Materials Science and Engineering Commons^™

Influence Of Chitosan-Alginate Scaffold Stiffness On Bone Marrow Stromal Cell Differentiation, Isabel Arias Ponce

Electronic Theses and Dissertations

Tissue grafts are the gold standard for replacing large volume tissue defects. Yet, they present several risks, including infection, low functional outcomes, and reduced graft integrity. Tissue engineering (TE) combines cells and biomaterial scaffolds to foster tissue growth and remodeling. Bone marrow stromal cells (BMSCs) have been shown to respond to the stiffness of their microenvironment, resulting in differentiation into different lineages. 3D porous chitosan-alginate (CA) scaffolds have been previously demonstrated for bone TE with osteoblasts and BMSCs; however, only a single scaffold composition (4 wt%) was studied. Three CA scaffold compositions (2, 4, 6 wt% CA) were produced. Scanning …

Cell Printing: An Effective Advancement For The Creation Of Um Size Patterns For Integration Into Microfluidic Biomems Devices, Megan Aubin

Electronic Theses and Dissertations

The Body-on-a-Chip (BoaC) is a microfluidic BioMEMs project that aims to replicate major organs of the human body on a chip, providing an in vitro drug testing platform without the need to resort to animal model testing. Using a human model also provides significantly more accurate drug response data, and may even open the door to personalized drug treatments. Microelectrode arrays integrated with human neuronal or human cardiac cells that are positioned on the electrodes are essential components for BoaC systems. Fabricating these substrates relies heavily on chemically patterned surfaces to control the orientation and growth of the cells. Currently, …

Single-Site Catalyst Promoters Accelerate Metal- Catalyzed Nitroarene Hydrogenation, Liang Wang, Erjia Guan, Jian Zhang, Junhao Yang, Yihan Zhu, Yu Han, Ming Yang, Cheng Cen, Gang Fu, Bruce C. Gates, Feng-Shou Xiao

Faculty & Staff Scholarship

Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydro- genation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn- TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various …

Assisted Development Of Mesophase Pitch With Dispersed Graphene And Its Resulting Carbon Fibers, Aaron Owen

Theses and Dissertations--Mechanical and Aerospace Engineering

The efficacy of dispersed reduced graphene oxide (rGO) as a nucleation site for the growth of mesophase in an isotropic pitch was investigated and quantified in this study. Concentrations of rGO were systematically tested in an isotropic petroleum and coal-tar pitch during thermal treatments and compared to pitch without rGO. The mesophase content of each thermally treated pitch was quantified by polarized light point counting. Further characterization of softening temperature and insolubles were quantified. Additionally, the pitches with and without rGO were melt spun, graphitized, and tensile tested to determine the effects of rGO on graphitized fiber mechanical properties and …

Design And Analysis Of A 3d-Printed, Thermoplastic Elastomer (Tpe) Spring Element For Use In Corrective Hand Orthotics, Kevin Thomas Richardson

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis proposes an algorithm that determine the geometry of 3D-printed, custom-designed spring element bands made of thermoplastic elastomer (TPE) for use in a wearable orthotic device to aid in the physical therapy of a human hand exhibiting spasticity after stroke. Each finger of the hand is modeled as a mechanical system consisting of a triple-rod pendulum with nonlinear stiffness at each joint and forces applied at the attachment point of each flexor muscle. The system is assumed quasi-static, which leads to a torque balance between the flexor tendons in the hand, joint stiffness and the design force applied to …

Simultaneous Measurement Of Isotope-Free Tracer And Interdiffusion Coefficients In Sandwich Type Diffusion Couples, Esin Schulz

Electronic Theses and Dissertations

The experimental determination of the tracer or self-diffusion coefficient as a function of composition can be quite burdensome in alloys since separate measurements must be carried out for each alloy composition. A new formalism recently developed by I.V. Belova, N.S. Kulkarni, Y.H. Sohn and G.E. Murch, based on linear response theory combined with the Boltzmann–Matano method allows determination of tracer and interdiffusion coefficients simultaneously from a single, isotope-free solid to solid diffusion couple experiment. In this study, for the first time, an experimental investigation with an analytical approach based on the new formalism has been carried out in the binary …

Advanced Nanoscale Characterization Of Plants And Plant-Derived Materials For Sustainable Agriculture And Renewable Energy, Mikhael Soliman

Electronic Theses and Dissertations

The need for nanoscale, non-invasive functional characterization has become more significant with advances in nano-biotechnology and related fields. Exploring the ultrastructure of plant cell walls and plant-derived materials is necessary to access a more profound understanding of the molecular interactions in the systems, in view of a rational design for sustainable applications. This, in turn, relates to the pressing requirements for food, energy and water sustainability experienced worldwide. Here we will present our advanced characterization approach to study the effects of external stresses on plants, and resulting opportunities for biomass valorization with an impact on the food-energy-water nexus. First, the …

Structural And Optical Investigations Of Rbxcs1-Xh2po4, Alex D. Price

Open Access Theses & Dissertations

Proton conductor solid acid electrolytes RbxCs1-xH2PO4 (0≤x≤1) have been investigated using second harmonic generation and powder x-ray diffraction. Second harmonic generation is an optical technique which can be used to study the structural properties of materials. Microscopes of this nature have the ability to image objects with a variable penetration depth in a non-destructive manner, allowing for great potential to be used for in situ observations of the electrolyte’s structure when in a fuel cell under operating conditions.

X-ray powder diffraction was carried out on the series of samples and found for values of 0≤x≤0.5 the structure of the material …

Measurement Of Planar Fault Probabilities In Austempered Ductile Iron And 304l Stainless Steel, Nathan Peterson

Dissertations, Master's Theses and Master's Reports

During plastic deformation both stacking and twin faults can be generated in face-centered cubic materials, including iron-based metals that contain thermally stable austenite. These planar faults are a critical component of the austenite to martensite transformation, forming shear bands that can act as nucleation sites. The measurement of these faults via x-ray diffraction has been long established, however it has not been applied widely to austempered ductile irons. The ability to measure these faulting probabilities could give insights into the transformation as a function of deformation. In this work both planar fault densities were measured in austempered ductile iron to …

ผลของการเติมอะลูมินาต่อพฤติกรรมการไหลตัวของของไหลเชียร์ทิกเคนนิง, ณัฐณิชา นวมภักดี

Chulalongkorn University Theses and Dissertations (Chula ETD)

ของไหลเชียร์ทิกเคนนิงกำลังเป็นที่สนใจในงานหลายด้านรวมถึงงานทางด้านเกราะกันกระสุน ในงานวิจัยนี้ได้ทำการศึกษาอิทธิพลของปริมาณซิลิกาและการเติมสารตัวเติมอะลูมินาที่มีต่อพฤติกรรมการไหลตัวของของไหลเชียร์ทิกเคนนิงในระบบซิลิกา-พอลิเอทิลีนไกลคอล โดยทำการปรับเปลี่ยนปริมาณความเข้มข้นซิลิกาจาก 30% ถึง 52% โดยปริมาตร พบว่าเมื่อปริมาณซิลิกาต่ำกว่า 40% โดยปริมาตร ของไหลแสดงพฤติกรรมการไหลตัวแบบนิวโตเนียน และเมื่อปริมาณซิลิกาในสารแขวนลอยสูงกว่า 40% โดยปริมาตร การไหลตัวจะมีพฤติกรรมแบบเชียร์ทินนิง ณ ช่วงอัตราการเฉือนต่ำ และเปลี่ยนพฤติกรรมการไหลตัวเป็นแบบเชียร์ทิกเคนนิงเมื่ออัตราการเฉือนเพิ่มขึ้นถึงค่าหนึ่ง นอกจากนี้เมื่อปริมาณซิลิกาเพิ่มขึ้น อัตราการเฉือนวิกฤติหรือค่าอัตราการเฉือนที่เริ่มเกิดพฤติกรรมการไหลตัวแบบเชียร์ทิกเคนนิงมีค่าลดลง ในขณะที่อัตราการเกิดเชียร์ทิกเคนนิงเพิ่มสูงขึ้น ในการปรับปรุงประสิทธิภาพของเกราะกันกระสุนได้ทำการเติมอนุภาคของแข็งอะลูมินา ลงในของไหลเชียร์ทิกเคนนิงที่มีความเข้มข้นซิลิกาเท่ากับ 50% โดยปริมาตร พร้อมทั้งทำการปรับเปลี่ยนชนิดของสารตัวเติมอะลูมินา ได้แก่ TMDA AMS-9 และ A-32 รวมถึงปริมาณของสารตัวเติมจาก 1% ถึง 5% โดยปริมาตร พบว่า ขนาดอนุภาคสารตัวเติมที่เล็กลงและปริมาณสารตัวเติมที่เพิ่มขึ้น ส่งผลให้ความหนืดเพิ่มขึ้นในขณะที่อัตราการเฉือนวิกฤติมีค่าลดลง นอกจากนี้การเติมสารตัวเติมอะลูมินา AMS-9 และ A-32 ในสารแขวนลอยซิลิกา-พอลิเอทิลีนไกลคอล ทำให้อัตราการเกิดเชียร์ทิกเคนนิงเพิ่มสูงขึ้น ของไหลที่มีสภาวะเหมาะสมได้ถูกนำมาใช้ในกระบวนการจุ่มแช่สิ่งทอเคฟล่าเพื่อผลิตชิ้นงานเกราะชนิดของเหลว โดยการเติม A-32 ปริมาณ 5% โดยปริมาตร เนื่องจากแสดงอัตราการเกิดเชียร์ทิกเคนนิงสูงที่สุด จากนั้นชิ้นงานที่ผ่านกระบวนการจุ่มแช่ได้ถูกนำมาตรวจสอบความต้านทานต่อการแทง โดยในงานวิจัยนี้ยังไม่อาจสรุปได้แน่ชัดว่าชิ้นงานเกราะรูปแบบใดสามารถต้านทานต่อการแทงได้ดีที่สุด

Atomic Probe Tomography And Creep Deformation Studies Of Highly Dynamic Metallic Systems: Copper-Zirconium Based Metallic Glass Alloys And Tin-Based Alloy, Chetarpa Yipyintum

Chulalongkorn University Theses and Dissertations (Chula ETD)

The early crystallization process of a Cu-Zr binary metallic glass was investigated by transmission electron microscopy (TEM) and atomic probe tomography (APT). The microstructural analysis was carried out using different characterization methods to see if the phase separation in different chemical compositions and chemical short-range orders were investigated by applying heat treatment under argon atmosphere in differential scanning calorimetry (DSC) chamber. Such a difference in the atomic arrangement of a given amorphous metallic structure is important, the actual characterization of such small difference is not practically easy. For the reason that there is an effect of the sample preparation method …

Effect Of Hierarchical Structure And Orientation On Water-Repellent Legs Of Water-Walking Insects, Georgia Hurchalla

Dissertations, Master's Theses and Master's Reports

Some insects have the ability to walk on water surface due to hierarchical leg structure and wax coating. This work presents studies of water strider and fire ant leg immersion force profiles to measure resistance of legs to submersion and show orientation effects. A high-sensitivity microbalance measured force during immersion of insect legs at various angles into water droplets. Legs oriented parallel to water surface could support three to five times as much force before immersion, compared to legs in a perpendicular orientation. Water pressure affects the setae structure differently at parallel and perpendicular approaches, and complete wetting is more …

Effects And Limitations Of Residual Alloying Elements In Silicon Solid Solution Strengthened Ferritic Ductile Iron, Julia Scruton

Dissertations, Master's Theses and Master's Reports

Transitioning from traditional grades of ductile iron to solution strengthened ferritic ductile iron (SSFDI) grades can be difficult because of the need to reduce the amount of pearlite promoting elements, particularly copper and manganese, which are used in traditional grades. Knowing the acceptable threshold of residual alloying elements will allow for more cost-effective tailoring of the charge stream. Data were generated from a series of casting trials with the target grade of EN-GJS-500-14 where the levels of copper and manganese were varied from 0.05% to 0.3% and 0.15% to 0.4% respectively while maintaining silicon in the 3.8%-4.3% range. The pearlite …

Effect Of Curing Rate On The Microstructure And Macroscopic Properties Of Epoxy Fiberglass Composites, Ammar Patel, Olesksandr Kravchenko, Ica Manas-Zloczower

Mechanical & Aerospace Engineering Faculty Publications

Curing rates of an epoxy amine system were varied via different curing cycles, and glass-fiber epoxy composites were prepared using the same protocol, with the aim of investigating the correlation between microstructure and composite properties. It was found that the fast curing cycle resulted in a non-homogenous network, with a larger percentage of a softer phase. Homogenized composite properties, namely storage modulus and quasi-static intra-laminar shear strength, remained unaffected by the change in resin microstructure. However, fatigue tests revealed a significant reduction in fatigue life for composites cured at fast curing rates, while composites with curing cycles that allowed a …

The Influence Of Organic Pigments On Coating Properties, Sarah Medeiros

Williams Honors College, Honors Research Projects

Abstract

The purpose of this project was to identify the qualities of two synthesized organic pigments added to a coating. These high-performance pigments were benzodipyrrolidone and benzodifuranone, which are π-conjugated monomers. These pigments were each formulated into two different pigment concentrations and compared with a control that had no pigment. This project is limited by time constraints and the number of variables that can be tested in that time. Performance testing was conducted to evaluate the qualities of these coatings. The results demonstrated that the coatings were reproducible and most tests had results that were equal to or exceeded the …

Interfacial Corrosion Of Copper And The Formation Of Copper Hydroxychloride, Mary Teague, Shengxi Li, Hongbo Cong

Williams Honors College, Honors Research Projects

Electrical circuitry is an industry, among many others, heavily using the element of copper. Ensuring the mechanical integrity of Cu is crucial, especially in salt environments, for the multifaceted composition of circuits. 4N NaCl solution (equilibrium concentration in ~84% RH) simulated this three-phase system. Rectangular Cu samples were partially immersed in both ambient and continuous lab air sparging atmospheres to understand waterline corrosion of the metal. Open circuit potentials (OCP) were continuously taken during the immersion testing for a maximum of 5 days. A scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), Raman spectroscopy, and 3-D …

Direct Printing Of Single-Crystal Silicon By Microscale Nanoparticle Printing And Confined Laser Melting And Crystallization, Wan Shou

Doctoral Dissertations

"The transport and interfacial phenomena in laser melting and crystallization of silicon in micro-/nano-scale confinement lacks sufficient understanding. Uncovering the underlying mechanisms, and hence harness the melting and crystallization processes can help the formation of controllable single-crystal structures or patterns. In this dissertation, a molecular dynamics (MD) simulation was conducted to calculate the interfacial free energy of the silicon system in contact with flat and structured walls. Then the calculated interfacial energies were employed to predict the nucleation mechanisms in a slab of liquid silicon confined by two walls and compared with MD simulation results. Further, in combination with a …

Electrodeposited Semiconductor Nanostructures & Epitaxial Thin Films For Flexible Electronics, Naveen Kumar Mahenderkar

Doctoral Dissertations

"Single-crystal Si is the bedrock of semiconductor devices due to the high crystalline perfection which minimizes electron-hole recombination, and the dense native silicon oxide which minimizes surface states. To expand the palette of electronic materials beyond planar Si, an inexpensive source of highly ordered material is needed that can serve as an inert substrate for the epitaxial growth of grain boundary-free semiconductors, photonic materials, and superconductors. There is also a need for a simple, inexpensive, and scalable fabrication technique for the growth of semiconductor nanostructures and thin films. This dissertation focuses on the fabrication of semiconducting nanowires (polycrystalline Ge & …

Analysis Of Vibrational Modes Of Chemically Modified Tone Wood, Madison Flesch

Honors Program Theses

It is generally accepted that every violin has different tone quality in terms of intonation and the depth of the harmonics produced. The best violins are made by experienced luthiers that craft each with precision to produce the best possible tonal quality. The quality of the finished violin is dependent upon both the specific shape and the vibrational response of the wood used in its construction. Because the hard wood used in violin construction is inhomogeneous, the composition and structure of material used is critical to the final product.¹ Luthiers would initially rely on their experience to feel the …

Investigation Of Scanning Kelvin Probe Techniques, Nicholas D'Angelo Jr., Hongbo Cong

Williams Honors College, Honors Research Projects

The original scope of this work was to advance the understanding of corrosion properties of additively manufactured (AM) materials by correlating microstructural defects in AM materials to the material conventional counterparts utilizing a scanning kelvin probe [Ametek VeraSCAN Electrochemical System]. However, upon the initiation of project research, it was observed that the system was not operational due to unknown hardware and software problems. The evolved scope of this work was to reconcile the operational issues and develop a repair and mitigation plan. After extensive troubleshooting, it was determined that the software was not properly configured, and the electrometer had permanently …