fibers, 2018 Iowa State University
Fluid‐Induced Alignment Of Carbon Nanofibers In Polymer Fibers, Mingchang Lu, Farrokh Sharifi, Nicole N. Hashemi, Reza Montazami
Nicole N. Hashemi
Carbon nanofiber/polycaprolactone (CNF/PCL) composite fibers are fabricated using a microfluidic approach. The fibers are made with different content levels of CNFs and flow rate ratios between the core and sheath fluids. The electrical conductivity and tensile properties of these fibers are then investigated. It is found that at a CNF concentration of 3 wt%, the electrical conductivity of the composite fiber significantly increases to 1.11 S m−1. The yield strength, Young's modulus, and ultimate strength of the 3 wt% CNF increase relative to the pure PCL by factors of 1.72, 2.88, and 1 ...
Fiber Based Approaches As Medicine Delivery Systems, 2018 Iowa State University
Fiber Based Approaches As Medicine Delivery Systems, Farrokh Sharifi, Avinash C. Sooriyarachchi, Hayriye Altural, Reza Montazami, Marissa Nichole Rylander, Nicole Nastaran Hashemi
Nicole N. Hashemi
The goal of drug delivery is to ensure that therapeutic molecules reach the intended target organ or tissue, such that the effectiveness of the drug is maximized. The efficiency of a drug delivery system greatly depends on the choice of drug carrier. Recently, there has been growing interest in using micro- and nanofibers for this purpose. The reasons for this growing interest include these materials’ high surface area to volume ratios, ease of fabrication, high mechanical properties, and desirable drug release profile. Here, we review developments in using these materials made by the most prevalent methods of fiber fabrication: electrospinning ...
Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, 2018 The University of Southern Mississippi
Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, Kyoungtae Kim
Preparation and characterization of tin fluorophosphate glass (Pglass) matrix nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) were investigated on the structural, thermal, morphological, mechanical, and rheological properties. Various processes including synthesis, extrusion and sintering processes were applied to prepare the nanocomposite samples. Another application of POSS with hydrophobic functional groups on the well-structured nanoscale silicate cage with three silanol groups was investigated to present the feasibility to use POSS molecule as a coating material on the surface of the hydrophilic inorganic glass. In addition, Poly(ethylene terephthalate) polymer matrix composites incorporating Pglass was studied to present the benefits of the Pglass ...
Improving Ductility Of Slender Reinforced Concrete Shear Walls With Frp Sheets And Splay Anchors, 2018 California Polytechnic State University, San Luis Obispo
Improving Ductility Of Slender Reinforced Concrete Shear Walls With Frp Sheets And Splay Anchors, Luke M. Ostrom
The Sylmar earthquake of 1971 caused significant damage to slender, non-ductile reinforced concrete (RC) shear wall buildings in California. A later survey by the Concrete Coalition in 2011, under the guidance of EERI members, indicated that there are over 3000 vulnerable concrete buildings in California . This led to City of Los Angeles (LA) Ordinance 193893 enacted in 2015, which requires mandatory upgrades to these concrete buildings by 2035. Current practice to meet the requirements of this ordinance, with respect to RC wall buildings, involves adding new shear walls to the building plan or increasing the cross-sectional area of existing ...
Study Of Physically Transient Insulating Materials As A Potential Platform For Transient Electronics And Bioelectronics, Handan Acar, Simge Çınar, Mahendra Thunga, Michael R. Kessler, Nicole Nastaran Hashemi, Reza Montazami
Nicole N. Hashemi
Controlled degradation and transiency of materials is of significant importance in the design and fabrication of degradable and transient biomedical and electronic devices and platforms. Here, the synthesis of programmable biodegradable and transient insulating polymer films is reported, which have sufficient physical and chemical properties to be used as substrates for the construction of transient electronics. The composite structure can be used as a means to control the dissolution and transiency rate of the polymer composite film. Experimental and computational studies demonstrate that the addition of gelatin or sucrose to a PVA polymer matrix can be used as a means ...
Water Processable N-Type Organic Semiconductor, 2018 University of Kentucky
Water Processable N-Type Organic Semiconductor, Ruben S. Riquelme, Matthew Collins Weisenberger, Camila F. Gomez
Center for Applied Energy Research Faculty Patents
The present invention concerns a water-processable n-type semiconductor comprised of polyvinylpyrrolidone (PVP), carbon nanotubes (CNTs) and poly(ethyleneimine) (PEI). The semiconductors are prepared by providing PVP and CNTs in a hydrophilic slurry and dispersing therein small amounts of PEI.
Mechanical Characterization Of Expanded Polystyrene Spheres Embed Sandwich Composites For Packaging Applications, 2018 Mepco Schlenk Engineering College
Mechanical Characterization Of Expanded Polystyrene Spheres Embed Sandwich Composites For Packaging Applications, Maheswaran R, Arockia Reemas S
Journal of Applied Packaging Research
This paper addresses on study of development of new packaging material comprising Expanded Polystyrene Spheres (EPS) embedded epoxy polymer based sandwich composites with aluminium skin. The density of the packing material is controlled by varying the volume of embedded spheres. In this study, the Flexural and Compression performance of Expanded Polystyrene Spheres (EPS) embedded polymer based sandwich composites with aluminium skin are investigated. The EPS volume percent in the core is 25% with epoxy matrix which makes the the density less than 1 g/cm3 for the composite. The fabricated Sandwich Composite are very light weight, the density is less ...
Characterization Of Correlated Calcium Dynamics In Astrocytes In Pcl Scaffold: Application Of Wavelet Transform Coherence, 2018 University of Texas at Arlington
Characterization Of Correlated Calcium Dynamics In Astrocytes In Pcl Scaffold: Application Of Wavelet Transform Coherence, Bo Chen, Fenghua Tian, Nicole N. Hashemi, Marilyn C. Mcnamara, Michael Cho
Nicole N. Hashemi
While 2D culture models have been used extensively to elucidate the cell-to-cell communication, they do not recapitulate fully the 3D characteristics of microenvironment in vivo, e.g., polarized cell attachment and generally confer a considerably stiffer substrate than the endogenous extracellular matrix. Development of fibrous scaffolds that can better mimic the native microenvironment and improve the spatial arrangement of seeded cells should foster experimental strategies to monitor and determine the 3D cell-to-cell communication. In this study, poly(ε- caprolactone) (PCL) fibers were fabricated in different sizes using a microfluidic platform and spatially arranged to create a suitable 3D microenvironment in ...
Synthesis Of Graphene Nanosheets Through Spontaneous Sodiation Process, 2018 Iowa State University
Synthesis Of Graphene Nanosheets Through Spontaneous Sodiation Process, Deepak-George Thomas, Emrah Kavak, Niloofar Hashemi, Reza Montazami, Nicole N. Hashemi
Nicole N. Hashemi
Graphene is one of the emerging materials in the nanotechnology industry due to its potential applications in diverse areas. We report the fabrication of graphene nanosheets by spontaneous electrochemical reaction using solvated ion intercalation into graphite. The current literature focuses on the fabrication of graphene using lithium metal. Our procedure uses sodium metal, which results in a reduction of costs. Using various characterization techniques, we confirmed the fabrication of graphene nanosheets. We obtained an intensity ratio (ID/IG) of 0.32 using Raman spectroscopy, interlayer spacing of 0.39 nm and our XPS results indicate that our fabricated compound is ...
On-Chip Development Of Hydrogel Microfibers From Round To Square/Ribbon Shape, 2018 Iowa State University
On-Chip Development Of Hydrogel Microfibers From Round To Square/Ribbon Shape, Zhenhua Bai, Janet M. Mendoza Reyes, Reza Montazami, Nicole Nastaran Hashemi
Nicole N. Hashemi
We use a microfluidic approach to fabricate gelatin fibers with controlled sizes and cross-sections. Uniform gelatin microfibers with various morphologies and cross-sections (round and square) are fabricated by increasing the gelatin concentration of the core solution from 8% to 12%. Moreover, the increase of gelatin concentration greatly improves the mechanical properties of gelatin fibers; the Young's modulus and tensile stress at break of gelatin (12%) fibers are raised about 2.2 and 1.9 times as those of gelatin (8%) fibers. The COMSOL simulations indicate that the sizes and cross-sections of the gelatin fibers can be tuned by using ...
Cementitious Sensors Exhibiting Stopbands In Acoustic Transmission Spectra, 2018 University of New Mexico, Albuquerque
Cementitious Sensors Exhibiting Stopbands In Acoustic Transmission Spectra, Shreya Vemuganti
Shared Knowledge Conference
Ultrasonic monitoring in cementitious materials is challenging due to the high degree of attenuation. In wellbore environments, monitoring becomes more challenging due to inaccessibility. Meta materials, also known as acoustic bandgap materials, exhibit an interesting feature of forbidding the propagation of elastic/sound waves and isolate vibration in a certain frequency band. Traditionally, acoustic bandgap materials are developed with inclusions such as tin, aluminum, gold, steel in a polymer matrix. In this study, we present the development of three-dimensional cementitious sensors capable of exhibiting stopbands in the acoustic transmission spectra using carbon nanotubes. Relatively wide stopbands were engineered using Floquet-Bloch ...
Controlled Nanomorphology Of Hybrid Organic/Inorganic Multi-Component Composites Through Cooperative Non-Covalent Interactions, Lingyao Meng
Shared Knowledge Conference
Hybrid organic–inorganic nanocomposite polymers, with inorganic nanoparticles embedded in organic matrix have emerged as a special category of multifunctional materials. With rational materials design, these hybrids can show the synergistic effect of the properties from both phases. Homogenous dispersion and orderly arrangement of the organic and inorganic components are key in their functionalities. By controlling the interface and corresponding interfacial interactions between the organic and inorganic entities, we have developed a logical approach to form stable and controlled hybrid nanofiber structures. We demonstrate the formation of hybrid polymer/quantum dots (or iron oxide nanoparticles) nanocomposites through non-covalent interactions (hydrogen ...
A Systematic Investigation Of Condensation Heat Transfer Using Asymmetric Micro-Scale Surfaces, 2018 Louisiana State University and Agricultural and Mechanical College
A Systematic Investigation Of Condensation Heat Transfer Using Asymmetric Micro-Scale Surfaces, Emily Brown
LSU Master's Theses
Asymmetric surfaces been shown to inducing unidirectional motion in the Leidenfrost regime; however, very minimal research has been conducted to investigate whether these surface can enhance condensation through the same means. The investigation of heat transfer of ratchets in condensation is a relatively untapped area of study, specifically ratchets with superhydrophobic properties. Anticipated difficulty lies in creating surfaces features or coatings that retain the ratchets and can adequately sustain optimal wetting state of Cassie-Baxter required to improve heat transfer performance during condensation. This study serves to investigate whether ratchets are a feasible surface feature to enhance condensation heat transfer. First ...