Other Materials Science and Engineering Commons^™

Electrochemical Characterization Of Precious Metal Braze Alloys Using Potentiodynamic Polarization, Maxwell Glen Martin, Mason Gregory Morgan, Matthew David Vance

Materials Engineering

This study aimed to characterize the electrochemical behavior of six precious metal braze alloys by performing potentiodynamic polarization tests (ParStat 2273) based on ASTM Specifications G5 and G59. To determine the extent to which the alloys will contribute to galvanic corrosion in a marine environment (3.5 wt% NaCl), corrosion analysis software was used to produce fitted Tafel lines to determine the open circuit potential, V_oc, for each alloy. The V_oc values for the alloys were found to be -66.58 mV for Gold ABA, 13.01 mV for Nicoro^®, -39.00 mV for Nioro^®, 23.4 mV …

Material Composition And Toxicology Of Cosmetic Products, Hilda Gonzalez

Materials Engineering

In today’s modern society, the U.S. Food and Drug Administration regulates many industries to protect consumers’ health; the cosmetics industry is not one of them. Through self-regulation, companies continue to sell products for topical use on the body that have been known to contain toxic chemicals with little to no testing on the effects they have on the human body. The purpose of this project was to determine the content of such known toxins in five different brands of face powders. X-Ray Diffraction (XRD) was used to verify the primary component and Inductively Coupled Plasma-Optical Emissions Spectroscopy (ICP-OES) was used …

Prediction Of Tribological Behavior Of Candidate Materials For Rotor Seals, John W. Franzino, Will F. Michul

Materials Engineering

To reduce high costs associated with manufacturing and testing materials for rotor seals, a procedure needs to be developed to quickly and accurately test candidate materials as they are released. The test should reduce the amount of fabrication required and model working conditions in order to accurately assess the tribological behavior of candidate materials. A possible solution was examined that utilized a rig meant to model operational stresses and wear. Compression modulus data was then taken in order to quantify the accumulation of damage due to microcracking, the primary mode of failure, through a damage index parameter. Testing results concluded …

Development Of Low Temperature, Aqueous Synthesis Method Of Lead Sulfide Quantum Dots, Albert Nakao, Colin Yee

Materials Engineering

Quantum dots have become an active area of research in the past decade due to their unique properties. Quantum confinement effects allow for efficient spectral conversion and size tunable fluorescence and absorption peaks. Near infrared spectral converting lead sulfide quantum dots have potential applications in solar power, biological imaging and communications technology. However at Cal Poly, lead sulfide dots have not been synthesized. The quantum dot synthesis currently adapted at Cal Poly encompasses organometallic precursors at high reaction temperatures, producing cadmium selenium dots. The organometallic approach has been found to produce nanocrystals with high quality photoluminescence, but due to its …

Influence Of Nanofiller Morphology On The Viscoelastic Properties Of Cnf/Epoxy Resins, Liberata Guadagno, Marialuigia Raimondo, Khalid Lafdi, Annalisa Fierro, Salvatore Rosolia, Maria Rossella Nobile

Chemical and Materials Engineering Faculty Publications

In this paper we discuss the viscoelastic properties of CNF/Epoxy-Amine Resins for structural applications. The use of reactive diluent inside the unfilled and nanofilled epoxy mixture as proven to be of benefit to strongly decrease the viscosity.

A First-Principles Examination Of Dopants In Hfo2, Daniel Cunningham

Honors Scholar Theses

A systematic first-principles study using density functional theory was performed on dopants in HfO2, a material with great importance as a high-k dielectric. Sixteen dopants were tested, most of which came from the fourth period of the periodic table (K-Ge, Al and Si). The relative stability of the monoclinic, tetragonal, and cubic phases were calculated for HfO2 with each dopant in order to determine which dopants tend to stabilize which phases. It was found that the most important factor in determining relative phase stability of doped HfO2 was the ionic radius of the dopant, where dopants smaller than Hf tend …

Structural, Magnetic And Microstructural Studies Of Composition-Modified Sm–Co Ribbons, Xiujuan Jiang

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

There is an increasing interest in developing desirable microstructures in hard magnetic materials. Sm-Co-based magnets, bearing superior intrinsic magnetic properties, are good candidates for further development. Two Sm-Co-based alloys, (Sm₁₂Co₈₈)_100-x-yCr_yC_x (taking SmCo₇ phase) and SmCo_4-xFe_xB (a derivative of SmCo₅ phase), were produced using melt-spinning technique. The magnetic properties are correlated to the structural and microstructural properties.

Within the SmCo₇ stoichiometry, cumulative effects of Cr and C additions on the structural and magnetic properties have been investigated. Experimental results have shown that these additions along …

Degradation Of High Voltage Glass Fiber-Reinforced Polymer Matrix Composites By Aggressive Environmental Conditions, Tianyi Lu

Electronic Theses and Dissertations

Polymer matrix composites reinforced with either E glass or ECR glass fibers-reinforced are used in a variety of high voltage electrical applications because of their advantages like lower weight and cost. However, they can be damaged by aggressive in-service conditions such as high temperature, ultraviolet radiation, moisture, ozone and corrosive environments. Different degradation mechanisms can develop in high voltage PMCs under those extreme environments, which, in turn, can affect the long term structural durability of the composites. A set of PMCs reinforced with ECR-glass and E-glass fibers embedded in four different resins has been investigated in this study. In addition, …

Continuous Ultra-Thin Mos2 Films Grown By Low-Temperature Physical Vapor Deposition, Christopher Muratore, Jianjun Hu, Baoming Wang, M. Amanul Haque, John E. Bultman, Michael L. Jespersen, Michael E. Mcconney, R. D. Naguy

Chemical and Materials Engineering Faculty Publications

Uniform growth of pristine two dimensional (2D) materials over large areas at lower temperatures without sacrifice of their unique physical properties is a critical pre-requisite for seamless integration of next-generation van der Waals heterostructures into functional devices. This Letter describes a vapor phasegrowth technique for precisely controlled synthesis of continuous, uniform molecular layers of MoS2 on silicon dioxide and highly oriented pyrolitic graphite substrates of over several square centimeters at 350 °C. Synthesis of few-layer MoS2 in this ultra-high vacuum physical vapor deposition process yieldsmaterials with key optical and electronic properties identical to exfoliated layers. The films are composed of …

Optical Properties Of Carbon Microcoils, Muneaki Hikita, Li Cao, Khalid Lafdi

Chemical and Materials Engineering Faculty Publications

Carbon microcoils (CMCs) have emerged as versatile material artifacts for a variety of applications due to their helical and spiral structures. Embedded in matrix, CMCs have already been demonstrated for their potential tactile/proximity sensor application. In this study, CMCs were prepared using a conventional chemical vapor deposition method, and then were functionalized with octadecylamine.

Upon photoexcitation, the functionalized CMCs exhibited photoluminescence in the visible region, which has never been found before. Similar to carbon based nanoparticles, the photoluminescence of CMCs was attributed to electron-hole radiative recombination after surface passivation. The results suggested that this kind of fluorescent functionalized CMCs might …

Domain Engineering Of Physical Vapor Deposited Two-Dimensional Materials, Tarek Alam, Baoming Wang, Raghu Pulavarthy, M. Amanul Haque, Christopher Muratore, Nicholas R. Glavin, Ajit K. Roy, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

Physical vapor deposited two-dimensional (2D) materials span larger areas compared to exfoliated flakes, but suffer from very small grain or domain sizes. In this letter, we fabricate freestanding molybdenum disulfide (MoS2) and amorphous boron nitride (BN) specimens to expose both surfaces. We performed in situ heating in a transmission electron microscope to observe the domain restructuring in real time. The freestanding MoS2 specimens showed up to 100× increase in domain size, while the amorphous BN transformed in to polycrystalline hexagonal BN (h-BN) at temperatures around 600 °C much lower than the 850–1000 °C range cited in the literature.

Less Is More: Long-Term In Vitro Exposure To Low Levels Of Silver Nanoparticles Provides New Insights For Nanomaterial Evaluation, Kristen K. Comfort, Laura K. Braydich-Stolle, Elizabeth I. Maurer, Saber M. Hussain

Chemical and Materials Engineering Faculty Publications

In view of the vast number of new nanomaterials (NMs) that require testing and the constraints associated with animal models, the majority of studies to elucidate nanotoxicological effects have occurred in vitro, with limited correlation and applicability to in vivo systems and realistic, occupational exposure scenarios.

In this study, we developed and implemented a chronic in vitromodel coupled with lower, regulatory dosages in order to provide a more realistic assessment of NM-dependent consequences and illuminate the implications of long-term NM exposure. When keratinocytes were exposed to 50 nm silver nanoparticles (Ag-NPs), we determined that chronically dosed cells operated …

Precise Control Of Carbon Nanotube Membrane Structure For Enzyme Mimetic Catalysis, Nicholas W. Linck

Theses and Dissertations--Chemical and Materials Engineering

The ability to fabricate a charge-driven water pump is a crucial step toward mimicking the catalytic ability of natural enzyme systems. The first step towards making this water pump a reality is the ability to make a carbon nanotube (CNT) membrane with uniform, 0.8 nm pore diameter. Proposed in this work is a method for synthesizing these carbon nanotubes via VPI-5 zeolite templated, transition metal catalyzed pyrolysis. Using a membrane composed of these CNTs, it is possible to get water molecules to flow single file at a high flow rate, and to orient them in such a way that would …

Atomic Layer Deposition, Paul Kubicza

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Cnt Membrane Platforms For Transdermal Drug Delivery And Aptamer Modulated Transport, Tao Chen

Theses and Dissertations--Chemical and Materials Engineering

CNT membrane platforms are biomimetic polymeric membranes imbedded with carbon nanotubes which show fast fluid flow, electric conductivity, and the ability to be grafted with chemistry. A novel micro-dialysis probe nicotine concentration sampling technique was proposed and proved in vitro, which could greatly improve the efficiency and accuracy of future animal transdermal studies. To enhance the scope of transdermal drug delivery which was limited to passive diffusion of small, potent lipophilic drugs, a wire mesh lateral electroporation design was also proposed which could periodically disrupt the skin barrier and enhance drug flux.

It was shown that AMP binding aptamer …

Magnesium-Titanium Alloys For Biomedical Applications, Ilona Hoffmann

Theses and Dissertations--Chemical and Materials Engineering

Magnesium has been identified as a promising biodegradable implant material because it does not cause systemic toxicity and can reduce stress shielding. However, it corrodes too quickly in the body. Titanium, which is already used ubiquitously for implants, was chosen as the alloying element because of its proven biocompatibility and corrosion resistance in physiological environments. Thus, alloying magnesium with titanium is expected to improve the corrosion resistance of magnesium.

Mg-Ti alloys with a titanium content ranging from 5 to 35 at.-% were successfully synthesized by mechanical alloying. Spark plasma sintering was identified as a processing route to consolidate the alloy …

Microstructure And Work Function Of Dispenser Cathode Coatings: Effects On Thermionic Emission, Phillip D. Swartzentruber

Theses and Dissertations--Chemical and Materials Engineering

Dispenser cathodes emit electrons through thermionic emission and are a critical component of space-based and telecommunication devices. The emission of electrons is enhanced when coated with a refractory metal such as osmium (Os), osmium-ruthenium (Os-Ru), or iridium (Ir). In this work the microstructure, thermionic emission, and work function of thin film Os-Ru coatings were studied in order to relate microstructural properties and thermionic emission.

Os-Ru thin film coatings were prepared through magnetron sputtering and substrate biasing to produce films with an array of preferred orientations, or texture. The effect of texture on thermionic emission was studied in detail through closely-spaced …

Mode I Fracture Toughness Of Eight-Harness-Satin Carbon Cloth Weaves For Co-Cured And Post-Bonded Laminates, Josh E. Smith

Master's Theses

Mode I interlaminar fracture of 3k 8-Harness-Satin Carbon cloth, with identical fill and weft yarns, pre-impregnated with Newport 307 resin was investigated through the DCB test (ASTM D5528). Crack propagations along both the fill and weft yarns were considered for both post-bonded (co-bonded) and co-cured laminates. A patent-pending delamination insertion method was compared to the standard Teflon film option to assess its applicability to mode I fracture testing. The Modified Beam Theory, Compliance Calibration method, and Modified Compliance Calibration method were used for comparative purposes for these investigations and to evaluate the validity of the proposed Equivalent Stiffness (EQS) method. …

Evaluation Of Alternate Mouthpiece Material Types To Minimize Vibrations And Heat Loss - The Research And Execution Of Prototypes, Kristen Bobuk

Theses, Dissertations and Capstones

This paper is based on the idea of current horn mouthpieces being made solely out of brass with a limited market of stainless steel and titanium with plating being silver or gold. This is an opportunity to explore alternate materials; specifically steel, cast iron and aluminum for the base material and chrome, copper and nickel for plating materials. Readers will learn about metal properties such as hardness, thermal conductivity and specific heat and learn why certain materials are more beneficial than others.

Investigation Of Thermal Cycle And Hardness Distribution In The Laser Cladding Of Aisi H13 Tool Steel Produced By A High Power Direct Diode Laser, Parisa Farahmand, Prabu Balu, Fanrong Kong, Radovan Kovacevic

Mechanical Engineering Research

Laser cladding (LC) of tool steel has significant application in rapid tooling, and surface coating for worn-out components in different industries. During the LC process, several phase transformations influence the microstructural and mechanical properties of the deposited layer. In order to successfully implement the LC process, it is essential to understand the relationship between the thermal cycle (heating and cooling), phase transformations, and the output quantities of the deposited layer. In this study a direct diode laser with a power of up to 8 kW was used to deposit AISI H13 tool steel on mild steel grade A36 substrate to …