Seminars


	TCU DEPARTMENT of PHYSICS and ASTRONOMY
Department Home Page College Home Page TCU Home Page my.tcu.edu TCU Library Undergraduate Program On-Line Ugrad Bulletin Graduate Program On-Line Grad Bulletin Brochure (PDF) Student Information REU Program Summer 2007 Courses Physics Tutoring Center Individual Tutors eCollege Faculty Adjunct Faculty Staff Graduate Students Research Areas Undergraduate Students SPS SERC TCU Institute of Mathematics, Science and Technology Education Seminars TCU Sigma Xi Directions to dept. TCU Box 298840 Fort Worth, TX 76129 Phone: (817) 257-7375 Fax: (817) 257-7742 Email:physics@tcu.edu This page maintained by Kaoru Yoshida	Fall 2007 Seminar Information Friday December 7th at 1:30 p.m. in SWR 357 Escape in the Strong Quantum Regime Alejandro Puga Department of Physics and Astronomy TCU Refreshments Served 2:30pm The Dissertation Oral Examination will follow at 2:45 Sponsor: Dr. Miller Friday November 30th at 2:00 p.m. in SWR 357 Pre-Dissertation: Temperature dependence of the positron lifetime in rubber-carbon black composites Jingyi Wang Department of Physics and Astronomy TCU Sponsor: Dr. Quarles Thursday November 29th at 1:30 p.m. in SWR 357 Infrared Studies on the Spectra and Structures of Novel Carbon Molecules Rafael Cardenas Department of Physics and Astronomy TCU Refreshments Served The Dissertation Oral Examination will follow at 2:45 Sponsor: Dr. Graham Friday November 9th at 1:30 p.m. in SWR 357 Seminar: Structure of carbon nanotubes and nanodiamonds – diffraction measurements and molecular dynamics simulations Aleksander Brodka Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland Abstract: The neutron and X-ray diffraction data are used to study structure of the carbon nanotubes (CNTs) and nanodiamonds (nDs). The experimental techniques provide quantitative information about structure for the total sample volume that may be helpful for future industrial applications. To interpret the diffraction patterns molecular dynamics (MD) simulations are used. In the calculation the carbon-carbon interaction is represented by the reactive empirical bond order potential. In this method thermal vibrations are inherent property of the system, and calculation of the structure factor does not need the Debye-Waller factor. The experimental neutron and X-ray diffraction data of CNTs synthesized by various methods can be properly described introducing topological defects in the form of the pentagon-heptagon pairs. The simulation method was also used to reproduce results of the X-ray diffraction measurements of commercially available NDs. The structure factor and reduced radial distribution function obtained from MD simulation of nD particles with the shapes of a truncated octahedron and a sphere with an average size of about 2.3 nm, performed at 300 K, match quite well the experimental diffraction data. The obtained results showed diamond-like structure of the nD interior, however, interatomic distances were larger than those for the ideal diamond structure. At the same time rebuilt of the surface structure was observed. Additionally, graphitization process of the nDs with sizes of 2.3 and 3 nm at elevated temperatures up to 1800 K was studied. At lower temperatures, up to 600 K, the nDs had stable structure with diamond-like core and fragments of graphite layers in its outer shell, and at the highest temperature the nDs were transformed into carbon onions. Graphitization process of nDs was observed in temperature range from 1200 to 1500 K, and the transition temperature was higher for larger nD, and lower for nD in the shape of a truncated octahedron. In the latest case breaking of bonds between the neighboring {1,1,1} planes appear not only in the surface shell but also in the nD interior that leads to fast formation of relatively large fragments of graphite planes in the whole nD. Moreover, for nDs in the shape of a truncated octahedron with different sizes MD simulations were performed at temperatures 300 and 340 K. From atom positions we calculated reduced radial distribution functions, that were used to estimate the thermal expansion coefficient. The obtained results showed the decrease of the coefficient with the nD size, and for larger nD the coefficient is close to the value obtained from simulation of bulk diamond. Sponsor: Dr. Zerda Friday November 2nd at 1:30 p.m. in SWR 357 The Stellar Content and Star Formation Rates of Dwarf Irregular Galaxies Jackie Dunn Department of Physics and Astronomy TCU Refreshments Served The Dissertation Oral Examination will follow at 2:45 Sponsors: Dr. Pamela Marcum Dr. Mike Fanelli Thursday November 1st at 4:00 p.m. in SWR 357 High Energy Particle Physics at Rice from Top to Bottom Michelle Prewitt Department of Physics and Astronomy Rice University Sponsor: Dr. Quarles Friday September 28th at 1:30 p.m. in SWR 357 Pre-Dissertation: Dislocations and Planar Defects in Silicon Carbide after High Pressure and High Temperature Sintering Stephen Nauyoks Department of Physics and Astronomy TCU Sponsor: Dr. Zerda Friday October 12th at 1:30 p.m. in SWR 357 Pre-Dissertation: Surface Stress Distribution in Diamond Crystals in Diamond-SiC Composites Monika Wieligor Department of Physics and Astronomy TCU Sponsor: Dr. Zerda Previous Seminar Pages Summer 2007 Spring 2007 Fall 2006 Summer 2006 Spring 2006 Fall 2005 Spring 2005 Fall 2004 Spring 2004 Fall 2003 Summer 2003 Spring 2003 Fall 2002 Summer 2002 Spring 2002 Fall 2001
	Copyright © 2002-06 Magnus Rittby / Kaoru Yoshida; Last Updated: Thursday, November 29, 2007

TCU DEPARTMENT of PHYSICS and ASTRONOMY

Fall 2007 Seminar Information

Previous Seminar Pages