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121.
Cheol Park John Wilkinson Sumanth Banda Zoubeida Ounaies Kristopher E. Wise Godfrey Sauti Peter T. Lillehei Joycelyn S. Harrison 《Journal of Polymer Science.Polymer Physics》2006,44(12):1751-1762
While high shear alignment has been shown to improve the mechanical properties of single‐wall carbon nanotube (SWNT)‐polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field‐induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high‐resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1751–1762, 2006 相似文献
122.
The improvement of the lean blowout limit of bluffbody stabilized methane flames is investigated. The flame configuration
consists of a hybrid of partially and fully premixed flames, which is produced by injecting methane jets from a streamline-shaped
bluffbody into a fully premixed methane/air crossflow. Additional geometric modifications from the original bluffbody base
are such that the base has two-dimensionally modified geometries and three-dimensional local cavities. We observe that the
blowout limit of the hybrid configuration is extended by up to ~12% (in terms of the equivalence ratio of the crossflow) with
the modified geometries. Gas chromatographic sampling and particle image velocimetry (PIV) show that high fuel mole fraction
regions coexist with regions of low speed flow for the modified geometries. Further PIV analysis shows that the downstream
flow fields of the modified bases generally have a larger number of incoherent vortices and lower strain rate in comparison
with those of the unmodified base. 相似文献
123.
Cheol Park Jae‐Woo Kim Godfrey Sauti Jin Ho Kang Conrad S. Lovell Luke J. Gibbons Sharon E. Lowther Peter T. Lillehei Joycelyn S. Harrison Negin Nazem Larry T. Taylor 《Journal of Polymer Science.Polymer Physics》2012,50(6):394-402
Although many metal decorated nanotubes and nanowires appear in the literature, well‐dispersed metal decorated nanotube polymer composites have rarely been reported because of the excessive density mismatch between the decorated nanotubes and polymer matrix. Here, we report a novel method to prepare well‐dispersed, highly functional, metallized nanotube polymer composites (MNPCs) that possess remarkably improved electrical conductivity and mechanical toughness. The MNPCs are prepared by supercritical fluid impregnation of an organometal compound into a premade well‐dispersed single wall carbon nanotube‐polymer composite film. The infused precursor preferentially migrates towards the nanotubes to undergo spontaneous reduction and form nanometer‐scale metal particles leading to an increase in the conductivity of the MNPC films. The environmentally friendly supercritical fluid impregnation process significantly improved the toughness of the composite films, regardless of the presence of metal. Additional functionality can be imparted into the resulting MNPC by infusing other precursors such as magnetic and catalytic metal compounds. © 2011 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys, 2012 相似文献
124.
A search for mechanisms for benzoylation of dichlorobenzenes which are consistent not only with the nature and relative proportions of the eight products but also with the pattern of the non-additivity of substituent effects on the reaction rates, produced just one candidate. It involves chloronium ion migration and secondary protodechlorination in addition to the usual displacement of protons by acylium ions. 相似文献
125.
Brendan B. Godfrey 《General Relativity and Gravitation》1972,3(1-2):3-16
Static, axisymmetric, vacuum metrics (commonly called Weyl metrics) are classified according to the homothetic motions they admit, with all having more than two homothetic motions explicitly computed. Within the two new families of spacetimes so determined, none of the metrics is asymptotically flat. Although most of the horizons are unlike that of the Schwarzschild metric, it is shown that they nonetheless all fall within a classification scheme previously developed for two-dimensional static metrics. TheC — metric and the question of directional singularities are also briefly considered.Based on part of the author's doctoral dissertation submitted to Princeton University, 1970. This work has been assisted in part by NSF Grant No. GP7669. 相似文献
126.
I. Jenkins P. J. Nolan A. J. Kirwan M. J. Godfrey P. J. Bishop D. J. Thornley K. L. Ying R. Wadsworth 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):405-406
The decay scheme for134Nd has been extended to high spin and a new negative parity band discovered. These results are discussed in terms of particle alignments. 相似文献
127.
Michael J. Blandamer Elizabeth Godfrey Jill R. Membrey 《Journal of solution chemistry》1974,3(12):881-887
A treatment which predicts the solubilities of gases in solvent mixtures is examined in the context of the analysis of kinetic data for reactions in aqueous mixtures. The treatment is qualitatively successful to some extent in resolving the effects of changes in the initial state of the reacting substrate in the activation parameters. 相似文献
128.
Ngoc Thanh Thuy Tran Dipendra Dahal Godfrey Gumbs Ming-Fa Lin 《Structural chemistry》2017,28(5):1311-1318
We have investigated the way in which the concentration and distribution of adatoms affect the geometric and electronic properties of graphene. Our calculations were based on the use of first principle under the density functional theory which reveal various types of π-bonding. The energy band structure of this doped graphene material may be explored experimentally by employing angle-resolved photo-emission spectroscopy (ARPES) for electronic band structure measurements and scanning tunneling spectroscopy (STS) for the density-of-states (DOS) both of which have been calculated and reported in this paper. Our calculations show that such adatom doping is responsible for the destruction or appearance of the Dirac-cone structure. 相似文献
129.
Robert C. Godfrey Helen E. Jones Nicholas J. Green Andrew L. Lawrence 《Chemical science》2022,13(5):1313
The bicyclo[2.2.2]diazaoctane alkaloids are a vast group of natural products which have been the focus of attention from the scientific community for several decades. This interest stems from their broad range of biological activities, their diverse biosynthetic origins, and their topologically complex structures, which combined make them enticing targets for chemical synthesis. In this article, full details of our synthetic studies into the chemical feasibility of a proposed network of biosynthetic pathways towards the brevianamide family of bicyclo[2.2.2]diazaoctane alkaloids are disclosed. Insights into issues of reactivity and selectivity in the biosynthesis of these structures have aided the development of a unified biomimetic synthetic strategy, which has resulted in the total synthesis of all known bicyclo[2.2.2]diazaoctane brevianamides and the anticipation of an as-yet-undiscovered congener.A divergent biomimetic total synthesis of all known bicyclo[2.2.2]diazaoctane brevianamide alkaloids has been achieved. These synthetic studies have also resulted in the anticipation of an as-yet-undiscovered congener, which we name brevianamide Z. 相似文献
130.
Dr. Ngoc Thanh Thuy Tran Dr. Duy Khanh Nguyen Dr. Shih-Yang Lin Prof. Godfrey Gumbs Prof. Ming-Fa Lin 《Chemphyschem》2019,20(19):2473-2481
The revealing properties of transition metal (T)-doped graphene systems are investigated with the use of the first-principles method. The detailed calculations cover the bond length, position and height of adatoms, binding energy, atom-dominated band structure, adatom-induced free carrier density as well as energy gap, spin-density distributions, spatial charge distribution, and atom-, orbital- and spin-projected density-of-states (DOS). The magnetic configurations are clearly identified from the total magnetic moments, spin-split energy bands, spin-density distributions and spin-decomposed DOS. Moreover, the single- or multi-orbital hybridizations in T−C, T−T, and C−C bonds can be accurately deduced from the careful analyses of the above-mentioned physical quantities. They are responsible for the optimal geometric structure, the unusual electronic properties, as well as the diverse magnetic properties. All the doped systems are metals except for the low-concentration Ni-doped ones with semiconducting behavior. In contrast, ferromagnetism is exhibited in various Fe/Co-concentrations but only under high Ni-concentrations. Our theoretical predictions are compared with available experimental data, and potential applications are also discussed. 相似文献