1,721,095 research outputs found
24. Ferone (Claudio), Leisteia. Forme di predazione nell'Egeo in età classica
No full textJacquemin Anne. 24. Ferone (Claudio), Leisteia. Forme di predazione nell'Egeo in età classica. In: Revue des Études Grecques, tome 112, Janvier-juin 1999. pp. 293-294
Thermal conversion of (Ba, Sr)-exchanged zeolite A in BaAl2Si2O8-SrAl2Si2O8 solid solutions
No full text
Microwave assisted hydrothermal conversion of Ba-exchanged zeolite A into metastable paracelsian
No full textA microwave assisted crystallization of paracelsian, a metastable phase for which no synthetic occurrence is at present reported, was obtained. A sample of thoroughly Ba-exchanged zeolite A was prepared and reacted in alkaline media and hydrothermal conditions under the action of microwaves (frequency 2.45 GHz, irradiation power 1000 W). The alkaline environment was created by using aqueous solutions of LiOH and tetraethylammonium hydroxide. Treatment temperature, reaction time and weight solid/liquid ratio ranged between 150 and 230 degrees C, 40 and 120 min, 115 and 1/40, respectively. The pressure was autogeneous. The action of microwaves appears to strongly enhance the ability of hydrothermal systems to produce highly metastable phases, an important observation
Thermally induced structural and microstructural evolution of barium exchanged zeolite A to celsian
No full textEffect of residual Na on the low temperature synthesis of monoclinic celsian from zeolite Ba-A
No full textAlkali activated waste fly ash as sustainable composite: Influence of a curing and pozzolanic admixtures on the early-age physico-mechanical properties and residual strength after exposure at elevated temperature
No full textWaste fly ash, referred in literature also as "weathered", represents a major management issue for coal-fired power plants. The low qualification of this relevant fraction of produced fly ash is not adequate for recycling in structural concrete. Non-structural applications may represent an economically feasible solution to maximize the recovery of coal fly ash from power plants. A potentially valuable recycling track may be represented by alkaline activation for the production of sustainable precast elements based on geopolymeric binders. In this work, three mineral admixtures, namely blast furnace slag, silica fume and metakaolin, were used to synthesize binary alkali activated binders whose major volumetric fraction was waste fly ash. Three curing temperatures (20, 40, 60 °C) were also considered. Early age kinetics and properties development were assessed by means of strength development and ultrasonic pulse velocity. Residual compressive strength after exposure at high temperature was also assessed in order to highlight typical geopolymeric thermal resistance which is generally observed for higher value raw materials. Furthermore, microstructural analysis was carried out by means of scanning electron microscopy. Silica fume exhibited an increasing detrimental effect (formation of agglomerates/partial foaming) with early age curing temperature, while blast furnace slag and metakaolin revealed to be effective admixtures without strict need of higher curing temperatures
Fabrication and characterization of graphite-cement composites for microbial fuel cells applications
No full textGraphite-cement composites, with graphite up to 80% w/w, were prepared and characterized. The key feature of this novel material is its conductive and porous microstructure, due to a synergic effect between cementitious matrix and graphite particles. As graphite content increases, a characteristic percolation threshold exists. The threshold value depends on curing temperature and determines a remarkable change in electrical, physical and mechanical properties. In the proximity of the threshold, conductivity increased from 3.2∙10−5 S m−1 to 2 S m−1 and porosity increased from 48% to 60%. Compressive strength indicates a similar behaviour and thermally cured composites exhibit higher strength. The thermally treated composite with 50% w/w of graphite is chosen for electrochemical analysis. Cyclic voltammetry and kinetic study with linear sweep voltammetry confirmed that these materials can catalyse cathodic reactions with an interesting current density and low overpotential. The graphite-cement composite developed is an eligible material for microbial fuel cell applications
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