Showing papers on "Cerium published in 2004"
TL;DR: In this article, the nucleation and growth of the cerium-based conversion coating on AA2024 was studied using complementary surface analysis techniques, as atomic force microscopy in the Kelvin probe mode (SKPFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).
Abstract: The chemical conversion treatment for aluminium alloys based on the immersion in cerium chloride/hydrogen peroxide solutions is one of the possible alternatives to the chromate conversion process for the corrosion protection of aluminium alloys. The nucleation and growth of the cerium-based conversion coating on AA2024 was studied using complementary surface analysis techniques, as atomic force microscopy in the Kelvin probe mode (SKPFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of both the intermetallic particles and the copper in solid solution was considered. According to this aim, different surface preparation procedures prior to the conversion process were investigated. Acid pickling and Ce-based deoxidising, as well, were found to cause the formation of copper or copper oxide deposits, i.e. copper smut, on the AA2024 surface. While the intermetallics do not act as preferential nucleation sites, the deposition of copper on the surface is a necessary condition in order to form a thick cerium oxide film. On the other hand, the copper smut strongly decreases the adherence of the conversion layer to the aluminium substrate.
276 citations
TL;DR: In this article, the effects of various factors on the luminescence intensity of the phosphor were investigated, such as sintering time, repeated calcinations, reaction temperature, and quantities of urea used in combustion with urea.
Abstract: Phosphor yttrium aluminum garnet Y3Al5O12 (YAG), activated with trivalent cerium (Ce3+) was synthesized by different methods: solid-state reaction (SS), co-precipitation (CP) with ammonium bicarbonate, sol–gel (SG) with citric acid and combustion (CB) with urea. The crystallization, morphologies, particle size and luminescent character of the phosphors obtained under different experimental conditions were studied. The influences of various factors on the luminescence intensity of the phosphor were investigated, such as sintering time, repeated calcinations, reaction temperature, and quantities of urea used in CB.
272 citations
Book•
15 Nov 2004
TL;DR: Elements Under High Pressure: Hydrogen Deuterium Tritium Lithium Sodium Potassium Rubidium Cesium Beryllium Magnesium Calcium Strontium Barium Boron Aluminium Gallium Indium Thallium Carbon Fullerene C60 Fulleren C70 Silicon Germanium Tin Lead Nitrogen Phosphorus Arsenic Antimony Bismuth Oxygen Sulfur Selenium Tellurium Fluorine Chlorine Bromine Iodine Helium - 4 Helium- 3 Neon Argon Krypton Xenon Scandium Yttrium Titanium
Abstract: Elements Under High Pressure: Hydrogen Deuterium Tritium Lithium Sodium Potassium Rubidium Cesium Beryllium Magnesium Calcium Strontium Barium Boron Aluminium Gallium Indium Thallium Carbon Fullerene C60 Fullerene C70 Silicon Germanium Tin Lead Nitrogen Phosphorus Arsenic Antimony Bismuth Oxygen Sulfur Selenium Tellurium Fluorine Chlorine Bromine Iodine Helium - 4 Helium - 3 Neon Argon Krypton Xenon Scandium Yttrium Titanium Zirconium Hafnium Vanadium Niobium Tantalum Chromium Molybdenium Tungsten Manganese Technecium Rhenium Iron Ruthenium Osmium Cobalt Rhodium Iridium Nickel Palladium Platinum Copper Silver Gold Zinc Cadmium Mercury Lanthanum Cerium Praseodymium Neodymium Prometium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thullium Ytterbium Lutecium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Crystallographic Data for the High-Pressure Phases of the Elements
233 citations
TL;DR: In this article, a multilayered system for delaying corrosion advance in metals requires that both the alteration mechanisms of the metal and the behaviour and properties of the protective coatings be known.
200 citations
TL;DR: The effects of the concentration of urea and hydrothermal treatment temperature on the morphology and crystallite size of the synthesized particles were investigated in this article, where they were angular, ultrafine cerium(IV) oxide powders with a cubic fluorite structure.
Abstract: Nanocrystalline cerium(IV) oxide (CeO2) powders were prepared by heating solutions of cerium(IV) salts in the presence of urea under hydrothermal conditions at 120° to 180°C. The effects of the concentration of urea and hydrothermal treatment temperature on the morphology and crystallite size of the synthesized particles were investigated. The synthesized particles were angular, ultrafine CeO2, with a cubic fluorite structure. Their crystallite size decreased from 20 to 10 nm with increasing urea concentration from 2 times to 8 times that of the Ce4+ ion. The size only slightly changed by calcining at temperatures below 600°C.
193 citations
Patent•
24 Feb 2004TL;DR: In this paper, the authors provide a method for generating a long-persistent phosphorescence at a selected color, including those activated by cerium and those in which persistent energy transfer occurs from a donor ion to an acceptor ion, producing persistent emission largely characteristic of the acceptor.
Abstract: The disclosure provides long-persistent phosphors, methods for their manufacture and phosphorescent articles. The disclosure also provides a method for generating a longpersistent phosphorescence at a selected color. The phosphors of the disclosure may be alkaline earth aluminates, alkaline earth silicates, and alkaline earth aluminosilicates. The phosphors include those activated by cerium. The phosphors also include those in which persistent energy transfer occurs from a donor ion to an acceptor ion, producing persistent emission largely characteristic of the acceptor ion.
189 citations
TL;DR: In this article, the effect of the incorporation of cerium ions in silica sol-gel coatings on aluminum alloys as potential replacement of chromate treatments was studied. But, the main idea was to combine the barrier effect of silica coatings with the corrosion inhibitor effect of Cerium inside the coatings.
Abstract: Chromates are among the most common substances used as corrosion inhibitors. However, these compounds are highly toxic, and an intense effort is being undertaken to replace them. Cerium compounds seem to fulfil the basic requirements for consideration as alternative corrosion inhibitors. The aim of this work was to study the effect of the incorporation of cerium ions in silica sol–gel coatings on aluminum alloys as potential replacement of chromate treatments. The main idea was to combine the ‘barrier’ effect of silica coatings with the ‘corrosion inhibitor’ effect of the cerium inside the coatings. Thin (below 1 μm for a single layer) and transparent cerium doped silica sol–gel coatings were prepared by dipping 3005 aluminum alloys in sol–gel solutions. Ultra-violet–visible spectra (UV–vis) show that cerium ions, Ce 3+ and Ce 4+ , always are present in the coatings, independently of the cerium salt or firing atmosphere used. Active protection with single and two layer coatings prepared with Ce (IV) salt seems to improve corrosion protection of the coated aluminum while coatings prepared with Ce(III) salt only entails a protection when applied as a two layer, possibly due to sealing of pre-existent defects in the first layer. The improvement of active protection with immersion time would imply that corrosion is inhibited by cerium ions that migrate through the coating to the site of the attack (a defect in the coatings) and then react to passivate the site.
143 citations
TL;DR: In this article, a golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO4 and sulfuric acid.
139 citations
TL;DR: An improved process has been developed for the spontaneous deposition of cerium oxide conversion coatings for corrosion protection of aluminum alloy 7075-T6 as mentioned in this paper, which inhibited corrosion up to two weeks in ASTM B117 salt fog testing, compared to approximately 20% for previous processes.
Abstract: An improved process has been developed for the spontaneous deposition of cerium oxide conversion coatings for corrosion protection of aluminum alloy 7075-T6. Approximately 80% of panels prepared using the improved process inhibited corrosion up to two weeks (336 h) in ASTM B117 salt fog testing, compared to approximately 20% for previous processes. Coatings were deposited from water-based solutions of CeCl3 and other compounds. Coating thickness, surface morphology, and performance in salt fog testing were sensitive to process parameters including surface preparation prior to coating, immersion time in the coating solution, and post-treatment. Surface preparation of the alloy was a critical first step in the deposition process. Desmutting followed by degreasing in a water solution of a commercial alkaline cleaner at a specific temperature was found to be an acceptable pre-treatment. Coating thickness, as determined by Auger electron spectroscopy depth profiling, varied depending on the surface pre-treatment and time that the panel was immersed in the coating solution. Immersion of desmutted, degreased panels for 15 min produced coatings 200 nm thick. Post-treatment, which converted Ce4+ in the as-deposited coating to Ce3+ as shown by X-Ray photoelectron spectroscopy, consisted of immersion in a phosphate sealing solution. Transmission electron microscopy analysis indicated that the as-deposited coatings were composed of a heretofore unidentified nano-crystalline cerium compound, presumably a hydrated Ce4+ oxide or Ce4+ hydroxide.
123 citations
TL;DR: In this paper, the effects of the treatment temperature, salt concentration, and the addition of sulfate ions on the crystallite size and morphology of the synthesized particles were investigated.
Abstract: Crystalline cerium(IV) oxide nanoparticles with a cubic fluorite structure could be synthesized from cerium(IV) ammonium nitrate solutions with a relatively high concentration of cerium(IV) (such as 0.5 mol/dm3) via thermal hydrolysis at 150°–240°C. The effects of the treatment temperature, the salt concentration, and the addition of sulfate ions on the crystallite size and morphology of the synthesized particles were investigated. The crystalline nanoparticles had a tendency to agglomerate and form spherical secondary particles with the addition of either ammonium sulfate or sulfuric acid. The existence of sulfate ions in the acidified solution was confirmed to be a factor of consequence for spherical agglomeration of the nanoparticles.
115 citations
TL;DR: In this paper, high quality monodisperse cerium(IV) oxide (CeO2) particles with a particle size less than 2nm were synthesized easily in large scale by a hydrothermal hydrolysis reaction at 120°C using (NH4)2Ce(NO3)6 as precursor in the presence of a double hydrophilic block copolymer.
TL;DR: In this paper, the effect of calcination at different temperatures on the morphology, size, and surface area of CeO2 particles was discussed and a salt byproduct coating prevented agglomeration of the particles.
Abstract: CeO2 ultrafine particles were prepared by solid-state reactions at room temperature. These particles were found to have very fine particle sizes (∼3 nm) with a fluorite structure (a= 5.42 A). BET measurements showed that the surface area of the particles was 96.2 m2/g. The use of two different precursors was found to affect the size of the CeO2 particles. We discuss the effect of calcination at different temperatures on the morphology, size, and BET surface area of CeO2 particles. A salt byproduct coating prevented agglomeration of the CeO2 particles.
TL;DR: A mild solution method has been designed for the selective synthesis of orthorhombic and hexagonal CeOHCO(3), as well as cubic CeO(2) crystals in an ethanol/water mixed solvent, adding a new example for selectively controlling different cerium compounds by manipulating the balance between kinetics and thermodynamics in a mixed solvent system.
Abstract: A mild solution method has been designed for the selective synthesis of orthorhombic and hexagonal CeOHCO(3), as well as cubic CeO(2) crystals in an ethanol/water mixed solvent. This study added a new example for selectively controlling different cerium compounds by manipulating the balance between kinetics and thermodynamics in a mixed solvent system. The competitive reactions taking place in the ethanol/water system, phase transition, and shape evolution were fully investigated: they were found to be strongly dependent on the composition of the reaction media. The influence of the ethanol content in the mixed solvent and that of the reaction time on the phase transition and shape of orthorhombic and hexagonal CeOHCO(3) crystals is discussed in detail. Metastable hexagonal CeOHCO(3) can be trapped, even at 80 degrees C, in the ethanol/water solvent mixture without the need for the high temperature adopted by previous hydrothermal approaches. The evolution process of orthorhombic and metastable hexagonal phases under mild solution conditions is discussed for the first time. Supersaturation will become faster and more evident when water is replaced by ethanol, because the inorganic salts have a lower solubility in ethanol than in water, and this will generally favor the formation of the kinetic phase, such as the hexagonal CeOHCO(3) phase reported in this paper. The optical properties of the products with different phases and composition were investigated.
TL;DR: In this article, perovskite-type oxide powders were prepared by a conventional solid-state reaction method and a subsequent mechanical milling using a planetary ball-milling machine.
01 Oct 2004-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: Cerium-doped lutetium oxyorthosilicate crystals with dimension of ∅40×60mm3 were grown by Czochralski method from an inductively heated iridium crucible as mentioned in this paper.
Abstract: Cerium-doped lutetium oxyorthosilicate crystals with dimension of ∅40×60 mm3 were grown by Czochralski method from an inductively heated iridium crucible. The crystal structure was examined by XRD and confirmed to be monoclinic symmetry. Its optical transmission, UV-excited, X-ray excited emission and light yield were measured at room temperature. Its decay time was also tested under optical excitation and gamma excitation, respectively.
TL;DR: In this paper, the corrosion protection properties of unpassivated and chromium-passivated tinplates in contact with a 0.1 M citric-citrate buffer solution were studied using polarisation (DC) and electrochemical impedance spectroscopy (EIS) methods.
TL;DR: In this article, the effect of several parameters, such as temperature, time of immersion, cerium ions and hydrogen peroxide concentration, pH of the conversion solution, on the composition and morphology of conversion layer are investigated as well as on its corrosion resistance in chloride environments.
Abstract: In this paper the effect of several parameters, such as temperature, time of immersion, cerium ions and hydrogen peroxide concentration, pH of the conversion solution, on the composition and morphology of the conversion layer are investigated as well as on its corrosion resistance in chloride environments. The cerium-based chemical conversion coatings ennobles the corrosion potential and inhibits both the cathodic and anodic reactions rate. Using a cerium (III) chloride solution a not homogeneous coating is obtained and agglomerates with a “dry-mud” morphology of mixed cerium-aluminium oxide are deposited above the cathodic intermetallic particles, while using a cerium (III) nitrate solution the coating is more uniform but thinner than that obtained with cerium (III) chloride. Solution temperature below 50°C and time of immersion of 10 minutes produces a coating with better corrosion resistance.
TL;DR: In this article, the Ce-based conversion coatings were applied on a 2024-T3 Al alloy sheet using Rutherford backscattering spectroscopy, scanning electron microscopy, Auger electron spectrography, x-ray photoelectron spectrograms, and atomic force microscopy.
Abstract: The deposition of Ce-based conversion coatings onto 2024-T3 Al alloy sheet was studied using Rutherford backscattering spectroscopy, scanning electron microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy and atomic force microscopy. The Al sheet was pretreated with an alkaline clean followed by treatment in a Ce(IV) and H2SO4-based desmutter. The Ce(IV)-based conversion coating solution contained 0.1 M CeCl3·7H2O and 3% H2O2 and was acidified to pH 1.9 with HCl. Upon immersion, there was an induction period that included activation followed by aluminium oxide growth over the matrix and cerium oxide deposition onto cathodic intermetallic particles and along rolling marks on the surface. After the induction period cerium oxide deposited generally across the whole surface and thickened. The strongest anodic sites initially were adjacent to the intermetallic cathodes and resulted in aluminium dissolution but also oxide thickening. Copyright © 2004 John Wiley & Sons, Ltd.
TL;DR: In this paper, a wide variety of primary amines were successfully examined in the presence of catalytic amounts of cerium chloride heptahydrate in ionic liquid and solvent-free conditions under mild reaction conditions.
Abstract: Enamination of a wide various primary amines was successfully carried out in the presence of catalytic amounts of cerium chloride heptahydrate in ionic liquid and solvent-free conditions as 'green' media under mild reaction conditions.
TL;DR: In the 30 years since tunable ultraviolet (UV) lasers based on 5d /spl rarr/4f transition of trivalent lanthanides doped into solid-state hosts were first demonstrated, tremendous progress has been made in these unique laser systems as discussed by the authors.
Abstract: In the 30 years since tunable ultraviolet (UV) lasers based on 5d /spl rarr/ 4f transition of trivalent lanthanides doped into solid-state hosts were first demonstrated, tremendous progress has been made in these unique laser systems. Today, cerium-doped fluoride lasers offer wide tunability (280-333 nm), high efficiency (up to 62%) and narrow-band output. These lasers can also be used for femtosecond pulse amplification in the UV. Cerium lasers represent a logical route to generation of tunable UV in all-solid-state systems. In this paper, we review the current state-of-the-art cerium laser crystal development and cerium laser systems.
TL;DR: In this paper, the authors investigated the facilitated transport of cerium(III) ions using the PIMs and found that the transport rate was strongly influenced by the experimental conditions such as the solvent/polymer ratio, the operating temperature, the membrane thickness, the carrier concentration and the feed concentration.
TL;DR: In this article, samarium-doped ceria powders for solid electrolyte ceramics were synthesized by a microwave-induced heating combustion process, and the effects of fuel type on the crystallite size of Ce1−xSmxO2−x/2 powders were studied.
TL;DR: In this paper, the nano size cerium oxides (CeO 2 ) were successfully synthesized by homogenous precipitation of ammonium cerium nitrate and urea.
Abstract: The nano size cerium oxides (CeO 2 ) were successfully synthesized by homogenous precipitation of ammonium cerium nitrate and urea. The precipitated cubic cerium oxide had primary particle size ∼8 nm with lattice constant about 5.61 A identified by diffraction pattern of transmission electron microscopy (TEM) analysis. The polishing performance of these powders had been discussed in this present work. The best polishing performance had been found. One weight percent sample C slurry has the removal rate 2258 A/min for SiO 2 film and 220 A/min for Si 3 N 4 (i.e. the selectivity=10.2). High concentration of urea or the addition of H 2 O 2 in the process seems hurt the polishing performance of these slurries.
TL;DR: In this article, accelerated methods for obtaining cerium-rich conversion coatings on aluminium-magnesium alloys are proposed, which have been characterised by SEM and EDS, revealing that the coatings have a mixed or heterogeneous nature, being composed of a layer of alumina covering the matrix, together with islands of cerium formed over the cathodic intermetallics that are present on the surface of the alloy.
TL;DR: In this article, a low-cost and facile route to the synthesis of bimetallic glycolato zirconate (Na 2Zr(C2H4O2)3) and homometallic gaseous cerate (Ce(C 2H 4O2)) was developed from the reaction of inexpensive starting materials via the oxide onepot synthesis (OOPS) process.
TL;DR: The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the Cerium target are absorbed effectively by iodine-based contrast mediums.
Abstract: The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, a unit with a Cockcroft-Walton circuit and a fixed anode x-ray tube, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5−mm-thick beryllium window. The maximum tube voltage and current were 65kV and 0.4mA, respectively, and the focal-spot sizes were 1.0×1.3mm. Cerium Kα lines were left using a barium sulfate filter, and the x-ray intensity was 0.48μC/kg at 1.0m from the source with a tube voltage of 60kV, a current of 0.40mA, and an exposure time of 1.0s. Angiography was performed with a computed radiography system using iodine-based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately 100μm with high contrasts.
TL;DR: The overall results from the preliminary screening program revealed that all of the new Nd (III) complexes reach 50% inhibition of the malignant cells proliferation and thus could be considered as biologically active.
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TL;DR: In this article, the inhibition mechanism of CeCl3·7H2O in a range of concentrations, 100 to 1000 ppm, on hot dip galvanized steel in 35 wt% NaCl solution was investigated.
Abstract: The present paper investigates the inhibition mechanisms of CeCl3·7H2O in a range of concentrations, 100–1000 ppm, on hot dip galvanised steel in 35 wt% NaCl solution Following 4 h immersion in the studied solution, galvanised steel develops a yellow layer on the surface X-ray photoelectron spectroscopy (XPS) revealed that the layer is composed of two regions: a surface region, which is a mixture of a hydrated oxide/hydroxide of cerium (III) and ZnO, and an internal region, which is a mixture of ZnO and cerium (III) oxide
TL;DR: The root/organic soil concentration ratio (R/S) of 50 cationic mineral elements was related to their ionic properties, including ionic radius, ionic charge, and ionic potential, which accounted for approximately 60% of the variability in R/S among elements.