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TEM Analysis (tem + analysis)
Selected AbstractsTEM Analysis of Hcp-Co Films Deposited by Gas Flow SputteringIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2008Hiroshi Sakuma Member Abstract In this study, the crystal structure of Co thin films deposited by a low-energy sputtering, gas flow sputtering (GFS) and conventional RF magnetron sputtering (MS) is investigated. The emphasis is on whether fcc-like regions are present in a hcp-Co film. X-ray diffraction (XRD) shows no fcc peak for both films deposited by GFS and MS. Electron diffraction reveals that fcc structure is present in the film deposited by MS. Lattice images are observed by using transmission electron microscopy. Every other line in the lattice image of the film deposited by GFS is bright or dark, which is suggestive of the ABAB stacking of the hcp structure. In addition, stacking faults are observed. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Transmission Electron Microscopy and UV,vis,IR Spectroscopy Analysis of the Diameter Sorting of Carbon Nanotubes by Gradient Density UltracentrifugationADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Romain Fleurier Abstract Diameter separation of single-walled carbon nanotubes is achieved via the density gradient ultracentrifugation process. Statistical analysis of the separated samples is performed using high-resolution transmission electron microscopy (HRTEM). The evolution of the diameter distribution with respect to the gradient density is extracted by analyzing hundreds of HRTEM images, and the results are found to be consistent with those estimated by UV,vis,IR spectroscopy. The efficiency of the separation process can be quantitatively characterized by the standard deviation of the diameter distribution, which is determined from the TEM analyses. This particular study indicated that for electric arc nanotubes dispersed in sodium cholate, diameter sorting is more efficient in the upper part of the gradient. [source] Acrylic Nanocomposite Resins for Use in Stereolithography and Structural Light Modulation Based Rapid Prototyping and Rapid Manufacturing Technologies,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2008Matthias Gurr Abstract A novel family of optically transparent acrylic nanocomposites containing up to 30,wt,% silica nanoparticles with an average diameter of 20,nm was developed for application in structural light modulation (SLM) and stereolithography (SL) technologies. The uniform dispersion of nanoparticles affords a significantly improved toughness/stiffness-balance of the photopolymerized and postcured nanocomposites. It is possible to increase stiffness, as expressed by Young's modulus, from 1290 to 1700,MPa without encountering the embrittlement typical for many other conventional filled polymers. Fracture behaviour is examined by means of fracture mechanics investigation and SEM analyses of fracture surfaces. According to TEM analyses and measurement of optical transmittance remarkable uniform dispersion of silica nanoparticles was achieved. The silica nanoparticle concentrations up to 17,wt,% give only marginally higher viscosities and do not affect transmittance, while slightly increasing the exposure times needed in photopolymerization. Moreover, the silica nanoparticles afford materials with reduced shrinkage and improved properties. The green effective ankle splay out (EASO) measured on H-shaped diagnostic specimens, is significantly reduced for the nanocomposite materials from 1.38,mm for the unfilled material to 0.82,mm for nanocomposites containing 30,wt,% nanosilica. The building accuracy is increased significantly with increasing content of silica nanofillers. [source] Seed-Mediated Synthesis of Truncated Gold Decahedrons with a AuCl/Oleylamine Complex as PrecursorADVANCED MATERIALS, Issue 17 2010Yanyun Ma A seed-mediated growth method is described for the synthesis of a novel type of Au nanoparticles,truncated decahedrons with a pentagonal, platelike structure (see figure). The precursor is based on the AuCl/oleylamine complex. TEM analyses reveal that the truncated Au nanoparticle has two types of truncation: one is parallel to the five-fold axis and the other is perpendicular to the five-fold axis. [source] Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studiesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2005Elisabetta Gavini Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was peformed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (dvs) in the range of about 3,10 ,m. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1,3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug. [source] Effects of Thermal Annealing on the Structure of Ferroelectric Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2006Jiang-Li Cao The effects of thermal annealing on the structure of polycrystalline Pb(Zr0.3Ti0.7)O3 (PZT) ferroelectric thin films prepared by chemical solution deposition on Pt/TiOx electrode stacks were studied using scanning electron microscopy, transmission electron microscopy (TEM), and grazing incidence X-ray specular and diffuse reflectivity of synchrotron radiation. The stratified multilayered structure and element diffusions in the sample were characterized by TEM. Global statistical structural parameters including the density, surface or interface roughness and thickness of each layer in the samples were obtained from fitting the X-ray specular reflectivity using a homogeneous stratified multilayer model of PZT/Pt/TiOx/SiO2. The results showed that the PZT surface and PZT/Pt interface roughness changed slightly during thermal annealing in oxygen at 700°C. By contrast, the density increase of the PZT ceramic and density decrease of the Pt-bottom electrode during annealing were observed. A high density value of the PZT ceramic film after the annealing was found, up to 99.8% of the theoretical value of the corresponding bulk ceramics. The density changes of the PZT and Pt layers were further confirmed by X-ray diffuse reflectivity. The influences of the annealing treatment on the density changes of the PZT and Pt layers were attributed to the further densification of the PZT ceramic and incorporation of light elements such as Zr, Ti and O from the neighboring layers into the Pt layer, respectively, as discussed in correlation with the TEM analyses. [source] Preparation and Characterization of Hybrid Nanocomposites Coated on LDPEMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2006Laura Mazzocchetti Abstract Summary: Hybrid organic-inorganic nanocomposites containing hyperbranched structures were prepared through a dual-curing process, which involves photopolymerization and condensation alkoxysilane groups. In particular, an oligomer containing PEO units and ,,, -methacrylate groups was used together with a HBP bearing acrylic groups as the organic phase precursors. MEMO, as the organic-inorganic linker, and TEOS, as inorganic phase precursor, were also employed. The kinetics of both photopolymerization and condensation reactions were investigated by double bond conversion analysis (via FT-IR) and weight loss determination, respectively. The mobility of the organic phase was studied by means of DSC and DMTA and correlated with hybrid composition. TEM analyses performed on microtomed film slices indicated the formation of nanoscale silica domains. Hybrids were coated onto an LDPE film previously subjected to a plasma treatment, and substrate-coating interfacial adhesion was investigated through stress-strain and DMTA experiments. Reaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction. [source] Preparation and Characterization of Hyperbranched Polymer/Silica Hybrid Nanocoatings by Dual-Curing ProcessMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Ezio Amerio Abstract Summary: Organic-inorganic nanocomposite hybrid coatings were prepared through a dual-cure process involving cationic photopolymerization of a hyperbranched epoxy functionalized resin and subsequent condensation of an alkoxysilane inorganic precursor. All the formulations investigated gave rise to photocured films characterized by high gel content values. An increase in glass transition temperature and an increase in storage modulus above Tg in the rubbery plateau is observed with increasing TEOS content in the photocurable formulation. The important role of GPTS on reducing the inorganic domain size and avoiding macroscopic phase separation was demonstrated by TEM analyses. TEM obtained for one of the cured films in the presence of GPTS. [source] Characterization of HDPE /Polyamide 6/ Nanocomposites Using Scanning-and Transmission Electron MicroscopyMACROMOLECULAR SYMPOSIA, Issue 1 2007Eleonora Erdmann Abstract Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed. [source] Alloying with copper to reduce metal dusting of nickelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2005J. Zhang Abstract Copper is thought to be noncatalytic to carbon deposition from gas atmospheres, and owing to its extremely low solubility for carbon, inert to the metal dusting reaction. Thus, the addition of copper to nickel, which forms a near perfect solid solution, may be able to suppress or greatly retard the metal dusting of the alloy, without the need for a protective oxide scale on the surface. The dusting behaviour of Ni-Cu alloys containing up to 50 wt% Cu, along with pure Cu, was investigated in a 68%CO-31%H2 -1%H2O gas mixture (aC: 19) at 680°C for up to 150 h. Surface analysis showed that two types of carbon deposits, graphite particle clusters and filaments, were observed on pure Ni and Ni-Cu alloys with Cu contents of up to 5 wt%. Alloys with more than 10 wt% Cu showed very little coking, forming filaments only. SEM and TEM analyses revealed metal particles encapsulated by graphite shells within the graphite particle clusters, and metal particles at filament tips or embedded along their lengths. A kinetic investigation showed that alloy dusting rates decreased significantly with increasing copper levels up to 10 wt%. At copper concentrations of more than 20 wt%, the rate of metal dusting was negligible. Although pure copper is not catalytic to carbon formation, scattered carbon nanotubes were observed on its surface. The effect of copper on alloy dusting rates is attributed to a dilution effect. [source] Atmospheric Cold Plasmas for Synthesizing Nanocrystalline Anatase TiO2 using Dielectric Barrier DischargesPLASMA PROCESSES AND POLYMERS, Issue 5 2007Long-Hui Nie Abstract Nanocrystalline anatase TiO2 has been successfully synthesized using TiCl4 and O2 as precursors by atmospheric cold plasmas generated by dielectric barrier discharges (DBD) without extra heating or thermal treatment. For the TiO2 powders synthesized by DBD plasma at an energy density of 5.9 kJ,·,L,1, XRD and TEM analyses revealed that the nanocrystallite size is about 10,15 nm. Only a single crystalline structure of anatase was observed performing XRD, HRTEM and SAED measurements. It was found that the particle size decreased with increasing the discharge power, and that the chlorine contamination dramatically decreased when using high discharge power levels. [source] Conducting nanocomposites of polyacrylamide with acetylene black and polyanilinePOLYMER COMPOSITES, Issue 4 2009Pramod Kumar Verma A conducting nanocomposite of polyacrylamide (PAA) with acetylene black was prepared via Na2AsO3 -K2CrO4 redox initiated polymerization of acrylamide in water containing a suspension of acetylene black. FTIR analyses confirmed the presence of PAA in the nanocomposites. The composite possessed lower thermal stability than AB and exhibited three stages of decomposition upto 430°C. DSC thermogram revealed three endotherms due to minor thermal degradation (at ,100°C), melting and decomposition (at ,230°C) and major decomposition (at ,430°C). TEM analyses indicated the formation of globular composite particles with sizes in 30,70 nm range. In contrast to the very low conductivity of the base polymer the composite showed a dramatic increase in conductivity (0.19,6.0 S/cm) depending upon AB loading. Log (conductivity) ,1/T plot showed a change in slope at ,127°C indicating the manifestation of an intrinsic conductivity region and an impurity conductivity region. The activation energy for conduction as estimated from the slope of region I was 0.008 eV/mol. The C,V plot was linear showing a metallic behavior. For comparison in conductivity PAA-polyaniline composite was also prepared which however displayed much lower conductivity values. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Studies on nylon-6/EVOH/clay ternary compositesPOLYMER COMPOSITES, Issue 1 2006N. Artzi Nylon-6 (Ny-6)/EVOH blends are interesting host multiphase systems for incorporation of low clay contents. The Ny-6/EVOH blend is a unique system, which tends to chemically react during melt-mixing, affecting thermal, morphological and mechanical properties of the ternary systems containing clay. The addition of clay seems to interrupt the chemical reaction between the host polymers at certain compositions, leading to lower blending torque levels when clay is added. A competition between Ny-6 and EVOH regarding the intercalation process takes place. Ny-6 seems to lead to exfoliated structure, whereas EVOH forms intercalated structure, as revealed from XRD and TEM analyses, owing to thermodynamic considerations and preferential localization of the clay in Ny-6. Hence, the ternary systems have combined intercalated and delaminated morphology or complete exfoliated morphology depending on blend composition and clay content. Selective extraction experiments (gel content) indicate the formation of chemical reaction between the Ny-6 and EVOH, and give an indirect indication of the polymer content residing in the galleries. The thermal properties of the polymers were found to be affected by the occurrence of chemical reaction, the level of intercalation and exfoliation and plasticizing effect of the low molecular weight onium ions treating the clay. Of special interest is the increased storage modulus attained upon the addition of only 1.5 wt% clay. POLYM. COMPOS. 27:15,23, 2006. © 2005 Society of Plastics Engineers [source] The legwd mutant uncovers the role of starch phosphorylation in pollen development and germination in tomatoTHE PLANT JOURNAL, Issue 1 2009Shai Nashilevitz Summary Starches extracted from most plant species are phosphorylated. ,-Glucan water dikinase (GWD) is a key enzyme that controls the phosphate content of starch. In the absence of its activity starch degradation is impaired, leading to a starch excess phenotype in Arabidopsis and in potato leaves, and to reduced cold sweetening in potato tubers. Here, we characterized a transposon insertion (legwd::Ds) in the tomato GWD (LeGWD) gene that caused male gametophytic lethality. The mutant pollen had a starch excess phenotype that was associated with a reduction in pollen germination. SEM and TEM analyses indicated mild shrinking of the pollen grains and the accumulation of large starch granules inside the plastids. The level of soluble sugars was reduced by 1.8-fold in mutant pollen grains. Overall, the transmission of the mutant allele was only 0.4% in the male, whereas it was normal in the female. Additional mutant alleles, obtained through transposon excision, showed the same phenotypes as legwd::Ds. Moreover, pollen germination could be restored, and the starch excess phenotype could be abolished in lines expressing the potato GWD homolog (StGWD) under a pollen-specific promoter. In these lines, where fertility was restored, homozygous plants for legwd::Ds were isolated, and showed the starch excess phenotype in the leaves. Overall, our results demonstrate the importance of starch phosphorylation and breakdown for pollen germination, and open up the prospect for analyzing the role of starch metabolism in leaves and fruits. [source] Epitaxial Sn1-xPbxS nanorods on iso-compositional thin filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2010K. Bente Abstract Based on SnS (Herzenbergite) , SnPbS2 (Teallite) mixed crystals with orthorhombic layer structures, thin films and lawns of Sn1-xPbxS nanorods were produced using hot wall vacuum deposition method (HWVD). The lawn was formed onto the surface of an underlying thin Sn1-xPbxS film which is build by differently oriented blocks. The density of rods arranged like a lawn depends on the metal ratio and substrate temperature. X-ray and TEM analysis of the epitaxial material showed preferential (001) orientation perpendicular to the surface of the glass substrate. The roughness of the films measured by atomic force microscopy was in the range of Rq = 49.5,86.3 nm depending on lead concentration The rods were about 500 nm high and 300 nm in diameter. As revealed by TEM-EDX experiments the droplet at the tip of rods consists of tin. Therefore it is assumed the rods grew via a self-consuming vapor,liquid,solid (VLS) mechanism. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Drosophila nucleoporin gene nup154 is required for correct microfilament dynamics and cell death during oogenesisCYTOSKELETON, Issue 8 2007Maria Giovanna Riparbelli Abstract The Drosophila nucleoporin gene nup154 is required in both male and female germline for successful gametogenesis. Mutant flies lack differentiated sperm and lay abnormal eggs. We demonstrated that the egg phenotype was associated with specific alterations of the actin cytoskeleton at different stages of oogenesis. Actually, mutant egg chambers displayed an abnormal organization of both subcortical microfilaments and cytoplasmic actin bundles, that led to defective nurse cell dumping. TUNEL analysis also showed that the dumpless phenotype was associated with delayed apoptosis. The nup154 gene product was localized by conventional immunofluorescence microscopy to the nuclear envelope in a distinct punctuate pattern, characteristic of nuclear pore complex components. TEM analysis revealed that the protein was mainly distributed along filamentous structures that extended radially on the nuclear side of the pore, suggesting that Nup154 could be an integral component of the basket filaments associated with the nuclear pore complexes. We propose that Nup154 is necessary for correct nuclear pore complex functions and that the proper regulation of the actin cytoskeleton dynamics strongly relies upon nuclear pore integrity. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source] In Situ Growth of Mesoporous SnO2 on Multiwalled Carbon Nanotubes: A Novel Composite with Porous-Tube Structure as Anode for Lithium Batteries,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007Z. Wen Abstract A novel mesoporous-nanotube hybrid composite, namely mesoporous tin dioxide (SnO2) overlaying on the surface of multiwalled carbon nanotubes (MWCNTs), was prepared by a simple method that included in situ growth of mesoporous SnO2 on the surface of MWCNTs through hydrothermal method utilizing Cetyltrimethylammonium bromide (CTAB) as structure-directing agents. Nitrogen adsorption,desorption, X-ray diffraction and transmission electron microscopy analysis techniques were used to characterize the samples. It was observed that a thin layer tetragonal SnO2 with a disordered porous was embedded on the surface of MWCNTs, which resulted in the formation of a novel mesoporous-nanotube hybrid composite. On the base of TEM analysis of products from controlled experiment, a possible mechanism was proposed to explain the formation of the mesoporous-nanotube structure. The electrochemical properties of the samples as anode materials for lithium batteries were studied by cyclic voltammograms and Galvanostatic method. Results showed that the mesoporous-tube hybrid composites displayed higher capacity and better cycle performance in comparison with the mesoporous tin dioxide. It was concluded that such a large improvement of electrochemical performance within the hybrid composites may in general be related to mesoporous-tube structure that possess properties such as one-dimensional hollow structure, high-strength with flexibility, excellent electric conductivity and large surface area. [source] Biodistribution of Stealth and Non-stealth Solid Lipid Nanospheres after Intravenous Administration to RatsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2000VALERIO PODIO Drug-free stealth and non-stealth solid lipid nanospheres (SLNs) were administered intravenously to rats to evaluate their tissue distribution and their transport across the blood-brain barrier. Two types of experiments were performed using unlabelled and labelled SLNs. Rats were administered labelled non-stealth or stealth nanospheres (NSSLNs and SSLNs) and their tissue distribution was monitored for 60 min. In another experiment, rats were injected with unlabelled NSSLNs or SSLNs and the cerebrospinal fluid (CSF) was analysed using transmission electron microscopy (TEM) to confirm the presence of the SLNs. Some differences were found in the biodistribution between labelled NSSLNs and SSLNs. In particular, the radioactivity in the liver and the lung was much lower for SSLNs than for NSSLNs, confirming a difference in their uptake. Both types of SLNs were detected in the brain. TEM analysis showed both types of SLNs in rat CSF. [source] DOMOIC ACID PRODUCTION By PSEUDO-NITZSCHIA SERIATA (BACILLARIOPHYCEAE) IN SCOTTISH WATERS,JOURNAL OF PHYCOLOGY, Issue 4 2004Johanna Fehling In 1999, a 49,000 km2 area in western Scottish waters was closed to shellfish harvesting due to the amnesic shellfish poisoning (ASP) toxin domoic acid (DA). The only previously confirmed DA producer identified had been Pseudo-nitzschia australis Frenguelli. The toxin has appeared every year since and has led to more harvesting closures. We isolated and cultured two strains of Pseudo-nitzschia seriata f. seriata (P. T. Cleve) H. Peragallo from western Scottish waters in 2001 and 2002. They were identified using TEM analysis of their morphological fine structure and sequencing of the internal transcribed spacer (ITS)1, 5.8S, ITS2, and partial large subunit (LSU) rDNA. The morphology of the Scottish P. seriata f. seriata strains differed slightly, for example, in the number of poroid rows, from descriptions in identification keys. Comparison of P. seriata sequences with those of two co-occurring Pseudo-nitzschia australis isolates showed an overall divergence of only 0.012. Sequence divergence between both species was highest in the ITS1 region (0.036). Combined morphological and genetic approaches are needed to identify closely related Pseudo-nitzschia species. The P. seriata strains grew successfully at 15°C, suggesting that although seen as a psychrophilic species, it may also occur at higher water temperatures. All isolates produced DA in stationary phase (measured on day 25): 0.16,0.23 pg DA·cell,1 in P. seriata and 0.15,1.68 pg DA·cell,1 in P. australis. Our study is the first to identify P. seriata f. seriata as a DA producer in Scottish waters and indicates that at least it and P. australis can be responsible for ASP toxicity in that region. [source] Fabrication of high-performance, gradient-refractive-index plastic rods with surfmer-cluster-stabilized nanoparticlesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2006Jui-Hsiang Liu Abstract A novel method was developed with surfmer-cluster-stabilized silver nanoparticles to prepare high-performance, gradient-refractive-index (GRIN) plastic rods based on methyl methacrylate. To fabricate the GRIN plastic rods, a novel polymerizable surfactant (surfmer) of 4-(11-acryloxyundecyloxy)benzoic acid (AUBA) was synthesized. Silver nanoparticles were prepared with a reverse micelle method in the presence of the novel surfmer. During the fabrication of the silver nanoparticles, the sodium salt of AUBA was formed. GRIN plastic rods were fabricated through centrifugal polymerization and then were heat-treated at 100 °C under 0.1 Torr for 24 h to remove residual monomers and water. The distribution of the surfmer-cluster-stabilized nanoparticles inside the plastic rods was studied with transmission electron microscopy (TEM). The real-image transmission through the fabricated rods was also confirmed. The results obtained in this investigation suggested that the control of the distribution of surfmer-cluster-stabilized nanoparticles could be used to fabricate GRIN rods. Furthermore, the existence of the crosslink-like surfmers increased the thermal stability of the plastic rods. The GRIN distribution of the rods was established by the dispersion of nanoparticles inside the plastic rods through TEM analysis, refractive-index analysis, and real-image transmission. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5933,5942, 2006 [source] Positive Temperature Coefficient of Resistivity Effect in Highly Donor,Doped Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2001Darko Makovec BaTiO3 ceramics doped with different La concentrations (0,12 mol%) were prepared by sintering under the reducing conditions of a nitrogen atmosphere containing 1% hydrogen. The critical donor concentration that causes blocking of the exaggerated grain growth was observed to be ,10 mol% La. The samples, which were semiconducting after sintering under reducing conditions, were subsequently reoxidized by annealing in air to induce the positive temperature coefficient of resistivity (PTCR) effect. After reoxidation at 1150°C a noticeable PTCR effect was observed in the samples doped with La concentrations as high as 2.5 mol%. The room-temperature resistivity after reoxidation was found to increase with increasing donor concentration due to an increase in the thickness of the insulating layers at the grain boundaries. TEM analysis showed that reoxidation of the samples caused precipitation of the Ti-rich compound Ba6Ti17O40 inside the doped BaTiO3 -matrix grains. [source] Synthesis of Au@SiO2 Core/Shell Nanoparticles and their Dispersion into an Acrylic Photocurable Formulation: Film Preparation and CharacterizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2008Marco Sangermano Abstract Au core/silica shell (Au@SiO2) nanoparticles were synthesized by coating gold NPs with sol/gel silica in alcoholic solution. The alcoholic dispersion was added, in the range of 1,5 wt.-%, to TPGDA and photocured by means of UV light. Transparent coatings were obtained and they can find suitable applications. It was shown that the NPs can restrict the segmental motion and decrease the free volume of the polymer network, with a consequent increase in glass transition temperature. TEM analysis put in evidence that the particles are well dispersed without any macroscopic agglomeration, and many particles are present as isolated particles. [source] Thiol-ene Hybrid Organic/Inorganic Nanostructured Coatings Based on Thiol-Functionalized Zirconium OxoclustersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2007Marco Sangermano Abstract The thiol-functionalized zirconium oxocluster Zr12(µ3 -O)8(µ3 -OH)8(MP)24,·,4MPA was used as inorganic nanosized building block in the thiol-ene photopolymerization of APE and TH in a 1:1 molar mixture. Transparent and crack-free coatings were obtained, and TEM analysis showed that the inorganic particles are well dispersed within the polymeric network with no significant macroscopic agglomeration. An increase of Tg values, storage modulus in the rubbery region, and thermal stability were evidenced by increasing the zirconium oxocluster content in the photocurable formulations. XPS analysis and SIMS depth profile were carried out on UV cured films and showed the presence of a homogeneously distributed zirconium oxocluster. [source] Use of Single-Walled Carbon Nanotubes as Reinforcing Fillers in UV-Curable Epoxy SystemsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2008Marco Sangermano Abstract CNT were dispersed in an epoxy matrix and cured by means of UV light. An increase on elastic modulus and Tg values was measured by DMTA analysis and attributed to the constraint effect of CNT on polymer chain mobility. Excellent scratch resistant coatings characterized by high critical load, small cracks and high recovery were obtained in the presence of a very low CNT content (0.025 wt.-%). TEM analysis showed some isolated CNT and some cluster agglomerations of size of about 250 nm. It was shown that it was possible to decrease the surface resistivity of the cured samples by three orders of magnitude in the presence of 0.1 wt.-% of SWCNT content. [source] Preparation and Characterization of Nanostructured TiO2/Epoxy Polymeric FilmsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2006Marco Sangermano Abstract Summary: Titania-containing coatings were prepared by cationic photopolymerization of an epoxy resin either by dispersion of preformed TiO2 nanoparticles or by their in-situ generation through a sol-gel dual-cure process. The kinetics of photopolymerization was evaluated by real-time FT-IR, studying the effect of the TiO2 concentration. The properties of cured films were investigated, showing an increase of hydrophilicity on the surface of the coatings with increasing TiO2 content. TEM analysis demonstrated that it is possible to achieve a significantly better control of the dispersion of the inorganic particles within the organic matrix by in-situ generation of TiO2, thus completely avoiding macroscopic phase separation and obtaining homogeneous, transparent coatings. Bright-field TEM micrograph for TIP20 dual-cured film. [source] Thermal histories of IVA iron meteorites from transmission electron microscopy of the cloudy zone microstructureMETEORITICS & PLANETARY SCIENCE, Issue 3 2009J. I. GOLDSTEIN Thin sections for TEM analysis were produced by a focused ion beam instrument. Use of the TEM allowed us to avoid potential artifacts which may be introduced during specimen preparation for SEM analysis of high Ni particles <30 nm in size and to identify microchemical and microstructural changes due to the effects of shock induced reheating. No cloudy zone was observed in five of the eight moderately to highly shocked (>13 GPa) IVA irons that were examined in the TEM. Shock induced reheating has allowed for diffusion from 20 nm to 400 nm across kamacite/taenite boundaries, recrystallization of kamacite, and the formation, in Jamestown, of taenite grain boundaries. In the eleven IVA irons with cloudy zone microstructures, the size of the high-Ni particles in the cloudy zone increases directly with increasing bulk Ni content. Our data and the inverse correlation between cooling rate and high-Ni particle size for irons and stony-irons show that IVA cooling rates at 350-200 °C are inversely correlated with bulk Ni concentration and vary by a factor of about 15. This cooling rate variation is incompatible with cooling in a metallic core that was insulated with a silicate mantle, but is compatible with cooling in a metallic body of radius 150 ± 50 km. The widths of the tetrataenite regions next to the cloudy zone correlate directly with high-Ni particle size providing another method to measure low temperature cooling rates. [source] Synthesis and photoluminescence properties of silicon nanowires treated by high-pressure water vapor annealingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007B. Salhi Abstract This paper reports on silicon nanowires (SiNWs) growth on porous silicon (PS) template using vapor-liquid-solid (VLS) technique and the effect of high-pressure water vapor annealing (HWA) on their optical properties. Gold nanoparticles (Au NPs) with average mean diameter of 50 and 20 nm were used as catalysts. The SiNWs were obtained by thermal decomposition of silane gas (SiH4) at high temperature (540 °C) catalyzed by the Au NPs. The resulting nanostructures display comparable diameter to the initial gold catalysts and are few microns long without a preferential growth direction. We have next examined the optical properties of the 20 nm diameter SiNWs. As-prepared SiNWs display a weak photoluminescence (PL), which is related to the recombination emissions from defect centers. High-pressure water vapor annealing (HWA) at 260 °C and 2.6 MPa of the SiNWs led to an increase of the PL by a factor 10 without significant changes in the emission band. TEM analysis of the HWA-treated SiNWs showed a crystalline silicon core surrounded by an amorphous oxide layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of the Mn compositional distribution on the magnetic order in diluted GaMnN layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008D. Mai Abstract GaMnN is a prototypical GaN-based dilute magnetic semiconductor (DMS) and its potential as a room temperature ferromagnetic material is still a controversial question to be answered. Diluted GaMnN layers with Mn concentrations up to several percent have been grown by plasma-assisted MBE on MOVPE-GaN templates either on p-Si(111) or on Al2O3(0001) substrates. None of the samples reported here shows second phase precipitates in XRD or in the TEM analysis. However different composition distributions have been evidenced by EDX during the scanning TEM analysis. GaMnN grown at a substrate temperature of TS = 650 °C exhibits extended structural defects and strong compositional inhomogeneity. This could be indicative of decomposition due to local strain. Samples grown at TS = 775 °C with a Mn concentration of about 3% show a homogeneous Mn distribution in the layer. The magnetic properties are found to vary from spin glass to ferromagnetic behaviour at room temperature among different samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Deep level transient spectroscopy and TEM analysis of defects in Eu implanted GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005A. Colder Abstract Deep level transient spectroscopy (DLTS) and transmission electron microscopy (TEM) are used to study europium implanted gallium nitride layers. The implantation was realised at room temperature in the random and channeled geometries. From DLTS, we determine intrinsic defects with associated levels located in the band gap (below the conduction band). Besides, we point out a new electron trap named Eu2. Its associated level is located at about Ec ,0.36 eV and the defect is probably related to the europium rare-earth ion. TEM investigation shows a difference in structure caused by changing the geometry of implantation. The random implanted sample contains numerous planar defects. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impact modified polyamide-6/organoclay nanocomposites: Processing and characterizationPOLYMER COMPOSITES, Issue 2 2008Isil Isik The effects of melt state compounding of ethylene-butyl acrylate-maleic anhydride (E-BA-MAH) terpolymer and/or three types of organoclays (Cloisite® 15A, 25A, and 30B) on thermal and mechanical properties and morphology of polyamide-6 are investigated. E-BA-MAH formed spherical domains in the materials to which it is added, and increased the impact strength, whereas the organoclays decreased the impact strength. In general, the organoclays increased the tensile strength (except for Cloisite 15A), Young's modulus and elongation at break, but the addition of E-BA-MAH had the opposite effect. XRD patterns showed that the interlayer spacing for the organoclays Cloisite 25A and Cloisite 30B increased in both polyamide-6/organoclay binary nanocomposites and in polyamide-6/organoclay/impact modifier ternary systems. TEM analysis showed that exfoliated-intercalated nanocomposites were formed. The crystallinities of polyamide-6/organoclay nanocomposites were in general lower than that of polyamide-6 (except for Cloisite 15A). In ternary nanocomposites, crystallinities generally were lower than those of polyamide-6/organoclay nanocomposites. Cloisite 15A containing ternary nanocomposites had higher tensile and impact strengths and Young's modulus than the ternary nanocomposites prepared with Cloisite 25A and Cloisite 30B, owing to its surface hydrophobicity and compatibility with the impact modifier. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers [source] | |||||||||||||||||||||||||||||||