906 resultados para powders
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A range of catalysts based on Pd nanoparticles supported on inorganic supports such as BETA and ZSM-5 zeolites, a silicoaluminophosphate molecular sieve (SAPO-5) and γ-alumina as a standard support have been tested for the total oxidation of naphthalene (100 ppm, total flow 50 ml/min) showing a conversion to carbon dioxide of 100% between 165 and 180 °C for all the analysed catalysts. From the combined use of zeolites with PVP polymer protected Pd based nanoparticles, enhanced properties have been found for the total abatement of naphthalene in contrast with other kinds of catalysts. A Pd/BETA catalyst has been demonstrated to have excellent activity, with a high degree of stability, as shown by time on line experiments maintaining 100% conversion to CO2 during the 48 h tested.
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Hess Rise, in the western Pacific Ocean, formed in the mid-Cretaceous south of the equator and moved north with the Pacific Plate (Lancelot and Larson, 1975; Lancelot, 1978; Valuer et al., 1979). Southern Hess Rise was a volcanic archipelago, at least until late Albian time, after which it subsided to become one of the major aseismic rises in the present western Pacific. A second pulse of volcanic activity apparently occurred in the Campanian-Maastrichtian interval, which may be related to tectonic uplift of Hess Rise (Valuer and Jefferson, this volume). Trachytic rocks underlie 412 meters of carbonate sediments at Site 465 on southern Hess Rise. Twenty-four meters of trachyte were recovered from a 64-meter cored interval. The rocks are relatively homogeneous in texture, color, and composition, indicating that the cored sequence was probably part of only one magmatic event (Seifert et al., this volume). Large (> 5-mm) vesicles and oxidized parts of some flows suggest subaerial or shallow-water extrusions. The rocks are high in silica and relatively rich in Na2O, K2O, and light rare-earth elements. The upper part of the volcanic-rock sequence is a breccia, the fragments cemented by calcite, pyrite, and rare barite. Some of the resultant veins are more than 1 cm thick. In addition to the veins, many vesicles are also filled with these minerals. Brecciation and the number and thickness of veins decrease with depth in the hole. The degree of weathering, as indicated by water content, also decreases with depth.
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"Contract AT-30-1 GEN-366."
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Mode of access: Internet.
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"Translation of: Nekotoryye voprosy teorii protsessa pressovaniva metallicheskih poroshkov i ikh smesey." (romanized form)
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Polycrystalline cerium hydroxysulfate powders have been prepared by soft solution processing using various basic solvents. The crystals prepared have varying morphologies, spherical and flaky, depending on the solvent used. The crystals obtained from distilled water-pyridine and aqueous ammonia solvent mixtures are spherical, whereas those obtained from mixtures of distilled water and ethylenediamine or hydrazine hydrate are flaky. All the crystalline cerium hydroxysulfate samples display luminescence properties. It was found that the flaky crystals generally show a much stronger luminescence than their spherical counterparts.
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The importance of sticky behaviour of amorphous food powders has been recognized over many decades in the food industry due to its influence on process and handling abilities and quality of the powders. This paper emphasizes the role of stickiness in the food powder industry as well as reviews the stickiness characterization techniques developed to date. This paper also attempts to correlate the stickiness behaviour of food powders to the instrumental analysis such as glass transition temperature. (C) 2004 Elsevier B.V All rights reserved.
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The cyclone stickiness test (CST) technique was applied to measure the stickiness temperature and relative humidity of whey, honey, and apple juice powders. A moisture sorption isotherm study was conducted to analyze the surface moisture content of whey powder. The glass transition temperatures of the sample powder were analyzed using differential scanning calorimetry (DSC). The stickiness results of these products were found within 20 degrees C above their surface glass transition temperatures, which is well within the normal temperature range for glass transition in general. The results obtained by the CST technique were found consistent with DSC values.