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Surface Mechanical Attrition Treatment (SMAT) of 7075 Aluminum Alloy to Induce a Protective Corrosion Resistant Layer

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This paper investigates Surface Mechanical Attrition Treatment (SMAT) and the influence of treatment temperature and initial sample surface finish on the corrosion resistance of 7075-T651 aluminum alloy. Ambient SMAT was performed on AA7075 samples polished to 80-grit initial surface roughness.

This paper investigates Surface Mechanical Attrition Treatment (SMAT) and the influence of treatment temperature and initial sample surface finish on the corrosion resistance of 7075-T651 aluminum alloy. Ambient SMAT was performed on AA7075 samples polished to 80-grit initial surface roughness. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used to characterize the corrosion behavior of samples before and after SMAT. Electrochemical tests indicated an improved corrosion resistance after application of SMAT process. The observed improvements in corrosion properties are potentially due to microstructural changes in the material surface induced by SMAT which encouraged the formation of a passive oxide layer. Further testing and research are required to understand the corrosion related effects of cryogenic SMAT and initial-surface finish as the COVID-19 pandemic inhibited experimentation plans.

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2020-05

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In situ SEM Testing for Fatigue Crack Growth: Mechanical Investigation of Titanium

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Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack growth that occurs in titanium alloys, specifically Grade 5 Ti-6Al-4V,

Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack growth that occurs in titanium alloys, specifically Grade 5 Ti-6Al-4V, at the sub-cycle scale, or within a single loading cycle. Using scanning electron microscopy (SEM), imaging analysis is performed to observe crack behavior at ten loading steps throughout the loading and unloading paths. Analysis involves measuring the incremental crack growth and crack tip opening displacement (CTOD) of specimens at loading ratios of 0.1, 0.3, and 0.5. This report defines the relationship between crack growth and the stress intensity factor, K, of the specimens, as well as the relationship between the R-ratio and stress opening level. The crack closure phenomena and effect of microcracks are discussed as they influence the crack growth behavior. This method has previously been used to characterize crack growth in Al 7075-T6. The results for Ti-6Al-4V are compared to these previous findings in order to strengthen conclusions about crack growth behavior.

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2018-05

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Simulation of Atomic Structure around Defects in Anatase

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Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and

Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and sunscreen. Titanium dioxide exists in several polymorphic structures, of which the most common are rutile and anatase. We focused on anatase for the purposes of this research, due to its promising results for hydrolysis.

Anatase exists often in its reduced form (TiO2-x), enabling it to perform redox reactions through the absorption and release of oxygen into/from the crystal lattice. These processes result in structural changes, induced by defects in the material, which can theoretically be observed using advanced characterization methods. In situ electron microscopy is one of such methods, and can provide a window into these structural changes. However, in order to interpret the structural evolution caused by defects in materials, it is often necessary and pertinent to use atomistic simulations to compare the experimental images with models.

In this thesis project, we modeled the defect structures in anatase, around oxygen vacancies and at surfaces, using molecular dynamics, benchmarked with density functional theory. Using a “reactive” forcefield designed for the simulation of interactions between anatase and water that can model and treat bonding through the use of bond orders, different vacancy structures were analyzed and simulated. To compare these theoretical, generated models with experimental data, the “multislice approach” to TEM image simulation was used. We investigated a series of different vacancy configurations and surfaces and generated fingerprints for comparison with TEM experiments. This comparison demonstrated a proof of concept for a technique suggesting the possibility for the identification of oxygen vacancy structures directly from TEM images. This research aims to improve our atomic-level understanding of oxide materials, by providing a methodology for the analysis of vacancy formation from very subtle phenomena in TEM images.

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2019-05

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Burkina Faso Hospital Microgrid Case Study

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This paper analyzes Burkina Faso’s Souro Sanou University Hospital Center’s energy needs and discusses whether or not solar panels are a good investment. This paper also discusses a way to limit the damage caused by power outages. The hospital has

This paper analyzes Burkina Faso’s Souro Sanou University Hospital Center’s energy needs and discusses whether or not solar panels are a good investment. This paper also discusses a way to limit the damage caused by power outages. The hospital has a history of problems with power outages; in the summer they have power outages every other day lasting between one to four hours, and in the rainy season they have outages once every other week lasting the same amount of time.
The first step in this analysis was collecting relevant data which includes: location, electricity rates, energy consumption, and existing assets. The data was entered into a program called HOMER. HOMER is a program which analyzes an electrical system and determines the best configuration and usage of assets to get the lowest levelized cost of energy (LCOE). In HOMER, five different analyses were performed. They reviewed the hospital’s energy usage over 25 years: the current situation, one of the current situation with added solar panels, and another where the solar panels have single axis tracking. The other two analyses created incentives to have more solar panels, one situation with net metering, and one with a sellback rate of 0.03 $/kWh. The result of the analysis concluded that the ideal situation would have solar panels with a capacity of 300 kW, and the LCOE in this situation will be 0.153 $/kWh. The analysis shows that investing in solar panels will save the hospital approximately $65,500 per year, but the initial investment of $910,000 only allows for a total savings of $61,253 over the life of the project. The analysis also shows that if the electricity company, Sonabel, eventually buys back electricity then net metering would be more profitable than reselling electricity for the hospital.
Solar panels will help the hospital save money over time, but they will not stop power outages from happening at the hospital. For the outages to stop affecting the hospital’s operations they will have to invest in an uninterrupted power supply (UPS). The UPS will power the hospital for the time between when the power goes out and when their generators are turning on which makes it an essential investment. This will stop outages from affecting the hospital, and if the power goes out during the day then the solar panels can help supplement the energy production which will take some of the strain from their generators.
The results of this study will be sent to officials at the hospital and they can decide if the large initial investment justifies the savings. If the solar panels and UPS can save one life, then maybe the large initial investment is worth it.

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2019-05

Structural Health Monitoring: Acoustic Emissions

Description

Non-Destructive Testing (NDT) is integral to preserving the structural health of materials. Techniques that fall under the NDT category are able to evaluate integrity and condition of a material without permanently altering any property of the material. Additionally,

Non-Destructive Testing (NDT) is integral to preserving the structural health of materials. Techniques that fall under the NDT category are able to evaluate integrity and condition of a material without permanently altering any property of the material. Additionally, they can typically be used while the material is in active use instead of needing downtime for inspection.
The two general categories of structural health monitoring (SHM) systems include passive and active monitoring. Active SHM systems utilize an input of energy to monitor the health of a structure (such as sound waves in ultrasonics), while passive systems do not. As such, passive SHM tends to be more desirable. A system could be permanently fixed to a critical location, passively accepting signals until it records a damage event, then localize and characterize the damage. This is the goal of acoustic emissions testing.
When certain types of damage occur, such as matrix cracking or delamination in composites, the corresponding release of energy creates sound waves, or acoustic emissions, that propagate through the material. Audio sensors fixed to the surface can pick up data from both the time and frequency domains of the wave. With proper data analysis, a time of arrival (TOA) can be calculated for each sensor allowing for localization of the damage event. The frequency data can be used to characterize the damage.
In traditional acoustic emissions testing, the TOA combined with wave velocity and information about signal attenuation in the material is used to localize events. However, in instances of complex geometries or anisotropic materials (such as carbon fibre composites), velocity and attenuation can vary wildly based on the direction of interest. In these cases, localization can be based off of the time of arrival distances for each sensor pair. This technique is called Delta T mapping, and is the main focus of this study.

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2019-05

Algal Fuels: A Future Less Green than the Plant

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The algal fuel industry has existed since the 1980s without fully commercializing a product. Algal fuels are potentially viable replacements for fossil fuels due to their fast cultivation, high oil content, carbon dioxide sequestration during growth, and ability to

The algal fuel industry has existed since the 1980s without fully commercializing a product. Algal fuels are potentially viable replacements for fossil fuels due to their fast cultivation, high oil content, carbon dioxide sequestration during growth, and ability to be grown on non-arable land. For this thesis, six companies from 61 investigated were interviewed about their history with biofuels, technological changes they have gone through, and views for the future of the industry. All companies interviewed have moved away from fuel production largely due to high production costs and have moved primarily toward pharmaceuticals and animal feed production as well as wastewater treatment. While most do not plan to return to the biofuel industry in the near future, a return would likely require additional legislation, increased technological innovation, and coproduction of multiple products.

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2019-05

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2D or Not To Be: The Story and Science of Graphene

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The story of graphene truly began in what was simply a stub in the journal Physical Review not two years after the end of World War II. In 1947, McGill University physicist P.R. Wallace authored “The Band Theory of Graphite”

The story of graphene truly began in what was simply a stub in the journal Physical Review not two years after the end of World War II. In 1947, McGill University physicist P.R. Wallace authored “The Band Theory of Graphite” and attempted to develop a foundation on which the structure-property relationship of graphite could be explored; he calculates the number of free electrons and conductivity of what he describes as “a single hexagonal layer” and “suppos[es] that conduction takes place only in layers” in bulk graphite to predict wave functions, energies at specific atomic sites in the hexagonal lattice, and energy contours using a tight binding approximation for a hypothesized version of what we now call ‘armchair-style’ graphene. While Wallace was the first to explore the band structure and Brillouin Zones of single-layer graphite, the concept of two-dimensional materials was not new. In fact, for years, it was dismissed as a thermodynamic impossibility.

Everything seemed poised against any proposed physical and experimental stability of a structure like graphene. “Thermodynamically impossible”– a not uncommon shutdown to proposed novel physical or chemical concepts– was once used to describe the entire field of proposed two-dimensional crystals functioning separately from a three-dimensional base or crystalline structure. Rudolf Peierls and Lev Davoidovich Landau, both very accomplished physicists respectively known for the Manhattan Project and for developing a mathematical theory of helium superfluidity, rejected the possibility of isolated monolayer to few-layered crystal lattices. Their reasoning was that diverging thermodynamic-based crystal lattice fluctuations would render the material unstable regardless of controlled temperature. This logic is flawed, but not necessarily inaccurate– diamond, for instance, is thermodynamically metastable at room temperature and pressure in that there exists a slow (i.e. slow on the scale of millions of years) but continuous transformation to graphite. However, this logic was used to support an explanation of thermodynamic impossibility that was provided for graphene’s lack of isolation as late as 1979 by Cornell solid-state physicist Nathaniel David Mermin. These physicists’ claims had clear and consistent grounding in experimental data: as thin films become thinner, there exists a trend of a decreasing melting temperature and increasing instability that renders the films into islands at somewhere around ten to twenty atomic layers. This is driven by the thermodynamically-favorable minimization of surface energy.

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2018-05

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Social-Life Cycle Assessment: Oil Extraction in Section 1002 of the National Arctic Wildlife Refuge

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Drilling in Section 1002 has been an ongoing debate since the region was designated as a potential area for drilling projects, pending congressional approval in 1980. In 2017, the area was officially opened up for oil and gas development through

Drilling in Section 1002 has been an ongoing debate since the region was designated as a potential area for drilling projects, pending congressional approval in 1980. In 2017, the area was officially opened up for oil and gas development through its passage in the GOP Tax Cuts and Jobs Act of 2017. This act requires 2 lease sales of 400,000 acres, with an allowed 2,000 acre physical footprint (not including pipelines, ice roads, or gravel mines). Using Social-Life Cycle Assessment methodology to assess the process of oil extraction in Section 1002, significant benefits and drawbacks of drilling in this region, with economic, cultural, and social impacts ranging from the local level to the state level to the national level were identified.

Stakeholders impacted by oil development in the Section 1002 region include the Kaktovik community who lives within the Program Area, the Gwich’in people who live south of ANWR, the corporations who will be leasing the land, as well as the employees who will be working on the projects. These stakeholders share similar values and interests, however, when it comes down to the attainment of these values, there are significant differences in opinion. This debate comes down specifically to the desire to ensure stability for one’s family and community, as this means 2 different things to the majority stakeholders on this issue: The Inupiaq and the Gwich’in. The Inupiaq ,who live in Kaktovik specifically ,are particularly keen on the idea of drilling in the Section 1002 region, because the revenues and opportunities that come with the oil and gas development provide access to better standards of living and a more westernized way of life. The Gwich’in, however, value their relationship to the land and the caribou that are at risk of significant change. These 2 groups are critical to the debate, but the state and federal governments have the final say, and a financial incentive to move forward with the lease sales.

Utilizing the S-LCA framework, life cycle impacts of drilling on society are found using indicators that are identified and assessed using both qualitative and quantitative means. Although some conclusions are uncertain due to the forward-looking nature of this S-LCA, the Increasing/Decreasing trends can be identified and confidently attributed to the specific indicators.

Significant Results:
Significant issues this study has highlighted include the resulting impacts, both positive and negative, on the communities affected by oil and gas development in Section 1002. Significant stakeholders include the Kaktovik community, the Gwich’in people, the oil and gas workers in the state of Alaska, and the oil and gas companies themselves. The local residents are the most affected by the impacts of development, with significant issues pertaining to potential for significant lifestyle change, the increased risk of impact on subsistence species, the risks associated with pollution, and the effect on the economy through revenues and job availability.

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2019-05

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Assessing the Economic Impact on Counties in the United States to a Loss of Fossil Fuel Dependence for Energy Production

Description

This project seeks to provide a general picture of the economic dependence on fossil fuels per County in the United States. The purpose for this study is creating a foundation for conversations about the future of fossil fuel workers and

This project seeks to provide a general picture of the economic dependence on fossil fuels per County in the United States. The purpose for this study is creating a foundation for conversations about the future of fossil fuel workers and counties that depend heavily on fossil fuels. The main indicators utilized for this were employment and payroll data extracted from United States Census Bureau’s County Business Patterns dataset. A section on similarities between fossil fuel workers and other occupations was included, which shows possible alternative industries for fossil fuel workers. The main goal of the project is to provide possible solutions for mitigating job losses in the future. Some proposed solutions include retraining, expanding higher education, and investing in new industries. It is most important for future work to include input from most vulnerable counties and understand the social and cultural complexities that are tied to this problem.

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2020-05

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Hydrothermal Liquefaction of Micro-Algae to Produce Liquid Biofuels

Description

Fossil fuels are currently the main source of energy in the world’s transportation sector. They are also the primary contributor to carbon emissions in the atmosphere, leading to adverse climate effects. The objective of the following research is to increase

Fossil fuels are currently the main source of energy in the world’s transportation sector. They are also the primary contributor to carbon emissions in the atmosphere, leading to adverse climate effects. The objective of the following research is to increase the yield and efficiency of algal biofuel in order to establish algal-derived fuel as a competitive alternative to predominantly used fossil fuels. Using biofuel commercially will reduce the cost of production and ultimately decrease additional carbon emissions. Experiments were performed using hydrothermal liquefaction (HTL) to determine which catalyst would enhance the algal biocrude oil and result in the highest quality biofuel product, as well as to find the optimal combination of processing temperature and manure co-liquefaction of biomass ratio. For the catalytic upgrading experiments, Micractenium Immerum algae was used in conjunction with pure H2, Pt/C, MO2C, and HZSM-5 catalysts at 350℃ and 400℃, 430 psi, and a 30-minute residence time to investigate the effects of catalyst choice and temperature on the crude oil yield. While all catalysts increased the carbon content of the crude oil, it was found that using HZSM-5 at 350℃ resulted in the greatest overall yield of about 75%. However, the Pt/C catalyst increased the HHV from 34.26 MJ/kg to 43.26 MJ/kg. Cyanidioschyzon merolae (CM) algae and swine manure were utilized in the co-liquefaction experiments, in ratios (algae to swine) of 80:20, 50:50, and 20:80 at temperatures of 300℃ and 330℃. It was found that a ratio of 80:20 at 330℃ produced the highest biocrude oil yield of 29.3%. Although the 80:20 experiments had the greatest biomass conversion and best supported the deacidification of the oil product, the biocrude oil had a HHV of 33.58 MJ/kg, the lowest between the three different ratios. However, all calorific values were relatively close to each other, suggesting that both catalytic upgrading and co-liquefaction can increase the efficiency and economic viability of algal biofuel.

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2020-05