bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibrational and Electronic Properties of RbC60 Thin Films
Authors: Lopinski G.P. , Mitch M.G. , Fox J.R. , Lannin J.S. 
Published: April 2011

ABSTRACTIn situ Raman scattering, UPS and HREELS measurements have been used to study the fcc to orthorhombic phase transition in RbC60 thin films. Large changes in the Raman spectra are interpreted in terms of increased interfullerene coupling in the orthorhombic phase. However, the data do not support the proposed polymer model for this phase. Photoemission measurements indicate only small differences in the electronic states between the two phases in contrast with photopolymerized C60 where additional states are observed. Low energy metallic-like excitations and screening of intramolecular vibrations are observed in HREELS.
Lattice-Type Polymers from an Adduct of C60 and 2-Methylaziridine
Authors: Nigam A. , Shekharam T. , Bharadwaj T. N. , Giovanola J. , Narang S. C. , Malhotra R. 
Published: April 2011

ABSTRACTA one to ten adduct of C60 and 2-methylaziridine was prepared and copolymerized with Novolac, Epon and Bisphenol A to obtain three dimensional polymers containing C60 with low coefficients of friction and good wear properties, which bode well for their potential use as solid lubricants.
Embedding Fullerenes in Thin Sol-Gel Films
Authors: Prato Maurizio , Maggini Michele , Scorrano Gianfranco , Brusatin Giovanna , Innocenzi Plinio , Guglielmi Massimo , Meneghetii Moreno , Bozio Renato 
Published: April 2011

ABSTRACTFullerene C60 can be considered an interesting molecule for the preparation of new materials with attractive optical properties. In the present work we report the preparation of sol-gel derived, glass-like materials containing C60 and a C60 derivative prepared by 1,3-dipolar cycloadditions of azomethine ylides to C60. The optical characterisation of the films confirms the presence of C60 and its derivative, in the glass matrix.
Disilene Addition to C70
Authors: Jacobs S. J. , Rohlfing C. M. , Cahill P. A. 
Published: April 2011

ABSTRACTSemiempirical and ab initio Hartree Fock computational results indicate that the highly reactive dienophile tetramethyldisilene, Me2Si=SiMe2, is an excellent candidate for a novel functionalization of the equator of C70 via a [2+4] cycloaddition to the 21, 22, 23, 42 carbons. Thermal or photochemical generation of tetramethyldisilene in the presence of C70 results in similar complex mixtures in which the major product appears to be that of [2+2] cycloaddition to the 7,8 carbons of C70. A minor product clearly results from [2+2] cycloaddition to the 1,9 carbons. Both of these products are hydrolytically unstable and are converted nonspecifically to mixtures of 1,9- and 7,8-C70H2 which are also present in HPLC traces of the reaction mixtures.
Fullerenes as Nanoscale “Connectors”
Authors: Meier Mark S. , Rice Douglas J. , Thomas Craig , Majidi Vahid , Pogue Robert , Poplawska Magdalena 
Published: April 2011

ABSTRACTThe construction of nanoscale devices is a potentially important area of technology. Efforts in this area of chemistry have largely concentrated on the preparation of rigid organic molecules for use as spacers. These compounds are used to separate electronically active units, usually metal complexes, by defined distances.We have been investigating the use of fullerenes as connectors in the construction of these extended assemblies. In this paper we will present our results on the preparation of these compounds, including discussions of the regiochemistry of the second addition of a nitrile oxide to a fullerene isoxazoline.
Heteroepitaxial Growth of Epitaxial C60-Thin Films on Mica(001)
Authors: Henke S. , Thürer K.H. , Geier S. , Rauschenbach B. , Stritzker B. 
Published: April 2011

ABSTRACTOn mica(001) thin C60-films are deposited by thermal evaporation at substrate temperatures from room temperature up to 225°C. The dependence of the structure and the epitaxial alignment of the thin C60-films on mica(001) on the substrate temperature and the film thickness up to 1.3 μm at a well-defined deposition rate (0.008 nm/s) is investigated by atomic force microscopy and X-ray diffraction. The shape and the size of the C60-islands, which have an influence on the film quality at larger film thicknesses, are sensitively dependent on the substrate temperature. At a film thickness of 200 nm the increase of the substrate temperature up to 225°C leads to smooth, completely coalesced epitaxial C60-thin films characterized by a roughness smaller than 1.5 nm, a mosaic spread Δω of 0.1° and an azimuthal alignment ΔΦ of 0.45°.
Low Temperature Formation of β-SiC by C60Deposition on Silicon
Authors: Henke S. , Rauschenbach B. , Stritzker B. 
Published: April 2011

ABSTRACTBy deposition of C60 on silicon at moderate temperatures (800°C … 900°C) the formation of thin epitaxial β-SiC-films on Si could be proved. C60 -molecules were deposited onto Si(001) and Si(111) in high-vacuum at constant deposition rates for some hours. The thickness and the composition of the formed layers are determined by Rutherford-Backscattering (RBS). The thickness of the layers varied between about 50nm and 200nm in dependence of the deposition parameters. From the shape of the RBS-spectra only β-SiC can be identified. SiC-grains with a mean size of about 500 nm have been observed by atomic force microscopy (AFM). X-ray diffraction (XRD) pole figure measurements demonstrate the heteroepitaxial growth of β-SiC on Si It can be shown by XRD that only the cubic structure (β-SiC) of the different polytypes of SiC was formed during the carbonization process. The formation of growth defects (twins) can be observed.
Nano and micro structure of laser damaged fullerite single crystal
Authors: Manfredini M. , Milani P. 
Published: April 2011

ABSTRACTWe have studied the nano and micro structure of the product resulting from high fluence laser irradiation of C60 single crystal. Raman spectra reveal that, in the presence of oxygen, amorphous carbon (a-C) is formed. The laser heating of the sample promotes fullerene o:ddation and cage opening reactions: the new carbon phase is originated by the coalescence of C60 fragments. The irradiance threshold tbr a-C tbrmation is discussed. Brillouin spectroscopy shows that the acoustic properties of the irradiated material are typical ofa higly porous material similar to carbon aerogels. Under irradiation in an inert environment C60 degradation is not observed, even for high power densities.
Morphology of Nanometric Boron Nitride Powders Produced by Laser Pyrolysis
Authors: Willaime F. , Boulanger L. , Cauchetier M. 
Published: April 2011

ABSTRACTUltrafine boron nitride powders were synthesized by laser driven reactions in BC13-NH3 mixtures. The structure and morphology of the graphitic nanoparticles generated in this process were investigated by high-resolution electron microscopy. Polyhedral concentric shells (ranging in size from 30 nm to more than 100 nm) are a major constituent of the as-pyrolyzed powder. This onion-like configuration is very similar to that observed in carbon materials. After heat treatment at 1650°C under nitrogen atmosphere, plate-like particles with a few perfectly flat graphitic sheets (10 to 50 layer thick, 50 nm in diameter) are formed.
Characterization of C60 Fullerene in Carbon Disulfide Solvent Using Intermediate Angle Neutron Scattering
Authors: Spooner Steve , Zarestky J. L. , Affholter K. A. 
Published: April 2011

ABSTRACTIn recent characterization of fullerenes by small angle neutron scattering use was made of the Guinier scattering regime to determine the radius of gyration of the fullerene molecules. In the present work the HB-1A spectrometer at the High Flux Isotope Reactor at Oak Ridge National Laboratory was used to measure the scattering from C60 in CS2 solvent. The scattering covers a range which includes scattering intensity oscillations associated with the C60 shell structure. These oscillations are used to measure the C60 molecule size. Assumption of a carbon shell radius of 3.57Å fits the scattering minima. This radius and the assumption of a solvent cavity radius of 5.93 Å gives a good fit to the whole scattering range. However, modeling to remove a remaining scattering intensity discrepancy at low angles requires the addition of a small solvent density excess near the C60 molecule.
The Binary Phase Diagram Naphthalene-C60
Authors: Hidalgo-Quesada Rafael , Zhang Xin-Yu , Giessen Bill C. 
Published: April 2011

ABSTRACTMolten naphthalene has considerable solubility for C60 (∼5 10−3 in mole fraction) making it a potential solvent for fullerenes; the phase diagram is therefore important. It was also of interest to study whether C60 displays the same anomalous solubility behavior in naphthalene as in hexane, CS2, and toluene, where the solubility increases with temperature up to a maximum near room temperature and decreases subsequently.The naphthalene-C60 eutectic temperature was determined by DSC; the solubility of C60 in the liquid solution up to ∼180 °C was derived by UV spectrophotometry and found to decrease monotonically with increasing temperature from a mole fraction of 5 · 10−3 at the eutectic (∼79.5 °C) to 1.5 · 10−3 at 165 °C; thus, it shows a higher-temperature C60 solubility decrease (with increasing temperature) analogous to the other solutions, while a potential lowertemperature solubility increase (with increasing temperature) is masked by the eutectic. A binary phase diagram based on these data is proposed.
Field Emission and Growth of Fullerene Nanotubes
Authors: Rinzler Andrew G. , Hafner Jason H. , Colbert Daniel T. , Smalley Richard E. 
Published: April 2011

ABSTRACTEfforts to control the growth of individual carbon nanotubes from nanotube seed crystals have led to a characterization of their field-induced electron emission behavior. The application of a bias voltage in our growth apparatus was motivated by the prolific formation of nanotubes in the carbon arc growth method, in which the electric field appears to play a central role. We report here the ability to achieve various tube tip configurations by the controlled application of voltage, heat and chemicals to an individual nanotube, and that these states are well characterized by the emission currents they induce.
MOCVD of Ferroelectric Pb(Zr,Ti)O3 and (Pb,La)(Zr,Ti)O3 Thin Films for Memory Device Applications
Authors: Shimizu Masaru , Shiosaki Tadashi 
Published: April 2011

ABSTRACTThe advantages of MOCVD for the growth of Pb(Zr,Ti)O3 (PZT) and (Pb,La)(Zr,Ti)O3(PLZT) thin films were discussed, with emphasis on the controllability of film composition, crystalline structure and electrical properties. The possibilities of lowering the processing temperature and scaling up the process to commercial-based production were investigated. The preparation of PZT films and electrodes with a specific focus on improving the I-V and fatigue characteristics was also investigated.
Effects of Rheological Characteristics of Sol on Preferential Orientation of Pb(Mg,Zn)1/3Nb2/3O3 Thin Films
Authors: Jang Hyun M. , Cho Mun K. 
Published: April 2011

ABSTRACTThin films of Pb(Mg,Zn)1/3Nb2/3O3 were fabricated by spin casting the Pb-Mg-Zn-Nb-0 complex alkoxide sols on (111)Pt-coated MgO (100) planes. It was observed that the rheological characteristics of sol greatly influenced the orientation of perovskite grains after thin-film formation. A strong preferential orientation of (100)-type planes of the perovskite grains was obtained in the thin films derived from the sols exhibiting pseudoplastic behavior. Small angle X-ray scattering experiment in the Porod region was performed to correlate the observed preferential orientation with the network structure of precursors at various stages of aging. It was shown that weakly branched precursor chains led to highly oriented grains after thin-film formation.
Preparation and Characterization of PMN (PbMgxNb1−xOz) Films by Sputtering
Authors: Cross J.S. , Tsukada M. , Kurihara K. , Kamehara N. , Niwa K. 
Published: April 2011

ABSTRACTThin films of Pb(MgxNb1−x)Oz were produced by reactive sputtering from a lead target and columbite magnesium niobate powder targets at temperatures of 500–700°C on Pt/Ti/Si, Pt/SiO2/Si, MgO(lOO) and SrTiO3(100) substrates. The films in general deposited on Pt consisted of PbO and pyrochlore phases depending upon the deposition temperature. ICP analysis revealed that the films contained slightly less Mg than the target. This was attributed to negative ion preferential resputtering of the film within the discharge. However, films deposited at 650°C on MgO and SrTiO3 substrates from a lead target and magnesium niobate target which contained excess MgO, contained a highly oriented perovskite (100) Pb(Mg1/3Nb2/3)O3 [PMN] phase according to X-ray diffraction analysis. It was observed that the substrate composition and orientation greatly influenced the crystallinity of the deposited films.
SrxBa(1−x)TiO3 Thin Films for Active Microwave Applications
Authors: Horwitz J.S. , Pond J.M. , Tadayan B. , Auyeung R.C.Y. , Dorsey P.C. , Chrisey D.B. , Qadri S.B. , Muller C. 
Published: April 2011

ABSTRACTThe dielectric constant, loss tangent and Curie temperature for SrxBa(1−x)TiO3 (SBT) thin films with x = 0.2 – 0.8 have been investigated at microwave frequencies. SBT films (0.5 -3 μm thick) were grown on (100) MgO and LaAlO3 substrates by pulsed laser deposition at substrate temperatures from 850 – 900 °C in 0.35 Torr of oxygen. Deposited ferroelectric films were single phase, highly oriented, and characterized by x-ray rocking curve widths of < 0.5°. Highly oriented SBT films with x-ray rocking curve widths of 72 arc seconds were observed. In general, the thin film dielectric constant at microwave frequencies is low (200–950) compared to the reported bulk value, but strongly dependent on the Sr/Ba ratio. Biasing of a ferroelectric interdigital capacitor (< 200 kV/cm) produces a change in the dielectric constant which resulted in a phase shift in the reflected signal (S11) measured as a function of frequency from 100 MHz to 10 GHz. The dielectric loss tangent measurement, as measured at room temperature and 9.2 GHz, ranges from 0.1 to 1.2 × 10−3 and depends on the Sr/Ba ratio. These data show that SBT thin films are suitable for the development of frequency tunable microwave circuits and components.
Pulsed Laser Deposition of Ferroelectric Multilayer Capacitors YBa2Cu3O7−δ/BaTiO3/YBa2Cu3O7−δ on Si(100) Substrates
Authors: Luo J. , Li Q. , Fenner D.B. , Liu S. , Hamblen W.D. , Wu X.D. 
Published: April 2011

ABSTRACTFerroelectric multilayer capacitors (YBCO/BTO/YBCO) are fabricated on YSZ buffered Si (100) substrates by using pulsed-laser deposition technique. The deposition process is monitored in situ by using a Fourier Transform Infrared Spectrometer (FTIR), which measures the film's deposition rate and dielectric constant during the growth process. All four oxide layers in such a multilayer capacitor are grown in situ without breaking the vacuum, and without lowering the substrate temperature to below 600°C. The electrical properties and microstructures of the multilayer capacitor are studied and the optimal deposition condition are identified. Sharp resistive transitions are achieved for both the top and the bottom YBCO layers with on-sets at 90 K, zero resistance at 89 K for the bottom layer and 88K for the top layer. X-ray diffraction θ-2θand φ scans indicate that all four deposited oxide layers have their c-axis perpendicular to the substrate, and have less that 10% in-plane misorientation. The dielectric constant of the BTO layer is over 210. Hysteresis P-E characteristics and current-voltage curves are also measured to determine dielectric properties of the barium titanate films. Preliminary results with LaSrCoO (LSCO) electrode layer are also presented.
Pulsed Excimer Laser Deposition and Rapid Thermal Annealing of Ferroelectric Pb(Zr0.52Ti0.48)O3 Thin Films on Si-on-Insulator
Authors: Chen Yiqing , Zheng Lirong , Lin Chenglu , Xu Xinglong , Zou Shichang 
Published: April 2011

ABSTRACTStoichiometric films of Pb(Zr0.52Ti0.48)O3 (PZT) were successfully deposited on Si-on-Insulator (SOI) substrates, with and without a platinum electrode, by an ArF (λ=193nm) pulsed excimer laser. Rapid thermal annealing (RTA) was used to transform amorphous or pyrochlore phase into ferroelectric perovskite phase. The film structure, composition, morphology, interface and electrical properties were studied by x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM) and Sawyer-Tower circuit, respectively. It was found that there was a narrow operational window of annealing time for PZT films at fixed annealing temperature. Pure ferroelectric perovskite phase with mainly (100) and (110) orientations could be obtained in PZT films on Pt coated SOI substrates. The interfaces between the PZT films and both Si and Pt//Si were very abrupt, indicating there was no interdiffusion between them. Ferroelectric hysteresis loops showed a remanent polarization of 15μC/cm2 and a coercive field of 50KV/cm.
Pulsed Laser Deposition of Epitaxial LiNbO3 Films on Sapphire Substrates Using a Single Crystal Targets
Authors: Lee See-Hyung , Noh Tae W. , Lee Jai-Hyung , Kim Young-Gi 
Published: April 2011

ABSTRACTPulsed laser deposition was used to grow epitaxial LiNbO3 films on sapphire(0001) substrates with a single crystal LiNbO3 target. Using deposition temperatures below 450 °C, LiNbO3 films with correct stoichiometry could be grown without using Li-rich targets. Rutherford backscattering spectrometry measurements showed that the oxygen to niobium ratio is 3.00 ± 0.15 to 1.00. It was also found that the crystallographic orientations of the LiNbO3 films could be controlled by adjusting the oxygen pressure during deposition. An x-ray pole figure shows that epitaxial LiNbO3 films were grown on sapphire(0001), but with twin boundaries.
Reactive Ion Etching Damage to Ferroelectric Thin Films Capacitors
Authors: Pan W. , Thio C.L. , Desu S.B. , Chung Cheewon 
Published: April 2011

ABSTRACTReactive ion etching damage to sputtered Pt/PZT/Pt ferroelectric capacitors was studied using Ar and CHCIFCF3 etch gases. Electrical properties, hysteresis, fatigue, and leakage current of PZT capacitors, before and after etching, were compared to examine the etching damage. It is found that the damage effects depend on etching time and are mainly due to the physical bombardment effect. The PZT capacitors etched with CHCIFCF3 plasma showed less damage than those etched in Ar plasma. The electric properties of etched Pt/PZT/Pt capacitors are recovered by annealing at 400 °C for 30min.
Processing and Oxidation of Nitride Stabilized 18Cr-20Ni Stainless Steel
Authors: McDowell C. S. , Basu S. N. , Ando T. 
Published: April 2011

AbstractThe present investigation explores the use of nitride precipitates for grain-size stabilization in a 18Cr-2ONi austenitic stainless steel for high temperature applications in oxidizing atmospheres. The potential for reductions in alloying contents of such steels has become a focus of research out of concern for the conservation of strategic alloying elements such as Cr. In order for the alloy to maintain superior oxidation resistance, it must sustain a fine grain size by virtue of effective grain boundary pinning by stable precipitates.Al and Ti microalloyed 18Cr-20Ni steels have been nitrided using rapid solidification processing (spray forming) and subjected to thermomechanical treatments to precipitate nitrides from the supersaturated solid solutions. The spray formed deposits were cold rolled to increase the density of dislocations, which act as sites for nucleation of nitride precipitates. The alloys were then annealed to nucleate and grow the precipitates, followed by cold rolling and recrystallization to generate a stable, fine grained microstructure. The Ti-microalloyed steel demonstrated high-temperature grain size stability by maintaining a grain size of≈7μm after 600h at 1000°C.The Ti-microalloyed steel has been subjected to isothermal oxidation in air at 900°C. The results of preliminary oxidation experiments are reported. The spray deposited and thermomechanically processed alloy demonstrated high-temperature oxidation behavior superior to conventionally processed (hot rolled and annealed) alloys.
Mechanical Behavior of Energetic Materials During High Acceleration in An Ultracentrifuge
Authors: Lanzerotti M. Yvonne D. , Sharma J. 
Published: April 2011

AbstractThe mechanical behavior of explosives subjected to high acceleration (high g) has been studied in an ultracentrifuge. The experiments reported here reveal new information on the mechanical behavior of such materials and the influence of grain size on the fracture process. Through measurement and analysis of fracture surfaces, we have found that predominately intergranular failure occurs when the shear or tensile strength of the explosive is exceeded. We have found that the mechanical strength of melt-cast polycrystalline TNT varies inversely with crystal size. That is, if the sample consists of large, homogeneous crystals, these are found to separate from the sample at lower g-levels due to the larger mass-to-binding surface area ratio of the crystals. Conversely, smaller original crystallites are found to separate at higher g-levets due to the smaller mass-to-binding surface area ratio. Our results show that single crystals of TNT fracture under a higher g-level at crystal defects. We have also found that the fracture acceleration of Octol decreases with increasing percent TNT and decreasing percent HMX. Hexanitrostilbene (HNS) has been shown by other investigators to be an effective additive to prevent growth of large TNT grains. We have found that the fracture acceleration increases when HNS is added to Octol.
Synthesis of Nickel and Iron Ultrafine Powders and Mechanical Properties of Their Compacts
Authors: Alymov M. I. , Leontieva O. N. , Myshilyaev M. M. 
Published: April 2011

AbstractNickel and iron ultraflne powders have been produced by the method of hydrogen reduction of the low-water hydroxides obtained by geterogeneous interaction between solid salt and alkaline solution. Suggested method allows to obtain ultrafine powders with narrow particle size distribution and low impurity contents. Bulk samples based on nickel and iron ultrafine powders were produced by hot Isostatic pressing and high-temperature gas extrusion methods.
Mass Transport Through Polycrystalline Microstructures
Authors: Swiler T. P. , Holm E. A. , Young M. F. , Wright Steven A. 
Published: April 2011

AbstractMass transport properties are important in polycrystalline materials used as protective films. Traditionally, such properties have been studied by examining model polycrystalline structures, such as a regular array of straight grain boundaries. However, these models do not account for a number of features of real grain ensembles, including the grain size distribution and variations in grain shape. In this study, a finite difference scheme is developed to study transient and steady-state mass transport through realistic two dimensional polycrystalline microstructures. Comparisons with the transport properties of traditional model microstructures provide regimes of applicability of such models. The effects of microstructural parameters such as average grain size are examined.
Reaction Rate of Liquid-Quenchied Water-Floating Alloy
Authors: Aida T. , Nishi Y. 
Published: April 2011

AbstractWe investigate a reaction rate of Mg-Li Al alloy (specific gravity is 0.95) in water. The hydrogen gas is mainly generated as follows : Li + H2O → LiOH + 1/2 H2 ↑. Using the volume of hydrogen gas, the reaction rate is estimated. The apparent activation energy (E) is 4.63 kcal/mol for the early reaction period. It is approximately equal to that of the water diffusion. On the other hand, the E is 9 kcal/mol after the early reaction period at the 2 ml (the volume of hydrogen gas). Furthermore, we succeed to prevent the sample against the reaction by the use of coating paints.