1,720,993 research outputs found
Structural and hydrogen storage properties of Mg-x wt% ZrCrMn composites
No full textMagnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350°C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. Composite formation with Zr based laves phase alloys, especially ZrCr2 family, is an effective method to improve the hydriding properties of MgH2. This work presents the synthesis, structural, morphological, and hydrogenation properties of Mg-x wt% ZrCrMn composites. Both phases i.e. Mg & ZrCrMn remain their presence after milling and several hydriding cycles as well. SEM results suggest the homogeneous distribution of alloy particles on Mg matrix. Pressure composition temperature (PCT) analysis shows a reduction in desorption temperature down to 250°C for these composites. TG experiments suggest a total hydrogen capacity of 5.9% and 4.35% for x =25, 50 in Mg-x wt% ZrCrMn composites respectively. The enthalpy of hydride formation is also calculated using Van't Hoff plots, which is found similar to the parent material i.e. MgH2. A remarkable enhancement in the kinetics of hydrogen absorption / desorption is reported here by forming these composites
Siloxanes removal from biogas by high surface area adsorbents
No full textBiogas utilized for energy production needs to be free from organic silicon compounds, as their burning has damaging effects on turbines and engines; organic silicon compounds in the form of siloxanes can be found in biogas produced from urban wastes, due to their massive industrial use in synthetic product, such as cosmetics, detergents and paints. Siloxanes removal from biogas can be carried out by various methods (Mona, 2009; Ajhar et al., 2010 May; Schweigkofler and Niessner, 2001); aim of the present work is to find a single practical and economic way to drastically and simultaneously reduce both the hydrogen sulphide and the siloxanes concentration to less than 1ppm. Some commercial activated carbons previously selected (Monteleone et al., 2011) as being effective in hydrogen sulfide up taking have been tested in an adsorption measurement apparatus, by flowing the most volatile siloxane (hexamethyldisiloxane or L2) in a nitrogen stream, typically 100-200ppm L2 over N2, through an activated carbon powder bed; the adsorption process was analyzed by varying some experimental parameters (concentration, grain size, bed height). The best activated carbon shows an adsorption capacity of 0.1g L2 per gram of carbon. The next thermogravimetric analysis (TGA) confirms the capacity data obtained experimentally by the breakthrough curve tests. The capacity results depend on L2 concentration. A regenerative carbon process is then carried out by heating the carbon bed up to 200. °C and flushing out the adsorbed L2 samples in a nitrogen stream in a three step heating procedure up to 200. °C. The adsorption capacity is observed to degrade after cycling the samples through several adsorption-desorption cycles. © 2013 Elsevier Ltd
Use of active carbon for the removal of sulphur impurities from a biogas stream for SOFC application
No full textAn interesting application of solid oxide fuel cell (SOFC) technology is the micro-cogeneration (μ-CHP) in the residential area fed with a sustainable (renewable) source such as biogas produced from anaerobic digestion (AD) of organic waste. Even though the major components of biogas are CH4 and CO2, several contaminants can be inside the biogas and have to be removed before entering the cell. Sulphur compounds are the most harmful for SOFC systems. The aim of this work is to study the removal of sulphur compounds using activated carbon adsorption trapping and test the obtained results in a SOFC single cell. Two different carbon filters were tested under the following sulphur contaminants: H2S, THT, COS, DMS and single cells were performed with a simulated biogas enriched with a selected small amounts of the contaminants in order to evaluate tolerance and degradation process
A composite electrode based on sub-micrometric iron metal and lithium fluoride
No full textIn this paper a general method to obtain a mixture of a transition metal embedded in a matrix of lithium fluoride is proposed. The method consists in the reduction of the oxide of the transition metal with lithium hydride to form the correspondent transition metal and lithium oxide. This latter is then converted into lithium fluoride by solid state reaction with ammonium fluoride. In this work the proposed method was applied to iron(III) oxide to obtain a mixture of iron metal and lithium fluoride. The crystal structure and phase purity of the intermediate as well as the final product were analyzed by X-ray diffraction measurement and the crystallite dimensions evaluated by using the Scherrer's formula. The iron metal/lithium fluoride mixture was used as a conversion material and its electrochemical properties evaluated by galvanostatic charge discharge cycles, impedance spectroscopy and galvanostatic intermittent titration technique. As the conversion material is in its reduced state it can be coupled with a carbonaceous negative electrode to build a lithium ion battery, opening new perspectives for using conversion materials in lithium ion batteries technology. © 2013 Elsevier Ltd. All rights reserved
Ricerca su materiali e processi per la realizzazione di materiali catodici con prestazioni migliorate. Analisi morfologica dei prodotti finali
Full text linkI sali d’ammonio preparati con differenti metodologie sono stati trattati termicamente in presenza di litio per trasformarli in LiFePO4. Il trattamento termico è stato effettuato normalmente a 600°C per 2 ore mentre in due casi lo stesso è stato effettuato a differenti temperature (550 e 700°C). Le morfologie dei materiali così ottenuti sono state valutate sia in funzione della preparazione del precursore sia, per lo stesso precursore, in funzione del trattamento termico
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Modeling AC losses in the ITER NbTi poloidal field full size joint sample (PF-FSJS) using the THELMA code
No full text
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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