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Transmission Electron Microscopy Studies (transmission + electron_microscopy_studies)
Selected AbstractsNon-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical dischargeMETEORITICS & PLANETARY SCIENCE, Issue 7-8 2007Yuki Kimura The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in 17O and 18O. The maximum ,17O observed is + 4.7, for an iron oxide produced in flowing hydrogen, using O2 as the oxidant. More typical displacements are 1,2, above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation. [source] Donor,acceptor nanocomposite structures for organic photovoltaic applicationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009Konstantinos Fostiropoulos Abstract We investigated the effect of substrate temperature TS on the growth of 80,nm donor,acceptor nanocomposite (DAN) layers consisting of co-evaporated Zn-phthalocyanine (ZnPc) and C60 as absorber materials in organic solar cells. High temperature devices show lower series resistances RS but also reduced VOC. Both effects are diminished when the upper 20,nm of the blend are deposited at room temperature (RT). Moreover, the temperature profile improves the photocurrent density JSC. Best efficiencies (up to 2.1%) were achieved applying a 90,°C/RT profile. Transmission electron microscopy studies on the corresponding DAN revealed the temperature-dependent formation of crystalline C60 phases (already at low TS) and crystalline ZnPc phases (at highest TS). The strong phase separation at 90,°C results in less compact and mechanical unstable films. Such devices exhibit low parallel resistance RP. When the cold cover layer is applied RP doubles. [source] Three-Dimensional Bulk Heterojunction Morphology for Achieving High Internal Quantum Efficiency in Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Jang Jo Abstract Here, an investigation of three-dimensional (3D) morphologies for bulk heterojunction (BHJ) films based on regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) is reported. Based on the results, it is demonstrated that optimized post-treatment, such as solvent annealing, forces the PCBM molecules to migrate or diffuse toward the top surface of the BHJ composite films, which induces a new vertical component distribution favorable for enhancing the internal quantum efficiency (,IQE) of the devices. To investigate the 3D BHJ morphology, novel time-of-flight secondary-ion mass spectroscopy studies are employed along with conventional methods, such as UV-vis absorption, X-ray diffraction, and high-resolution transmission electron microscopy studies. The ,IQE of the devices are also compared after solvent annealing for different times, which clearly shows the effect of the vertical component distribution on the performance of BHJ polymer solar cells. In addition, the fabrication of high-performance P3HT:PCBM solar cells using the optimized solvent-annealing method is reported, and these cells show a mean power-conversion efficiency of 4.12% under AM 1.5G illumination conditions at an intensity of 100,mW cm,2. [source] Novel Synthesis of SrBi2Nb2O9 Powders From Hydroxide PrecursorsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2008Upendra Nath Gupta Simple hydroxide precursors were used for the first time for the synthesis of a typical Aurivillius compound (SrBi2Nb2O9 (SBN)) at a low temperature. This method is very advantageous because it circumvents the use of SrCO3 in the case of conventional ceramics as well in the coprecipitation methods, thereby lowering the formation of the product phase. Commercially purchased strontium hydroxide is mixed thoroughly with freshly precipitated bismuth and niobium hydroxides in a stoichiometric ratio and heated at different temperatures ranging from 100°C to 750°C for 12 h. The sequence of the reaction and evolution of the product phase was monitored by X-ray diffraction (XRD) studies by recording the XRD for samples calcined at different temperatures. The incipient SBN phase begins to form at temperatures as low as 400°C, and phase formation was complete only at 650°C as revealed by the XRD observations. The differential thermal/thermogravimetric analyses) also corroborate this result. The morphology and average particle size of these powders were investigated by transmission electron microscopy studies. [source] Structural 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] Is Diurodrilus an annelid?JOURNAL OF MORPHOLOGY, Issue 12 2008Katrine Worsaae Abstract Interstitial marine meiofaunal worms of the genus Diurodrilus have always been considered part of Annelida, either as basal or derived, though generally with reference to Dinophilidae. New evidence shows that Diurodrilus has a unique anatomy, and lacks key annelid features, possibly even segmentation. We assessed the systematic position of Diurodrilus among other protostome animals via light microscopy, confocal laser scanning microscopy, and transmission electron microscopy studies of anatomy, focusing on musculature, the nervous system, as well as molecular sequence data. We show that there is little morphological or molecular evidence to support a relationship with Dinophilidae or any other annelids. Diurodrilus has some similarities to Micrognathozoa, though the latter shows complex jaws. On the basis of the configuration of the nervous system and the cuticle we regard Diurodrilus to belong to Spiralia, possibly close to Annelida; however, until further evidence is acquired it should be regarded as incertae sedis in this large animal clade. J. Morphol., 2008. © 2008 Wiley-Liss, Inc. [source] Metathetic Reaction in Reverse Micelles: Synthesis of Nanostructured Alkaline-Earth Metal PhosphatesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Purnendu Parhi For the past few years, hydroxyapatite (HAp) has been identified as a potential biomaterial due to its excellent biocompatibility and bioactivity. The preparation of nanostructured HAp with controlled powder characteristics is a pre-requisite for processing it into useful biocomposites. Here, the synthesis of nanorods of calcium hydroxyapatite (Ca-HAp), strontium hydroxyapatite (Sr-HAp), and barium hydroxyapatite (Ba-HAp) by exploiting the metathetic reaction taking place in reverse micelles in the presence of cetyltrimethylammonium bromide has been reported. Powder X-ray diffraction analysis and thermogravimetric measurements confirm the formation of monophasic Ca-HAp and Sr-HAp. The growth of nanorods was further confirmed using transmission electron microscopy studies. The average lengths of Ca-HAp and Sr-HAp were ,60 and 30 nm, respectively. However, the preparation of Ba-HAp invariably yielded a multiphasic mixture with other competitive phases like BaHPO4 and Ba(H2PO4)2. [source] Low-Temperature Synthesis of Nanocrystalline Yttrium Aluminum Garnet Powder Using TriethanolamineJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2003Yangqiao Liu Nanocrystalline yttrium aluminum garnet (YAG, Y3Al5O12) was synthesized by pyrolysis of complex compounds of aluminum and yttrium with triethanolamine [(HOCH2CH2)3N, (TEA)]. Loose and porous precursor was obtained on complete dehydration of the metal ion,triethanolamine complexes. Pure YAG powder was obtained by calcination of the precursor at 950°C. The precursor was characterized by simultaneous thermogravimetry, differential scanning calorimetry, and mass spectra analyses (TG,DSC,MS). The heat-treated powders were characterized by X-ray diffractometry (XRD), specific surface area measurements, and transmission electron microscopy (TEM). The average crystallite size as determined from X-ray line broadening and transmission electron microscopy studies was ,40 nm. The effects of the calcination temperature and the ratio of triethanolamine to mixed metal ions were also studied. [source] Preparation of Bismuth Oxide Quantum Dots and their Photocatalytic Activity in a Homogeneous SystemCHEMCATCHEM, Issue 9 2010Prof. Hua Zhang Abstract Colloidal oil-soluble Bi2O3 quantum dots (QDs) are synthesized through an alcoholysis route in organic media. Water-soluble Bi2O3 QDs are then obtained from the initial oil-soluble QDs through phase transfer by surface modification with mercaptopropionic acid. X-ray diffraction and transmission electron microscopy studies show that the crystallinity is enhanced and particles grow larger after phase transfer. The water-soluble Bi2O3 QDs exhibit excellent photocatalytic activity for the degradation of methyl orange at a wide range of pH values. After several cycles, the Bi2O3 QDs retain high degradation efficiency. Simulation according to the first-order reaction dynamics indicates that the degradation reaction may follow complicated quasi-homogeneous photocatalysis. [source] Structures and Solvatochromic Phosphorescence of Dicationic Terpyridyl,Platinum(II) Complexes with Foldable Oligo(ortho -phenyleneethynylene) Bridging LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2008Ming-Xin Zhu Abstract A series of binuclear organoplatinum(II) complexes, [(tBu3tpy)Pt(CC1,2-C6H4)nCCPt(tBu3tpy)][ClO4]2 (1,7, n=1, 2, 3, 4, 5, 6, 8; tBu3tpy=4,4,,4,,-tri- tert -butyl-2,2,:6,,2,,-terpyridine) with foldable oligo(ortho -phenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 3,2.5,CH3OH, 5,CH3CN, and 6,4,CH3CN, each of the bridging ortho -phenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40,%, the emission of complexes 3,7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho -phenyleneethynylene linkers in acetonitrile/water mixtures is postulated. [source] | ||||||||||||||||