Posts Tagged ‘Spring 2011’

Friday, May 6, 2011 10:00 am – 11:00 am
Room 610, M&M Building

Prof. Randall Q. Snurr
Department of Chemical & Biological Engineering
Northwestern University, Evanston, IL

Abstract

Metal-organic frameworks (MOFs) are a new class of nanoporous materials synthesized
in a “building-block” approach by self-assembly of metal or metal-oxide vertices
interconnected by rigid organic linker molecules. The rational synthesis approach opens
up the possibility of incorporating a wide variety of functional groups into the materials,
and these materials may lead to new advances in adsorption separations, gas storage,
sensing, and catalysis. Some of the most intensively studied applications are related to
solving energy and environmental problems, including hydrogen storage for fuel cell
vehicles, capture of CO2 from power plant exhaust, and energy efficient separations.
Because of the predictability of the synthetic routes and the nearly infinite number of
variations possible, molecular modeling is an attractive tool for screening new structures
before they are synthesized. Modeling can also provide insight into the molecular-level
details that lead to observed macroscopic properties. This talk will provide an overview
of MOFs and their potential applications, as well as efforts to predict their properties
using molecular modeling.

Biography

Randy Snurr is a Professor of Chemical and Biological Engineering at Northwestern University. He holds BSE and PhD degrees in chemical engineering from the University of Pennsylvania and the University of California, Berkeley, respectively. From 1994-95, he performed post-doctoral research at the University of Leipzig in Germany supported by a fellowship from the Alexander von Humboldt Foundation. Other honors include a CAREER award from the National Science Foundation and the Leibniz professorship at the University of Leipzig in 2009. He is a Senior Editor of the Journal of Physical Chemistry and has served on the editorial boards of the Journal of Molecular Catalysis A, Catalysis Communications, and Current Nanoscience. His research interests include development of new nanoporous materials for energy and environmental applications, molecular simulation, adsorption separations, diffusion in nanoporous materials, and catalysis.

Monday, April 18, 2011 1:00 pm – 2:00 pm
Room 610, M&M Building

Dr. Vladimir Shapovalov
Department of Materials Science
National Metallurgical Academy of Ukraine

Abstract

This presentation will present a broad classification of gas-eutectic material (gasars) structures, based on experimental data obtained in former USSR, Russia, Ukraine, China, Japan and USA from 1979 to the present time. The presentation will also review gasar production methods and designs of gasar devices for laboratory and industrial manufacturing.

Biography

Dr. Shapovalov is an adjunct professor at the National Metallurgical Academy of Ukraine and seniorresearcher at Materials and Electrochemical Research Corporation of Tuscon, Arizona.  He graduated with a PhDfrom the National Metallurgical Academy of Ukraine in 1972 and has since worked there as a lecturer and professorof Materials Science.  From 1997-2000 he was project manager at Sandia National Laboratory in charge of Gasarmetallic foam research.  He has authored numerous papers on hydrogen equilibrium and advanced materialsprocessing with an emphasis on metallic foam.  His current research interests include advanced plasma processingof Gasar foams for coatings.

Friday, March 25, 2011 3:00 pm – 4:00 pm
Room 610, M&M Building

Dr. John Y. Fu
Department of Mechanical and Aerospace Engineering
State University of New York

Abstract

Historically, the study of flexoelectricity is closely related to that of piezoelectricity though the physicalmechanisms behind these phenomena are completely different [1]. In solid dielectrics, bothpiezoelectricity and flexoelectricity can be derived from the energy coupling in crystalline structures,which are based on equilibrium thermodynamics. However, those phenomena in polymers and liquidcrystals are more complicated due to their complex molecular chains and conformations. Recently, agiant flexoelectric phenomenon has been observed in bent-core nematic liquid crystal elastomers(BCLCEs) [2], which attracts much scientific attention since the nematic phase cannot be regarded asthe ferroelectric phase in most mesomorphic materials. It was believed that the giant flexoelectric effectmight only be observed in certain mesomorphic materials with the chiral smectic C* phase, a ferroelectricphase predicted by Meyer in the 1970s for liquid crystals [3]. Inspired by this study, we investigatedcertain polyvinylidene fluoride (PVDF) polymer films. A giant flexoelectric effect in a PVDF polymer filmwith mixed α- and β-phases has been observed in our group [4], which contradicts the previoustheoretical estimation that the flexoelectric coupling is small, on the order of 10 pC/m. In this seminar, Iwill re-visit the definitions of both piezoelectricity and flexoelectricity in solid dielectrics, and then comparethem with their counterparts in liquid crystals and polymers. Some peculiar physical phenomena relatedto both piezoelectricity and flexoelectricity in polymers will also be discussed. Finally, I will demonstratethat such a giant flexoelectric effect can be exploited to fabricate soft flexoelectric piezoelectriccomposites and devices by using non-piezoelectric soft materials.

References: [1] P. G. de Gennes, Physics of Liquid Crystals (Oxford University Press, London, 1974). [2] J. Hardenet al., Appl. Phys. Lett. 96, 102907 (2010). [3] R. B. Meyer, L. Liebert, L. Strzelecki, P. Keller, J. Phys. Lett. (Paris)36, 69 (1975). [4] J. Y. Fu et al., “Giant flexoelectricity in a polyvinylidene fluoride film”, submitted to Applied PhysicsLetters.

Biography

Dr. John Y. Fu is an assistant professor of mechanical engineering. He came to Buffalo and joined theMAE Department in August 2008. Between 2005 and 2008, Dr. Fu worked as a postdoctoral scholar in a navysponsored materials research laboratory. He completed his college education in China, and received his Ph.D.degree in electrical engineering from the Pennsylvania State University at University Park in December 2004. Dr.Fu holds one American patent and four American and international pending patents. His current research interestsfocus on polymer physics, dielectric polymers, ferroelectric polymers, liquid crystal polymers, flexoelectricpiezoelectric polymer composites and devices, and flexoelectric and flexoviscous phenomena in polymers andbiomaterials.

Friday, March 18, 2011 3:00 pm – 3:30 pm
Room 610, M&M Building

Joe Licavoli
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Gasarite metallic foams are those in which porosity is elongated due to eithergas-metal eutectic growth or evolution of gas from particulate during chillcasting.  Gasarite foams have several superior properties compared to othermetallic foam types, but in general repeatability of experimental results is amajor issue when studying such systems.  The current study replicatesexperiments conducted by other research groups in which ambient pressurewas varied during chill casting of pure aluminum on titanium hydride.According to ideal gas behavior it is expected that decreasing pressure at aconstant temperature will increase pore size and thus porosity, howeverquasi-boiling conditions and subsequent escape of gases from thesolidification front may nullify this effect.  Additional information provided inthis study includes the velocity profile of the solidification front, vacuumlevels, titanium hydride particle size, microstructure around pores andpackaging of the particulate are reported.  In agreement with previousstudies, it was found that operating under vacuum conditions increasesporosity and the tendency to form columnar pores.  Disagreement has beenfound in the propensity to form pores more than 10mm in length and inuniformity of pore radii.  Potential reasons for this disagreement have beendeduced from micro and macrostructural information.  Further studies andintegration of results into process models will be discussed.

Friday, March 4, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Bruce P. Lee
Director of New Technology
Nerites Corporation, Madison, WI

Abstract

Bioadhesives have a wide range of important applications in the biomedical field.  Tissueadhesives simplify complex surgical procedures to achieve effective wound closure and surgicalrepair. Despite these important functions, currently available adhesives seldom meet the basicrequirements for in vivo applications because of possible disease transmission, poor adhesivequality, or toxicity concerns. Thus, there is an ongoing need for the development of tissueadhesives with improved characteristics. Nature provides many outstanding examples ofadhesive strategies from which chemists and materials scientists can draw inspiration in theirpursuit of new biomaterials. Of particular interest is the mussel adhesive protein (MAP) secretedby marine mussels. MAP is initially secreted as a proteinaceous fluid, and then subsequentlyharden in situ to form an adhesive plaque, which allow mussels to bind tenaciously to varioustypes of surfaces underwater. One of the unique structural features of MAP is the presence of L-3,4-dihydroxyphenylalanine (DOPA), an amino acid post-translationally modified from tyrosine,which is believed to fulfill the dual role as the adhesive moiety and the crosslinking precursor.Our research focuses on the incorporation of DOPA and its derivatives in creating syntheticmimics of MAPs for various medical applications. In this seminar, I will discuss the design andapplication of these biomimetic adhesive materials.

Friday, February 25, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Leela Mohana Reddy Arava
Postdoctoral Research Fellow, Department of Mechanical Engineering and Materials Science
Rice University

Abstract

In response to the needs of modern society and emerging ecological concerns, it is nowessential to provide efficient, low-cost, and environmentally friendly electrochemicalenergy conversion and storage devices. These electrochemical devices are expected tohave pronounced technological impact on the society – especially for powering anincreasingly diverse range of portable electronic and vehicular applications.Rechargeable Lithium-ion batteries and Fuel cells are amongst the most promisingcandidates in terms of their wide spread applicability, owing to their high energy andpower densities. The performance of these devices depends intimately on the propertiesof materials used to build them. This talk will focus on the new designs and performanceof the next generation of energy and power delivery devices by the use of tailorednanostructured materials and by nanoscale engineering. Some of the current challengespertaining to the energy storage technology and the effective utilization of new electrodematerials such as graphene and carbon nanotubes will be discussed. Furthermore, thetalk will also evaluate approaches for optimization of the Li-ion battery performance withnovel designs, leading to prototype nanoscale 3D battery architectures offeringimprovements in energy and power density with respect to the geometrical foot print ofdevices.

Monday, February 21, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Shenqiang Ren
Department of Materials Science and Engineering
Massachusetts Institute of Technology

Abstract

Nanostructured materials – including atomic clusters, quantum dots, nanowires or nanotubes –have dimensions in the range of 1 to 100 nm, the length scale that offers unique and sizetunable properties. They provide solutions to some of the current challenges in science andengineering, and would potentially lead to discoveries of new phenomena and novelapplications that are impossible to realize with their bulk counterparts. A challenging task in thisarea is to manipulate nanostructured materials and assemble them into desired structural forms– one, two or three-dimensional structures – so that their unique physical properties can beharvested. Among the bottom-up strategies, self-assembly of nanostructured materials andorganic conjugated polymers provides a promising route to the build-up of complex systems withimmense flexibility in terms of nanoscale building blocks and resulting novel physical properties.Current research is focused mainly on nanostructured hybrid solar cells that combine thebenefits of inorganic materials (thermal and chemical stability, high charge transport, solutionprocessing) and organic materials (strongly absorbing, mechanical flexibility, low-cost).

In this talk, I will discuss my research on rational design of self-assembling nanostructuredphotovoltaic systems on scales from molecular through macroscopic, to the development of“synthetic” strategies. Specifically, I will focus on three main topics: (a) bridging quantum dotsand conjugated polymer nanowires for efficient (>4%) hybrid solar cells; the data provides aunique new insight into the operation of hybrid bulk heterojunction devices and providesdirections to further improvements; (b) drying mediated self-assembly of inorganic nanowirehybrid solar cell; prospects for further enhancement will be discussed; (c) self-assembly of allconjugated block copolymers combined with metal oxide. The key aim of this study is to developa better understanding of the parameters that control such interfacial charge transfer processes.Another critical aim of this work is to develop quantitative structure-function relationships thatcan be used to guide the design and development of efficient nanostructured organic-inorganichybrid solar cells

Friday, February 18, 2011 3:30 pm – 4:30 pm
Room G05, Rekhi Hall

Jeramy D. Zimmerman
Department of Electrical Engineering and Computer Science
University of Michigan

Abstract

Simple lens systems generally suffer from Petzval field curvature aberrations and focus on a curvedsurface; therefore, complicated lens systems are needed to create the flat focal surface required byconventional semiconductor fabrication techniques. To simplify the optics systems, we are designingimagers with curved imaging surfaces, which reduces other optical aberrations as well as system weight.The adoption of curved focal planes requires the development of new processing techniques and newmaterials for conformal surfaces. This talk will focus on two infrared-sensitive organic semiconductorphotodetector systems developed at the University of Michigan for use on conformal substrates.

Organic photodetectors are efficient (20-80% quantum efficient) in the visible region of the spectrum, butvery few organic materials exist with useful photoresponse beyond λ ≈ 1000 nm. Carbon nanotubes(CNTs) have band gaps that absorb in the λ ≈ 1000 to 2000 nm region, motivating our development of aprocedure to use single-wall CNTs wrapped with conjugated polymers as a photoactive component inphotodetectors. We have demonstrated that excitons on CNTs can be dissociated at CNTC60 interfaces, and have created the first photovoltaic detectors fabricated from bulk CNT films. Detectorspecific detectivities above D*=1010 cm-Hz½/W were demonstrated from λ ≈ 400 to 1400 nm, with peakexternal quantum efficiencies of approximately EQE=2% at λ ≈ 1155 and 1300 nm.[1]

More recently, we demonstrated a new porphyrin tape-based organic semiconductor materials systemwith the highest quantum efficiencies demonstrated to date at peak wavelengths greater than λ ≈ 1000nm. The porphyrin tapes consist of two porphyrin units triply linked to form a rigid tape with variousfunctional groups at the terminus of the tape, notably a pyrene group bonded in either one or twolocations. We have demonstrated quantum efficiencies of up to EQE=4% (D*=9×1011 cm-Hz½/W) at λ ≈1080 nm for a singlybonded pyrene end group and EQE=13% (D*=8×1010 cm-Hz½/W) at λ ≈ 1400 nm fora doubly-bonded pyrene end group.[2]

The presentation will discuss fabrication and analysis of devices and materials and conclude with afuture outlook and other applications for these materials.

1. M. S. Arnold, J. D. Zimmerman, C. K. Renshaw, X. Xu, R. R. Lunt, C. M. Austin and S. R. Forrest, Nano Lett.9 (9), 3354-3358 (2009).
2. J. D. Zimmerman, V. V. Diev, K. Hanson, R. R. Lunt, E. K. Yu, M. E. Thompson and S. R. Forrest, Adv. Mater.22 (25), 2780-2783 (2010).

Monday, February 14, 2011 2:00 pm – 3:00 pm
Room G06, Rekhi Hall

Dr. Joshua M. Pearce
Department of Mechanical and Materials Engineering
Queen’s University, Canada

Abstract

Although, solar photovoltaic (PV) electrical production is technologically feasible, growing rapidlyand a environmentally-benign solution to society’s energy requirements, its costs must declinefor deployment at the necessary TW scale. This presentation will review two fundamentalapproaches to reach this goal using microstructural engineering of PV devices. The firstapproach uses relatively inefficient, but proven hydrogenated amorphous silicon (a-Si:H)-basedsolar cells. Thin film cells from a-Si:H are currently the least expensive PV and possess anexcellent ecological balance sheet.  Utilizing AFM, TEM, and real time spectroscopicellipsometry to track the phase of Si:H, the evolutionary nature (protocrystallinity) and substratedependence of its growth were established. This enabled the contributions of the carrierrecombination from the p/i interface regions and the bulk to the dark and light current-voltage (IV) characteristics of a-Si:H p-i-n and n-i-p solar cells to be separated and identified. By applyingthis knowledge of both microstructure and recombination a-Si:H solar cell performance can beimproved to improve efficiency and the cost of electricity provided. The second approach usespotentially ultra-high efficiency indium gallium nitride (InGaN) PV. InGaN shows such incrediblepromise as a PV material due to the ability to modify its band gap by adjusting the ratio ofindium and gallium in the film. A multi-layered cell of InGaN can be made with band gapsranging from 0.7eV (InN) to 3.4eV (GaN), which nearly covers the entire range of the solarspectrum. InGaN has been grown by plasma enhanced evaporation in nanocolumn crystals,which provide optical enhancement and reduce strain during growth and defects. Thus, a welldesigned InGaN solar cell could absorb and convert a much higher fraction of solar energy intoelectricity. The presentation reports on the first stage of research on the characterization andmicrostructural engineering of InGaN nanocolumns. Conclusions are drawn from theexperimental evidence and a path is outlined for future research using both of these approachesto assist society move towards a sustainable energy system using solar photovoltaic devices.

Friday, February 4, 2011 3:00 pm – 4:00 pm
Room 610, M&M Building

Zheng Zhang
Graduate Student
Materials Science and Engineering
Michigan Technological University

Abstract

Storage and transportation of hydrogen in large quantities at small volume iscurrently a big obstacle on the way of hydrogen application. The primaryissue for hydrogen adsorption is weak interactions between hydrogen andthe surface of solid materials, which results in negligible sorption capacity atroom temperature. To solve this problem, electric field was introduced to theprocess of hydrogen adsorption at ambient temperature. For a certaincommercial activated carbon (NAC) with surface area of 1836m2/g, 12.5%and 18.5% enhancements were obtained at 80 bar under 1500V and 2000V.The enhancements were considered to be brought by strong orbitalinteractions between electrically charged sorbent and hydrogen. Moreover,dielectric phase, TiO2, was added to activated carbon to hold electricalcharges around carbon particles without distributing onto the body surface.Employing 2000V electric potential to the samples showed up to 100%enhancement.