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Fuel savings through drag reduction in high deformation rate turbulent flows using novel nanomaterials (Antony Beris)

A promising new application of nanomaterials is as drag reducing agents in high deformation rate turbulent flows. At the moment, polymer additives cannot be used to save fuel during ship motion (incidentally 1/5 of the navy’s budget is spend on fuel!) as the current leader for usage in water environments, polyethylene oxide (PEO) (along with all other standard polymers) degrades too quickly under the high flow stresses encountered in the turbulent boundary layer where the polymers are supposed to act. We have successfully simulated polymer-induced drag reduction in direct numerical simulations (DNS) of viscoleastic turbulent channel flow using molecularly-based constitutive equations to model the polymer’s additive contribution to the stress, and we are currently developing novel computational methods to test novel nanomaterials, (based on carbon nanotubes), as drag reducers for turbulent flows 14, 15. In that process we have developed computational tools that are fairly easy to use, yet powerful in their predictions.

An REU student with a background and interest in programming will help in the analysis of the mechanical behavior of carbon nanotubes, and other candidate materials, in high deformation rate turbulent flows using data from already developed DNS simulations and simple mechanical models for the nanoscale behavior. The student will be exposed to micromechanical modeling by exploring the interactions between nanoscale Monte Carlo simulations and our DNS hydrodynamic simulations to predict the stochastic events of material deformation and breakage in turbulent flow. The student will help to interpret the results in an effort to optimize the properties of candidates for a pioneering energy-saving application (drag reduction in ship motion).

Synthesis and characterization of new vanadium- and niobium-substituted bismuth molybdates (Douglas J. Buttrey)

For several decades, bismuth molybdates have been used for commercial production of acrolein and acrylonitrile by selective oxidation and ammoxidation of propylene. Recently, a new homologous series of bismuth molybdate phases has been reported by Vila et al.4 having composition Bi2n+4MonO6(n+1) with n = 3-6. Vanadium, and perhaps also niobium, has the potential to introduce paraffin activating functionality to (amm)oxidation processes, which might allow changes in feedstocks from propylene to less-expensive propane. Such a catalyst would then be in competition with the so-called “Mitsubishi system” phases (Mo-V-(Nb,Ta)-Te-O phases), M1 and M2, that are currently attracting a great deal of attention for conversion of propane to acrylic acid or acrylonitrile.5

The REU student will follow modified low-temperature / high pH procedures recently developed at UD for producing the new vanadium- and niobium-substituted bismuth molybdates. The pH will be varied, as well as the vanadium/niobium substitution level and calcination temperature, to explore the range of appropriate synthetic conditions and the vanadium solubility limits for these new phases. Initial characterization will involve X-ray powder diffraction, and collaborative TEM work with a graduate student in the CCST. Evaluation of catalytic performance will be explored in CCST reactor systems.

Developing electrocatalysts for hydrogen PEM fuel cells (Jingguang Chen)

Polymer Electrode Membrane (PEM) hydrogen fuel cells have been recognized as the next generation energy sources in a wide range of applications. However, the full potential of the hydrogen fuel cell technology has not been materialized, in large part due to the poisoning of the anode electrocatalysts, such as supported Platinum (Pt), by carbon monoxide (CO). We have synthesized a novel class of alternative electrocatalytic materials, tungsten carbides (WC) and Pt-modified WC.6-8 In addition to their potential CO-tolerance, these materials also offer the possibility of replacing, or significantly reducing the loading of the expensive Pt electrocatalysts. We are especially interested in determining the following electrochemical properties: (1) The electrooxidation of hydrogen in the presence of CO to determine the level of CO-tolerance. (2) The electrooxidation of CO to test the possibility of using WC and Pt/WC to preferentially remove CO in the hydrogen feed in fuel cells.

The REU undergraduate student will perform electrochemical evaluation of the electrooxidation of hydrogen to determine the CO-tolerance of these materials. He or she will work with a graduate student to evaluate the hydrogen and methanol electrooxidation on these alternative electrocatalysts. This electrochemical evaluation will utilize a half-cell configuration in acid electrolyte solution. The activity of the electrocatalysts will be measured using two standard techniques, cyclic voltammetry (CV) and chronoamperometry (CA). Then, the stability of the electrocatalysts will be determined by utilizing surface spectroscopy to compare the surface compositions before and after the electrochemical measurements.

Orienting block copolymer thin films to generate nanostructured conducting membranes (Thomas H. Epps)

Block copolymers present the opportunity to design materials with attractive chemical and mechanical properties based on their ability to self-assemble into periodic structures with nanoscale domain spacings. These soft materials are especially suited for fuel cell and lithium battery membrane applications where block copolymer self-assembly creates the large internal interfacial area and well-defined diffusion pathways necessary for optimal function. To employ block copolymers for conducting membrane applications, it is essential to understand how the interfacial interactions in ultrathin (~nm) films affect copolymer morphologies. In this project, we will control thin film interfacial interactions using solvent vapor exposures, as humidity and surface vapors have been known to influence the assembly of polymeric thin films.

The REU student will flow-coat block copolymers directly onto UV-ozone cleaned silicon wafers at thicknesses ranging from approximately 10 - 100 nm. The flow-coating process is controllable, and uniform films can be generated on modified substrates. The initial block copolymer system envisioned for this study is poly(styrene-b-ethylene oxide) [PS-PEO], where PEO is a model ion-conductor. Initial experiments will be conducted in a “bell jar” apparatus, where the film and solvent reservoir are housed in an enclosed environment. Changes in polymer morphology and the degree of long-range order resulting from solvent vapor annealing will be characterized by optical microscopy and atomic force microscopy (AFM).

High-throughput analysis of NH3 decomposition catalysts (Jochen Lauterbach)

Due to multiple difficulties in storing pure hydrogen as compressed gas or liquid, hydrogen needs to be produced on site for stationary fuel cell applications and on-board for mobile applications. Several approaches for on board generation of hydrogen have been investigated over the past few years. One avenue, ammonia feedstocks, has shown promise as a feasible hydrogen carrier, as it can dissociate into hydrogen and nitrogen in the presence of a suitable catalyst.9 We have chosen to employ our high throughput approach for the discovery of new and more efficient ammonia decomposition catalysts.10-12

The REU student will learn to prepare single metal catalysts (from metal precursors containing Ni, Ir, Ru, Rh, Fe, Pd, and Pt) on a variety of supports (such as Al2O3 and SiO2) to systematically study the influence of the transition metal and the support on the reaction. These catalysts will be evaluated in a diluted stream of ammonia in helium for kinetic studies and in high ammonia concentrations to simulate real operating conditions. Next, the REU student will be trained in the preparation of libraries of bimetallic catalysts using two synthetic approaches – conventional co-impregnation and synthesis from molecular cluster precursors. The properties of materials made from each of these methods will be compared through ammonia decomposition studies. As a starting point, we will study bimetallic clusters containing some of the following metals in various combinations: Pt, Cu, Au, Ru, Co, Fe, Ir, and Re.

Acid catalysis with novel mesoporous carbons (Raul Lobo)

We propose to extend the one-step synthesis of ordered mesoporous carbons developed by Liang and Shen to prepare carbons containing sulphonate groups for acid catalysis of large molecules 13. The original process for making mesoporous carbons consist of adding phloroglucinol, formaldehyde and HCl to an ethanolic solution containing polyethyleneoxide-polypropyleneoxide triblock copolymers (Pluronic-type copolymers). Through hydrogen bonding, the phloroglucinol segregates to the PEO-rich regions of the liquid crystal formed by the triblock copolymer. The phloroglucinol is polymerized in-situ, and the resultant composite material is carbonized at high temperatures (500 °C). We propose to modify this procedure by adding a sulphonate-containing polymerizable unit (such as 4-hydroxy­benzenesulphonic acid) that will mix and copolymerize within the original phloroglucinol.

The REU student will perform the following tasks during the 10-week period: synthesis of sulphonate-containing ordered mesoporous carbons (in collaboration with a graduate student), structural characterization using X-ray diffraction and nitrogen adsorption, and acid catalysis testing in a controlled, test reaction such as the synthesis of Bisphenol-A from phenol and acetone.

Modified aqueous gels for conducting devices (Raul Lobo and Eric Furst)

We will investigate the electrical properties of a fixed junction between two aqueous gels containing a negatively charged oxide framework and a positively charged oxide framework, respectively. This combination should act as a polyelectrolyte rectifier allowing current to flow in one direction but not the other. We plan to suspend zeolite (|Na+|[SiAlO4–], the negatively charged oxide) on an agarose gel film supported on a gold electrode. Similarly, we will suspend a hydrotalcite (|Cl-|[Mg3Al(OH)8+] on a separate agarose gel backed on a gold electrode. The two gels will be joined to form the junction and the properties of the composite will be investigated using DC and AC fields.

The REU student will create the mixed agarose gel and zeolite films, along withe the hydrotalcite/agarose gels. Then, the student will test the properties of these materials when subjected to electric fields.

Nanoparticle self assembly in polymer-based photovoltaic devices (Michael Mackay and Thomas Epps)

In this project the student will use a unique coating technique to continuously vary the polymer - nanoparticle blend composition and concentration in a thin film deposited on a substrate, then determine the effect on photovoltaic device efficiency at various positions. It is well known that certain relative concentrations of nanoparticles in polymer films produces higher efficiency, presumably due to the nanoparticle morphology developed during the assembly/coating process. However, a systematic study of this variable has not been performed.

The REU student will also perform photovoltaic device characterization at various positions on the film and correlate efficiency with nanoparticle - polymer structure measured through other techniques.

Biomass conversion to fuels and chemicals (Dion G. Vlachos)

Experiments and simulations on renewables (biomass conversion to fuels and chemicals) will be conducted in Prof. Vlachos' laboratory. We are interested in measuring and modeling the kinetics of typical derivatives of biomass hydrolysis into valuable chemicals, green hydrogen, and fuels that can be added to gasoline or diesel.

The REU student working on this project will learn how to setup an experimental system for biomass conversion to fuels, along with suitable instrumentation, measure kinetics, synthesize catalysts, and run chemistry and reactor models.

Directed Self Assembly of Photonic Nanomaterials (Norman J. Wagner and Michael Mackay)

The critical aspects of nanomaterials requiring the most immediate research attention include the ability to understand and characterize nanoparticles and their interactions, as well as robust, controllable, and scalable methods for assembly of functional nanoparticle "building blocks" into photonic devices for lower energy and high efficiency computing and media storage. Fabricating these nanostructured devices will most certainly employ self-assembly techniques and requires control and understanding of the thermodynamics and kinetics of self-assembly of nanoscale "building blocks" in solution. Functional arrays are also useful to improve the efficiency of organic solar cells, as well as the performance of LEDs. The REU student will employ dielectrophoretic (DEP) directed self-assembly to bias or modulate thermodynamic and mechanical driving forces in order to assemble large numbers of particles in parallel with high selectivity and precision. We will assemble colloidal particles into arrays through controlled application of electric fields, and detect that assembly by optical scattering methods.

The REU student will perform confocal microscopy, laser light scattering, and nanoparticle characterization techniques to study the assembly of these ordered materials under an applied electric field.