• Plasma enhanced chemical vapor deposition synthesis of metal carbide membranes for high temperature H2 separations

      Finegan, Donal; Ostwal, Mayur; Way, J. Douglas; Wolden, Colin Andrew
      Approximately 80% of the global energy demand comes from fossil fuels and this reliance is expected to increase at least until the year 2020. Combustion of these fossil fuels to generate power produces CO2. Hydrogen gas is a highly sought after chemical within industry and its uses in society are continuously increasing. The annual production of H2 currently stands at around 50 million tonnes. The primary method of production of H2 is steam reforming which produces a gaseous mixture of H2 and CO2. Consequently, methods are sought to separate CO2 and purify H2.
    • Raman characterization of ZnO and Si nanowires

      Whalen, Jessica; Collins, Reuben T.; Furtak, Thomas E.
      Organic Photovoltaics (OPVs) have gained favor recently for low production cost and potential for roll-to-roll flexible substrates. Though efficiency is fundamentally less than commercial PVs, low production temperature and costs potentially make up the difference. To increase efficiency of OPVs, Zinc Oxide (ZnO) and Silicon (Si) nanowires (NWs) are used to create hybrid organic photovoltaics. The nanowires increase electron pathways and electron mobility, thereby increasing efficiency. Zinc Oxide is used for its high band gap energy, polar structure, low material cost, optoelectronic potential, and microelectronic potential. Silicon is already used in commercial PV, has potential of creating more efficient cells, and Tsakalakos estimates nanowire silicon can reach up to 15%-18% efficiency.
    • High performance computing applications for material physics

      Kaiser, Timothy; Johnson, Matthew
      The Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) is a powerful modeling tool that analyzes the electrodynamics of a molecule or solid. It can also evaluate the photoelectric characteristics of N-body systems like Si clathrate QDs. SIESTA has two solvers for finding Eigenvalues, of which one is chosen as default based on the number of atoms in the molecule or solid being characterized: the Order-N solver is the default solver for problems with more than 1000 atoms; and the Diagon solver is the standard diagonalization algorithm. In an application in renewable energy materials, SIESTA can be used to characterize the electrical properties of many different molecular structures. By offering multiple solution algorithms, SIESTA is able to efficiently characterize molecules of many different sizes. This allows SIESTA to be scaled based on the size of the molecule it is characterizing.
    • Synthesis and characterization of Br- and Cl- anion exchange membranesfor use in alkaline polymer electrolyte fuel cells

      Tansey, Emily; Herring, Andrew M.; Horan, James L.; Vandiver, Melissa A.
      Proton exchange membrane (PEM) fuel cells utilize pure hydrogen fuel and platinum-based catalysts. Hydrogen has a relatively low energy density, so large-scale fuel storage is required to operate PEMs. Pt-based catalysts further constrict the manufacturability of PEMs due to scarcity of platinum. As a fuel source, methanol has a greater energy density than hydrogen; however, as PEMs require H+ ionic transport, a fuel processor must be included with the fuel cell assembly to convert CH3OH to hydrogen. Alkaline anion-exchange membrane (AAEM) fuel cells operate directly with methanol. Improved oxidation of CH3OH occurs due to the alkaline nature of AAEMs. Furthermore, AAEMs require significantly less Pt-based metal in their catalysts and benefit from the mechanical and chemical stability that accompany a solid-state electrolyte.
    • Investigating the metastabilities surrounding hydrogen hydrates for energy storage applications

      Shebowich, Michelle; Arias, Melissa; Grim, Robert Gary; Kerkar, Prasad; Sum, Amadeu; Koh, Carolyn
      Hydrogen hydrate in its most thermodynamically stable form, sII, holds a maximum 3.8 wt. % hydrogen, less than the 5.5 wt. % needed to meet the Department of Energy 2015 goal. This novel work explored H2 hydrate structure, occupancy, and metastability during seeding/templating and guest substitution to ultimately increase hydrogen storage capacity in hydrates. The phenomenon of templating was evaluated by mixing pre-formed hydrate of a desired structure with ice to propagate its structure with another guest. Experiments studying the diffusion of hydrate guests (H2, D2) were also performed.
    • Chemical bath deposition of hematite nanostructures for photo-electrochemical water splitting

      Sale, Alex; Morrish, Rachel; Wolden, Colin Andrew
      Storing solar energy in the form of chemical bonds presents a sustainable approach to meet future energy demands. However, improvements in efficiency and cost are needed before photo-electrochemical (PEC) water splitting can be practically utilized. Hematite has emerged as a promising material for PEC hydrogen generation. The advantages of hematite include its ideal band gap and that it is cheap, earth abundant and chemically stable. The challenges of hematite include low photocurrents, short h+ diffusion lengths, a mismatch with optical penetration depth, barriers for oxygen evolution reaction (OER), and conduction band edge position (additional bias needed). In this work, hematite nanostructures were deposited using a chemical bath deposition to demonstrate how different morphologies of hematite thin films can be made by controlling the solution chemistry of the chemical bath deposition.
    • Successive ionic layer adsorption and reaction for organic/inorganic interfaces

      Hunt, Heather; Collins, Reuben T.; Furtak, Thomas E.
      Zinc oxide is a promising material for use in organic electronics, particularly organic photovoltaics (OPVs). ZnO has a large band gap around 3.3 eV, has a high electron mobility, is non-toxic, and can be processed using solution based methods at atmospheric and room temperature conditions. It has gathered attention in OPVs because it can be used as an electron acceptor at its interface with organic hole conducting molecules. ZnO can also be used as a contact layer in bulk heterojunction OPV devices to carry the electrons from a separated exciton to an external circuit. Both of these uses in OPVs require great control over the ZnO surface.
    • Effect of environmental aging on the mechanical properties of PMMA material used in concentrating photovoltaics, The

      Carloni, Joseph D.; Wilkinson, Taylor M.; Miller, David C.; Packard, Corinne E.
      Concentrating photovoltaics (CPV) modules use focused light. A frensed lens requires less material and is lighter than a bulky and expensive traditional domed lens. A promising lens material is poly(methyl methacrylate) or PMMA. This polymer is a lightweight and mechanically robust optical grade material, benefitting the CPV application. It is relatively unknown how its performance will be affected by environmental weathering conditions. An ATLAS Ci-4000 Weather-Ometer simulates environmental wreathing at >8x acceleration. The samples tested here are two different, commercially available, solar grade formulations of PMMA, aged at NREL and provided to CSM for testing.
    • Characterization of defect density of varying crystal volume fraction in nano crystalline silicon

      Gomez, Stephanie; Riskey, Corey; Taylor, P. Craig
      The objective of this research is to determine how the volume fraction of nano crystalline silicon affects the number of defects caused by dangling bond spins.
    • Recovery of iodine from produced water through anion resin exchange

      Fruit, John Terrell; Xu, Pei; Hoppe-Jones, Christiane; Cath, Tzahi Y.
      The element iodine, I2, is very important to current society. It is used to make products such as film, dye, supplements, medicine and many organic compounds. The use of iodine will continue to expand in application and market use in the future. Iodide is commonly found in seawater at very low concentration. Recovery of iodide can only be economical at high concentrations, such as from mining or extraction from industrial waste. To meet the world's growing demand for iodine, more energy efficient and cost effective methods must be discovered and improved. One way to obtain this resource is through extraction of iodide present in produced water and oxidation of the iodide adsorbed on anion exchange resins.
    • Altering shear thickening of chemical mechanical polishing slurries through the addition of electrolytes and organic solvents

      Yohe, Benjamin; Crawford, Nathan; Liberatore, Matthew W.; Williams, S. Kim R.
      Chemical mechanical polishing (CMP) planarizes and polishes semiconducting materials commonly used in microelectronics. The CMP process depends highly on the slurry composition, particle size and concentration, pH, and added chemicals, which determine the slurry's stability and effectiveness. During the CMP process, the slurry film thickness (between the polishing pad and wafer surface) can vary. It is hypothesized that particles agglomerate during the polishing process, leading to structural damages on the wafer surface (i.e., scratches, gouges, pits, etc.), which costs the semiconductor industry billions of dollars.
    • NMR analysis of passivated silicon quantum dots

      Sorenson, Blaire; Yang, Yongan; Cheng, Jifang; Williams, S. Kim R.
      The increased demand for energy calls for the development of new approaches towards renewable energy sources. Solar energy is one of the most abundant energy resources that can be converted to thermal, chemical and electrical energy. The demand to increase solar energy production to the terra watt level motivated our project, and our research focused on better efficiency of photovoltaics. Silicon is the most developed semi-conductor in the world and because it has been well studied, techniques to manipulate and control its properties have been well established. Plasma enhanced chemical vapor deposition was employed as our method of synthesis. Passivation using chemistries containing alkyl chains promote Si-C bonds close to the surface area. Functionalizing these quantum dots will prevent the unwanted oxide layer and also decrease electron hole recombination rates. Nuclear Magnetic Resonance (NMR)- 1H and 13C - was utilized as a characterization tool to quantify and determine the degree of passivation of the synthesized quantum dots. Passivated samples were subjected to proton and carbon experiments to obtain structural information of the product. The obtained spectras show passivation of the desired ligand occurred with minimal impurities and contamination. Conductivity and photoluminescence results will also be correlated with the NMR data.
    • Renewable energy applications for oil shale production

      Boak, Jeremy; Robles, Elsa
      To reduce the environmental impact of oil shale extraction it would be valuable to use renewable energy sources to provide power to heat the oil shale. This poster presents analysis of different renewable resources that could be used to provide this energy. This work is based on calculations by Alan Burnham of American Shale Oil (AMSO) of how much power is needed to extract 100,000 barrels per day for a medium oil shale (20gal/ton) and rich oil shale (30gal/ton).
    • Renewable energy and climate change education

      Howell, Cynthia; Munakata Marr, Junko; Mitcham, Carl; Azari, Abigail
      In order to address the challenges in the infusion of climate change science into high school and community college renewable energy course offerings, this study focused on administrators and faculty of community colleges and high schools. Nineteen community college and four high school instructors in a Sustainable Energy Education Training (S.E.E.T.) workshop were interviewed regarding the challenges of designing courses that include climate change. The interviews addressed barriers and opportunities for effective integration of climate change as a dimension of any energy curriculum and the need for renewable energy as a solution and potentially important part of a world energy portfolio.
    • Bandgap engineering in graphene nanomesh for photovoltaics

      Vodnik, Douglas; Oswald, William; Wu, Zhigang
      Graphene, a flat monolayer of carbon atoms tightly packed into a two-dimensional honeycomb lattice, was first isolated in 2004. Graphene has attracted a great deal of research interest due to its many amazing properties, including its high electron transport speed which could be very useful for charge transfer in photovoltaic cells. Bulk graphene is a semimetal with zero bandgap, limiting its usages in electronic and optoelectronic devices. Graphene nanoribbons, structurally defected graphene, and other approaches have been proposed to open up a sizable bandgap, but none of these are suitable for practical devices. A recent publication reported a new semiconducting graphene nanostructure, the graphene nanomesh (GNM), created by punching a high-density array of nanoscale holes in graphene. GNMs have the potential to overcome the hurdles plaguing other nanostructures; however, the values and origin of the bandgap remain unknown.
    • Vertical alignment of gold nanorods with AC voltage

      Smith, Lois; Wu, Ning
      The ability to easily and efficiently align nanorods would improve solar cells and sensors by leaps and bounds. We choose Au nanorods as a model system and studied their alignment under an electric field. The alignment of semiconductor nanorods perpendicular to the substrate has been previously accomplished using evaporation techniques and DC voltage, yet vertical uniform alignment of Au nanorods has not been achieved. Thus, we decided to experiment with AC voltage to find a frequency and voltage equilibrium that would align the rods perpendicularly on substrate.
    • Photoluminescence quenching and hot carrier transfer in nanocrystalline silicon

      Miller, Levi; Fields, Jeremy; Collins, Reuben T.; Taylor, P. Craig
      The maximum efficiency of silicon photovoltaic cell is not 31% but 74%. Collecting hot carriers before they thermalize is a means to achieve this. In this regard, amorphous semiconductors are potentially useful materials. Nanocrystalline silicon (nc-Si:H) is unique in that carriers of wide energy distribution generated in amorphous regions may be in range of crystalline regions. These carriers can benefit from higher mobility and a lesser probability of thermalization. The motivation behind this project is to determine whether hot-carrier transfer occurs in thin-film nc-Si:H, and thus provide a potential material for hot carrier collection.
    • Methods in data clustering

      Parker, Charley; Coffey, Mark
      Data clustering methods explored included: K-means algorithm, which minimizes the distances from all data points to the centroid of each point's associated cluster; power iteration, which approximates eigenvectors of a similarity matrix used to embed the data into a space where K-means can be useful; and wordplay for clustering a set of documents and using a word count to construct a similarity matrix.