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Electron Microscopy Measurements (electron + microscopy_measurement)
Kinds of Electron Microscopy Measurements Selected AbstractsStructural characterization of manganese-substituted nanocrystalline zinc oxide using small-angle neutron scattering and high-resolution transmission electron microscopyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2009B. Roy A series of zinc oxide (ZnO) nanoparticles, substituted with manganese di-oxide, have been synthesized through a modified ceramic route using urea as a fuel. X-ray diffraction and high-resolution transmission electron microscopy studies indicate that the sizes of the ZnO particles are of nanometer dimension. Particles remain as single phase when the doping concentration is below 15,mol%. Small-angle neutron scattering indicates fractal-like agglomerates of these nanoparticles in powder form. The size distributions of the particles have been estimated from scattering experiments as well as microscopy studies. The average particle size estimated from small-angle scattering experiments was found to be somewhat more than that obtained from X-ray diffraction or electron microscopy measurement. [source] Abrupt Morphology Change upon Thermal Annealing in Poly(3-Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Minjung Shin Abstract The in situ morphology change upon thermal annealing in bulk heterojunction blend films of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) is measured by a grazing incidence X-ray diffraction (GIXD) method using a synchrotron radiation source. The results show that the film morphology,including the size and population of P3HT crystallites,abruptly changes at 140,°C between 5 and 30,min and is then stable up to 120,min. This trend is almost in good agreement with the performance change of polymer solar cells fabricated under the same conditions. The certain morphology change after 5,min annealing at 140,°C is assigned to the on-going thermal transition of P3HT molecules in the presence of PCBM transition. Field-emission scanning electron microscopy measurements show that the crack-like surface of blend films becomes smaller after a very short annealing time, but does not change further with increasing annealing time. These findings indicate that the stability of P3HT:PCBM solar cells cannot be secured by short-time annealing owing to the unsettled morphology, even though the resulting efficiency is high. [source] Carbon Nanotube Junctions: Multibranched Junctions of Carbon Nanotubes via Cobalt Particles (Adv. Mater.ADVANCED MATERIALS, Issue 44 200944/2009) Junctions between different carbon nanotubes (CNTs) created using cobalt particles as central nodes (background) are demonstrated by Ming-Sheng Wang and co-workers on p. 4477. The process involves high-temperature electron irradiation of areas where a metal particle is located at the overlapping region of two CNTs. In situ transmission electron microscopy measurements show that the junctions are electrically conductive and mechanically robust. The extension of this technique towards creating more complicated structures, such as a 3D CNT network, is also depicted in the cover. [source] Multibranched Junctions of Carbon Nanotubes via Cobalt ParticlesADVANCED MATERIALS, Issue 44 2009Julio A. Rodríguez-Manzo Junctions between different carbon nanotubes are created using cobalt particles as central nodes (see image). The process involves high temperature and electron irradiation of areas where a metal particle is located at the overlapping region of two nanotubes. In situ transmission electron microscopy measurements show that the junctions are electrically conductive and mechanically robust. A high breaking strength of 1,5,GPa is found for the junctions. [source] Synthesis of cyclodextrin-based polymers and their use as debittering agentsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Arianna Binello Abstract Cyclodextrins (CDs) and their derivatives are used to suppress unpleasant tastes and odors or to achieve a controlled release of certain food constituents. This article describes the synthesis by nonconventional methods of (1) crosslinked, insoluble CD polymers and (2) water-soluble, CD-grafted carboxymethylchitosan and carboxymethylcellulose. The CD polymers were obtained by the reaction of ,-CD with one of the following crosslinking agents: epichlorohydrin, diphenyl carbonate, or hexamethylene diisocyanate. Their preparations were usually carried out under high-intensity ultrasound, which resulted in much shorter reaction times and narrower distributions of particle size (as determined by scanning electron microscopy measurements). A novel, insoluble CD polymer was obtained by reticulation under microwaves of propargyl-,-CD with 1,3-bis(azidomethyl)benzene through Huisgen 1,3-dipolar cycloaddition. Short columns packed with the insoluble polymers were found to efficiently sequester naringin from aqueous solutions; successively, they could be easily regenerated by a counter-current ethanol wash that also achieved an excellent recovery of the flavonoid. Differential scanning calorimetry thermograms showed that the crosslinked CD polymers formed inclusion complexes with naringin. The soluble polymers also interacted with bitter flavonoids of citrus fruits (naringin and limonin), as shown by the results of sensorial panel tests, in which they behaved as bitter-masking agents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Fast and Almost Complete Nitridation of Mesoporous Silica MCM-41 with Ammonia in a Plug-Flow ReactorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Fumitaka Hayashi The title reaction proceeded well to yield silicon (oxy)nitride at 973,1323 K using a plug-flow reactor. The degree of nitridation was studied as a function of temperature and time of nitridation, the sample weight, and the flow rate of ammonia. It was dependent on the reaction temperature and the amount of ammonia supplied per sample weight. The nitridation at 1273 K for 10,25 h yielded the oxynitride with 36,39 wt% nitrogen, which was very close to 40 wt% of Si3N4. Characterization with X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy measurements, and nitrogen adsorption revealed the conversion of MCM-41 to the corresponding oxynitride without essential loss of the mesoporous structure, the decrements of the lattice constant and the pore diameter by 20,35%, and the increments of the wall thickness by ca. 45%. Solid-state 29Si nuclear magnetic resonance spectra during the nitridation clearly showed fast decrease in SiO4 species and slow in SiO3(OH). Various intermediate species, SiOxNy(NH2 or NH)z, were observed to be formed and finally, ca. 70% SiN4 species, ca. 20% SiN3(NH2 or NH), and ca. 10% SiON2(NH2 or NH) were produced, being consistent with the results of the above mentioned elemental analysis. [source] Using forward calculations of the magnetic field perturbation due to a realistic vascular model to explore the BOLD effectNMR IN BIOMEDICINE, Issue 6 2008José P. Marques Abstract This paper assesses the reliability of the infinite cylinder model used previously in the literature to simulate blood oxygenation level dependent (BOLD) signal changes. A three-dimensional finite element method was applied to a realistic model of the cortical vasculature, and the results compared with those generated from a simple model of the vasculature as a set of independent, randomly oriented, infinite cylinders. The realistic model is based on scanning electron microscopy measurements of the terminal vascular bed in the superficial cortex of the rat. Good agreement is found between the two models with regard to the extravascular R2* and R2 dependence on the cerebral blood volume and blood oxygenation fraction. Using the realistic model, it is also possible to gain further understanding of the relative importance of intravascular and extravascular BOLD contrast. A simple parameterisation of the dependence of the relaxation rates on relative cerebral blood volume and blood,tissue susceptibility difference was carried out, allowing discussion of the variation in the form of the haemodynamic response with field strength. Copyright © 2007 John Wiley & Sons, Ltd. [source] Dispersing silicon nanoparticles in a stirred media mill , investigating the evolution of morphology, structure and oxide formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2007A. Reindl Abstract Silicon nanoparticles were dispersed for 24 hours in 1-butanol using a stirred media mill. Via this process intrinsically stable suspensions (in regard to aggregation) of Si nanoparticles were produced after 6 hours of dispersing. The evolution of morphology, particle size and structure was investigated by dynamic light scattering, X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy as a function of dispersing time. The average crystallite size decreased from about 18 nm down to about 10 nm within 24 hours of milling as determined by X-ray diffraction and Raman scattering measurements. In addition careful analysis of the Raman spectra revealed a decrease of the crystalline volume fraction from 75% down to 24% and a corresponding increase of the amorphous phase. The microstructural development with varying crystallite size and crystalline volume fraction was directly confirmed by transmission electron microscopy measurements. Elemental analysis showed an increase of oxygen content that was directly proportional to the increase in specific surface area of the silicon nanoparticles during the dispersing process. The surface chemistry of the Si nanoparticles was analyzed by diffuse reflectance infrared Fourier transform spectroscopy that indicated vibrational bands of HSi,Si3,xOx, SiOx, and residual 1-butanol. The final product of the dispersing process seems to be a two-phase mixture of amorphous Si and Si nanocrystallites covered with SiOx on the surface. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] GaN nanorods and LED structures grown on patterned Si and AlN/Si substrates by selective area growthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Shunfeng Li Abstract GaN nanorods (NRs) show promising applications in high-efficiency light emitting diodes, monolithic white light emission and optical interconnection due to their superior properties. In this work, we performed GaN nanostructures growth by pre-patterning the Si and AlN/Si substrates. The pattern was transferred to Si and AlN/Si substrates by photolithography and inductively-coupled plasma etching. GaN NRs were grown on these templates by metal-organic vapour phase epitaxy (MOVPE). GaN grown on Si pillar templates show a truncated pyramidal structure. Transmission electron microscopy measurements demonstrated clearly that the threading dislocations bend to the side facets of the GaN nanostructures and terminate. GaN growth can also be observed on the sidewalls and bottom surface between the Si pillars. A simple phenomenological model is proposed to explain the GaN nanostructure growth on Si pillar templates. Based on this model, we developed another growth method, by which we grow GaN rod structures on pre-patterned AlN/Si templates. By in-situ nitridation and decreasing of the V/III ratio, we found that GaN rods only grew on the patterned AlN/Si dots with an aspect ratio of about 1.5 - 2. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hybrid metal/silicon nanocomposite systems and their catalytic activityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009Sergej Polisski Abstract In this work we studied the reduction of metal salts and their mixtures on extended hydrogen-terminated porous silicon surfaces. For these experiments we employed salts of Au, Ag, Pt and their mixtures. We show that the size and shape of resulting metal and metal alloy nanoparticles depends on the pore morphology. This has been confirmed by transmission electron microscopy measurements and plasmon resonance experiments. Finally we demonstrate catalytic activity of formed Pt nanoparticles in PSi matrix via monitoring the conversion of carbon monoxide. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cure kinetics and conductivity of rigid rod epoxy with polyaniline as a curing agentPOLYMER COMPOSITES, Issue 10 2009Tiezhu Fu The samples of rigid rod epoxy resin (4,4,-diglycidyl (3,3,,5,5,-tetramethylbiphenyl) epoxy resin (TMBP)) with different weight contents of polyaniline (PANI) as a curing agent were prepared. The kinetics of curing reaction between TMBP and PANI was analyzed by dynamic differential scanning calorimetry in the temperature range of 25,300°C. The results showed that the heat of cure reaction of TMBP/PANI sample with 10 wt% PANI was larger than those of others. The active energies with different curing conversions of TMBP/PANI sample with 10 wt% PANI were calculated by iso-conversional method using the Coats-Redfern approximation. The results showed that the activation energy was dependent on the degree of conversion. The morphology of the cured samples was detected by scanning electron microscopy measurements. The relationship between morphology and conductivity of cured samples was researched. The conductivities increased from 2.7 × 10,4 to 9.5 × 10,4 S/cm with the increase of PANI from 5 to 20 wt% in cured samples. The thermal stabilities of cured TMBP/PANI samples were examined by thermogravimetric analysis. The results showed that the cured TMBP/PANI can be promising to use as a conducting adhesive. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Synthesis, and structural and morphological characterization of iron oxide,ion-exchange resin and ,cellulose nanocomposites,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2001Lorenza Suber Abstract The synthesis and the comparative structural and morphological study of iron oxide nanoparticles in polystyrene-based ion-exchange resins and cellulosics are reported. The synthesis of magnetite was performed under nitrogen atmosphere by an in situ method in the presence of the matrix itself. Scanning and transmission electron microscopy measurements led to a detailed characterization of matrix morphology and of magnetic particle structure, size and morphology. The results show that the matrix influences the iron oxide particle size; the average size is about 7,nm in the resins and 25,nm in the celluloses. In the resins, particles are present inside the pores and as aggregates on the surface of the resin beads, whereas in the cellulose they are present on the surface and in the swollen network of the microfibers constituting the single fibers. Copyright © 2001 John Wiley & Sons, Ltd. [source] Evolution of the cercal sensory system in a tropical cricket clade (Orthoptera: Grylloidea: Eneopterinae): a phylogenetic approachBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010LAURE DESUTTER-GRANDCOLAS The diversity of sensory systems in animals has poorly been explored on a phylogenetic basis at the species level. We addressed this issue using cricket cerci, comprising abdominal appendages covered with touch- and air-sensitive hairs. Scanning electron microscopy measurements and spatial analyses of hair positioning were used to quantify the structural diversity of cercal structures. Eighteen Eneopterinae and two Gryllidae (outgroups) were studied from a phylogenetic perspective. Cerci were revealed to be complex, diverse, and variable between cricket species. Based on maximum likelihood estimations, the ancestral Eneopterinae cercus had a small size, and its hair equipment allowed the use of both air and touch mechanoreception. The evolution of Eneopterinae cerci was mainly unconstrained by the phylogeny; it was rather a punctuated process, involving apical transformations, and was mostly unrelated to environmental patterns. All studied species have enhanced their overall perceptive capacities compared to the ancestor. Most have longer cerci with more and/or longer hairs. Sensory abilities have improved either in the direction of touch or air movement detection, or both, without discarding the potential for any sensory capacity that was already present ancestrally. This pattern is consistent with the hypothesis of an evolutionary trade-off for sensory performances. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 614,631. [source] | ||||||||||||||||