1,720,976 research outputs found
Mechanosynthesis and Process Characterization of Nanostructured Manganese Ferrite
No full textNanocrystalline MnFe2O4 particles were synthesized by a high-energy ball milling technique, starting from a manganosite (MnO) and hematite (alpha-Fe2O3) stoichiometric powder mixture. The mechanosynthesis process was performed at room temperature both in hardened steel and in tungsten carbide vials. X-ray powder diffraction quantitative phase analysis by the Rietveld method was used to study the chemical transformations promoted by the milling action. The nanocrystalline MnFe2O4 spinel phase begins to appear after 10 h of milling and reaches its maximum content (approximate to0.8 molar fraction) after 35 h of milling. A prolonged milling time induces a dramatic contamination of the powder mixture, when hardened stainless steel was adopted, due to metallic iron originating from vial and balls debris. Ball milling is able to induce a redox reaction between Fe-III and metallic iron, transforming the MnFe2O4 spinel phase into a wustite type (Fe, Mn)O phase. The yield of the hydrogen production reaction on synthetised materials is reported
Hydrogen Production by Using Manganese Ferrite: Evidences and Benefits of a Multi-Step Reaction Mechanism
No full textHydrogen production by water splitting with MnFe2O4/Na2CO3 system was studied at 973 K. An intermediate phase, resulting from decarbonatation of MnFe2O4/Na2CO3 mixture in inert atmosphere, proved to be effective in hydrogen reduction from water with stoichiometric yield. The presence of a highly reactive intermediate phase suggests the feasibility of a high efficiency, three-step, thermochemical cycle for hydrogen production. In fact, the possibility of obtaining CO2 separately from the gases mixture dramatically enhances process efficiency
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
Procedimento Termolitico per la Produzione di Idrogeno dall’Acqua mediante Miscele Reagenti di Ferriti Miste e Carbonati
No full textAdvances in Water Splitting Process Promoted by Nanocrystalline MnFe2O4 Reactant, Synthetised by Mechanochemical route
No full textSynthesis and Characterization of Nanocrystalline MnFe2O4: Advances in Thermochemical Water Splitting
No full textNanostructured MnFe2O4 was prepared by high-energy ball milling of a stoichiometric mixture of MnO and Fe2O3 powders
and characterized by XRD, TEM and TGA techniques. The ball milling process leads to strained nanocrystals with an average
size of about 5 nm, agglomerated in sizes of about 100 nm. It was used with mechanically activated Na2CO3 to produce
hydrogen from water in the temperature range 973–1073 K. At 1023K the mixture shows a hydrogen production five times
higher than that obtained with manganese ferrite prepared by thermally activated solid-state reaction
Metodo di Preparazione Meccanochimica di Ferriti Miste Nanostrutturate da Utilizzare per la Produzione di Idrogeno da Acqua
No full textVariations 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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