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Coating Layer (coating + layer)
Selected AbstractsTEM/STEM Observation of ZrC Coating Layer for Advanced High-Temperature Gas-Cooled Reactor Fuel, Part IIJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Jun Aihara The Japan Atomic Energy Agency (JAEA) has started to study and develop zirconium carbide (ZrC)-coated fuel particles for advanced high-temperature gas-cooled reactors. The ZrC coating layer has been fabricated at JAEA by chemical vapor deposition using a pyrolytic reaction of zirconium bromide. The microstructures of the ZrC layers, whose nominal deposition temperatures could be measured and controlled during the deposition process, were characterized by means of TEM and STEM. In the present study, three batches were prepared and compared with each other as well as the previous batches. The crystallographic orientation of ZrC with regard to the growth direction in the ZrC layers deposited at a constant temperature of 1630 K was different from that deposited at varying temperatures in the 1493,1823 K range. A thin layer of turbostratic carbon was observed at the boundary between pyrolytic carbon and ZrC in particles deposited at the highest temperature among those used in this study (the nominal temperature was 1769 K); no such structure was found in a batch deposited at a lower temperature (the nominal temperature was 1632 K). Therefore, precise control of temperature is shown to be critical to the formation of good ZrC coatings. [source] Microstructure Characterization of Tool Steel Claddings Co-Extruded on Low Alloyed Steel Substrates,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Pedro Augusto da Souza e Silva Low-alloyed steel bars are hot extruded with pre-sintered tool-steel powders with or without the addition of tungsten carbides (W2C/WC) as hard particles. An extrudate is formed consisting of a wear resistant coating layer and a bulk steel bar as the substrate core. The microstructure at the interface between coating and substrate of different coatings is characterized using OM, SEM and EBSD. [source] Laser shock peening on fatigue crack growth behaviour of aluminium alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8 2004Y. TAN ABSTRACT The effect of laser shock peening (LPS) in the fatigue crack growth behaviour of a 2024-T3 aluminium alloy with various notch geometries was investigated. LPS was performed under a ,confined ablation mode' using an Nd: glass laser at a laser power density of 5 GW cm,2. A black paint coating layer and water layer was used as a sacrificial and plasma confinement layer, respectively. The shock wave propagates into the material, causing the surface layer to deform plastically, and thereby, develop a residual compressive stress at the surface. The residual compressive stress as a function of depth was measured by X-ray diffraction technique. The fatigue crack initiation life and fatigue crack growth rates of an Al alloy with different preexisting notch configurations were characterized and compared with those of the unpeened material. The results clearly show that LSP is an effective surface treatment technique for suppressing the fatigue crack growth of Al alloys with various preexisting notch configurations. [source] Defect-Related Optical Behavior in Surface Modified TiO2 NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 1 2005M. Prokes Abstract The surface modification of TiO2 nanostructures to incorporate nitrogen and form visible light absorbing titanium oxynitride centers is studied. Anatase TiO2 structures in the 5,20,nm range, formed by a wet chemical technique, were surface modified and the nitridation of the highly reactive TiO2 nanocolloid surface, as determined by X-ray photoelectron spectroscopy (XPS) studies, is achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also simultaneously accompanied by metal seeding resulting in a metal coating layer on the TiO2 structures. The structure of the resultant titanium oxynitride nanostructures remains anatase. These freshly prepared samples exhibited a strong emission near 560,nm (2.21,eV), which red-shifted to 660,nm (1.88,eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitrogen doped and metal seeded TiO2 nanocolloids. Electron spin resonance (ESR) performed on these samples identified a resonance at g,=,2.0035, which increased significantly with nitridation. The resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity. [source] Cylindrical Silver Nanowires: Preparation, Structure, and Optical Properties,ADVANCED MATERIALS, Issue 21 2005M. Sun Cylindrical and pentagonal Ag nanowires (see Figure) are selectively prepared in amorphous carbonaceous sheaths via a controlled hydrothermal reaction. Results indicate that the amorphous coating layer is responsible for the cross-section symmetry selected synthesis. The distinctive optical properties measured fit well with the theoretical predictions, and applications in electronic nanodevices are envisaged. [source] Estimation of cobalt coating layer thickness on acicular Fe3O4 powder using HR-TEMJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2001Keitarou Sakai The thicknesses of cobalt coating layers grown on four different types of acicular Fe3O4 particles were estimated from the analysis of lattice images and from the determination of the Co depth profile using high-resolution transmission electron microscopy (HR-TEM) coupled with an energy dispersive X-ray (EDX) analysis system. It was observed that the coating thickness might vary with the crystallite size resulting from the growth mechanism of the coating layer. In this study, two different layer thicknesses, 40,Å and less than 10,Å, were evidenced for crystallite sizes of 390,Å and 350,Å, respectively. [source] Colonic delivery of ,-lactamases does not affect amoxicillin pharmacokinetics in ratsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2008Sandrine Bourgeois Abstract Pectin beads containing ,-lactamases were designed for the hydrolysis of colonic residual antibiotics responsible for the emergence of resistance. Beads were prepared by ionotropic gelation in CaCl2 and stabilized by coating with polyethylenimine (PEI) to resist disintegration in the upper GI tract. Particle characterization showed that dried beads had a diameter around 1 mm independently of the presence of PEI. Seven to ten percent (w/w) of PEI was located on bead surface forming a coating layer as observed by scanning electron microscopy. PEI improved considerably bead stability in simulated intestinal medium while affecting slightly the encapsulation efficiency of active ,-lactamases. Coated beads were able to preserve ,-lactamases from premature leakage in the upper GIT whereas, in simulated colonic medium, pectinases induced matrix degradation and reduction of ,-lactamase content especially in beads coated in a 0.8% PEI solution. Finally, the pharmacokinetics of amoxicillin in rat after oral administration was not modified by the co-administration of beads containing ,-lactamases. In conclusion, PEI-coated beads are stable in the upper GIT but remain sensitive to the action of pectinolytic enzymes allowing release of ,-lactamases in a colonic medium without modification of the absorption of a ,-lactam antibiotic when co-administered with loaded beads. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 1853,1863, 2008 [source] Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Ping-Hua Xiang NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO3)2·6H2O, and NH4HCO3 as the starting materials. The amorphous NiCO3·2Ni(OH)2·2H2O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ,8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ,30 nm. [source] Water-Based Gelcasting of Surface-Coated Silicon Nitride PowderJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Yong Huang A layer of Y2O3,Al2O3, used as a sintering aid, was coated onto the surface of Si3N4 particles by the precipitation of inorganic salts from a water-based solution containing Al(NO3)3, Y(NO3)3, and urea. The electrokinetic and colloidal characteristics of the Si3N4 powder were changed significantly by the coating layer. As a result, dispersion of the Y2O3,Al2O3 -coated Si3N4 powder was significantly greater than that of the original powder. Furthermore, the Y2O3,Al2O3 coating layer prevented the hydrogen-gas-discharging problem that occurred during gelcasting of the original Si3N4 powder because of reaction between the uncoated powder and the basic aqueous solution in suspension. Surface coating, as well as the gelcasting process, significantly improved the microstructure, room-temperature bending strength, and Weibull modulus of the resulting ceramic bodies. [source] Improvement of the optical properties of GaN epilayers on Si(111): Impact of GaAs layer thickness on Si and pre-growth strategyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Bablu K. Ghosh Abstract This paper reports the effect of the GaN coating layer on the optical properties of GaN epilayers grown on GaAs/Si(111). Almost crack free GaN epilayers are found to be grown when a thin (,25 nm) GaN coating layer is inserted on 0.5 and 2 ,m GaAs layers at 550 °C. Then nitridation of the GaAs layer is done through the coating layer by NH3 flow while the substrate temperature is ramped at 1000 °C for epilayer growth. An attempt has also been made by implementing an additional GaN interlayer at 800 °C while growth is continued for epilayer growth. For this growth strategy, cracks also happened without improvement of the epilayer quality. PL measurements show high excitonic peak energy and high excitonic to yellow band intensity ratio for GaN epilayers grown on the 0.5 ,m GaAs converted layer (CL) using a thin GaN coating layer. Those values are also found to be comparable/ better than for epilayers grown on 2 ,m CL. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microencapsulation of ammonium polyphosphate: Preparation, characterization, and its flame retardance in polypropylenePOLYMER COMPOSITES, Issue 8 2008Kun Wu Microencapsulated ammonium polyphosphate (MCAPP) with a melamine,formaldehyde (MF) resin coating layer was prepared by in situ polymerization. MCAPP was characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, and so on. The results show that the microencapsulation with MF resin leads to a decrease in the particles' size and water absorption. The flame retardant action and mechanism of MCAPP and ammonium polyphosphate (APP) in polypropylene are studied using limiting oxygen index (LOI) and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis. The LOI value of the PP/MCAPP composite at 30 wt% loading is 30.5%, whereas the corresponding value of the PP/APP composite is only 20%. Moreover, the LOI values of the PP/MCAPP/PER composites are higher than the ones of the PP/APP/PER composites. In the UL 94 test, the PP/MCAPP/PER composites with suitable ratios of MCAPP to PER can reach the V-0 rating, and the best rating of the PP/APP/PER composites is V-1. V-1. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Properties and interfacial bonding for regenerated cellulose,polyurethane/amylose acetate sipn composite filmsPOLYMER COMPOSITES, Issue 6 2000Jiahui Yu Composite films were obtained by placing a polyurethane/amylose acetate semi-interpenetrating polymer network (SIPN) coating onto the surfaces of regenerated cellulose (RC) film. The properties of the composite film, such as tensile strength, 79.9 MPa (in dry state), 49.5 MPa (in wet state), water resistance (R), 0.62, dimensional stability (Sc), 3.0%, and water vapor permeability (P), 5.96 × 10,5 Kgm,2h,1, are better than those of the uncoated RC film or RC film with PU coating. The interfacial strength was characterized with infrared spectroscopy (IR), ultraviolet spectroscopy (UV), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). The results showed the existence of covalent and hydrogen bonds between the SIPN coat layer and the RC layer. It was also found that the PU prepolymer in the coating layer penetrated into the cellulose bulk, and reacted with the cellulose molecules, which formed another SIPN. [source] Preparation and characterization of microcapsulated red phosphorus and its flame-retardant mechanism in halogen-free flame retardant polyolefinsPOLYMER INTERNATIONAL, Issue 8 2003Qiang Wu Abstract Microcapsulated red phosphorus (MRP), with a melamine,formaldehyde resin coating layer, was prepared by two-step coating processes. The physical and chemical properties of MRP were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen-free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine,formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame-retardant mechanism that RP can promote the formation of charred layers with the P,O and P,C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry [source] Inorganic Layers on Polymeric Films , Influence of Defects and Morphology on Barrier PropertiesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2003M. Hanika Abstract Flexible polymeric films are not only widely used in conventional packaging as substitute for glass and aluminum foil packaging but are also proposed as encapsulation for novel products, like flexible solar cells or organic light-emitting devices. The two essential properties of the polymeric packaging are flexibility and good permeation barrier properties against gases and vapors. This article deals with vacuum web coating as a common way of increasing barrier properties of polymeric films and the problems related to this procedure. Defects caused by particles and surface imperfections are found to dominate the permeation rate for such coated polymeric films. Atomic force microscopy, electron and also optical microscopy was used for analysis of the coating layer. Three-dimensional numerical simulations were performed for modeling of the influence of defect size, spacing and film thickness. Results of numerical modeling and of many practical experiments show that the permeability is almost independent of the substrate film thickness when a critical thickness is exceeded. In most cases the defects can be treated as independent of each other. The gas permeability of vacuum web-coated polymeric films can be quantitatively predicted by a simple formula. For gases, like oxygen, it is shown that a statistic analysis of the defect sizes by optical microscopy is sufficient. For water vapor transmission, however, the structure of the coating layer itself has also to be taken into account. [source] Electrode Reactions of Catechol at Tyrosinase-Immobilized Latex SuspensionsELECTROANALYSIS, Issue 8 2004Patsamon Rijiravanich Abstract Tyrosinase was immobilized on polystyrene latex particles in order to control amounts of the enzyme. The tyrosinase-coated latex particles were composed of the core polystyrene and four successive coating layers: polystyrene sulfonate, polyallylamine, tyrosinase and polyallylamine again, built up by the layer-by-layer technique. They showed catalytic currents for the enzymatic oxidation of catechol to o -quinone. The enzyme activity per particle was evaluated as 2.3×10,7 units from UV absorption of o -quinone. The relation between the catalytic current and the concentration of catechol leads to a Michaelis-Menten type kinetic equation. The layer-by-layer method was found to have a deactivating effect on enzyme catalysis. In spite of this, the catechol oxidation current was larger than the current from free tyrosinase at a common value of enzyme units per volume. This is ascribed to strong adsorption of the latex particles on the electrode, leading to the enhancement of the local concentration of tyrosinase. [source] Estimation of cobalt coating layer thickness on acicular Fe3O4 powder using HR-TEMJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2001Keitarou Sakai The thicknesses of cobalt coating layers grown on four different types of acicular Fe3O4 particles were estimated from the analysis of lattice images and from the determination of the Co depth profile using high-resolution transmission electron microscopy (HR-TEM) coupled with an energy dispersive X-ray (EDX) analysis system. It was observed that the coating thickness might vary with the crystallite size resulting from the growth mechanism of the coating layer. In this study, two different layer thicknesses, 40,Å and less than 10,Å, were evidenced for crystallite sizes of 390,Å and 350,Å, respectively. [source] Effect of Flaw State on the Strength of Brittle Coatings on Soft SubstratesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Hae-Won Kim A study is made of the role of flaw state on the strength properties of brittle ceramic coating layers bonded to soft polycarbonate substrates. We introduce Vickers radial cracks at prescribed loads into the coating undersurfaces prior to bonding to control the sizes and locations of the starting flaws. A spherical indenter is then loaded on the top bilayer surfaces, directly above the Vickers indentation sites, subjecting the radial cracks to flexural tensile stress. Radial crack responses are monitored in situ, using a camera located below the transparent substrate. Critical loads to cause radial crack instability, and ensuing growth of the arrested cracks, are recorded. Conventional biaxial flexure tests on corresponding monolith coating materials provide a baseline for data comparison. Relative to the monolith flexure specimens, the bilayers show higher strengths, the more so the larger the flaw, indicating enhanced flaw tolerance. A simple fracture mechanics analysis of the radial crack evolution in the concentrated-load field, with due account for distribution of flexural tensile stresses at the coating undersurface, is unable to account completely for the enhanced bilayer strengths for the larger Vickers flaws. It is hypothesized that the epoxy used to bond the bilayer components enters the cracks, causing crack-wall adherence and providing an increased resistance to radial crack instability. The fracture mechanics are nevertheless able to account for the arrest and subsequent stable extension of the radial cracks beyond the critical loads once this extraneous adherence has been overcome. [source] Characterization of spin crossover crystal surface by AFMPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010C. Chong Abstract Imaging nano-domains in spin crossover (SCO) compounds remains so far an unreached goal. We report on the first AFM tapping-mode investigation of SCO single crystals, performed at room temperature with the well known mononuclear compound [Fe(ptz)6](BF4)2 (ptz,=,1-propyl-tetrazole) and the trinuclear supramolecular compound [Fe3(hyetrz)6(H2O)6](CF3SO3)6 (hyetrz,=,4-(2,-hydroxyethyl)-1,2,4-triazole) which shows a gradual spin conversion centred at room temperature. The natural surface of the former crystal revealed a volatile coating of the scanned area attributed to the transport of adsorbed water under the effect of interaction with the AFM tip. The second one showed astonishing leopard-skin patterns assigned to the effect of atmospheric humidity on this hygroscopic compound. Their origin is discussed. We suggest the use of fluid coating layers as a general method for revealing the nano-patterning of physical properties (e.g. like-spin domains) at the surface of dielectric materials. AFM-tapping images of [Fe3(hyetrz)6(H2O)6](CF3SO3)6 at room temperature and ambient atmosphere. [source] | ||||||||||||||||