Matching Items (438)

Filtering by

Clear all filters

A Study of the Mechanical Behavior Of Nanocrystalline Metals Using Micro-Electro-Mechanical Systems (MEMS)

Description

The study of the mechanical behavior of nanocrystalline metals using microelectromechanical systems (MEMS) devices lies at the intersection of nanotechnology, mechanical engineering and material science. The extremely small grains that

The study of the mechanical behavior of nanocrystalline metals using microelectromechanical systems (MEMS) devices lies at the intersection of nanotechnology, mechanical engineering and material science. The extremely small grains that make up nanocrystalline metals lead to higher strength but lower ductility as compared to bulk metals. Effects of strain-rate dependence on the mechanical behavior of nanocrystalline metals are explored. Knowing the strain rate dependence of mechanical properties would enable optimization of material selection for different applications and lead to lighter structural components and enhanced sustainability.

Contributors

Agent

Created

Date Created
  • 2014-05

135828-Thumbnail Image.png

Improving Life Outcomes for Children in Arizona: Educational Social Impact Bond

Description

"Improving Life Outcomes for Children in Arizona: Educational Social Impact Bond" is a creative project that is structured as a pitch to the Arizona Department of Education to consider social

"Improving Life Outcomes for Children in Arizona: Educational Social Impact Bond" is a creative project that is structured as a pitch to the Arizona Department of Education to consider social impact bonds as a way to fund pilot education programs. The pitch begins with a brief overview of the umbrella of impact investing, and then a focus on social impact bonds, an area of impact investing. A profile of Arizona's current educational rankings along with statistics are then presented, highlighting the need for an educational social impact bond to help increase achievement. The pitch then starts to focus particularly on high school drop outs and how by funding early childhood education the chances of a child graduating high school increase. An overview of existing early education social impact bonds that are enacted are then presented, followed by a possible structure for an early education social impact bond in Arizona. An analysis of the possible lifetime cost savings of investing in early childhood education are then presented, that are as a result of decreasing the amount of high school drop outs. Lastly, is a brief side-by-side comparison of the Arizona structure to the precedent social impact bonds.

Contributors

Agent

Created

Date Created
  • 2016-05

134663-Thumbnail Image.png

Densification of Li7La3Zr2O12 Electrospun Nanowires Through Processing Control of Intermediate La2Zr2O7 Phase (Electrospinning Synthesis of Electrolytes for Solid-state Lithium-ion Batteries)

Description

Solid-state lithium-ion batteries are a major area of research due to their increased safety characteristics over conventional liquid electrolyte batteries. Lithium lanthanum zirconate (LLZO) is a promising garnet-type ceramic for

Solid-state lithium-ion batteries are a major area of research due to their increased safety characteristics over conventional liquid electrolyte batteries. Lithium lanthanum zirconate (LLZO) is a promising garnet-type ceramic for use as a solid-state electrolyte due to its high ionic conductivity. The material exists in two dierent phases, one that is cubic in structure and one that is tetragonal. One potential synthesis method that results in LLZO in the more useful, cubic phase, is electrospinning, where a mat of nanowires is spun and then calcined into LLZO. A phase containing lanthanum zirconate (LZO) and amorphous lithium occursas an intermediate during the calcination process. LZO has been shown to be a sintering aid for LLZO, allowing for lower sintering temperatures. Here it is shown the eects of internal LZO on the sintered pellets. This is done by varying the 700C calcination time to transform diering amounts of LZO and LLZO in electrospun nanowires, and then using the same sintering parameters for each sample. X-ray diraction was used to get structural and compositional analysis of both the calcined powders and sintered pellets. Pellets formed from wires calcined at 1 hour or longer contained only LLZO even if the calcined powder had only undergone the rst phase transformation. The relative density of the pellet with no initial LLZO of 61.0% was higher than that of the pellet with no LZO, which had a relative density of 57.7%. This allows for the same, or slightly higher, quality material to be synthesized with a shorter amount of processing time.

Contributors

Agent

Created

Date Created
  • 2017-05

135315-Thumbnail Image.png

Quantifying Microstructural Effects on the Strain Localization During Fatigue

Description

The goal of this research is to compare the mechanical properties of CP-Ti and Ti-O and to understand the relationship between a material's microstructure and its response to fatigue. Titanium

The goal of this research is to compare the mechanical properties of CP-Ti and Ti-O and to understand the relationship between a material's microstructure and its response to fatigue. Titanium has been selected due to its desirable properties and applicability in several engineering fields. Both samples are polished and etched in order to visualize and characterize the microstructure and its features. The samples then undergo strain-controlled fatigue tests for several thousand cycles. Throughout testing, images of the samples are taken at zero and maximum load for DIC analysis. The DIC results can be used to study the local strains of the samples. The DIC analysis performed on the CP-Ti sample and presented in this study will be used to understand how the addition of oxygen in the Ti-O impacts fatigue response. The outcome of this research can be used to develop long-lasting, high strength materials.

Contributors

Agent

Created

Date Created
  • 2016-05

135325-Thumbnail Image.png

Social Impact Bonds to Address Phoenix Homelessness

Description

Social impact bonds (SIBs) are a multi-year contract between social service providers, the government, and private investors. The three parties agree on a specific outcome for a societal issue. Investors

Social impact bonds (SIBs) are a multi-year contract between social service providers, the government, and private investors. The three parties agree on a specific outcome for a societal issue. Investors provide capital required for the service provider to operate the project. The service provider then delivers the service to the target population. The success of the project is evaluated by outside party. If the target outcome is met, the government repays the investors at a premium. Nonprofit service providers can only serve a small community as they lack the funding to scale their programs and their reliance on government funding and philanthropy leads to a lot of time focused on raising money in the short-term and inhibits them from evolving their programs and projects for long-term strategic success. Government budgets decline but social problems persist. These contracts share risk between the government and the investors and allow governments to test out programs and alleviate taxpayer burdens from unsuccessful social service programs. Arizona has a severe homelessness problem. Nightly, 6000 people are homeless in Maricopa County. In a given year, over 32,000 individuals were homeless, composed of single adults, families, children, and veterans. Homelessness is not only a debilitating and difficult experience for those who experience it, but also has considerable economic costs on society. Homeless individuals use a number of government programs beyond emergency shelters, and these can cost taxpayers billions of dollars per year. Rapid rehousing was a successful intervention model that the state has been heavily investing in the last few years. This thesis aimed to survey the Arizona climate and determine what barriers were present for enacting an SIB for homelessness. The findings showed that although there are many competent stakeholder groups, lack of interest and overall knowledge of SIBs prevented groups from taking responsibility as the anchor for such a project. Additionally, the government and nonprofits had good partnerships, but lacked relationships with the business community and investors that could propel an SIB. Finally, although rapid rehousing can be used as a successful intervention model, there are not enough years of proven success to justify the spending on an SIB. Additionally, data collection for homelessness programming needs to be standardized between all relevant partners. The framework for an SIB exists in Arizona, but needs a few more years of development before it can be considered.

Contributors

Agent

Created

Date Created
  • 2016-05

136442-Thumbnail Image.png

Optimal Modeling of Knots in Wood

Description

A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses

A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses that change the local bending stiffness has been shown to improve the fit of a theoretical beam displacement function to edge-line deflection data extracted from digital imagery of experimentally loaded beams. In addition, an Ellipse Logistic Model (ELM) has been proposed, using L1-regularized logistic regression, to predict the impact of a knot on the displacement of a beam. By classifying a knot as severely positive or negative, vs. mildly positive or negative, ELM can classify knots that lead to large changes to beam deflection, while not over-emphasizing knots that may not be a problem. Using ELM with a regression-fit Young's Modulus on three-point bending of Douglass Fir, it is possible estimate the effects a knot will have on the shape of the resulting displacement curve.

Contributors

Created

Date Created
  • 2015-05

136455-Thumbnail Image.png

Tribological Failures of Wind Turbine Bearings

Description

Although wind turbine bearings are designed to operate 18-20 years, in the recent years premature failure among these bearings has caused this life to reduce to as low as a

Although wind turbine bearings are designed to operate 18-20 years, in the recent years premature failure among these bearings has caused this life to reduce to as low as a few months to a year. One of the leading causes of premature failure called white structure flaking is a mechanism that was first cited in literature decades ago but not much is understood about it even today. The cause of this mode of failure results from the initiation of white etched cracks (WECs). In this report, different failure mechanisms, especially premature failure mechanisms that were tested and analyzed are demonstrated as a pathway to understanding this phenomenon. Through the use of various tribometers, samples were tested in diverse and extreme conditions in order to study the effect of these different operational conditions on the specimen. Analysis of the tested samples allowed for a comparison of the microstructure alterations in the tested samples to the field bearings affected by WSF.

Contributors

Agent

Created

Date Created
  • 2015-05

136173-Thumbnail Image.png

An Effective Characterization Methodology for Sub-micron Copper Oxides and Oxide-preventing Surface Finishes with a Short Essay on the Role of SEM in the Continuing Miniaturization of Integrated Circuits

Description

The transition to lead-free solder in the electronics industry has benefited the environment in many ways. However, with new materials systems comes new materials issues. During the processing of copper

The transition to lead-free solder in the electronics industry has benefited the environment in many ways. However, with new materials systems comes new materials issues. During the processing of copper pads, a protective surface treatment is needed to prevent the copper from oxidizing. Characterizing the copper oxidation underneath the surface treatment is challenging but necessary for product reliability and failure analysis. Currently, FIB-SEM, which is time-consuming and expensive, is what is used to understand and analyze the surface treatment-copper oxide(s)-copper system. This project's goals were to determine a characterization methodology that cuts both characterization time and cost in half for characterizing copper oxidation beneath a surface treatment and to determine which protective surface treatment is the best as defined by multiple criterion such as cost, sustainability, and reliability. Two protective surface treatments, organic solderability preservative (OSP) and chromium zincate, were investigated, and multiple characterization techniques were researched. Six techniques were tested, and three were deemed promising. Through our studies, it was determined that the best surface treatment was organic solderability preservative (OSP) and the ideal characterization methodology would be using FIB-SEM to calibrate a QCM model, along with using SERA to confirm the QCM model results. The methodology we propose would result in a 91% reduction in characterization cost and a 92% reduction in characterization time. Future work includes further calibration of the QCM model using more FIB/SEM data points and eventually creating a model for oxide layer thickness as a function of exposure time and processing temperature using QCM as the primary data source. An additional short essay on the role of SEM on the continuing miniaturization of integrated circuits is included at the end. This paper explores the intertwined histories of the scanning electron microscope and the integrated circuit, highlighting how advances in SEM influence integrated circuit advances.

Contributors

Agent

Created

Date Created
  • 2015-05

135735-Thumbnail Image.png

Effects of Aging and Crystallization Time and Temperature in the Synthesis of Ideal Zeolite Linde Type A

Description

One of the grand challenges of engineering is to provide access to clean water because it is predicted that by 2025 more than two thirds of the world’s population will

One of the grand challenges of engineering is to provide access to clean water because it is predicted that by 2025 more than two thirds of the world’s population will face severe water shortages. To combat this global issue, our lab focuses on creating a novel composite membrane to recover potable water from waste. For use as the water-selective component in this membrane design Linde Type A zeolites were synthesized for optimal size without the use of a template. Current template-free synthesis of zeolite LTA produces particles that are too large for our application therefore the particle size was reduced in this study to reduce fouling of the membrane while also investigating the nanoparticle synthesis mechanisms. The time and temperature of the reaction and the aging of the precursor gel were systematically modified and observed to determine the optimal conditions for producing the particles. Scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray analysis were used for characterization. Sub-micron sized particles were synthesized at 2 weeks aging time at -8°C with an average size of 0.6 micrometers, a size suitable for our membrane. There is a limit to the posterity and uniformity of particles produced from modifying the reaction time and temperature. All results follow general crystallization theory. Longer aging produced smaller particles, consistent with nucleation theory. Spinodal decomposition is predicted to affect nucleation clustering during aging due to the temperature scheme. Efforts will be made to shorten the effective aging time and these particles will eventually be incorporated into our mixed matrix osmosis membrane.

Contributors

Agent

Created

Date Created
  • 2016-05

136339-Thumbnail Image.png

Local Mechanical Behavior of Hastelloy-X at High Temperatures and Its Relationship to Failure

Description

The following is a report that will evaluate the microstructure of the nickel-based superalloy Hastelloy X and its relationship to mechanical properties in different load conditions. Hastelloy X is of

The following is a report that will evaluate the microstructure of the nickel-based superalloy Hastelloy X and its relationship to mechanical properties in different load conditions. Hastelloy X is of interest to the company AORA because its strength and oxidation resistance at high temperatures is directly applicable to their needs in a hybrid concentrated solar module. The literature review shows that the microstructure will produce different carbides at various temperatures, which can be beneficial to the strength of the alloy. These precipitates are found along the grain boundaries and act as pins that limit dislocation flow, as well as grain boundary sliding, and improve the rupture strength of the material. Over time, harmful precipitates form which counteract the strengthening effect of the carbides and reduce rupture strength, leading to failure. A combination of indentation and microstructure mapping was used in an effort to link local mechanical behavior to microstructure variability. Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were initially used as a means to characterize the microstructure prior to testing. Then, a series of room temperature Vickers hardness tests at 50 and 500 gram-force were used to evaluate the variation in the local response as a function of indentation size. The room temperature study concluded that both the hardness and standard deviation increased at lower loads, which is consistent with the grain size distribution seen in the microstructure scan. The material was then subjected to high temperature spherical indentation. Load-displacement curves were essential in evaluating the decrease in strength of the material with increasing temperature. Through linear regression of the unloading portion of the curve, the plastic deformation was determined and compared at different temperatures as a qualitative method to evaluate local strength.

Contributors

Agent

Created

Date Created
  • 2015-05