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Metal Deposition (metal + deposition)
Selected AbstractsDeveloping a critical load approach for national risk assessments of atmospheric metal deposition,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2006Jane R. Hall Abstract The critical load approach has been proposed for evaluation of the need to reduce atmospheric emissions of metals that lead to transboundary transport and deposition across Europe. The present study demonstrates and evaluates the application of a critical load approach for national-scale risk assessment of metal deposition in the United Kingdom. Critical load maps, calculated using critical limits based on pH-dependent free metal ion activities, are presented. Current concentrations of lead and cadmium in soils are compared with two sets of critical limit values: First, limits based on the reactive soil concentration, and second, a pH-dependent free ion critical limit function, which takes into account variable soil characteristics across the country. The use of these two models leads to different conclusions about which areas of the United Kingdom are at greatest risk, partly because of differences in the range of values of pH and organic matter in soils used in ecotoxicological experiments and in the national database. Critical loads were calculated based on free ion critical limits; the critical loads were lowest in the south and east of the country and were associated with higher soil pH, lower runoff, and lower soil organic matter. [source] Humus forms and metal pollution in soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2002S. Gillet Summary Smelters in northern France are a serious source of soil pollution by heavy metals. We have studied a poplar plantation downwind of an active zinc smelter. Three humus profiles were sampled at increasing distance from the smelter, and the thickness of topsoil horizons was measured along a transect. We analysed the vertical distribution of humus components and plant debris to assess the impact of heavy metal pollution on the humus forms and on soil faunal activity. We compared horizons within a profile, humus profiles between them, and traced the recent history of the site. Near the smelter, poplar trees are stunted or dead and the humus form is a mor, with a well-developed holorganic OM horizon. Here faunal activity is inhibited, so there is little faecal deposition and humification of plant litter. At the distant site poplar grows well and faunal activity is intense, so there are skeletonized leaves and many organo,mineral earthworm and millipede faecal pellets. The humus form is a mull, with a well-developed hemorganic A horizon. The passage from mor to mull along the transect was abrupt, mor turning to mull at 250 m from the smelter, though there was a progressive decrease in heavy metal deposition. This indicates that there was a threshold (estimated to be 20 000 mg Zn kg,1) in the resilience of the soil foodweb. [source] Tunable Nanowrinkles on Shape Memory Polymer SheetsADVANCED MATERIALS, Issue 44 2009Chi-Cheng Fu Controllable biaxial and uniaxial nanowrinkles (see figure) are fabricated by a simple two-step approach , metal deposition and subsequent heating , based on shape memory polymer (prestressed polystyrene) sheets. The wavelengths of the wrinkles can be tuned by controlling the thickness of deposited metal. The ready integration of the nanowrinkles into microchannels and their effectiveness in surface enhanced sensing is demonstrated. [source] Thermochemical Patterning of Polymer Thin Films With Tunable Size-Reduction Effects Using Metal-Coated Poly(dimethylsiloxane) StampsADVANCED MATERIALS, Issue 21 2009Fangfang Wang Metal-coated poly(dimethylsiloxane) (PDMS) stamps are treated as parallel microelectrodes to selectively induce thermochemical crosslinking of polymer thin films on Si substrates. Periodical polymer micro- and nanostructures with various size-reduction effects can be achieved by changing the conditions during metal deposition or modifying the surface of the metal-coated PDMS stamp. [source] Syntheses of Porous Self-Supporting Metal-Nanoparticle Assemblies with 3D Morphologies Inherited from Biosilica Templates (Diatom Frustules)ADVANCED MATERIALS, Issue 4 2009Zhihao Bao Porous 3D metal-nanoparticle assemblies with selectable morphologies are synthesized. Biosilica templates (diatom frustules) are first converted into silicon replicas via magnesiothermic reduction. Electroless metal deposition, followed by silicon dissolution, then yields metal-nanoparticle assemblies with the 3D template morphology (figure reveals a silver assembly; inset images reveal internal features after partial ion milling and EDX analysis). [source] Nanoporous Structures Prepared by an Electrochemical Deposition Process,ADVANCED MATERIALS, Issue 19 2003H.-C. Shin Free-standing metal foam structures with nano-dendritic walls of copper and tin are fabricated by an electrochemical deposition process. This unique structure is attributed to the concurrent generation of hydrogen bubbles with extremely fast metal deposition at high cathodic current densities. The Figure shows a typical example of the foam-like structure of tin deposits with walls composed of nano-dendritic branches. [source] Assemblies of Metal Nanoparticles and Self-Assembled Peptide Fibrils,Formation of Double Helical and Single-Chain Arrays of Metal Nanoparticles,ADVANCED MATERIALS, Issue 11 2003X. Fu Double helical and single-chain arrays of Au and Pd metal nanoclusters have been achieved by assembling the corresponding metal nanoparticles on peptide nanofibril templates at different pH values. The assembled metal nanoparticles are useful for studying the superstructures of the peptide nanofibrils. Pd nanowires of different shapes have also been prepared by varying the amount of metal deposition. [source] Charge and Mass Transfer Across the Metal/Solution InterfaceISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008Eliezer Gileadi Electrode reactions are characterized by charge transfer across the interface. The charge can be carried by electrons or by ions. It is shown here that when both mass and charge cross the interface, the charge must be carried by the ionic species, not by the electrons, as a result of the very large difference in the time scale for electron and ion transfer. A prime example of charge transfer by ions is metal deposition. It is proposed that ion transfer occurs by migration of the ions across the interface, under the influence of the high electrostatic field in the double layer. The rate constants observed for metal deposition are comparable to those for outer-sphere charge transfer. These unexpectedly high rate constants for metal deposition are explained by a model in which removal of the solvation shell and reduction of the effective charge on the metal ion occur in many small steps, and a make-before-break mechanism exists, which lowers the total Gibbs energy of the system as it moves along the reaction coordinate from the initial to the final state. [source] Fabrication of 2-D nanostructures via metal deposition through a colloidal mask: comparison between thermal evaporation and RF magnetron sputteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008Magdalena Ulmeanu Abstract We use spherical polystyrene beads in the size range from 500 nm - 2 ,m to form lithographic masks on surfaces. The masks consist of hexagonally arranged monolayers of these particles formed independently via a self-organized process upon solvent evaporation. With the help of the so called floating technique, the masks can be transferred to almost any arbitrary substrate. They have been utilized e.g. as masks for vacuum deposition, ion etching, or as masters for micro-contact-printing. Current research concentrates on the structure differences when the film deposition was done by thermal evaporation or RF magnetron sputtering. Investigations have been done on different metallic films, with emphasizes on Au thin film. The structures were investigated by atomic force microscopy (AFM) and scanning force microscopy (SEM). The differences in the nanostructures obtained after the removal of the colloidal mask will be evaluated in respect with the thin film deposition technique. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Generation of paramagnetic hybrid inorganic/organic thin filmsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2010Abhinav Bhushan Abstract There is a growing interest in developing advanced materials for thin film applications in biology, electronics, photonics and engineering. We report the development of hybrid inorganic/organic thin films containing nickel, iron and cobalt paramagnetic materials. By etching the resist in oxygen plasma after processing, most of the organic component of the resist was removed. The elemental chemical composition of the films was confirmed by energy dispersive X-ray spectroscopy. This process can potentially lead to patterning paramagnetic thin films containing paramagnetic materials by following standard photolithography protocols, obviating the need for a wet or vacuum metal deposition. Copyright © 2010 John Wiley & Sons, Ltd. [source] Use of recombinant rotavirus VP6 nanotubes as a multifunctional template for the synthesis of nanobiomaterials functionalized with metalsBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Germán Plascencia-Villa Abstract The structural characteristics and predefined constant size and shape of viral assemblies make them useful tools for nanobiotechnology, in particular as scaffolds for constructing highly organized novel nanomaterials. In this work it is shown for the first time that nanotubes formed by recombinant rotavirus VP6 protein can be used as scaffolds for the synthesis of hybrid nanocomposites. Rotavirus VP6 was produced by the insect cell-baculovirus expression vector system. Nanotubes of several micrometers in length and various diameters in the nanometer range were functionalized with Ag, Au, Pt, and Pd through strong (sodium borohydride) or mild (sodium citrate) chemical reduction. The nanocomposites obtained were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) with energy dispersive spectroscopy (EDS), dynamic light scattering, and their characteristic plasmon resonance. The outer surface of VP6 nanotubes had intrinsic affinity to metal deposition that allowed in situ synthesis of nanoparticles. Furthermore, the use of preassembled recombinant protein structures resulted in highly ordered integrated materials. It was possible to obtain different extents and characteristics of the metal coverage by manipulating the reaction conditions. TEM revealed either a continuous coverage with an electrodense thin film when using sodium citrate as reductant or a discrete coverage with well-dispersed metal nanoparticles of diameters between 2 and 9,nm when using sodium borohydride and short reaction times. At long reaction times and using sodium borohydride, the metal nanoparticles coalesced and resulted in a thick metal layer. HRTEM-EDS confirmed the identity of the metal nanoparticles. Compared to other non-recombinant viral scaffolds used until now, the recombinant VP6 nanotubes employed here have important advantages, including a longer axial dimension, a dynamic multifunctional hollow structure, and the possibility of producing them massively by a safe and efficient bioprocess. Such characteristics confer important potential applications in nanotechnology to the novel nanobiomaterials produced here. Biotechnol. Bioeng. 2009; 104: 871,881. © 2009 Wiley Periodicals, Inc. [source] Heavy Metal Distribution in Soils near the Almalyk Mining and Smelting Industrial Area, UzbekistanACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009Obidjon KODIROV Abstract: The present study demonstrates distribution and chemical forms of heavy metals in soils of the Almalyk mining and smelting industrial area along five transects. The study area is located in Almalyk, Uzbekistan, where the intensification of industrial enterprises negatively impacts the environment. The distribution of 17 heavy metals (Cu, Zn, Pb, Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th, and U) were studied in 21 sampling locations (21×3=63 soil samples) along five radial transects with a total length of 60 km downwind deposition gradient. Soil samples were collected from the upper layer (0,10 cm) at 4,6 km intervals. As a result of X-ray fluorescence spectrometry analyses by using X-ray fluorescence spectroscopy (XRF, Philips Analytical Ink, USA), a significant decrease in heavy metal (Cu, Zn, Pb) deposition was found going from the source in a downwind direction. Soil samples taken from the first location (near the pollution sources) showed higher concentrations of Cu, Zn and Pb, and lower concentrations with increasing distance from the source. Obtained data showed different impact of pollution sources to heavy metal deposition and distribution in soils. The Almalyk mining and smelting complex is the major source of Pb, Zn and Cu enrichment in soils. Distribution of other trace elements does not exceed background content and suggests lithogenic background. This allowed us to divide these elements into two groups: (1) technogenic (Cu, Zn and Pb); and (2) lithogenic (Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th and U) origins. [source] | ||||||||||||||||