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Special Seminar

Superconductivity: Challenges and Opportunities

by: Dr. George Crabtree

Date: Monday October 02, 2006

Time: 4:00 pm – 5:00 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

Electricity is the mainstay of our energy distribution system, providing instant power for light, refrigeration, transportation, industry, communication, and digital electronics at the flip of a switch. Demand for electricity will grow by 50% in the US and 100% in the world by 2030. Yet the electricity delivery system is threatened by increasingly inadequate capacity, reliability, and power quality, especially in urban areas where power density and demand growth are highest. Superconductivity can transform urban electricity delivery through (i) cables with five times the power capacity of copper wires; (ii) smart, self-healing fault current limiters and reactive power regulators that instantaneously control current, voltage, and phase angle variations; and (iii) small, robust transformers that use no contaminating or flammable oil and are safe for urban areas. Transforming the power grid with these superconducting technologies requires aggressive research to improve the current carrying performance of present-generation superconducting wires, and high risk, high payoff basic research on next-generation materials, their electromagnetic behavior mediated by superconducting vortices, and the pairing mechanisms responsible for high temperature superconductivity. The electricity challenges facing the power grid, the breakthroughs in basic research needed to overcome them, and the grand challenges facing superconductivity will be presented.

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Bi-Weekly Seminar

Lattice-strained Nanoparticle Electrocatalysts for PEMFC Cathodes — From Combinatorial Discovery to Structure-property Relationships

by: Dr. Peter Strasser

Date: Friday September 29, 2006

Time: 12:00 pm – 1:00 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

The cell voltage and performance of Polymer-Electrolyte-Membrane Fuel Cells (PEMFCs) deviate strongly from their theoretical values due to severe kinetic overpotentials at the cathode where oxygen is electroreduced to water. The overpotentials are a manifestation of the sluggish rate of adsorption and reaction of molecular oxygen on Pt cathode electrocatalysts. The identification of more active, cost-effective and corrosion stable electrocatalysts for the oxygen reduction reaction (ORR) therefore continues to be a scientific priority in Fuel Cell catalysis research.

We report the combinatorial discovery, bulk synthesis and physico-chemical characterization of a new structural class of Pt electrocatalysts for use for the ORR in PEM fuel cell cathodes. The catalysts exhibit outstanding performance characteristics in terms of their Pt mass based as well as their Pt surface specific activity for the ORR, meeting Department of Energy performance targets for 2010.

Electrochemical Rotating Disk Electrode (RDE) measurements and physico-chemical characterization - including synchrotron X-ray diffraction (XRD) and synchrotron Small Angle X-ray Scattering (SAXS) - show that rapid de-alloying and corrosion processes of base metal rich alloy nanoparticles of a catalyst precursor compound result in the formation of Pt particle lattices with unusually high lattice strain. The data suggests that the formation of strained Pt lattices is correlated with the favorable catalytic activity. SAXS results further show how the electrochemical treatment affects the particle size and metal composition distributions of the catalytic particles inside their ionomer-carbon matrix. Our synchrotron studies allow us to formulate relationships between synthetic conditions, structural characteristics and electrochemical activity. Experimental observations are compared to DFT computational predictions as to the impact of strain on the ORR activity of Pt lattices.

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Conferences and Workshops

Superworld Community Outreach

by: TcSUH Administration

Date: Friday September 01, 2006

Time: 12:30 pm – 2:30 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

Prof. Paul Chu – The Science of Superconductors: From Discovery to Useful Materials (12:35—12:55 p.m.)

Prof. Chu will share the excitement of discovering the first high temperature superconductor (HTS), explain the unique properties of HTSs, and discuss progress and challenges to date in making practical materials for revolutionary applications.

Prof. Chu and colleagues discovered the first superconducting compound above LN2 temperatures in 1987, setting off a worldwide race and creating an exciting new field. He is the founding director of the Texas Center for Superconductivity at the University of Houston, where he is the T. L. L. Temple Chair of Science, Professor of Physics, and Executive Director; and President of the Hong Kong University of Science and Technology.

Dr. Alan Lauder – Applications of Superconductors: Changing our World (12:55—1:15 p.m.)

Dr. Lauder will share the exciting progress made to date on applications that are environmentally friendly and cost effective and are revolutionizing our world in the areas of medicine, transportation, electric power, industry, communications, and scientific research.

Alan Lauder is President of Alan Lauder Inc., a business strategy consulting company, and Executive Director of the Coalition for the Commercial Application of Superconductors. He was Director and General Manager of DuPont Superconductivity prior to his retirement in 2003. Dr. lauder spent 35 years at DuPont in a variety of businesses bringing research from the bench to the plant site and the marketplace.

Demos

Science and Applications (1:15—2:30 p.m.)

How do superconductors work? How will they change our world? Participate in exciting hands-on demonstrations and see prototypes and applications in energy and power, medicine, communications, transportation, high energy physics, and scientific research.

RSVP

jmeen@uh.edu or sbutler@uh.edu; 713-743-8289 or -8212;

Bi-Weekly Seminar

Strain and n-Type Doping Effects on Colossal Magnetoresistance Films

by: Prof. Hsiung Chou

Date: Friday August 18, 2006

Time: 12:00 pm – 1:00 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

The mechanism of strain effect and the achievement of n-type doping on colossal magnetoresistance (CMR) films has been debated and tried for the past decade. It has been believed, but there has been a lack of direct evidence to support, that the distorted MnO6 octahedron due to in-plane strain effect causes the change of transport and magnetic properties. To investigate the origin of the strain effect, La0.7Ca0.3MnO3 and La0.8Ba0.2MnO3 films with various thicknesses grown on SrTiO3 substrates were examined by Near Edge X-ray Absorption Spectroscopy (NEXAS). This study finds that the strain doesn’t affect the MnO6 octahedron significantly, but weakens substantially the La-O and Ca-O (or Ba-O) hybridization, which is responsible for the reduction and the enhancement of TC in La0.7Ca0.3MnO3 and La0.8Ba0.2MnO3 strain films, respectively. For the n-type CMR issue, it has been believed that an n-type CMR can be realized by partially substituting tetravalent ions on trivalent La3+ sites. By investigating the La0.7(Ce or Te)0.3MnO3 bulks with SEM and EDS, it is found that the compound decomposed into La0.9-&epsilonCe&epsilonMnO3+&epsilon, Mn-O, and CeO2, none of which contained original stochiomatry. The n-type compound cannot be formed in thermal equilibrium process, such as post annealing. Only those under metastable processing such as in-situ epitaxial films can possibly assist in forming n-type CMR.

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Bi-Weekly Seminar

Neutron Reflectivity from NbTi/Nb Multilayers

Dr. Wolfgang  Donner

by: Dr. Wolfgang Donner

Date: Friday August 04, 2006

Time: 12:00 pm – 1:00 pm

Location: Houston Science Center – Building 593 — Room 102

Overview

Thin film multilayers of superconducting materials display unusually high pinning forces compared to their bulk counterparts. One such system is NbTi/Nb multilayers: here it was found that the critical current density of such multilayers sensitively depends on the multilayer periodicity. It has been speculated that the vortex lattice in those multilayers would “match” the multilayer period under an applied external field of sufficient magnitude.

The talk presents results on the growth, x-ray and neutron characterization of NbTi/Nb multilayers in an effort to test the hypothesis of vortex lattice “matching.”

Download: Event PDF

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