Engineering Science and Materials Commons^™

Interface Structure And Deformation Mechanisms Of Mg/Nb Multilayers, Xinyan Xie

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Magnesium (Mg) and its alloys, as the lightest structural materials, are very attractive for a range of weight sensitive applications, such as aircraft engine, transportation industry and so on. However, their further applications are limited due to the weak properties, such as the low strength and poor ductility. In recent years, advanced techniques aiming at the modification of the microstructures, have been developed to promote the properties of Mg and its alloys, such as modifying the texture, refining the grain size, forming the intermetallic phase, and introducing the interfaces or stacking faults into the systems. Constructing Mg/Nb multilayers, which introduces …

Dynamic Behavior Of Granular Earth Materials Subjected To Pressure-Shear Loading, Jeff Wilson Lajeunesse

Dissertations (1934 -)

The dynamic response of granular earth materials such as sand has been of interest for many years. Multiple previous works have explored the shock response of sand in various grain shapes, sizes, and moisture contents, but the response during rapid combined loading has been relatively unexplored. The current study contributes to that lack of data by performing pressure-shear experiments on Oklahoma #1 silica sand, with quasi-smooth grains of 63 - 120 micron diameter and 99.8 wt.% Si02 composition. In these experiments, an oblique flyer plate impacts an equally inclined target, imparting a longitudinal (pressure) and transverse (shear) wave into a …

Recent Progress For Fe-N-C Electrocatalysts In Alkaline Fuel Cells, Xin Deng, Heng-Quan Chen, Ye Hu, Qing-Gang He

Journal of Electrochemistry

Fuel cells are highly recommended nowadays due to their intrinsic advantages such as high energy conversion efficiency, nearly no pollution, and convenient operation. With the development of anion exchange membrane, alkaline fuel cells have gone through a renaissance thanks to their superiorities such as faster reaction kinetics, wider choices for both fuels and electrocatalysts. It is essential to find an appropriate electrocatalyst for oxygen reduction reaction (ORR) to improve the performance of alkaline fuel cells. Further commercialization of the widely used Pt-based materials has suffered from disadvantages such as scarcity and high cost. As alternatives to largely investigated Pt-based materials, …

Pt/G-C3N4 Nanosheet For Visible Light-Induced Enhancement Of The Activity For Formic Acid Electro-Oxidation, Yong-Rong Sun, Chun-Yu Du, Guo-Kang Han, Ya-Jing Wang, Yun-Zhi Gao, Ge-Ping Yin

Journal of Electrochemistry

By using graphitic carbon nitride nanosheet (g-C₃N₄ nanosheet) as a support,Pt/g-C₃N₄ nanosheet catalyst was fabricated by microwave assisted polylol process. The nanoparticles size,composition,structure and optical properties of Pt/g-C₃N₄ nanosheet were characterized by TEM,XRD,XPS and UV-Vis diffuse reflectance spectroscopy. Comparing with the catalytic activities toward formic acid electro-oxidation under dark and visible light illumination,the superior activity of Pt/g-C₃N₄ nanosheet catalyst was achieved under visible light illumination. This visible light-driven enhancement in the formic acid performance could be attributed to the plasmon-induced electron-hole separation on g-C₃N₄ with …

Carbon Composite Fe3O4 Nanoparticles Based Electrochemical Sensor For Hydrogen Peroxide Detection, Si-Yu Zhang, Hui-Juan Wang, Shu-Fang Li, Jian-Ying Qu

Journal of Electrochemistry

In this work, a novel hydrogen peroxide electrochemical sensor was constructed with ferroferric oxide (Fe₃O₄) magnetic nanoparticles, which demonstrated good electrocatalytic activity for hydrogen peroxide. There existed a good linear relationship between the concentration of hydrogen peroxide and the oxidation peak current in the range of 1.00 × 10^-6 ~ 1.00 × 10^-3 mol·L^-1 (R = 0.9980) with the detection limit of 6.60 × 10-7 mol·L^-1. The sensor exhibited good anti-interference ability, high reproducibility and stability.

Simulation Of Fractal Growth On Metal Wire Electrode, Li-Feng Ding, Pei-Yuan Mao, Jun Cheng, Yu-Lan Niu, Yu-Hao Wen, Wei Chen

Journal of Electrochemistry

During processes of metal electrodepostion, there exist many complex morphological forms such as dendritic growing in the cathode deposited metal edge, which will seriously affect the quality of the electrodeposited product and current efficiency during machining. Investigations on dendritic crystal growing process and morphology could help controlling growth of electrolysis precipitate. In this work, Python and Matlab softwares were used, and the model of parallel electrode electrodeposition was established based on the diffusion-limited aggregation (DLA) model. By analyzing the law of fractal growth at different conditions of the particles number, probability, electrode spacing, the movement step length and orientation drift, …

Lead Modified Nanoporous Platinum Electro-Catalysts For Formic Acid Oxidation, Yuan-Yuan Zhang, Qing-Feng Yi, Ge-Kun-Kun Zuo, Tao Zou, Xiao-Ping Liu, Xiu-Lin Zhou

Journal of Electrochemistry

Platinum (Pt) catalysts modified by other suitable metals significantly enhance their electrochemical activities for formic acid oxidation. In this work, a titanium-supported nanoporous network platinum (nanoPt/Ti) electrode was prepared using a hydrothermal method. The as-prepared nanoPt/Ti electrode was modified with a certain amount of lead by using cyclic voltammetry for different scan cycle numbers (n), namely, n = 10, 15, 20 and 30, to synthesize the novel lead-modified nanoporous Pt (nanoPb_(n)-Pt/Ti) electrodes. Electro-oxidation of formic acid on these electrodes was studied with cyclic voltammetry (CV), chronoamperometry and chronopotentiometry in sulfuric acid solution. CV curves showed that both nanoPt/Ti …

Co3(Hcoo)6@Rgo As A Promising Anode For Lithium Ion Batteries, Heng Jiang, Jing-Min Fan, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

Metal–organic framework(MOF) is a kind of novel electrode materials for lithium ion batteries. Here, a composite material Co₃(HCOO)₆@rGO was synthesized for the first time by in situ loading of Co₃(HCOO)₆ on rGO (reduced oxide graphene) through a solution chemistry method. As an anode material for lithium ion batteries, it exhibited an excellent cycle stability as well as a large reversible capacity of 926 mAh·g^-1 at a current density of 500 mA·g^-1 after 100 cycles within the voltage range of 0.02 ~ 3.0 V vs. Li/Li⁺ with a good rate capability. …

Preparations And Electrochemical Performances Of Carbon Coated Silicon/Graphite Composites, Tian-Yi Gao, Zheng-Liang Gong

Journal of Electrochemistry

In this work, the carbon coated silicon (Si@C) composite materials were synthesized based on the industrial silicon powder (600 meshes) via a high energy ball milling combing with in-situ carbon coating (carbonization) method. The Si@C/graphite (Si/C) composite anode materials were prepared by a simple mechanical ball-milling approach. The effects of carbon coating and the ratio of Si to graphite on electrochemical performances of Si/graphite composite materials were investigated systematically. Compared with the nano-Si/graphite composites, the Si/C composites showed higher reversible capacity, better rate capability and cycle performance. The Si@C materials composited of amorphous carbon and crystal silicon with the primary …

Preparation And Electrochemical Performance Of Ag-Tio2-Mno2 Composites, Ling-Xiao Zhang, Hui-Hui Zhao, Li-Juan Zhang, Yu Fu

Journal of Electrochemistry

The silver-titanium dioxide  co-modified manganese dioxide (Ag-TiO₂-MnO₂) cathode material was prepared through high temperature solid state reaction. The microstructure, phase composition and electrochemical performance of the prepared samples were characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS), Cyclic voltammetry (CV), galvanostatic discharge and electrochemical impedance spectroscopy (EIS). Results showed that the unmodified and Ag-TiO₂ modified MnO₂ samples both exhibited β-MnO₂ structurebut with different morphologies. The EDS mapping results revealed that Ag was uniformly dispersed on the surface of …

Migration Resistance Of Esophageal Stents: The Role Of Stent Design, Hozhabr Mozafari, Pengfei Dong, Shijia Zhao, Yonghua Bi, Xinwei Han, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

Objective: Stenting is one of the major treatments for malignant esophageal cancer. However, stent migration compromises clinical outcomes. A flared end design of the stent diminishes its migration. The goal of this work is to quantitatively characterize stent migration to develop new strategies for better clinical outcomes.

Methods: An esophageal stent with flared ends and a straight counterpart were virtually deployed in an esophagus with asymmetric stricture using the finite element method. The resulted esophagus shape, wall stress, and migration resistance force of the stent were quantified and compared.

Results: The lumen gain for both the flared stent and the …

Chemical Stability Investigations Of Catalyst Layer In Pemfc, Yan-Yan Gao, Ming Hou, Yong-Yi Jiang, Dong Liang, Jun Ai, Li-Min Zheng

Journal of Electrochemistry

This work was intended to study the effect of free radicals on the chemical stability of catalyst layer via ex situ accelerated stress test (AST). Fenton reagent was used as the free radical provider in this research. Apart from the decomposition of Nafion in catalyst layer, the agglomerated Pt nanoparticles and the corroded carbon support were also observed after being treated in Fenton reagent for 100 h. Firstly, the existence of fluoride (F) ions evidenced the chemical decomposation of Nafion after being attacked by trace radical species, which was supported by the intensity decrease in the C-F stretching and vibration …

A Study Of Pulse Electrodeposition On Suppressing The Formation Of Lithium Dendrite, Wen-Jun Guo, Zi-Qiong Li, Ruo-Hao Ke, Dong-Fang Niu, Heng Xu, Xin-Sheng Zhang

Journal of Electrochemistry

A pulse charge method was used to suppress the formation of lithium dendrite on the copper electrode in 0.5 mol·L^-1 LiBr/propylene carbonate (PC) electrolyte. The surface variation of lithium deposition was investigated by scanning electron microscope and impedance measurement. The SEM test showed that the lithium dendrites were formed on the copper electrode during the traditional process of electrodeposition. However, the formed dendrite was suppressed by pulse charge method. The results of the impedance measurement confirmed that the pulse electrodeposition could suppress the dendrite under the optimized duty ratio (0.5). The long single pulse deposition time decreased the resistance …

Energy Conversion System For Travelers (Ecost), Thipok Bovornratanaraks

The International Student Science Fair 2018

We have innovated “The Energy Conversion System for Travelers” or the ECoST. With the fact that most travelers have wheeled cabin-bags, whilst walking, the wheels will rotate so why don’t we harvest electricity from this kinetic energy? We thus install our innovation, the ECoST, to the bag to generate electricity from the spinning wheels. The electricity is then kept in the storage unit and ready to charge your empty battery devices in an emergency case via a USB port. To make life easy, our ECoST was designed to replicate the power bank charging method; therefore, we can charge …

A Coupled Thermo-Mechanical Theory Of Strain Gradient Plasticity For Small And Finite Deformations, Yooseob Song

LSU Doctoral Dissertations

In this work, a thermodynamically consistent coupled thermo-mechanical gradient enhanced continuum plasticity theory is developed for small and finite deformations. The proposed model is conceptually based on the dislocations interaction mechanisms and thermal activation energy. The thermodynamic conjugate microstresses are decomposed into energetic and dissipative components. This work incorporates the thermal and mechanical responses of microsystems. It addresses phenomena such as size and boundary effects and in particular microscale heat transfer in fast-transient processes. Not only the partial heat dissipation caused by the fast transient time, but also the distribution of temperature caused by the transition from the plastic work …

Me-Em Enewsbrief, June 2018, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Analysis Of The Low-Cycle Fatigue Behavior Of Silicone Rubber For Biomedical Balloons, Chase Cooper

Materials Engineering

The development of a medical drug delivery device that allows for the deployment drugs into the adventitial tissue of blood vessels requires the inflation of a silicone elastomer. The inflated silicone must be able to consistently endure multiple loading cycles without failing so that the device can operate reliably. There are multiple methods of processing the silicone for the device and the goal of this study is to examine the effect of the various processing methods on the characteristics of the silicone. The Dynamic Mechanical Analysis Machine (DMA) is used to model the conditions of the device’s application by performing …

Direct Synthesis Of Graphene On Niobium And Niobium Nitride, Robin Ekeya, Otto Zietz

Maseeh Summer Undergraduate Research Experience

Since its isolation by mechanical exfoliation in 2004, graphene has attracted enormous interest from the scientific community not the least because of its unique physical and electronic properties. Among these, graphene’s ballistic electron transport and proximity induced superconductivity make graphene-superconductor (GS) hybrid structures a scientifically promising area.

System And Method For Controlling Operations Of Air - Conditioning System, Mouhacine Benosman, Petros Boufounos, Boris Kramer, Piyush Grover

Department of Mechanical and Materials Engineering: Faculty Publications

A method controls an operation of an air - conditioning system generating airflow in a conditioned environment . The method updates a model of airflow dynamics connecting values of flow and temperature of air conditioned during the operation of the air - conditioning system . The model is updated interactively iteratively to reduce an error between values of the airflow determined according to the model and values of the airflow measured during the operation . Next , the method models the airflow using the updated model and controls the operation of the air - conditioning system using the model .

Modeling Kidney Transplantation Decisions: Regulatory Oversight, Information Sharing, And Post-Transplant Drug Choice, Zahra Gharibi

Operations Research and Engineering Management Theses and Dissertations

The United States and many other nations are encountering a disturbing obstacle: A shortage of available organs for patients who are in need of kidney transplantation. This dissertation strives to analyze this trend and present potential solution by focusing on three different aspects, namely regulatory oversight, information sharing, and post-transplant immunosuppressant drug choice. In my first essay, I propose a stochastic model that identifies a socially-optimal kidney transplant choice given the inherent trade-off between the expected wait time (driven by supply and demand) and the quality of received donor kidney.

I modify the model to account for changes made by …