TcSUH EventS
TcSUH Annual Student Research Symposium
30th Semiannual TcSUH Student Symposium
by: TcSUH Administration
Date: Friday December 16, 2005
Time: 9:00 am – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
All members of TcSUH are invited to attend the 30th Semiannual TcSUH Fall Student Symposium for presentations of original student work.
The Student Symposium will begin at 9:00 a.m. with a brief review of the Center's progress. The morning will then continue with a series of 15-minute presentations representing novel work by undergraduate and graduate students from each TcSUH group. A Symposium Program, including the schedule and abstracts for each presentation, will be provided at the door.
The Holiday Buffet will be served immediately following the symposium for all TcSUH presenters and attendees. Please RSVP to Annie Foster at x-38210, by Tuesday, December 13, 2005.
Download: Event PDF
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Special Seminar
Optical Properties of Semiconductor Surfaces and Interfaces: First Principle Study
by: Prof. Vladimir I. Gavrilenko
Date: Monday December 12, 2005
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Electron energy structure and linear and non-linear optical properties of group III-nitride compounds, as well as group IV semiconductors (bulk, surfaces, and interfaces) are studied by first principle evaluation of eigen-value and eigen-vector problems using full potential linearized augmented plane wave (FLAPW) and ab initio pseudopotentials (PP) approaches. Equilibrium surface/interface geometries are determined through the total energy minimization method. Optical responses from solid surfaces and effects of the adsorption of inorganic elements and organic molecules are studied. Intermolecular interaction is shown to be responsible for substantial modifications of optical spectra of molecular aggregates. Predictions of second harmonic generation (SHG) from semiconductor surfaces and interfaces are discussed. Effects of rehybridization of atomic bonds and electric field induced second harmonic (EFISH) response are considered. Strong contributions to the SHG efficiency of electron excitations from surface atom orbitals are demonstrated for Si(001) and GaN(0001) surfaces and the Ge/Si(001) interface. Adsorption of Ga on the N-terminated GaN(0001) surface results in a substantial evolution of the surface related SHG features. The predicted spectroscopic results from semiconductor surfaces and interfaces are discussed in comparison with experiment.
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Bi-Weekly Seminar
MOD Development of Coated Conductors at TcSUH
by: Prof. Kamel Salama
Date: Friday December 02, 2005
Time: 1:00 pm – 2:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Currently, first-generation high temperature superconducting (HTS) wires/tapes are commercially available for practical applications. However, second-generation HTS wires/tapes (coated conductors) exhibit the capability of carrying a larger current operating at higher temperatures and stronger magnetic fields. Development of the second generation will accelerate the applications of HTS products into the marketplace. Highlights of our research on YBCO coated conductors at TcSUH include results on textured substrates, metal-organic deposition (MOD) buffer layers and YBCO films. The sharpest cube textured non-ferromagnetic Ni-9at%W alloy substrates were successfully achieved for the first time using the powder metallurgy process and give promise for coated conductors with reduced AC losses. Also, new MOD buffer layers have been developed to simplify coated conductor architectures, leading to a lower cost/performance ratio. In addition, chemically doped MOD YBCO films with enhanced critical current density (Jc) were developed and Jc exceeding 5 MA/cm2 at 77 K was obtained. Finally, we will present results of electric-mechanical properties of SuperPower IBAD coated conductors as part of the collaboration between TcSUH and SuperPower.
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Bi-Weekly Seminar
Magnetoelectric Effects, Spin Frustration, and Ferroelectricity in Multiferroic Manganites
by: Bernd Lorenz
Date: Friday November 18, 2005
Time: 1:00 pm – 2:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
The interaction between electric and magnetic fields in matter and/or between dielectric and magnetic orders is one of the fundamental problems in condensed matter physics. The magnetoelectric effect that allows the control of magnetic (dielectric) properties by electric (magnetic) fields is of principal physical interest and it bears the potential for the development of a new type of magnetoelectric memory. The topic has attracted renewed interest quite recently with the discovery of the coexistence of ferroelectricity and magnetic orders in multiferroic rare earth manganites. We discuss the complex physical properties of multiferroic RMnO3 and RMn2O5 (R=rare earth, Y) and show that magnetic frustration as well as strong spin-lattice coupling are the origin of a wealth of interesting phenomena such as incommensurate magnetic orders, frustration-induced ferroelectricity, magnetic field control of ferroelectric polarization, etc. The interactions between the Mn spins, the rare earth magnetic moments, and the ferroelectric polarization in these compounds give rise to an unprecedented phase complexity, e.g. as observed in hexagonal HoMnO3. In orthorhombic RMn2O5, our high-resolution thermal expansion measurements provide unambiguous proof that the ferroelectric transitions are accompanied by strong structural anomalies resulting in anisotropic lattice strain along the principal crystallographic directions.
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Special Seminar
High-Temperature Superconducting Wire and Power Applications Research and Development in the USA
by: Robert Hawsey
Date: Friday November 11, 2005
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
U.S. efforts to develop and deploy “second generation” (2G) high-temperature superconducting (HTS) wires that use the compound Y1Ba2Cu3Ox (YBCO) or other rare-earth (RE) superconducting materials are described. Wires have been demonstrated in 20-m to >200-m lengths with the RE-BCO deposited using vapor deposition or wet chemical processes in thin layers onto textured templates, which force the grains of the RE-BCO into near perfect alignment. Critical currents for these pre-commercial wires are now within striking distance of those achieved for commercial BSSCO wires. One expected advantage of 2G wire is a projected 5-fold decrease in cost of wire compared with first generation wires. Another advantage of 2G wire is the intrinsic behavior of YBCO in the presence of a strong magnetic field at intermediate temperatures (viz., 50 K), where single-stage cryocoolers may be used for certain applications. Enhancements in flux pinning of at least a factor of two have been demonstrated for MOCVD and MOD deposited YBCO films. U.S. progress towards meeting the challenging goals for the year 2006, including current exceeding 300 A/cm width (77 K, self field) in 100-m lengths and engineering current density exceeding 15,000 A/cm2 (65 K, 3-T) is reported. In addition, initial efforts toward engineering the conductor for the mechanical and electrical properties needed for strong magnetic field applications are described. These projects include striation or other means to subdivide the superconducting film into filaments, as well as lamination or other innovative processes. Finally, an overview of U.S. demonstration projects for superconducting cables, synchronous condensers, motors, generators, and other power applications will be presented.
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