1,720,967 research outputs found
Assessment of Chernobyl radioactive fallout over Padua
No full textIncreased atmosphere radioactivity from the Chernobyl nuclear reactor accident was first detected on air filters taken in Padua on 30 April 1986. Air activities reached the maximum values of 28.6, 19.2, 3.3, 1.7 and 7.5 Bq m-3 for 131I, 132Te(132I), 137Cs, 134Cs and 103Ru respectively, on 1 May; about ten days later the activities declined to less than 1% of peak values. The distribution of radionuclides in Padua was evaluated on the basis of radioactivity measurements detected on natural collectors; it was estimated an average committed dose equivalent to thyroid of 0.37 mSv for adult people in Padua due to 131I inhalation. -English summar
Transfer of Chernobyl radioisotopes to mushrooms
No full textMeasurements of radionuclide activities, following the Chernobyl accident, on some common mushrooms taken in NE Italy, during July-November 1986, are reported together with the corresponding soil analyses. Some species tend to concentrate Cs and Ag isotopes; other species present low concentration levels according to their different characteristics and metabolic behaviours. -English summar
Electrodeposition of Cu+PdO and (Cu-Pd) +PdO composites
No full textThe codeposition of PdO particles with a Cu matrix has been investigated with the aim of extending the composite deposition procedure to the preparation of materials potentially capable of catalyzing the low temperature combustion of methane. Cu+PdO composites with a low dispersed phase content were obtained from either basic pyrophosphate or acid sulfate baths. Codeposition of PdO particles with a Cu-Pd alloy matrix was effectively achieved by electrolyzing suspensions of PdO in solutions containing both Cu2+ and Pd 2+ ions, with large [Cu2+] / [Pd2+] ratios. (Cu-Pd) +PdO deposits with 20-25 Pd atom % were obtained in which only 1-2 atom % of Pd were alloyed in the matrix. These (Cu-Pd) +PdO composites were mechanically stable and highly porous throughout their thickness (their pore volume being ca. 60% of the total volume). Their true surface area was some thousands of times higher than their geometric area. © 2010 The Electrochemical Society
Effective and Low-Cost Synthesis of Sulphur-Modified TiO2Nanopowder with Improved Photocatalytic Performances in Water Treatment Applications
No full textIn the present paper, sulphur-modified titanium dioxide (S-TiO2) is prepared as nanopowder in mixed rutile-anatase phase by an unprecedented simple, reproducible and cheap synthetic procedure, directly employing elemental sulphur powder as sulphur source. TiO2 and several reference TiO2 samples obtained in pure rutile or anatase phase were also prepared with nanometric size and compared to S-TiO2 as well as Degussa P25. The prepared samples and the reference benchmark were characterised by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), BET specific surface area and X-ray Photoelectron Spectroscopy (XPS) techniques, while their photoactivity was determined with respect to methyl red degradation as typical probe reaction. The results from the characterisation and photocatalytic measurements were discussed and inter-correlated, thus providing a complete and consistent analysis of the samples performances. The prepared sulphur modified titanium dioxide appeared as a very efficient and long-lasting photocatalyst with respect to the unmodified TiO2 and to the benchmark Degussa P25 (S-TiO2 appears to be two times faster than P25) for the methyl red removal under UV lighting, also in repeated cycles
Electrodeposition of compact and porous Cu-Zn alloy electrodes and their use in the cathodic reduction of nitrate
No full textCompact and porous Cu-Zn alloys were electrodeposited from citrate baths. The latter deposits, consisting of a spongy material with a macroscopic interconnected porosity (pore diameter of tens of microns), were obtained at large current densities (-3 A cm-2) causing strong hydrogen evolution. Porous deposits with compositions between Cu62Zn38and Cu91Zn9were obtained by varying the ions concentrations in the deposition baths, with optimal morphology for the Cu70Zn30composition. The lattice parameter of the samples, estimated from XRD data, showed in the explored range a linear dependence on composition, consistent with formation of a solid solution of Zn in Cu. The alloy materials were tested in nitrate reduction in alkali by voltammetry, chronoamperometry and constant potential electrolysis. Their performances were compared with those of similar (compact and porous) Cu electrodes. The nitrate reduction current decayed rapidly at compact Cu electrodes and was stable at the other electrodes, being the highest at porous Cu70Zn30. In all cases, the main product was ammonia
Electrodeposition of Cu-Rh alloys and their use as cathodes for nitrate reduction
No full textCu-Rh alloys have been electrodeposited from sulfate solutions, pH 3.4. Although Rh is more noble than Cu, the reduction peak of Rh3 +was ca. 0.4 V more negative than that of Cu2 +. Therefore, the Rh/Cu ratio in the deposited alloys, determined by EDS analyses, increased as the deposition potential became more negative. XRD analyses showed that the deposited alloys were polycrystalline and suggested that metastable CuxRh1 - xsolid solutions were formed for 0.1 ≤ x ≤ 0.8, although for such compositions a miscibility gap is known to exist. The Cu-Rh alloys were tested as cathodes for the reduction of nitrates and found to have significant catalytic activity. © 2012 Elsevier B.V
Electrodeposition of Cu-Ni alloy electrodes with bimodal porosity and their use for nitrate reduction
No full textCu-Ni alloy layers with a bimodal porosity - a spongy material made of submicron dendrites, featuring macroscopic pores tens of microns large - can be deposited from baths containing the metal ions, sodium citrate and ammonium sulfate, using large current densities (-3 A cm-2) producing vigorous hydrogen evolution. Alloys with a broad range of compositions are obtained using baths with different Cu(II)/Ni(II) concentration ratios. Voltammetric experiments of nitrate reduction at compact and porous Cu-Ni RDEs show, in the latter case, lower overvoltage and higher peak currents, resulting from enhanced transport and improved catalytic activity. © 2013 The Electrochemical Society
Electrodeposition of compact and porous Cu-Pd alloy layers and their application to nitrate reduction in alkali
No full textCompact Cu-Pd alloys of compositions extending over the entire range are deposited at low overpotentials, from acidic sulphate/perchlorate baths of the two metal ions. XRD data show a lattice parameter following Vegard's law. Porous alloy layers can be deposited from acidic chloride baths under large current densities causing vigorous hydrogen evolution. Good deposits with regular morphology are obtained only from Cu-rich baths, and for Pd contents up to ca 33 at%. XRD investigations indicate a biphasic structure, made of pure Cu and a Cu17Pd83phase, in variable ratios depending on composition. Single phase porous Cu-Pd materials are obtained by prolonged galvanic displacement of porous Cu layers. Selected electrode materials are tested in the nitrate reduction in alkaline media, comparing the effects of composition and surface area
Hybrid synergic methodology to prepare ALD honey-comb anatase films
No full textMacroporous inorganic structures with high surface-to-volume ratio have been recognized as a centre of interest in many fields. Here, attention is focused on a hybrid synergic methodology to prepare honey-comb (HC) anatase TiO2 films with increased specific surface area. The breath figures (BFs) method is exploited to produce HC polystyrene (PS) templates and atomic layer deposition (ALD) is used to conformally cover them with a TiO2 coating. Different approaches are tested to preserve the HC-TiO2 structure during the conversion of the hybrid organic/inorganic materials into crystalline anatase films. Best results are obtained operating with ALD at 180 °C on pre-UV cross-linked substrates
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