Materials Science and Engineering Commons^™

Anisotropic Character Of Low-Order Turbulent Flow Descriptions Through The Proper Orthogonal Decomposition, Nicholas Hamilton, Murat Tutkun, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Proper orthogonal decomposition (POD) is applied to distinct data sets in order to characterize the propagation of error arising from basis truncation in the description of turbulence. Experimental data from stereo particle image velocimetry measurements in a wind turbine array and direct numerical simulation data from a fully developed channel flow are used to illustrate dependence of the anisotropy tensor invariants as a function of POD modes used in low-order descriptions. In all cases, ensembles of snapshots illuminate a variety of anisotropic states of turbulence. In the near wake of a model wind turbine, the turbulence field reflects the periodic …

Fifty-Plus-Year Postflight Analysis Of First Fluid Experiment Aboard A Spacecraft, Mark M. Weislogel, Yongkang Chen, William J. Masica, Fred J. Kohl, Robert D. Green

Mechanical and Materials Engineering Faculty Publications and Presentations

This year marks the 55th anniversary of the first fluid physics experiment performed aboard a spacecraft during the Mercury-Atlas 7 mission. Since then, NASA has conducted over 80 fluids physics experiments aboard a variety of spacecraft, many of which have enhanced the understanding of large-length-scale capillary phenomena relevant to liquid management in the weightless state. As both celebration and demonstration, the Mercury-Atlas 7 fluids experiment is revisited in light of the current understanding of large-length-scale capillary fluidics. Employing a modern numerical tool, a rich variety of experimental outcomes are discovered that were not observed during the flight experiment. Interestingly, experimental …

Comprehensive Finite Element Modeling Of Ti-6al-4v Cellular Solids Fabricated By Electron Beam Melting, Edel Arrieta

Open Access Theses & Dissertations

Additive manufacturing permits the fabrication of cellular metals which are materials that can be highly customizable and possess multiple and extraordinary properties such as damage tolerance, metamorphic and auxetic behaviors, and high specific stiffness. This makes them the subject of interest for innovative applications. With interest in these materials for energy absorption applications, this work presents the development of nonlinear finite element models in commercial software platforms (MSC Patran/Nastran) that permit the analysis of the deformation mechanisms of these materials under compressive loads. In the development of these models, a detailed multiscale study on the different factors affecting the response …

Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle

Open Access Theses & Dissertations

A density functional theory (DFT) study on the geometric and electronic structure of C60 and Sc3N@C80 along with their adsorption on pristine single layer graphene (SLG) is presented. C60 is found to adsorb in two nearly degenerate configurations: (i) with a pentagon facing the SLG, which is the most stable one, and (ii) with a hexagon facing the SLG in a face-to-face perfect alignment, rarely common in Ï?â??Ï? interactions, 0.06 eV higher in energy. The calculated binding energy of 0.76 eV, which includes dispersion effects, is in good agreement with previous theoretical and experimental reports. On the contrary, Sc3N@C80 adsorption …

Organic-Inorganic Graphite And Transition Metal Dichalcogenide Based Composites For 3d Printing, Jorge Alfredo Catalan Gonzalez

Open Access Theses & Dissertations

This project was multipronged to help fuse together topics of additive manufacturing and two-dimensional (2D) layered materials, and studying the mechanical and electrical properties of the composites produced. The composites are made from the thermoplastic polymer acting as a matrix and the graphite and 2D transition metal dichalcogenides (TMDs) serving as the filler or reinforcement. Different concentrations of TMD's were added to the matrix to study the effect of composition on the mechanical and electrical properties. To shed insights into the mechanical properties, test coupons were produced as "dog bone" structures for tensile testing using the ASTM D638 type 5 …

Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer

Open Access Theses & Dissertations

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On Demand 3d Printed Hybrid Scaffolds For Tissue Engineering Applications, Ivan D. Hernandez

Open Access Theses & Dissertations

A composite 3D printed polymer scaffold with inbuilt porosity and filled with a hydrogel can provide an ideal support system for cell growth, proliferation, and vascularization. Therefore, a hybrid system of 3D printed polycaprolactone (PCL) scaffold and a hydroxyapatite-based hydrogel was developed for application in the reconstruction of bone defects, which are inherently difficult to repair without any guided therapies. In the present study, a 3D printed gyroid structure of PCL allowed the loading of a higher amount of hydrogel as compared to conventionally used 3D printed mesh structure of the same volume and strut thickness. The hydrogel was composed …

Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala

Open Access Theses & Dissertations

We have investigated the superspin dynamics of 5 nm and 10 nm mixed state Mn3O4 nanoparticles utilizing ac-susceptibility and electron paramagnetic resonance measurements. The out of phase component of the ac-susceptibility measurements show a magnetic anomaly below (T

Protonic Conductors For Intermediate Temperature Fuel Cell Electrolytes: Superprotonic Csh2po4 Stabilization And In-Doped Snp2o7 Structure Study, Heber Jair Martinez Salinas

Open Access Theses & Dissertations

Proton conductor solid electrolytes CsH2PO4 and In-doped tin pyrophosphate have been investigated as candidates to fill a gap of suitable electrolytes for fuel cells at the intermediate temperature range due their unusually high conductivities between 200 and 300 °C. Unfortunately, in the case of CsH2PO4, complicated experimental conditions, like a humidified environment, or high pressure, are needed to preserve the sought high conducting phase.

In the first stage of this work, X-ray diffraction on CsH2PO 4 samples performed in air, and under normal conditions of humidity and pressure, evidence of the cubic phase of CsH2PO4 was observed during short intervals …

Structural And Mechanical Characterization Of Nanocrystalline Tungsten And Tungsten-Based Alloy Thin Films For Extreme Environment Applications, Gustavo Martinez

Open Access Theses & Dissertations

Extreme environments associated with nuclear applications often results in degradation of the physical, mechanical and thermo-mechanical properties of the materials. Tungsten (W) exhibits unique physical and mechanical properties, which makes tungsten a good candidate for nuclear applications; however, intrinsic W exhibits low fracture toughness at all temperatures in addition to a high ductile to brittle transition. In the present work, nanocrystalline W, W-Y and W-Mo alloys were nanoengineered for nuclear applications. Nanocrystalline tungsten coatings with a thickness of ~1 µm were deposited onto Silicon (100) and Sapphire (C-plane) using RF and DC sputtering techniques under various growth conditions. Yttrium content …

Impact Of Clip Connection And Insulation Thickness On Bracing Of Purlins In Standing Seam Roof Systems, Michael W. Seek, Daniel Mclaughlin

Engineering Technology Faculty Publications

The flexural strength of purlins in standing seam roof systems is highly dependent upon the extent to which the sheathing provides lateral and torsional restraint. Typical models to predict the restraint provided by the sheathing assume that the plane of lateral resistance occurs at the top flange of the purlin. In reality, depending on the configuration of the clip and the amount of insulation located between the purlin and the clip, the plane of lateral resistance and corresponding center of rotation shifts above the top flange. This distance, referred to as the effective standoff, is important to evaluate the effectiveness …

Electrospinning Novel Aligned Polymer Fiber Structures For Use In Neural Tissue Engineering, Rachel Martin

Dissertations, Master's Theses and Master's Reports

A suitable tissue scaffold to support and assist in the repair of damaged tissues or cells is important for success in clinical trials and for injury recovery. Electrospinning can create a variety of polymer nanofibers and microfibers, and is being widely used to produce experimental tissue scaffolds for neural applications. This dissertation examines various approaches by which electrospinning is being used for neural tissue engineering applications for the repair of injuries to the central nervous system (CNS) and the peripheral nervous system (PNS). Due to the poor regeneration of neural tissues in the event of injury, tissue scaffolds are being …

Processing, Microstructure And Mechanical Properties Of Beta-Type Titanium Porous Structures Made By Additive Manufacturing, Yujing Liu

Theses: Doctorates and Masters

Tissue engineering through the application of a low modulus, high strength format as a potential approach for increasing the durability of bone implants has been attracting significant attention. Titanium alloys are widely used for biomedical applications because of their low modulus, high biocompatibility, specific strength and corrosion resistance. These reasons affirm why titanium alloy is selected as the specific material to research. The development of low modulus biomaterials is considered to be an effective method to remove the mismatch between biomaterial implants and surrounding bone tissue, thereby reducing the risk of bone resorption. So far, Ti–24Nb–4Zr–8Sn alloy (abbreviated hereafter as …

Light Soaking Phenomena In Organic-Inorganic Mixed Halide Perovskite Single Crystals, Hye Ryung Byun, Dae Young Park, Hye Min Oh, Gon Namkoong, Mun Seok Jeong

Electrical & Computer Engineering Faculty Publications

Recently, organic inorganic mixed halide perovskite (MAPbX₃; MA = CH₃NH₃^+, X = Cl^-, Br^-, or I^-) single crystals with low defect densities have been highlighted as candidate materials for high-efficiency photovoltaics and optoelectronics. Here we report the optical and structural investigations of mixed halide perovskite (MAPbBr_3-xI_x) single crystals. Mixed halide perovskite single crystals showed strong light soaking phenomena with light illumination conditions that were correlated to the trapping and detrapping events from defect sites. By systematic investigation with optical analysis, we found that the …

Syntheses Of Ag@Pd@Pt Nanoparticles With Tunable Shell Thickness For Electrochemical Oxidation Of Formic Acid, Xiao-Dong Lin, Du-Hong Chen, Zhong-Qun Tian

Journal of Electrochemistry

In an effort to lower cost of a catalyst, the silver (Ag) core with palladium (Pd) layer then platinum (Pt) island (Ag@Pd@Pt) nanoparticles were synthesized and the electrocatalytic activity of Ag@Pd@Pt nanoparticles on formic acid was compared with that of Au@Pd@Pt nanoparticles reported previously. The results showed that the existence of a small amount of Pt could significantly improve the activity of the catalyst. When the surface coverage of Pt approached 0.5 monolayers, the activity of Ag@Pd@Pt nanoparticles reached the maximum. Though the onset potential of the electro-oxidation was slightly more positive (about 50 mV), the overall electrocatalytic activity of …

Investigation On Laser Induced Deposition Of Cu-Based Materials At [Bmim]Bf4/Pt Electrode Interface, Min-Min Xu, Jin-Hua Mei, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

By controlling the negative potential, Cu-based materials were deposited at the [BMIm]BF₄/Pt electrode interface under the laser irradiation. The effects of laser power and irradiation time on the yield of deposition products were studied by using different laser powers and different irradiation time. The product yield could be directly determined by the size of deposition point through the observation from the optical microscope. Further mechanism study combined with the formula deduced that the thermal effect of the laser could make the electrode surface temperature rise 110 degrees, which can promote the occurrence of electrodeposition. By SEM characterization, the …

A Study On The Oxidation Of Hydrogen Peroxide At Au(111) And Au(100) Electrodes, Yong-Li Zheng, Jie Wei, Yan-Xia Chen

Journal of Electrochemistry

The oxidation reactions of hydrogen peroxide (H₂O₂) at Au(111) and Au(100) electrodes in 0.1 mol·L^-1 HClO₄ were investigated by using rotating disk electrode system. It was found that H₂O₂ could be readily oxidized to O₂ at both Au(100) and Au(111) surfaces with the onset potential close to its equilibrium potential. In contrast, the onset overpotential for H₂O₂ reduction was above 0.4 V, while the onset overpotential for H₂O₂ oxidation at Au(100) was ca. 0.1 V more negative than that at Au(111), this is probably …

Stm Investigation Of Oxygen Reduction Reaction On Solid Interface In Fuel Cell, Zhen-Feng Cai, Bing Sun, Wen-Jie Jiang, Ting Chen, Dong Wang, Li-Jun Wan

Journal of Electrochemistry

An electrocatalyst for oxygen reduction reaction (ORR) is an important component for fuel cells. An investigation at interfacial electrochemical reactions toward ORR at a molecular scale benefits mechanistic understanding as well as rational design of catalysts. Scanning tunneling microscopy (STM) has been proven to be a powerful tool to monitor chemical reactions and to provide in-situ information about the interfacial electrochemical reactions at a molecular level. This review summarizes the recent STM studies in monitoring the interface processes such as morphological changes, molecular changes, reaction intermediates, and oxidation products. The prospects of future development in this field are outlined.

Chitosan/Nonahydrate Gel Derived Fe-N-Doped Porous Carbon Sheet As High-Efficient Orr Electrocatalyst, Fan-Lu Meng, Xin-Bo Zhang, Jun-Min Yan

Journal of Electrochemistry

The chitosan/nonahydrate gel was used as a precursor to realize the uniform mixture of N-polymer and metal salt. After lyophilization treatment, the gel went through heat treatment and acid etch. Accordingly, the Fe-N-doped porous carbon sheet with homogenous composition and microstructure was prepared. Compared with the commercial Pt/C catalyst, the Fe-N-doped porous carbon sheet exhibited more positive onset potential and half-wave potential, higher current density, and especially, excellent durability. The power density of 318 mW·cm^-2 was obtained in alkaline fuel cell with the Fe-N-doped porous carbon sheet as a cathode catalyst, which is higher than 267 mW·cm^-2 with …

Synthesis Of Ultrathin Co3O4 Nanoflakes Film Material For Electrochemical Sensing, Hui-Juan Wang

Journal of Electrochemistry

Ultrathin cobalt oxide (Co₃O₄) nanoflakes film material was synthesized by using an electro-deposited cobalt layer as a raw material through a simple oxidation method and followed by a heat treatment at 350 ^oC. The physical characterizations of the Co₃O₄ nanoflakes film were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) technologies, and the electrochemical activity was measured by cyclic voltammetry (CV). As a promising material for electrochemical sensing, the as-synthesized ultrathin Co₃O₄ nanoflakes film material exhibited excellent electrochemical activity for H₂O …