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Hydrogen Treatment (hydrogen + treatment)
Selected AbstractsThe effect of ball milling before and after calcination on the magnetic properties of HTR processed strontium hexaferrite powderPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004S. A. Seyyed Ebrahimi Abstract HTR process (Hydrogen Treatment and Recalcination) is a very new method in which strontium hexaferrite powder, as produced conventionally from strontium carbonate and iron oxide, has been heated in a hydrogen static atmosphere and then recalcined in air. During the hydrogenation stage, the hard magnetic powder is changed to a soft magnetic material with a low intrinsic coercivity and high saturation magnetisation. However, after recalcination, the saturation magnetisation returns to its initial value, but intrinsic coercivity increases to a value much greater than its amount before hydrogenation. The intrinsic coercivity which has been reported in this regard is about 391 kA/m. In this work this HTR processed powder has been milled in a ball mill and effect of milling before and after calcination on microstructure and particularly magnetic properties has been investigated. The results show a good enhancement in the intrinsic coercivity of material. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth of Metal Nanoparticles in a Sol-Gel Silica Thin FilmEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Miroslava Malenovska Abstract Silica films on glass substrates with homogeneously dispersed platinum, gold or silver nanoparticles were prepared by sol-gel processing mixtures of tetraethoxysilane and {3-[(2-aminoethyl)amino]propyl}triethoxysilane complexes of the corresponding metal ions, followed by dip-coating and hydrogen treatment of the films at elevated temperatures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Carbon nanotube-supported bimetallic palladium,gold electrocatalysts for electro-oxidation of formic acidPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010Cheng-Han Chen Abstract It is known that palladium-based catalysts are initially very active in direct formic acid oxidation but they suffer from fast deactivation caused by a strongly adsorbed CO intermediate. Reactivation of the catalysts involving application of anodic potential may cause palladium dissolution. The aim of the present study is to increase the stability and performance of palladium-based catalysts in direct formic acid fuel cells (DFAFCs). Preparation and characterization of palladium/multiwalled carbon nanotubes (Pd/MWCNTs) and towards formic acid oxidation via different treatments are described. The catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). It was shown that the Pd and Pd,Au MWCNTs supported catalysts after reduction in H2,Ar at 200,°C (R200 treatment) were highly active in formic acid electro-oxidation, whereas the catalysts after heating in argon at 250,°C (C250 treatment) were inactive. The catalysts after hydrogen treatment have smaller metal particles and better contact with MWCNTs support. CV, simulating reactivation of the catalysts, showed that the Pd catalyst suffers from severe Pd dissolution, whereas for the Pd,Au selective leaching of Pd is considerably slower. [source] Trichlorofluoroethene: A reactive tracer for evaluating reductive dechlorination in large-diameter permeable columnsGROUND WATER MONITORING & REMEDIATION, Issue 2 2005Jennifer A. Field Trichlorofluoroethene (TCFE) was used as a reactive tracer to determine the in situ rate of reductive dechlorination in treatment zones impacted by three large-diameter permeable columns (LDPCs) that were installed at a trichloroethene (TCE),contaminated site. The LDPCs were part of a pilot study to evaluate the effectiveness of hydrogen, lactate, and zero-valent iron for remediating TCE-contaminated ground water. The rate of TCFE reductive dechlorination was determined for each LDPC by means of push-pull tests conducted in each treatment layer. In addition, the distribution of TCFE's lesser chlorinated transformation products was determined. The rates of TCFE reductive dechlorination ranged from 0.05/d to 0.20/d and corresponded to half-lives ranging from 3.5 to 13.9 d. cis -Dichlorofluoroethene was the dominant transformation product detected in all the tests, which is consistent with the findings from pilot tests conducted in the LDPCs prior to the TCFE push-pull tests. cis -Chlorofluoroethene (CFE) and 1,1-CFE also were detected and indicate the potential for vinyl chloride to form under all treatment regimes. Significant production of fluoroethene (FE), the analog of ethene, was observed for only one of the hydrogen treatments. Unambiguous and sensitive detection of the lesser chlorinated products, such as CFE and FE, is possible because TCFE and its transformation products are not found in the background ground water at contaminated sites. Good agreement between the rates and transformation product profiles for TCFE and TCE in both field and laboratory experiments indicates the suitability of TCFE as a surrogate for predicting the rates of TCE reductive dechlorination. [source] | ||||||||||