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Transmission Electron Microscopy Techniques (transmission + electron_microscopy_techniques)
Selected AbstractsSensory structures involved in prey detection on the labial palp of the ant-hunting beetle Siagona europaea Dejean 1826 (Coleoptera, Carabidae)ACTA ZOOLOGICA, Issue 3 2010Anita Giglio Abstract Giglio, A., Ferrero E.A., Perrotta, E., Talarico, F.F. and Zetto Brandmayr, T. 2010. Sensory structures involved in prey detection on the labial palp of the ant-hunting beetle Siagona europaea Dejean 1826 (Coleoptera, Carabidae). ,Acta Zoologica (Stockholm) 91: 328,334 The ultrastructure and distribution of sensilla on the labial palps of a myrmecophagous carabid beetle, Siagona europaea, were investigated using scanning and transmission electron microscopy techniques. Five types of sensilla were identified: three types of sensilla basiconica on the apical sensory area and two types, one sensillum trichodeum and one coeloconicum, on the external palp surface. On morphological grounds, the s. basiconica type 1 were considered as olfactory, the type 2 as gustatory, the type 3 and the s. trichodeum as mechanoreceptive, and the s. coeloconicum as a thermo/hygroreceptor. Their function is discussed in relation to prey detection and habitat adaptations. [source] Determination of Size, Morphology, and Nitrogen Impurity Location in Treated Detonation Nanodiamond by Transmission Electron MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Stuart Turner Abstract Size, morphology, and nitrogen impurity location, all of which are all thought to be related to the luminescent properties of detonation nanodiamonds, are determined in several detonation nanodiamond samples using a combination of transmission electron microscopy techniques. Results obtained from annealed and cleaned detonation nanodiamond samples are compared to results from conventionally purified detonation nanodiamond. Detailed electron energy loss spectroscopy combined with model-based quantification provides direct evidence for the sp3 like embedding of nitrogen impurities into the diamond cores of all the studied nanodiamond samples. Simultaneously, the structure and morphology of the cleaned detonation nanodiamond particles are studied using high resolution transmission electron microscopy. The results show that the size and morphology of detonation nanodiamonds can be modified by temperature treatment and that by applying a special cleaning procedure after temperature treatment, nanodiamond particles with clean facets almost free from sp2 carbon can be prepared. These clean facets are clear evidence that nanodiamond cores are not necessarily in coexistence with a graphitic shell of non-diamond carbon. [source] Nanocarbon materials: probing the curvature and topology effects using phonon spectraJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Sanju Gupta Abstract Much has been learned from the use of resonance Raman spectroscopy and high-resolution transmission electron microscopy techniques about the micro-/nanoscopic structure of various nanostructured carbons. However, they still possess some features that are not entirely understood particularly in terms of topological characteristics, which go beyond making a distinction with just the geometrical structure at nanoscale. To effectively utilize the potential of these materials for technological needs, understanding both the geometrical and topological structure and perhaps relating these attributes to physical (optical/electronic, lattice vibrational) properties become indispensable. Here, we make an attempt to describe the differences between various nanostructures and provide geometrical and topological property assessment semiquantitatively by monitoring the phonon spectra using resonance Raman spectroscopy thereby also capturing the electronic spectra. We elucidate the notion of global topology and curvature for a range of technologically important nanoscale carbons including tubular (single-, double- and multiwalled nanotubes, peapod), spherical (hypo- and hyperfullerenes, onion-like carbon) and complex (nanocones, nanohorns, nanodisks and nanorings) geometries. To demonstrate the proof-of-concept, we determined the variation in the prominent Raman bands of the respective materials, represented as D, G and D* (the overtone of D) bands, as a possible topological or curvature trend due to their sensitivity toward structural modification. The latter arises from local topological defects such as pentagons giving rise to curved nanocarbons. In this study, we provide systematics of their variation with respect to their geometric forms and compare with highly oriented pyrolytic graphite and monolayer graphene since the nanocarbons discussed are their derivatives. Once established, this knowledge will provide a powerful machinery to understand newer nanocarbons and indeed point to an unprecedented emergent paradigm of global topology/curvature , property , functionality relationship. We emphasize that these concepts are applicable to other topologically distinct nanomaterials, which include boron-nitride (BN) nanotubes and nanotori, helical gold nanotubes and Möbius conjugated organics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Texture Development in Silicon Nitride,Silicon Oxynitride In Situ Composites via Superplastic DeformationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2000Rong-Jun Xie Silicon nitride,silicon oxynitride (Si3N4,Si2N2O) in situ composites have been fabricated via either the annealing or the superplastic deformation of sintered Si3N4 that has been doped with a silica-containing additive. In this study, quantitative texture measurements, including pole figures and X-ray diffraction patterns, are used in conjunction with scanning electron microscopy and transmission electron microscopy techniques to examine the degree of preferred orientation and texture-development mechanisms in these materials. The results indicate that (i) only superplastic deformation can produce strong textures in the ,-Si3N4 matrix, as well as Si2N2O grains that are formed in situ; (ii) texture development in the ,-Si3N4 matrix mainly results from grain rotation via grain-boundary sliding; and (iii) for Si2N2O, a very strong strain-dependent texture occurs in two stages, namely, preferred nucleation and anisotropic grain growth. [source] Strain relaxation in AlN/GaN heterostructures grown by molecular beam epitaxyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008G. P. Dimitrakopulos Abstract The strain distribution and defects in a graded AlN/GaN heterostructure comprising AlN layers from 3 nm up to 100 nm grown by plasma-assisted MBE were studied using transmission electron microscopy techniques. Gradual strain relaxation was observed as well as strain partitioning between the GaN spacers and the thicker AlN layers. Elastic strain is retained even in the thicker layers of the heterostructure. Extensive introduction of threading and misfit dislocations is observed at and above the 7 nm AlN layer. The threading dislocations adopt inclined zig-zag line directions thus contributing to the relief of alternating compressive-tensile elastic strain across the the layers of the heterostructure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of clay with different cation exchange capacity on the morphology and properties of poly(methyl methacrylate)/clay nanocompositesPOLYMER COMPOSITES, Issue 11 2009Tsung-Yen Tsai PMMA/clay nanocomposites were successfully prepared by in situ free-radical polymerization with the organic modified MMT-clay using methyl methacrylate monomer and benzoyl peroxide initiator. Two clays with different cation exchange capacity have been used to prepare and compare the several properties. The clays have been modified using Amphoterge K2 by ion exchange reaction to increase the compatibility between the clay and polymer matrices. The modified clays have been characterized by wide-angle X-ray diffraction pattern, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA). The powdered X-ray diffraction and transmission electron microscopy techniques were employed to study the morphology of the PMMA/clay nanocomposites which indicate that the modified clays are dispersed in PMMA matrix to form both exfoliated and intercalated PMMA/modified clay nanocomposites. The thermomechanical properties were examined by TGA, differential scanning calorimetry, and dynamic mechanical analysis. Gas permeability analyzer shows the excellent gas barrier property of the nanocomposites, which is in good agreement with the morphology. The optical property was measured by UV,vis spectroscopy which shows that these materials have good optical clarity and UV resistance. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Effect of bifunctional modifiers of the clay on the morphology of novolac cured epoxy resin/clay nanocompositesPOLYMER COMPOSITES, Issue 10 2008Tsung-Yen Tsai Montmorillonite type clay, (PK-802) is modified by the bifunctional modifiers (2-phenylimidazole/benzalkonium chloride, PI/BEN or 2-methylimidazole/benzalkonium chloride, MI/BEN) with different ratio, which contain a curing agent, BEN, and the promoters/accelerator (PI and MI). These two modifying agents are simultaneously intercalated into the gallery space of pure PK-802. The novolac cured epoxy nanocomposites are prepared with this modified clay by crosslinking polymerization reaction. Wide-angle X-ray diffraction is used to measure the resulting d -spacing of modified PK-802 and the nanocomposites. Thermo-gravimetric analysis is used to characterize the thermal properties of the nanocomposites. The morphology of the nanocomposites is investigated using transmission electron microscopy techniques. Well dispersion of clay into the novolac cured epoxy-clay nanocomposites resulted when simultaneously both the modifying agents with 5:5 mole ratios are used to modify the clay instead of using single modified agent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] | ||||||||||