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Area Electron Diffraction (area + electron_diffraction)
Kinds of Area Electron Diffraction Selected AbstractsSynthesis and tribological properties of laminated Ti3SiC2 crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2010Qiong Wu Abstract Laminated Ti3SiC2 crystals are prepared of Ti, Si, C and Al powders by the method of hot isostatic pressing with NaCl additive in argon at 1350 °C. The laminated morphology of Ti3SiC2 is presented through the SEM and TEM observations. The results of high resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) patterns combined, it can be seen that the layers are of Ti3SiC2 crystals. The growth mechanism of Ti3SiC2 crystals, controlled by two-dimensional nucleation, is also explained. The tribological properties of Ti3SiC2 crystals as additives in HVI500 base oil are investigated by a UMT-2 ball-on-plate friction and wear tester. The study shows that under determinate conditions, the friction coefficient of the base oil containing Ti3SiC2 crystals is lower than that of pure base oil, and it decreases with the increase of mass percent of Ti3SiC2 nanolayers when its proportion is lower than 5wt. %. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Solvothermal production of CdS nanorods using polyvinylpyrrolidone as a templateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2009Titipun Thongtem Abstract CdS nanorods were solvothermally produced using Cd(NO3)2 and S powder in ethylenediamine containing different amounts of polyvinylpyrrolidone (PVP). The phase with hexagonal structure was detected using X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their SAED patterns were in accordance with those of the simulations. Scanning and transmission electron microscopies (SEM and TEM) revealed the presence of CdS nanorods with their lengths influenced by different amounts of PVP. The nanorods were also characterized using high resolution TEM (HRTEM). They grew in the [001] direction normal to the (002) parallel crystallographic planes composing the nanorods. Raman spectra showed the 1LO (first harmonic) and 2LO (second harmonic) modes at the same wavenumbers although the products were produced under different conditions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrothermal growth of boron nitride microcrystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2005Xiaopeng Hao Abstract Boron nitride (BN) crystals with size of several micrometers have been successfully synthesized by hydrothermal method. The reactants used in our experiments were boric acid (H3BO3), sodium azide (NaN3) and white phosphor (P). The samples were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), selective area electron diffraction (SAED). It is found that the existence of Cl - in the reaction mixture has much effect on the synthesis of BN. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Suppression of Ni4Ti3 Precipitation by Grain Size Refinement in Ni-Rich NiTi Shape Memory Alloys,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Egor A. Prokofiev Severe plastic deformation (SPD) processes, such as equal channel angular pressing (ECAP) and high pressure torsion (HPT), are successfully employed to produce ultra fine grain (UFG) and nanocrystalline (NC) microstructures in a Ti,50.7,at% Ni shape memory alloy. The effect of grain size on subsequent Ni-rich particle precipitation during annealing is investigated by transmission electron microscopy (TEM), selected area electron diffraction (SAD, SAED), and X-ray diffraction (XRD). It is observed that Ni4Ti3 precipitation is suppressed in grains of cross-sectional equivalent diameter below approximately 150,nm, and that particle coarsening is inhibited by very fine grain sizes. The results suggest that fine grain sizes impede precipitation processes by disrupting the formation of self-accommodating particle arrays and that the arrays locally compensate for coherency strains during nucleation and growth. [source] Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) NanofibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Wibren D. Oosterbaan Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source] Topotactic Conversion Route to Mesoporous Quasi-Single-Crystalline Co3O4 Nanobelts with Optimizable Electrochemical PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Li Tian Abstract The growth of mesoporous quasi-single-crystalline Co3O4 nanobelts by topotactic chemical transformation from , -Co(OH)2 nanobelts is realized. During the topotactic transformation process, the primary , -Co(OH)2 nanobelt frameworks can be preserved. The phases, crystal structures, morphologies, and growth behavior of both the precursory and resultant products are characterized by powder X-ray diffraction (XRD), electron microscopy,scanning electron (SEM) and transmission electron (TEM) microscopy, and selected area electron diffraction (SAED). Detailed investigation of the formation mechanism of the porous Co3O4 nanobelts indicates topotactic nucleation and oriented growth of textured spinel Co3O4 nanowalls (nanoparticles) inside the nanobelts. Co3O4 nanocrystals prefer [0001] epitaxial growth direction of hexagonal , -Co(OH)2 nanobelts due to the structural matching of [0001] , -Co(OH)2//[111] Co3O4. The surface-areas and pore sizes of the spinel Co3O4 products can be tuned through heat treatment of , -Co(OH)2 precursors at different temperatures. The galvanostatic cycling measurement of the Co3O4 products indicates that their charge,discharge performance can be optimized. In the voltage range of 0.0,3.0,V versus Li+/Li at 40,mA g,1, reversible capacities of a sample consisting of mesoporous quasi-single-crystalline Co3O4 nanobelts can reach up to 1400,mA h g,1, much larger than the theoretical capacity of bulk Co3O4 (892,mA h g,1). [source] Cover Picture: Tuning the Dimensions of C60 -Based Needlelike Crystals in Blended Thin Films (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 6 2006Mater. Abstract A new ordered structure of the C60 derivative PCBM is obtained in thin films based on the blend PCBM:P3HT, as detailed by Swinnen, Manca, and co-workers on p.,760. Needlelike crystalline PCBM structures, whose dimensions and spatial distribution ca be tuned by adjusting the blend ratio and annealing conditions, are formed. In typical solar-cell applications of these blended films, these results indicate that during long-term operation under normal conditions (50,70,°C) morphology changes and a decrease in cell performance could occur. A new ordered structure of the C60 derivative PCBM ([6-6]-phenyl C61 -butyric acid methyl ester) is obtained in thin films based on the blend PCBM:regioregular P3HT (poly(3-hexylthiophene)). Rapid formation of needlelike crystalline PCBM structures of a few micrometers up to 100,,m in size is demonstrated by submitting the blended thin films to an appropriate thermal treatment. These structures can grow out to a 2D network of PCBM needles and, in specific cases, to spectacular PCBM fans. Key parameters to tune the dimensions and spatial distribution of the PCBM needles are blend ratio and annealing conditions. The as-obtained blended films and crystals are probed using atomic force microscopy, transmission electron microscopy, selected area electron diffraction, optical microscopy, and confocal fluorescence microscopy. Based on the analytical results, the growth mechanism of the PCBM structures within the film is described in terms of diffusion of PCBM towards the PCBM crystals, leaving highly crystalline P3HT behind in the surrounding matrix. [source] Quantitative misorientation characteristics of interphase boundaries in compositesJOURNAL OF MICROSCOPY, Issue 1 2006K. SZTWIERTNIA Summary Specific crystallographic correlations between neighbouring grains in composites were established by the use of selected area electron diffraction in the transmission electron microscope. However, it was the development of orientation mapping techniques that made it possible to obtain a quantitative description of the distribution of boundaries between the grains of both the same phase and different phases. This study shows that orientation topography measurements made by electron backscatter diffraction in the scanning electron microscope allowed determination of the crystallographic relationships between grains of different phases. An alumina-based composite with a content of 10 vol% tungsten carbide was chosen for investigations. Misorientation distribution functions were calculated to describe the distribution density of misorientations with respect to the nearest neighbouring measured point located in the grain of the second phase. The analysis of misorientation distribution functions permitted the evaluation of preferences for some special crystallographic correlations between the grains of composite matrix and inclusions as well as shares of interphase boundaries characterized by those correlations. [source] Morphology Transformation of Hematite Nanoparticles Through Oriented AggregationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Lili Wang Hematite nanoparticles 30,45 nm in width and 15,25 nm in thickness were synthesized through oriented aggregation by a hydrothermal method. X -ray diffraction, transmission electron microscopy, high-resolution TEM, selected area electron diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy analyses were applied to characterize the nanocrystals. Morphology transformation of these hematite nanoparticles from irregularly shaped to flower like with the assistance of oleic acid was surveyed. Based on these results, possible formation mechanism of the hematite nanoflowers is discussed here. [source] Filling of carbon nanotubes for bio-applicationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007S. Costa Abstract Carbon nanotubes (CNT) provide a smart carrier system on the nanometer scale. The system can be used as a template for ferromagnetic fillers. Such a molecular hybrid is a promising potential candidate for the controlled heating of tumour tissue at the cellular level. This is a key reason why it is important to optimize the synthesis route of metal filled carbon nanotubes with regards bulk scale synthesis and purity. In the current study we present multiwalled carbon nanotubes filled with ,-iron phase (Fe-MWCNT). The influence of acid treatment on the stability of the filling and the sample purity is also presented. High resolution transmission microscopy, its Energy dispersive X-Ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) modes have been applied for the analysis of the morphology and chemical composition of the samples. The phase of iron nanowires encapsulated into the carbon nanotubes was determined with selected area electron diffraction (SAED) on a local scale. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] TEM characterization of M -plane InN grown on (100) LiAlO2 substrate by RF-MBEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Hirokazu Nozawa Abstract In this study, we characterized the microstructure of M -plane InN using transmission electron microscopy (TEM). The M -plane InN was grown on a (100) LiAlO2 substrate using radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). We determined the epitaxial relationships of the M -plane InN and LiAlO2 using selected area electron diffraction (SAED). The epitaxial relationships were exactly the same as the M -plane GaN grown on the same substrate. Also, the M -plane InN was grown on the (100) LiAlO2 despite the high lattice mismatches between M -plane InN and LiAlO2. We observed a high density of stacking faults parallel to (0001)InN. The density was estimated about 1.8×106 cm,1, which was one order of magnitude higher than that of non-polar GaN. The correlation between threading dislocations and stacking faults is investigated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Calcite microcrystals in the pineal gland of the human brain: First physical and chemical studiesBIOELECTROMAGNETICS, Issue 7 2002Simon Baconnier Abstract A new form of biomineralization has been studied in the pineal gland of the human brain. It consists of small crystals that are less than 20 ,m in length and that are completely distinct from the often observed mulberry-type hydroxyapatite concretions. A special procedure was developed for isolation of the crystals from the organic matter in the pineal gland. Cubic, hexagonal, and cylindrical morphologies have been identified using scanning electron microscopy. The crystal edges were sharp whereas their surfaces were very rough. Energy dispersive spectroscopy showed that the crystals contained only the elements calcium, carbon, and oxygen. Selected area electron diffraction and near infrared Raman spectroscopy established that the crystals were calcite. With the exception of the otoconia structure of the inner ear, this is the only known nonpathological occurrence of calcite in the human body. The calcite microcrystals are probably responsible for the previously observed second harmonic generation in pineal tissue sections. The complex texture structure of the microcrystals may lead to crystallographic symmetry breaking and possible piezoelectricity, as is the case with otoconia. It is believed that the presence of two different crystalline compounds in the pineal gland is biologically significant, suggesting two entirely different mechanisms of formation and biological functions. Studies directed toward the elucidation of the formation and functions, and possible nonthermal interaction with external electromagnetic fields are currently in progress. Bioelectromagnetics 23:488,495, 2002. © 2002 Wiley-Liss, Inc. [source] Ultrastructural Evidence for a Novel Accumulation of Ca in a Microbial Mat from a Slight Acidic Hot SpringACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2010Xiaotong PENG Abstract: Microbial mats are ecosystems that can control or induce the precipitation of calcium (Ca) carbonate on Earth through geological time. In the present study, we report on a novel accumulation of Ca, together with iron (Fe), in a microbial mat collected from a slight acidic hot spring (pH=5.9) in south China. Combining an array of approaches, including environmental scanning electron microscopy, X-ray microanalysis, transmission electron microscopy, and selected area electron diffraction, we provide ultrastructral evidence for amorphous acicular aggregates containing Ca and Fe associated with cyanobacteria precipitating in the microbial mats. Cyanobacterial photosynthesis and exopolymeric organic matrixes are considered to be responsible for the precipitation of Ca. These amorphous acicular aggregates might imply the early stage of calcification occurring in microbial mats. Ca and Fe coprecipitation indicates another potential important way of inorganic element precipitation in hot spring microbial mats. Our results provide insight into the possible mechanism of cyanobacterial calcification and microfossil preservation in slight acidic hot spring environments. [source] Tetraethylenepentamine-Directed Controllable Synthesis of Wurtzite ZnSe Nanostructures with Tunable MorphologyCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2008Baojuan Xi Dr. Abstract A novel tetraethylenepentamine (TEPA)-directed method has been successfully developed for the controlled synthesis of ZnSe particles with distinctive morphologies, including nanobelts, nanowires, and hierarchically solid/hollow spheres. These structures, self-assembled from nanobelts and nanorods, have been synthesized by adjusting the reaction parameters, such as the solvent composition, reaction temperature, and the aging time. Results reveal that the volume ratio of H2O and TEPA plays a crucial role in the final morphology of ZnSe products. The mechanisms of phase formation and morphology control of ZnSe particles are proposed and discussed in detail. The products have been characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), selected area electron diffraction, high-resolution TEM, Raman spectra and luminescence spectroscopy. The as-prepared ZnSe nanoparticles display shape- and size-dependent photoluminescent optical properties. This is the first time to report preparation of complex hollow structures of ZnSe crystals with hierarchy through a simple solution-based route. This synthetic route is designed to exploit a new H2O/TEPA/N2H4,H2O system possibly for the preparation of other semiconductor nanomaterials. [source] | |||||||||||||