Search results for "Metallurgy"
showing 10 items of 1419 documents
The Effect of Dopants on Sintering and Microstructure of Lead-free KNN Ceramics
2011
Lead-free potassium sodium niobate (K0.5Na0.5)NbO3 (KNN) has been prepared via conventional ceramic processing method. The influence of 0.5 wt% - 1.5 wt% MnO2 and WO3 addition on the sintering, crystallographic structure, microstructure and dielectric properties of KNN has been investigated. Optimal sintering temperatures of KNN ceramics were observed to be in the narrow interval: 1090 °C - 1110 °C for MnO2 doped KNN; 1150 °C - 1170 °C for pure KNN and doped with WO3. XRD patterns showed that all the samples have single perovskite structure with monoclinic structure. Microstructure of ceramics was changed greatly by using dopants.http://dx.doi.org/10.5755/j01.ms.17.1.251
Flash infrared annealing as a cost-effective and low environmental impact processing method for planar perovskite solar cells
2019
Abstract For successful commercialization of perovskite solar cells, straightforward solutions in terms of environmental impact and economic feasibility are still required. Flash Infrared Annealing (FIRA) is a rapid method to fabricate perovskite solar cells with efficiencies >18% on simple, planar architecture, which allows a film synthesis in only 1.2 s, faster than the previous report based in a meso architecture and all of them without the usage of antisolvent. In this work, through a comparative study with the common lab-scale method, the so-called antisolvent (AS), the main photovoltaic parameters and working mechanisms obtained from impedance spectroscopy (IS) measurements show simil…
The influence of NiTi alloy on the cyclic fatigue resistance of endodontic files
2020
Background: The aim of this study was to analyze the influence of NiTi alloy in endodontic rotary instruments on cyclic fatigue resistance. Methods: One hundred and sixty-four (164) sterile endodontic rotary files were selected and distributed into the following study groups: A: 25.08 F2 ProTaper Universal (PTU) (n = 41)
First combined flux chamber survey of mercury and CO2 emissions from soil diffuse degassing at Solfatara of Pozzuoli crater, Campi Flegrei (Italy): M…
2014
Abstract There have been limited studies to date targeting gaseous elemental mercury (GEM) flux from soil emission in enriched volcanic substrates and its relation with CO 2 release and tectonic structures. In order to evaluate and understand the processes of soil–air exchanges involved at Solfatara of Pozzuoli volcano, the most active zone of Campi Flegrei caldera (Italy), an intensive field measurement survey has been achieved in September 2013 by using high-time resolution techniques. Soil–air exchange fluxes of GEM and CO 2 have been measured simultaneously at 116 points, widely distributed within the crater. Quantification of gas flux has been assessed by using field accumulation chamb…
Sulphate removal over barium-modified blast-furnace-slag geopolymer
2016
Blast-furnace slag and metakaolin were geopolymerised, modified with barium or treated with a combination of these methods in order to obtain an efficient SO4(2-) sorbent for mine water treatment. Of prepared materials, barium-modified blast-furnace slag geopolymer (Ba-BFS-GP) exhibited the highest SO4(2-) maximum sorption capacity (up to 119mgg(-1)) and it compared also favourably to materials reported in the literature. Therefore, Ba-BFS-GP was selected for further studies and the factors affecting to the sorption efficiency were assessed. Several isotherms were applied to describe the experimental results of Ba-BFS-GP and the Sips model showed the best fit. Kinetic studies showed that th…
Introduction. La paléomanufacture métallique : une nouvelle méthode d’étude
2007
The aim of this introduction to the third part of the specialist theme is to clarify the roles and the themes studied by each associate concerning the metal artefacts. It is divided into two parts:— the history of the study of metal artefacts and the presentation of a new method : metal paleo-manufacturing ;— research guidelines for this new speciality.
Quel statut pour les espaces de montagne durant l'âge du Bronze ? Regards croisés sur les approches société-environnement dans les Pyrénées occidenta…
2005
After having been neglected for some time, mountain environments have now become an important research area for the study of anthropogenic impact on the environment and the interactions of societies with their environments. The recent development of several interdisciplinary programs in the Alps and in the Pyrenees reveals the interest and the scientific questions associated with these domains. In the Pyrenees, the work undertaken in the Basque Country illustrates the utility of the development of multidisciplinary research on a large scale, which is both diachronic and has a high resolution chronology. Combining environmental and archaeological data, allows us to present an image of popula…
Residual Stress Effects on Fatigue Crack Growth in Ti-6Al-4V Friction Stir Welds
2008
Recent studies have illustrated a predominant role of the residual stress on the fatigue crack growth in friction stir welded joints. In this study, the role of the residual stress on the propagation of fatigue cracks orthogonal to the weld direction in a friction stir welded Ti-6Al-4V joint was investigated. A numerical prediction of the fatigue crack growth rate in the presence of the residual stresses was carried out using AFGROW software; reasonable correspondence between the predictions and the experimental results were observed when the effects of residual stress were included in the simulation.
La métallurgie du fer au Sahel : Répartition spatiale de bas fourneaux au Sud-Ouest du Niger. Premiers résultats
2010
International audience; A 15 km à l'Est de Niamey (Sud-Ouest du Niger), une prospection pédestre exhaustive a permis de dénombrer plus de 4000 bas-fourneaux sur un bassin versant de 24 km². Ils sont identifiables par la présence de scories correspondant aux résidus de réduction du fer. Ce grand nombre de structures de réduction est lié au fonctionnement à usage unique des bas-fourneaux, qui est peu étudié dans la région ouest africaine. Les premières études de répartition spatiale montrent que l'implantation de ces bas-fourneaux est principalement soumise à la géomorphologie. Les forgerons ont installé leurs sites de réduction à proximité des talus de plateaux où affleure le minerai de fer …
Luminescence properties of neodymium-doped yttrium aluminium garnet obtained by the co-precipitation method combined with the mechanical process
2005
Nanopowders of yttrium aluminium garnet Y3Al5O12 (YAG) doped with neodymium ions were obtained by the co-precipitation method from the reaction of aluminium and yttrium nitrate and neodymium oxide with ammonia. After washing and drying the hydroxide precursors were calcined at 500, 700, 800 and 900 °C for 1 hour and at 1000 °C for 3 hours. This product was treated by ball milling in a zirconia vial for 0.5, 1.5 and 10 h in order to achieve smaller nanoparticles. The structure, microstructure, morphology and optical properties were investigated by means of diffractometric, microscopic and spectroscopic techniques. The course of the amorphous-to-crystalline transformation was complete after c…