Materials Science and Engineering Commons^™

Immune Modulation By Amphiphilic Oligonucleotides, Chunsong Yu

Wayne State University Dissertations

Immunotherapy is emerging as one of the most promising therapeutic strategies for cancer treatment in clinical practice. Immunotherapy leverages the host’s immune system to attack and kill tumor cells. Rationally-designed cancer vaccines are emerging as one of the powerful immunotherapies primarily because of the promise of inducing tumor antigen-specific immune responses. To improve immunogenicity of cancer vaccines, vaccine antigens are administered with vaccine adjuvants which can robustly activate innate immune system and subsequently lead to adaptive immune response. However, the major challenge of achieving significant therapeutic efficacy is lack of efficient targeted-delivery of vaccine components. By taking advantage of endogenous …

Novel Cathode Framework, Effective Electrolyte Modification, And Electrode Structural Modification Of High Performance Lithium Sulfur Batteries, Wenduo Zeng

Wayne State University Dissertations

Firstly, TiN nanotube arrays have been investigated as an effective skeleton in the cathode of lithium-sulfur batteries. A series of TiN nanotubes with various diameter and length have been synthesized and tested. Moreover, graphene nanoplatelets have been utilized as a structural anchor to support the TiN nanotubes, and the synergetic effect of composite material and its enhancement on Li-S battery electrochemical performance and cycling stability have been studied. Secondly, the improvement of electrode structural design has been evaluated for their effectiveness by using an in-situ characterization method with other electrochemical characterization. Lastly, the facile method of using transition metal cations …

Direct Laser Metal Deposition Of Nickel Based Superalloys, Abhishek Ramakrishnan-Sudha

Wayne State University Dissertations

Nickel-based superalloys are substantially used in the manufacturing of boilers for ultra-supercritical power plants and gas turbine hot-section as this grade of alloys provide higher yield strength with the rise in operating temperature and pressure owing to the presence of γʹ second phase precipitates. Conventionally, casting techniques such as centrifugal casting, investment casting, vacuum molding and several other casting based methods are used to fabricate the hot-section components. Nevertheless, a need for designing advanced materials with complex designs such as geometry, microstructure control, compositional changes, microstructure and property varying with the location as in functionally graded materials is not viable …

การเตรียมและลักษณะสมบัติของวัสดุเชิงประกอบคอร์เดียไรต์/สปอดูมีน/มุลไลต์ สำหรับภาชนะเซรามิกประเภทสัมผัสเปลวไฟโดยตรง, ปราณี จันทร์ลา

Chulalongkorn University Theses and Dissertations (Chula ETD)

ภาชนะเซรามิกหุงต้มที่สามารถใช้เป็นภาชนะสำหรับปรุงอาหารได้โดยตรงด้วยการตั้งบนเตาแก๊ส เตาไฟฟ้า เตาอบ และเตาไมโครเวฟได้ จะต้องทำจากวัสดุที่มีค่าสัมประสิทธิ์การขยายตัวทางความร้อนต่ำ มีค่าความแข็งแรงสูง มีค่าการดูดซึมน้ำต่ำ และมีความต้านทานต่อการเปลี่ยนแปลงอุณหภูมิอย่างฉับพลันได้ดี ซึ่งวัสดุสปอดูมีน คอร์เดียไรต์ และ มุลไลต์ มีสมบัติดังกล่าวข้างต้น เป็นวัสดุที่มีราคาไม่แพง และขึ้นรูปด้วยวิธีเซรามิกดั้งเดิมได้ ในงานวิจัยนี้จึงสนใจศึกษาการเตรียมวัสดุเชิงประกอบคอร์เดียไรต์/สปอดูมีน/มุลไลต์ ที่สามารถนำมาใช้ผลิตเป็นภาชนะเซรามิกหุงต้มได้ จากส่วนผสมของดินดำ ดินขาว สปอดูมีน ทัลค์แคลไซด์ อะลูมินา ซิลิกา และผงมุลไลต์ ผสมกันในอัตราส่วนของการเกิดเฟส คอร์เดียไรต์ ต่อ สปอดูมีน ในอัตราส่วน 1:1 และ เติมมุลไลต์ในอัตราส่วนร้อยละ 10-50 โดยน้ำหนัก บดผสมแบบเปียก ขึ้นรูปด้วยวิธีการหล่อแบบ เผาที่อุณหภูมิ 1250 และ1275 องศาเซลเซียส นำไปทดสอบสมบัติต่างๆ หลังเผา จากการทดลองพบว่าอัตราส่วนผสมของวัสดุเชิงประกอบที่เหมาะสม คือ สูตรการปรับส่วนผสมจากการคำนวณทางทฤษฎี ด้วยการเติมดินขาวนราตันร้อยละ 10 และซิลิการ้อยละ 5 โดยน้ำหนัก แทนที่อะลูมินา ของส่วนผสมการเกิดเฟสคอร์เดียไรต์ ต่อ สปอดูมีน 1:1 และเติมมุลไลต์ในอัตราส่วนร้อยละ 50 โดยน้ำหนัก (สูตร 50S5) เผาที่อุณหภูมิ 1275 องศาเซลเซียส พบ 4 เฟส คือบีตาสปอดูมีน คอร์เดียไรต์ มุลไลต์ และ คอรันดัม มีค่าการหดตัวรวมหลังเผาร้อยละ 9.72 ค่าการดูดซึมน้ำต่ำร้อยละ 1.10 ความแข็งแรงสูง 74.48 เมกะพาสคัล ค่าสัมประสิทธิ์การขยายตัวทางความร้อนต่ำ 2.76x10-6 ต่อองศาเซลเซียส ค่าการนำความร้อน 2.28 วัตต์ต่อเมตรเคลวิน สามารถต้านทานการเปลี่ยนแปลงอุณหภูมิอย่างฉับพลันได้สูง 350 องศาเซลเซียส ทดลองขึ้นรูปผลิตภัณฑ์ตัวอย่างหม้อต้มอาหาร เส้นผ่านศูนย์กลาง 20 เซนติเมตร ความจุ 1 ลิตร เผาที่อุณหภูมิ 1275 องศาเซลเซียส พบว่าไม่เกิดการยุบตัวของผลิตภัณฑ์ตัวอย่าง สามารถผลิตเป็นผลิตภัณฑ์ภาชนะเซรามิกหุงต้มที่สามารถตั้งไฟบนเตาแก๊สได้โดยไม่เกิดการแตกร้าว

การสังเคราะห์ผงโบรอนคาร์ไบด์ที่อุณหภูมิต่ำจากพรีเคอเซอร์ของกรดบอริกและแป้งข้าวเหนียวที่เตรียมด้วยกระบวนการแช่เยือกแข็ง-ละลาย, กรรณิการ์ เดชรักษา

Chulalongkorn University Theses and Dissertations (Chula ETD)

โบรอนคาร์ไบด์เป็นวัสดุเซรามิกที่มีความแข็งสูงมาก เนื่องด้วยสมบัติเด่นทั้งในเชิงกลและทางกายภาพของโบรอนคาร์ไบด์ ทำให้โบรอนคาร์ไบด์ถูกนำไปประยุกต์ใช้งานหลากหลายด้าน ได้แก่ หัวพ่นทราย ส่วนประกอบโครงสร้างเตาปฏิกรณ์นิวเคลียร์ วัสดุตัด และเกราะป้องกันกระสุนน้ำหนักเบา เป็นต้น งานวิจัยนี้มุ่งเน้นสังเคราะห์โบรอนคาร์ไบด์ความบริสุทธิ์สูง ที่อุณหภูมิต่ำด้วยวิธีคาร์โบเทอร์มิกรีดักชัน โดยใช้สารตั้งต้น ได้แก่ กรดบอริกและแป้งข้าวเหนียวเป็นแหล่งให้โบรอนและคาร์บอน ในการนี้ ได้ออกแบบการทดลองเพื่อศึกษาอิทธิพลของตัวแปรในกระบวนการ ได้แก่ อัตราส่วนโดยโมลระหว่างกรดบอริกและแป้งข้าวเหนียว อัตราส่วนโดยโมลของ C/B2O3 เมื่อผ่านกระบวนการเผาแคลไซน์ ผลของอุณหภูมิ เวลา อัตราการไหลของก๊าซอาร์กอนในขั้นตอนการสังเคราะห์ ที่มีต่อองค์ประกอบเฟส รูปร่างและขนาดอนุภาคของผลิตภัณฑ์ นอกจากนี้ยังได้ทดลองปรับปรุงวิธีการเตรียมสารตั้งต้น โดยการปรับเปลี่ยนเวลาที่ใช้ในการปั่นผสม และนำกระบวนการแช่เยือกแข็ง-ละลายมาใช้ในการขั้นตอนการเตรียมสารตั้งต้นผสม ผลจากการทดลองในงานวิจัยนี้แสดงให้เห็นว่า ตัวแปรในกระบวนการสังเคราะห์ที่กล่าวมาข้างต้นล้วนมีอิทธิพลต่อคุณลักษณะของผลิตภัณฑ์ โดยงานวิจัยนี้ ผลิตภัณฑ์สูตร 2BA1GR ซึ่งสารผสมตั้งต้นถูกเตรียมโดยการปั่นผสมให้ความร้อนอุณหภูมิ 80oC เป็นเวลา 4 ชั่วโมง เผาสังเคราะห์อุณหภูมิ 1450oC เวลายืนไฟ 5 ชั่วโมง ในบรรยากาศก๊าซอาร์กอน กำหนดอัตราการไหลของก๊าซอาร์กอน 3 ลิตรต่อที แสดงสัดส่วนความเข้มของพีคโบรอนคาร์ไบด์ในผลิตภัณฑ์หลังเผาสูงสุด ผลิตภัณฑ์มีความบริสุทธิ์ 90% และสามารถเพิ่มความบริสุทธิ์ของผลิตภัณฑ์เป็น 93% ผลิตภัณฑ์สูตร 2.5BA1GR ซึ่งสารผสมตั้งต้นถูกเตรียมด้วยกระบวนการแช่เยือกแข็ง-ละลาย 8 รอบ โครงสร้างจุลภาคของผลิตภัณฑ์ที่สังเคราะห์ได้ประกอบด้วยผลึกโบรอนคาร์ไบด์ขนาด 7-10 ไมครอน ที่มีรูปร่างแปดเหลี่ยมปลายตัด กระจายตัวปะปนกับอนุภาคโบรอนคาร์ไบด์รูปร่างหลายเหลี่ยมหลากหลายขนาด

Synthesis Of Geopolymers Using Low Alkali Activator Content, Sitthisak Prasanphan

Chulalongkorn University Theses and Dissertations (Chula ETD)

This research was interested in using kaolin processing waste in the preparation of geopolymer in order to reduce the amount and increase the value of recyclable waste. Moreover, metakaolin of Japan was also used to synthesize geopolymers. Thus, this work aims to study the geopolymerization reaction mechanical properties, and microstructure of calcined kaolin pressing waste-based and metakaolin-based geopolymers in the presence of low alkali activator solution. The low content of alkali activator solution was employed to synthesize geopolymers by pressing method. Findings showed that geopolymer with the low alkali activator solution formed by pressing might promote in the higher degree …

Preparation Of Antimicrobial And Water Repellent Cotton Fabric Coated With Organosilane-Modified Cellulose Nanofiber From Sugarcane Bagasse Waste, Intatch Hongrattanavichit

Chulalongkorn University Theses and Dissertations (Chula ETD)

Nosocomial infection or hospital acquired infection is the major factor for micro- and macro- economic issues since this contagion provides physical and psychological suffering of infected patients and their own families. Moreover, the government has to subsidize for new case reduction and relief in which this infection trends to increase every year. Thus, this research aimed to solve this main issue by reducing the pathway of cross-contamination on the textile products. Coating textiles with antimicrobial and water-repellent material was selected for this work. The coating material was produced using cellulose nanofibers from sugarcane bagasse waste which sugarcane is the important …

Microstructure Evolution Of Chalcogenide Materials Via Molecular Dynamics, Sharmin Abdullah

Open Access Theses & Dissertations

The properties of a material are defined by its granular microstructure which is determined by its grain evolution and the types of grain boundaries present in the structure. For example, the performance of Cadmium Sulfide/Cadmium Telluride (CdS/CdTe) solar cells can be affected by the presence of grain boundaries which makes the study of grain structure evolution a very important part of solar cell performance optimization. Grain boundary mobilities are important properties in material science and engineering as they determine grain structures under given processing and operating conditions.

In this thesis, several computational tools were used to analyze the formation and …

Development And Characterization Of Polyethylene Terephthalate (Pet)-Cotton Natural Fiber-Reinforced Composites From Waste Materials, Israel Alejandro Carrete

Open Access Theses & Dissertations

Unprecedented levels of production and consumption have caused a rapid exhaustion of the Earth's virgin resources, which is coupled with a fast accumulation of contaminants in the form of solid waste, especially in landfills. Two significant landfill constituents come from textile waste and discarded plastic bottles. Since there is a finite amount of space that can be feasibly used for landfills, solutions that make use of these post-consumer products are imperative. This study presents one possible solution by using surface modifications of cotton fibers to produce a natural fiber-reinforced polymer composite (NFRPC) from post-consumer textile waste and polyethylene terephthalate (PET) …

Tailoring Physical Properties Of Shape Memory Polymers For Fdm-Type Additive Manufacturing, Paulina Aileen Quinonez

Open Access Theses & Dissertations

Shape memory polymers (SMPs) have found applicability in biomedical settings as well as other uses that can take advantage of objects that can change shape upon exposure to stimulus. Integrating polymers with shape memory characteristics into additive manufacturing technologies such as fused deposition modeling (FDMâ?¢) can increase the number of applications this manufacturing platform can be utilized. Currently, polyurethane and polylactic acid (PLA) are two FDMâ?¢-compatible materials that possess shape memory properties. On their own these materials do not have tunable shape memory properties, namely shape recovery and shape fixation. The work presented here entails the development and characterization of …

Overview Of Homechem: House Observations Of Microbial And Environmental Chemistry, Delphine K. Farmer, Marina E. Vance, Jon P. D. Abbatt, Andrew Abeleira, Michael R. Alves, Richard Corsi, Peter F. Decarlo, Allen H. Goldstein, Vicki H. Grassian, Lea Hildebrandt Ruiz, Jose L. Jimenez, Tara Kahan, Multiple Additional Authors

Mechanical and Materials Engineering Faculty Publications and Presentations

The House Observations of Microbial and Environmental Chemistry (HOMEChem) study is a collaborative field investigation designed to probe how everyday activities influence the emissions, chemical transformations and removal of trace gases and particles in indoor air. Sequential and layered experiments in a research house included cooking, cleaning, variable occupancy, and window-opening. This paper describes the overall design of HOMEChem and presents preliminary case studies investigating the concentrations of reactive trace gases, aerosol particles, and surface films. Cooking was a large source of VOCs, CO2, NOx, and particles. By number, cooking particles were predominantly in the ultrafine mode. Organic aerosol dominated …

Characterization Of Nanostructure, Materials, And Electron Emission Performance Of Next-Generation Thermionic Scandate Cathodes, Xiaotao Liu

Theses and Dissertations--Chemical and Materials Engineering

Scandate cathodes, where scandia is added to the tungsten cathode pellets, have recently received substantial and renewed research interest owing to significantly improved electron emission capabilities at lower temperatures, as compared with conventional dispenser cathodes. However, there are several persistent issues including non-uniform electron emission, lack of understanding regarding scandium’s role in the emission mechanism, and unreliable reproducibility in terms of scandate cathode fabrication. As a result, scandate cathodes have not yet been widely implemented in actual vacuum electron devices (VEDs).

The surface structure and chemical composition of multiple scandate cathodes – prepared with the powder using the liquid-solid (L-S) …

Investigation Of Transition-Metal Ions In The Nickel-Rich Layered Positive Electrode Materials For Lithium-Ion Batteries, Shuang Gao

Theses and Dissertations--Chemical and Materials Engineering

Layered lithium transition-metal oxides (LMOs) are used as the positive electrode material in rechargeable lithium-ion batteries. Because transition metals undergo redox reactions when lithium ions intercalate in and disintercalate from the lattice, the selection and composition of transition metals largely influence the electrochemical performance of LMOs. Recently, a Ni-rich compound, LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811), has drawn much attention. It is expected to replace its state-of-the-art cousins, LiCoO₂ (LCO) and LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111), because of its higher capacity, lower cost, and reduced toxicity. However, the excess Ni, as a …

Synthesis, Design, And Evaluation Of The Fluorescent Detection Of Polychlorinated Biphenyls(Pcbs) In Aqueous System, Irfan Ahmad

Theses and Dissertations--Chemical and Materials Engineering

The exposure to halogenated persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), has been linked to numerous inflammatory diseases, including diabetes, cancer and lowered immune response. PCBs have low solubility in water, and they interact with other contaminants, making their detection quite challenging. While, there have been several attempts at improving the ease of detection and sensing of PCBs, gas chromatography-mass spectrometry (GC-MS) remains the gold standard. However, despite its ubiquitous use, GC-MS is a challenging technique that requires high skill and careful sample preparation, which are time-consuming and costly. As such, there is still a need to develop …

Understanding The Structure-Property-Performance Relationship Of Silicon Negative Electrodes, Jiazhi Hu

Theses and Dissertations--Chemical and Materials Engineering

Rechargeable lithium ion batteries (LIBs) have long been used to power not only portable devices, e.g., mobile phones and laptops, but also large scale systems, e.g., electrical grid and electric vehicles. To meet the ever increasing demand for renewable energy storage, tremendous efforts have been devoted to improving the energy/power density of LIBs. Known for its high theoretical capacity (4200 mAh/g), silicon has been considered as one of the most promising negative electrode materials for high-energy-density LIBs. However, diffusion-induced stresses can cause fracture and, consequently, rapid degradation in the electrochemical performance of Si-based negative electrodes. To mitigate the detrimental effects …

Lignin-Derived Carbon And Nanocomposite Materials For Energy Storage Applications, Wenqi Li

Theses and Dissertations--Biosystems and Agricultural Engineering

With a growing demand for electrical energy storage materials, lignin-derived carbon materials have received increasing attention in recent years. As a highly abundant renewable carbon source, lignin can be converted to a variety of advanced carbon materials with tailorable chemical, structural, mechanical and electrochemical properties through thermochemical conversion (e.g. pyrolysis). However, the non-uniformity in lignin structure, composition, inter-unit linkages and reactivity of diverse lignin sources greatly influence lignin fractionation from plant biomass, the pyrolysis chemistry, and property of the resulting carbon materials.

To introduce a better use of lignocellulosic biomass to biofuels and co-products, it is necessary to find novel …

Enhanced Surface Integrity With Thermally Stable Residual Stress Fields And Nanostructures In Cryogenic Processing Of Titanium Alloy Ti-6al-4v, James R. Caudill

Theses and Dissertations--Mechanical and Aerospace Engineering

Burnishing is a chipless finishing process used to improve surface integrity by severe plastic deformation (SPD) of surface asperities. As surface integrity in large measure defines the functional performance and fatigue life of aerospace alloys, burnishing is thus a means of increasing the fatigue life of critical components, such as turbine and compressor blades in gas turbine engines. Therefore, the primary objective of this dissertation is to characterize the burnishing-induced surface integrity of Ti-6Al-4V alloy in terms of the implemented processing parameters. As the impact of cooling mechanisms on surface integrity from SPD processing is largely unexplored, a particular emphasis …

Design And Process Of 3d-Printed Parts Using Composite Theory, Jordan Garcia

Theses and Dissertations--Mechanical and Aerospace Engineering

3D printing is a revolutionary manufacturing method that allows the productions of engineering parts almost directly from modeling software on a computer. With 3D printing technology, future manufacturing could become vastly efficient. However, it is observed that the procedures used in 3D printing differ substantially among the printers and from those used in conventional manufacturing. In this thesis, the mechanical properties of engineering products fabricated by 3D printing were comprehensively evaluated and then compared with those made by conventional manufacturing. Three open-source 3D printers, i.e., the Flash Forge Dreamer, the Tevo Tornado, and the Prusa, were used to fabricate the …

Structural Behavior Of Steel Plate Embedded Hybrid Gfrp Shapes, Piyush R. Soti

Graduate Theses, Dissertations, and Problem Reports (ETD)

The civil infrastructure industry has been dominated by traditional materials such as steel, timber, and concrete. Although these materials offer great advantages, they have major durability issues in terms of corrosion, decaying, and cracking. Traditional material-based structures deteriorate frequently and require regular-interval repairs with huge expenditures. To resolve these maintenance and durability issues associated with traditional materials, fiber reinforced polymer (FRP) composites have gained some popularity in the past few decades because of their superior mechanical properties and durability. Carbon-FRPs (CFRPs) and glass-FRP (GFRPs) are the most commonly used FRPs in the market. However, in civil engineering applications, CFRPs are …

Reflectivity And Photoemission Electron Microscopy Studies Of Magnetic Heterostructures, Chih-Yeh Huang

Graduate Theses, Dissertations, and Problem Reports (ETD)

When a thin film thickness becomes ultrathin, the magnetic properties of the thin film can be altered, degraded or even lost. The loss of magnetism has been called the magnetic dead layer (MDL). Considering the trend for miniaturization of information storage and other devices, the MDL is a significant challenge for materials science and engineering. La_1-xSr_xMnO₃ (LSMO) with x=0.3 is an excellent model material that exhibits ferromagnetism at room temperature to study the MDL. This dissertation focuses on understanding the MDL in LSMO films on their own and the effect of this dead layer when …

Experimental Measurement Of Dielectric Properties Of Powdery Materials Using A Coaxial Transmission Line, Robert Tempke

Graduate Theses, Dissertations, and Problem Reports (ETD)

This study proposes a standard methodology for coaxial dielectric property measurements of powdery materials (1-10GHz) using a coaxial transmission line. Four powdery materials with dielectric constants ranging from 3.5 to 70 (SiO2, Al2O3, CeO2, and TiO2) were experimentally investigated at varying volume loading fractions in a paraffin mixture. A statistically significant number of paraffin heterogeneous-mixtures was synthesized for all dielectric powders. The dielectric properties of the constitutive materials were determined using appropriate mixture equations. The sensitivity of the equations dielectric prediction to volume loading is discussed with guidance on selecting the best mixing equation. It was determined that low volume …

Development Of Multicomponent Eam Potential For Ni-Based Superalloy, Muztoba Rabbani

Graduate Theses/Dissertations

We initiated the development of multi-component EAM potentials for Aluminides and Carbides, key phases in Ni-based Superalloys. The goal is to utilize the MD simulation to understand the deformation dynamics that contribute to the formation of voids and creep initiation. For this purpose, we constructed the raw data from ab-initio (molecular dynamics) MD simulations fed into the potential development code and used Nickel as the base metal with the addition of a number of various elements including Aluminum, Chromium, Tungsten. We then developed the EAM potentials for the aluminide and carbide phases using the force-fitting code MEAMfit. Our generated potential …

Monitored Indoor Environmental Quality Of A Mass Timber Office Building: A Case Study, Jason Stenson, Suzanne L. Ishaque, Aurélie Laguerre, Andrew Loia, Georgia Maccrone, Ignace Mugabo, Dale Northcutt, Mariapaola Riggio, Andre Barbosa, Elliott T. Gall, Kevin Van Den Wymelenberg

Mechanical and Materials Engineering Faculty Publications and Presentations

A broad range of building performance monitoring, sampling, and evaluation was conducted periodically after construction and spanning more than a year, for an occupied office building constructed using mass timber elements such as cross-laminated timber (CLT) floor and roof panels, as well as glue-laminated timber (GLT) beams and columns. This case study contributes research on monitoring indoor environmental quality in buildings, describing one of the few studies of an occupied mass timber building, and analyzing data in three areas that impact occupant experience: indoor air quality, bacterial community composition, and floor vibration. As a whole, the building was found to …

Improvement Of The Tribological Characteristics Of Aisi 8620, 8640 And 52100 Steels Through Thermo-Reactive Treatments, Rafael Magalhães Triani, Fábio Edson Mariani, Lucas Fuscaldi De Assis Gomes, Pedro Gabriel Bonella De Oliveira, George E. Totten, Luiz Carlos Casteletti

Mechanical and Materials Engineering Faculty Publications and Presentations

The production of vanadium and niobium carbides (VC and NbC) layers on AISI 8620, 8640, and 52100 steels may increase hardness and wear resistance of substrates. Thermochemical treatments were performed at 1000 °C for 2 and 4 h. The characterization of the treated samples was carried out by means of Knoop microhardness tests, “calotest” type microadhesive wear test, layer adhesion test according to VDI 3198 standard, and X-ray diffraction. Compact and uniform layers of VC and NbC were obtained in all treatments, with hardness up to 2500 HK and microadhesive wear resistance far superior to that of the substrates, indicating …

Plasma-Enhanced Chemical Vapor Deposition Of Acetylene On Codeposited Bimetal Catalysts Increasing Graphene Sheet Continuity Under Low-Temperature Growth Conditions, Joshua Tracy, Otto Zietz, Samuel Olson, Jun Jiao

Mechanical and Materials Engineering Faculty Publications and Presentations

Here, we report a novel method for low-temperature synthesis of monolayer graphene at 450 °C on a polycrystalline bimetal Ni-Au catalyst. In this study, low-temperature chemical vapor deposition synthesis of graphene was performed at 450 °C on codeposited Ni-Au which shows successful monolayer graphene formation without an extra annealing process. The experimental results suggest that electron beam codeposition of bimetal catalyst is the key procedure that enables the elimination of the pre-growth high-temperature annealing of the catalyst prior to graphene synthesis, an indispensable process, used in previous reports. The formation was further improved by plasma-assisted growth in which the inductively …

3d Textile Preforms And Composites For Aircraft Strcutures: A Review, Abbasali Saboktakin

International Journal of Aviation, Aeronautics, and Aerospace

Over the last decades, the development of 3D textile composites has been driven the structures developed to overcome disadvantages of 2D laminates such as the needs of reducing fabrication cost, increasing through-thickness mechanical properties, and improving impact damage tolerance. 3D woven, stitched, knitted and braided preforms have been used as composites reinforcement for these types of composites. In this paper, advantages and disadvantages of each of them have been comprehensively discussed. The fabric architects and their specification in particular stitched preforms and their deformation mode for aerospace applications have been reviewed. Exact insight into various types of damage in textile …

An Investigation Into The Prediction Of Double-Skin Penetration Within Chromite Molds And Cores In Heavy Section Steel Casting Using Process Simulation Software, Nathaniel Bryant

Dissertations and Theses @ UNI

This investigation was conducted in response to a commercial steel foundry approaching the University of Northern Iowa for assistance with a recurring defect they experienced on a production casting. The defect was described as a mass of metal that penetrated and consumed the interstices of their chromite molds and cores, and it was determined to consist of fayalite. After an extensive literature review, it was concluded that the foundry experienced the double-skin defect, a niche quality issue that most commonly occurs in heavy-section steel casting with chromite molding materials

After it was determined that the double-skin defect was occurring, a …

A Review: Thermal Stability Of Methylammonium Lead Halide Based Perovskite Solar Cells, Tanzila Tasnim Ava, Abdullah Al Mamun, Sylvain Marsillac, Gon Namkoong

Electrical & Computer Engineering Faculty Publications

Perovskite solar cells have achieved photo-conversion efficiencies greater than 20%, making them a promising candidate as an emerging solar cell technology. While perovskite solar cells are expected to eventually compete with existing silicon-based solar cells on the market, their long-term stability has become a major bottleneck. In particular, perovskite films are found to be very sensitive to external factors such as air, UV light, light soaking, thermal stress and others. Among these stressors, light, oxygen and moisture-induced degradation can be slowed by integrating barrier or interface layers within the device architecture. However, the most representative perovskite absorber material, CH_{3 …}

Microstructural Evaluation Of Aluminium Alloy A365 T6 In Machining Operation, Bankole I. Oladapo, S. Abolfazl Zahedi, Francis T. Omigbodun, Edwin A. Oshin, Victor A. Adebiyi, Olaoluwa B. Malachi

Electrical & Computer Engineering Faculty Publications

The optimum cutting parameters such as cutting depth, feed rate, cutting speed and magnitude of the cutting force for A356 T6 was determined concerning the microstructural detail of the material. Novel test analyses were carried out, which include mechanical evaluation of the materials for density, glass transition temperature, tensile and compression stress, frequency analysis and optimisation as well as the functional analytic behaviour of the samples. The further analytical structure of the particle was performed, evaluating the surface luminance structure and the profile structure. The cross-sectional filter profile of the sample was extracted, and analyses of Firestone curve for the …

Ignition Of A Plasma Discharge Inside An Electrodeless Chamber: Methods And Characteristics, Mounir Laroussi

Electrical & Computer Engineering Faculty Publications

In this paper the generation and diagnostics of a reduced pressure (300 mTorr to 3 Torr) plasma generated inside an electrodeless containment vessel/chamber are presented. The plasma is ignited by a guided ionization wave emitted by a low temperature pulsed plasma jet. The diagnostics techniques include Intensified Charge Coupled Device (ICCD) imaging, emission spectroscopy, and Langmuir probe. The reduced-pressure discharge parameters measured are the magnitude of the electric field, the plasma electron number density and temperature, and discharge expansion speed.