MET REU

Statement of the Problem: According to the UN’s Intergovernmental Panel on Climate Change and US Environmental Protection Agency (EPA), the transportation sector is responsible for ~29% of greenhouse gasses (GHG). All Electric Transportation (AET), i.e., all-electric-airplanes (AEA) and electric vehicles (EV) tied to renewable energy sources, is proposed as a main solution.  However, the energy density in state-of-the-art energy storage devices, e.g., batteries, is a major weight penalty in AET vehicles, adversely affecting travel range as a major predictor of market penetration: As a result, currently, AEAs with stored energy needed for longer than ~2-hour flights are prohibitively heavy, keeping AEAs out of >95% of aviation.  Similarly, EV producers are engaged in an uphill battle for increased range on single charge to get more market share. Multifunctional energy-storing fibrous composites/panels have the potential to provide both electrochemical and mechanical performance within a single platform, thus allowing for energy storage with much less weight/volume penalties compared to conventional energy storage devices for applications that are restricted by weight and/or volume. These panels can be used in AEA, EVs, electric unmanned aerial vehicles (UAVs), and electric air taxis, representing the next generation of high-performance aviation technology with higher system-level energy density (onboard energy per unit mass). Nevertheless, the development of state-of-the-art multifunctional energy storage remains challenging, and the energy density of full cell battery composites, funded by different agencies like DOD, is often very low at under 30 Wh/kg (half-cell).

Participant Activities: We propose to demonstrate a novel concept for structural all-solid-state-Li-ion hybrid supercapacitor (LiHSC) composite frames/panels (replacement of structural frame in different devices with an energy-storing structural frame), in which the morphology of the electrodes (e.g., the porosity) is tuned to enhance energy storage with minimal impact on load bearing, and demonstrate the utility of it in drastically increasing the onboard energy capacity of the AEAs and thus their range. The participant will build LiHSC composite frames and measure porosity, energy storage, and load bearing capacity for a variety of morphologies. 

Statement of the Problem:  The Iski Lab uses Electrochemical[RH1]  Scanning Tunneling Microscopy (EC-STM) which is a technique that measures the physical height of conductive surfaces under a liquid layer and in an ambient environment to better understand surface interactions in biologically relevant conditions. This investigation will focus on the EC-STM study of simple amino acids, and the means by which these molecules interact with a Au(111) surface. Using EC-STM under relevant experimental conditions, previous studies have shown that the amino acids have a considerable interaction with the underlying surface. However, the adsorption mechanism and molecular orientation are still key questions that have yet to be answered and would be necessary to move in the direction of using these systems in applied areas.

Participant Activities:  The participant’s day-to-day work activities would include wet chemistry, using the microscope, setting up external EC cells for potentiostat testing, and simple computer programming for the modeling of the molecules. Iski’s lab provides a unique opportunity to learn about physics, physical chemistry, nanotechnology, and materials chemistry in an effort to gain a better understanding of how simple systems may be used in a stepwise manner to develop efficient and alternative methods to understand the properties of surfaces and their associated surface energies. Questions to be answered with the EC-STM experiments include: What is the orientation of the molecules when bound to the surface? What type of bond is being formed between the molecule and surface? How does that bonding change based on experimental parameters, like solvent choice and concentration?

Statement of the Problem:  Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that can be produced from renewable biomass sources, such as microalgae.  Microalgae are photosynthetic microorganisms that can grow rapidly and efficiently using sunlight, water, and carbon dioxide. Microalgae can synthesize and accumulate PHAs in their cells under certain conditions, such as nutrient limitation or stress induction. However, the isolation and purification of PHAs from microalgal biomass is still challenging and costly, due to the complex cell wall structure, the low PHA content, and the presence of impurities.  The aim of this project is to develop and optimize methods for isolating and blending PHAs from microalgae for 3D printing applications. The specific research questions are what are the most efficient and eco-friendly methods for harvesting, drying, and disrupting microalgal cells and extracting PHAs from their biomass and how can the isolated PHAs be blended with other polymers or additives to improve their performance and compatibility for 3D printing?

Participant Activities:  The participant will be responsible for the following tasks:

• Disrupting the microalgal cells and extracting the PHAs using physical, chemical, or enzymatic methods, such as sonication, microwave irradiation, solvent extraction, or lipase digestion.
• Blending the isolated PHAs with other polymers or additives, such as polylactic acid (PLA), polyethylene glycol (PEG), polyvinyl alcohol (PVA), glycerol, citric acid, or nanofillers, to improve their mechanical, thermal, optical, and biodegradable properties for 3D printing.
• Optimizing the processing parameters and methods for 3D printing PHA blends, such as extruder temperature, bed temperature, printing speed, layer thickness, infill density, cooling rate, and post-processing treatment.

Statement of the Problem:  Wind turbine blades are exposed to severe environmental conditions. Thus, they are prone to damage which can affect their performance significantly. Current research at TU is investigating the leading-edge erosion of wind turbine blades by water droplets experimentally. The literature assumes that the falling droplets are perfectly spherical and are not influenced by any local turbulence or vortex shedding. However, we have preliminary results which show that the droplets are affected by this turbulence thus require a way to measure and simulate this phenomenon in a controlled setting. Moreover, the current research does not account for different pH values or any impurities that water (rain) droplets may contain or brine (droplets containing salt such as sea spray).

Participant Activities: The proposed REU project focuses on measuring the falling droplets’ size and shape using Particle Image Velocimetry (PIV) in both “static” and “disturbed” flow and comparing the results for various flow rates. The experimental objectives involve testing different impact angles, flow rates, and various droplet sizes. The REU scholar will learn and use PIV for investigating all the parameters listed. The water properties are also a concern so testing will be conducted to analyze rainwater and replicate it inside the testing facility along with distilled water to compare any corrosion/erosion differences. The results of this project will be used in erosion modeling. Modeling of the erosion based on theoretical and experimental work currently relies on assuming a falling droplet in a static field and does not account for the side-to-side impact angle difference or non-spherical shapes that the droplets form when exposed to turbulence. Results based on the eroded specimens will be analyzed by recording mass loss before and after exposure as well as using scanning electron microscopy (SEM) to view the specimen’s surface in detail.

Statement of the Problem: The atmospheric concentration of CO₂ has increased by approximately 50% compared to the beginning of the industrial revolution. The effect of rising surface temperatures due to increased atmospheric CO₂ is evident from numerous and frequent natural disasters Consequently, there is a growing interest in reducing the concentration of atmospheric CO₂ by switching to renewable/low-emission energy sources and reducing CO₂ emissions by other means. Geological sequestration of CO₂ may safely sequester carbon emissions from large stationary sources and slow the harmful increase of CO₂ concentrations in the atmosphere. Deep saline aquifers are one of the major geological storage options because of their wide availability and huge storage potential. CO₂ is stored in deep saline aquifers by four primary trapping mechanisms: structural, residual, dissolution, and mineral trapping. Even though residual trapping is dominant at the early stages of CO₂ storage, dissolution trapping becomes the primary trapping mechanism with time, capturing almost two-thirds of CO₂ injected in the storage volume. Thus, it is vital to understand the complex CO₂ mass and momentum transport mechanisms in brine to improve the storage efficiency and storage security of CO₂ in subsurface formations.

Participant Activities: In this project, the student will study the dissolution of CO₂ in a transparent Hele-Shaw cell in various monovalent and divalent cations (e.g. Na⁺, Ca⁺⁺, etc.) typically present in an aquifer brine. In addition, the students will also analyze the impact of the presence of unconsolidated porous media represented by glass beads of different sizes. The students will collect the images and analyze them, using ImageJ, to understand the impact of various conditions on the dissolution of CO₂. The students will also use a field-scale numerical reservoir simulator (CMG-GEM) to model the dissolution of CO₂ in reservoir conditions.

Statement of the Problem: It is well established that film quality and layer thickness are critical components in next-generation photovoltaics. In perovskite-based solar cells, for example, not only does the thickness of the photoactive perovskite film play a role, but so do the thickness and quality of the hole-transport layer and the electron-transport layer. The quantification of thin film properties often requires specialized and expensive equipment that analyzes only a small fraction of the overall layer. Furthermore, techniques such as electron microscopy often have issues with some samples. For example, the plastic used in flexible photovoltaics requires metallic sputtering prior to analysis. A simple photograph of a film, on the other hand, captures a tremendous amount of information regarding the entire film without significant sample preparation, as demonstrated for perovskite thin films. The challenge then is to determine the relationships between photographic data and traditional thin film analytical methods. Participant Activities: Students on this project will gain practical experience with both traditional thin film analytical tools (e.g. atomic force and electron microscopy, profilometry) and image processing tools (e.g. ImageJ). Finding correlations between these data sets will provide rapid and macro-scale information, with implications far beyond photovoltaic technologies. If a photograph can capture subtle differences in film properties, it is reasonable that correlations exist between the photographic data and thin film properties that typically require advanced instrumentation.

Statement of the Problem:  Elastocaloric metals enable solid-state refrigeration technologies that could transform the way we cool our homes and offices, but we do not have a clear grasp of how these materials fail under the combined thermal and mechanical loading that they experience when cooling. Currently, about 10% of the electricity used around the globe goes into cooling our buildings. Furthermore, the dominant technology—vapor-compression—utilizes gases with high greenhouse gas warming potential and relatively low efficient.  Therefore, there is a great opportunity to increase sustainability by using new refrigeration technologies, and one attractive method is elastocaloric materials. Elastocaloric materials have been named by the U.S. Department of Energy and the EU Commission as the most promising alternative to existing heating and cooling technologies, [28] with a theoretical Carnot efficiency of up to 84% (about 10 times higher than the best vapor-compression systems).  However, to enable elastocaloric cooling systems, we need deeper fundamental understanding of the long-term durability of the materials. Currently, elastocalorics are plagued by short operating lifetimes (on the order of hours to days instead of years). This work will address the research question, “How does an elastocaloric metal fatigue and crack while under a continuous heating/cooling cycle?” Prior measurements have treated the various phases as binary/discrete transitions, probing specific points in the phase/temperature/ stress space. However, the phase transformation is a continuous process, so this work will be the first to characterize cracking with a custom methodology.  It is expected that these results will inform material models that will predict the useful service life of elastocaloric systems. Participant Activities:  The participant will measure the fatigue damage and cracking behavior of an elastocaloric metal (NiTi shape memory alloy) along a continuous range of temperatures. This will go beyond the state-of-the-art knowledge for NiTi cracking, which to date has only been captured at five different temperatures with respect to the different material phases (austenite, martensite, and R-phase). The knowledge gained from this experimental work is significant because it will inform the safe operating service life of future energy-efficient solid-state refrigeration systems.

Statement of the Problem: Carbon/carbon (C/C) composites of carbon fiber reinforcement embedded in a graphite matrix are ideal for high-temperature structural niche applications (hypersonic aerospace vehicles, nose cones and wing edges of space shuttle orbiters, rocket nozzles, heat shields, aircraft disc brakes, and nuclear fusion reactors) due to their superior mechanical properties and stability. At TU, we have been working on a novel micro-vascular Carbon/Carbon composite that can withstand the temperature and pressure conditions (800˚C and 200 bar) of the next generation of concentrated solar power (CSP) plants.  Currently, the metallic CSPs cannot go beyond these temperatures due to material limitations.  Our microvascular C/C composites manufacturing approach leverages the microVaSC technique to create flow channels via the thermal depolymerization of 3D printed poly(lactic acid). One of the current limitations is that the composites oxidize at temperatures above 500°C and are thus limited to inert atmospheres. Therefore, understanding and overcoming oxidation limitations is the most relevant and critical bottleneck in the long-term and broad application of C/C composites. Although there have been several studies to design reliable oxidation-resistant coating systems that can perform up to 1700°C, because of the difference in thermal expansion between the C/C composites and the coating, cracks can form, compromising the protective efficiency. For long-term application in extreme temperatures, it may be advantageous to have a porous, chemically compatible inner or base layer that could serve as a structural link between the brittle or dense top layer and the substrate (C/C composite) while the self-healing top layer should be chemically inert and act as a diffusion barrier. The hypothesis is that by filling the critical knowledge gap of how processing parameters influence coating robustness, we can significantly enhance the performance of these materials.

Participant Activities:  The Ramsurn lab has been exploring and evaluating how different slurry formulation processes and packed cementation (PC) powder concentrations combined with chemical vapor deposition (CVD) can be used for composite performance at ultra-high temperatures. The student will be trained on coating techniques, including CVD, which yields dense coating layers with good adhesion to the substrate, and PC combined with slurry, a simple technique suitable for synthesizing gradient porous coating. S/he will then systematically study several combinations and permutations of techniques and compounds to provide further insight into the interfacial interactions between the C/C composite surface and the first coating layer.

Statement of the Problem:  A great deal of work has been done to come up with new battery chemistries and electrode materials, but relatively little work has been done regarding electrolyte optimization, especially in cases where the electrolyte contains multiple dissolved ionic species. In these ‘complex’ electrolytes, specific ion effects (SIEs) will become very important and potentially useful tools to optimize the performance of electrochemical energy storage devices. SIEs, or Hofmeister Effects, are a complicated result of ion-ion binding interactions and ion-solvent interactions and have attracted a great deal of attention in recent years. The need for a deeper understanding of these effects is due to their broad impact on a wide range of research disciplines and applications from household cleaners to biomedicine to batteries. SIEs have avoided explanation for over 130 years, since every time a new ‘explanation’ is created, new experimental results find an exception to that particular ‘explanation’. Recent works have begun to investigate the use of SIEs to improve mechanical and electrochemical properties of materials for energy storage applications, but the work is still in the initial stages and has thus far only looked at fairly simple electrolyte solutions. The self-assembly of surfactants and colloidal particles is highly sensitive to SIEs, making it an excellent method for probing specific ion effects even in solutions containing numerous ionic species.

Participant Activities:  In this project, the student will study surfactant self-assembly and polymer viscoelasticity to explore how SIEs manifest in a few common (aqueous) energy storage chemistries, specifically looking at the effect of various zinc salts on the mechanical and electrochemical storage capabilities of zinc/sulfur batteries.