Luzzi, David E
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Publication Single Wall Carbon Nanotubes Filled with Metallocenes: a First Example of Non-Fullerene Peapods(2001-11-26) Stercel, Ferenc; Nemes, Norbert M; Fischer, John E; Luzzi, David EWe report the synthesis and analysis of metallocenes (ferrocene, chromocene, ruthenocene, vanadocene, tungstenocene-dihydride) encapsulated in single wall carbon nanotubes (SWNTs). In the case of ferrocene, efficient filling of the SWNTs was accomplished from both the liquid and the vapor phase. The other two metallocenes were filled from the vapor phase. High resolution transmission electron microscopy reveals single molecular chains of metallocenes inside SWNTs. Molecules move under the electron beam in the SWNTs indicating the absence of strong chemical bonds between each other and the SWNT wall. Their movement freezes after short illumination as a result of irradiation damage. Energy dispersive X-ray spectrometry confirms the presence of iron, chromium, ruthenium, vanadium and tungsten.Publication Encapsulated Molecules in Carbon Nanotubes: Structure and Properties(2001-04-16) Russo, Richard; Smith, Brian W.; Luzzi, David E; Satishkumar, B. C; Dorn, Harry CWe encapsulate a number of fullerenes inside single-walled carbon nanotubes (SWNTs) including La2@C80 and ErxSc3-xN@C80(x=0-3). The structural properties of these nanoscopic hybrid materials are described using high resolution transmission electron microscopy and electron diffraction. It is found that the encapsulated fullerenes selfassemble into long, one-dimensional chains. The thermal stability of these supramolecular assemblies are studied and large variations are found. The behavior is nominally consistent with the mass of the encapsulated metallofullerenes.Publication One-dimensional Diffusion-limited Relaxation of Photoexcitations in Suspensions of Single-walled Carbon Nanotubes(2006-07-26) Mele, Eugene J; Kane, Charles L; Russo, Richard M; Therien, Michael; Luzzi, David E; Rubtsov, I. VWe report pump-probe transient absorption spectroscopy on carbon nanotubes with a high initial excitation density. We find that the recovery of the ground state optical absorption is well described by a 1/√t relaxation, indicating that the long time population relaxation is controlled by one-dimensional diffusion limited two body recombination.Publication Structure and properties of C60@SWNT(2001-11-26) Russo, Richard M; Chikkannanavar, Satishkumar B; Stercel, Ferenc; Smith, Brian W; Luzzi, David EOur recent achievement of high-yield C60@SWNT synthesis facilitates characterization by various techniques, including selected area electron diffraction (SAD) and Raman spectroscopy. The obtained SAD patterns show that interior C60 molecules sit on a simple 1-D lattice having a parameter of 1.00 nm. Simulated SAD patterns and real-space measurements both support this determination and do not indicate a lattice with a more complex basis, e.g. a dimer basis. Empty and bulk-filled SWNTs (22%, 56%, and 90% yields), each subjected to identical processing steps, were examined by room temperature Raman spectroscopy. Systematic differences are seen between the spectra of filled and unfilled SWNTs, particularly with respect to the G- and RBM-bands of the nanotubes. We present a possible explanation for this behavior.Publication Imaging and Characterization of Molecules and One-Dimensional Crystals Formed within Carbon Nanotubes(2004-04-01) Sloan, Jeremy; Luzzi, David E; Kirkland, Angus I; Hutchison, John L; Green, Malcolm L.H.The imaging and characterization of individual molecules and atomically thin, effectively one-dimensional crystals of rock salt and other halides encapsulated within single-walled carbon nanotubes are reviewed in this article. These species were imaged by conventional and super-resolved high-resolution transmission electron microscopy and by scanning tunneling microscopy, revealing the detailed atomic structure of these nanoscopic species.Publication Dielectrophoretic Assembly of Carbon Nanofiber Nanoelectromechanical Devices(2005-09-01) Evoy, Stephane; Riegelman, Michael A; Naguib, Nevin; Ye, Haihui; Jaroenapibal, Papot; Luzzi, David E; Gogotsi, YuryWe report a technique for the assembly of bottom-up nanomechanical devices. This technique employs the dielectrophoretic manipulation of nanostructures within a multiple layer lithography process. Mechanical resonators were specifically produced by assembling and clamping tubular carbon fibers onto prefabricated pads. Our preliminary results showed that an assembled cantilevered fiber with length L = 5 µm and width of W = 180 nm possessed a resonant frequency of f = 1.17 MHz. A shorter L = 3-µm-long singly clamped resonator of similar width showed a resonance of f = 3.12 MHz. This frequency range is in agreement with the low gigapascal bending moduli previously reported for carbon structures showing extensive volume defects. This technology would allow the integration of bottom-up nanostructures with other more established fabrication processes, thus allowing the deployment of engineered nanodevices in integrated systems.Publication Characterizations of Lamellar Interfaces and Segregations in a PST-TiAl Intermetallic Alloy by an Analytical Scanning Transmission Electron Microscope(2000-11-27) Zhao, Wei (Wayne); Luzzi, David EPolysynthetically-twinned titanium aluminide (PST-TiAl), a fully lamellar γ-TiAl+α2- Ti3Al dual-phase alloy, is under evaluation for applications in rotary components in aircraft and automobile industries due to its high specific strength, and a high strength-retention capability at elevated-temperatures. However, the low ductility at room- to mid-high temperatures of the material hinders its application. Additions of certain tertiary elements to the binary TiAl system appear to improve the ductility at room- to mid-high temperatures, thus a balance among strength, ductility, and fracture toughness can be expected. In this article, segregation of tertiary elements to the lamellar interfaces is investigated. Single crystals of a TiAl with 0.6% atomic percentage tertiary additions are grown by an optical float-zone method. Segregation to the lamellar interfaces and the microstructure of the interfaces are investigated. Structures of the lamellar interfaces are characterized, and microchemistry and distribution habits of these elements along the γ+α2 lamellar boundaries as well as the γ-γ lamellar and domain boundaries are analyzed.Publication Atomic Structure of a Grain Boundary in a Metallic Alloy: Combined Electron Microscope and Theoretical Study(1991-09-30) Luzzi, David E; Yan, Min; Vitek, Vaclav; Šob, MojmírA synergistic high-resolution electron microscopy (HREM) and theoretical analysis of the structure of a grain boundary in copper containing bismuth is presented. The calculation of the structure of the boundary were carried out using N-body empirical potentials constructed using results of ab initio full-potential linear-muffin-tin-orbital calculations. Excellent agreement between the calculated and observed structures is shown by comparing a through-focal series of observed and calculated images. It is shown for the first time that HREM combined with computer modeling employing realistic empirical potentials can decipher with a great accuracy the structure of boundaries containing multiple atomic species.Publication Processing of single wall carbon nanotubes and implications for filling experiments(2001-11-26) Russo, Richard M; Chikkannanavar, Satishkumar B; Stercel, Ferenc; Smith, Brian W; Luzzi, David ESingle wall carbon nanotubes (SWNTs) have been processed in different schemes to get clean material for use in various filling experiments. The SWNTs synthesized by different methods require different processing schemes, and this is presumably due to heterogeneous nature of the various contaminants present along with the carbon nanotubes. For the pulsed laser synthesized SWNTs, a combination of nitric acid, hydrogen peroxide and hydrochloric acid treatment gives best results and the purified SWNTs give best ever filling fraction for fullerene, C60 of ~90%. The processing improves the surface cleanliness of SWNTs, in turn giving greater access for the target molecules, and hence the higher filling fraction. For the carbon arc produced SWNTs, air oxidation followed by treatment with nitric acid has been found to work best and the processed SWNTs have been used for filling experiments with metal chlorides. Both these processing schemes still leave a small fraction of catalyst impurities in the final material, thus the material quality of filled material and hence its properties depend on the processed material used for the filling experiments.Publication Microscopic and Quantitative Investigations on PST Ti-Al / Ti Reaction Diffusion Couples(2002-12-02) Pan, Ling; Luzzi, David EInterdiffusion in multi-phase diffusion couples of polycrystalline Ti and polysynthetically twinned (PST) Ti-49.3 at.% Al, with the diffusion direction parallel to the lamellar planes, is investigated in the temperature range 973 – 1173 K. A reaction zone (RZ) of the α2-Ti3Al phase forms between the end materials and exhibits deeper penetration in the α2 lamellae than in the primary γ lamellae. The mass balance and the lamellar thickness across the RZ / PST interface are believed to be the major factors that lead to the different behaviors in the penetration depth of the RZ. Direct measurements of the RZ thickness reveal a parabolic growth of the RZ, indicating a diffusion-controlled growth macroscopically. Concentration profiles from the Ti, through the RZ, into the PST γ and α2 lamellae are measured by x-ray spectroscopy in a transmission electron microscope. Deviations from a diffusion-controlled composition profile indicate some extent of interface-controlled growth. Plateaus are seen in the concentration profiles in the RZ adjacent to the RZ/PST interface, extending through most of the deeply penetrated well region. The interfacial energy and strain energy are possible reasons for the plateaus. The interdiffusion coefficients are found to be largely independent of composition with a temperature dependence that obeys the Arrhenius relationship.