1,720,989 research outputs found
Elemental concentration in atmospheric particulate matter: Estimation of nanoparticle contribution
No full textAtmospheric nanoparticles (NPs) are often contained in aggregates or included in larger particles. We show that some of these structures can be crushed in water media by the application of ultrasounds, leading to a suspension of insoluble NPs. The contribution of these NPs to the total elemental concentration is evaluated as the difference between the inductively coupled plasma (ICP-MS) analysis before and after the elution of the suspension from an ion exchange cartridge. Total elemental content in PM can be therefore fractionated into three contributions - soluble species, solid NPs released from larger structures, insoluble particles - that may likely have different health and environmental effects. The method was applied to both Certified Material NIST 1649a and size-segregated atmospheric PM samples collected by a 13-stage impactor. The results indicate that alkaline and alkaline earth metals are found in the suspension only as watersoluble species, also when they are contained in the fine fraction of PM. Instead, a significant fraction of most elements typically emitted from combustion sources (Pb, Sb, Sn, Cd, V and As) is present in fine PM as insoluble nanoparticles that are easily dispersed in water under ultrasound application. © Taiwan Association for Aerosol Research
Reactivity of Sodium Alanates in Lithium Batteries
No full textNovel chemistries for secondary batteries are investigated worldwide in order to boost the development of next-generation rechargeable storage systems and especially of lithium-devices. High capacity anode materials for Li-ion cells are at the center stage of R&D in order to improve the performances. In this view, conversion materials are an exciting playground. Among the various proposed class of conversion anodes, metal hydrides are probably the most challenging and promising due to the high theoretical capacities, instability toward the standard carbonate-based electrolytes, large volume variations upon cycling, and moderately low working voltages. Among them lightweight hydrides, like alkaline alanates, are an almost unexplored family of materials. In this study, we present a fundamental study on the electrochemical conversion reaction of sodium alanates: NaAlH4, Na3AlH6, and Na2LiAlH6. Our goal is to improve the understanding of the basic solid-state electrochemistry that drives the conversion reactions of these materials in lithium cells. Samples have been prepared mechanochemically and characterized by X-ray diffraction (XRD), infrared spectroscopy, and transmission electron microscopy. All materials have been assembled in lithium cells with a commercial liquid electrolyte to test their electrochemical activity. The Li incorporation/deincorporation mechanism for all materials has been explored by in situ XRD and interpreted also in view of density functional theory thermodynamic calculations. © 2015 American Chemical Society
Kinematic observations and energy modeling of a Zoz Simoloyer high-energy ball milling device
No full textHigh-energy ball milling is a material-processing method promoting near-room temperature transformations of powder mixtures. Obtained products possess peculiar properties, otherwise difficult or impossible to obtain by using conventional methods. Powder transformation is promoted by energy releases from milling media to trapped powder and the mechanism strongly depends by mechanical characteristics of the milling device. Planetary and horizontal ball mills, attritors, 1D and 3D vibrating apparatus are well-known and utilized in this powder-processing technology. This paper is focused on a ZOZ Simoloyer CM01 horizontal ball milling apparatus; a kinematic model characterizing balls motion and energy released have been found. For the purpose, an experimental setup, based on digital image acquisition, has been constructed and ball trajectories have been caught by using a properly developed software. Using image analysis results, tangential and radial components of balls speed distribution have been assessed and kinetic energies of the impacting balls inside the milling vial have been evaluated. The obtained results permits to evaluate the energy released to the powder during the milling action and to infer some expected consequences on mechanically activated reactions. © Springer-Verlag London 2013
Mechanical alloying of the Fe-Zr system. Correlation between input energy and end products
No full textKinematic equations describing velocity and acceleration of a ball in a vial of a planetary ball-mill have been derived. The consequent energy transfer from the mill to the system constituted by the powder, the balls and the vials have been evaluated by theoretical-empirical approach. Mixtures of elemental iron and zirconium powders corresponding to the average Fe2Zr composition have been mechanically alloyed in different milling conditions. The end products strongly depend on the operative milling conditions and a clear correlation between them and the input energy has been found. © 1991 Società Italiana di Fisica
Magnetic Metal-Organic Framework Composite by Fast and Facile Mechanochemical Process
No full textMagnetic porous metal-organic framework nanocomposite was obtained by an easy, efficient, and environmentally friendly fabrication method. The material consists in magnetic spinel iron oxide nanoparticles incorporated in an iron(III) carboxylate framework. The magnetic composite was fabricated by a multistep mechanochemical approach. In the first step, iron oxide nanoparticles were obtained via ball milling inducing mechanochemical reaction between iron chlorides and NaOH using NaCl as dispersing agent. Magnetic nanoparticles (MNs) were functionalized by neat grinding with benzene-1,3,5-tricarboxylic acid (1, 3, 5 BTC) and were then subjected to liquid assisted milling using hydrated FeCl3, water, and ethanol to obtain a magnetic framework composite (MFC) consisting of iron oxide nanoparticles encapsulated in a MOF matrix. We report, for the first time, the applicability of the grinding method to obtain a magnetic composite of metal-organic frameworks. The synthesized material exhibits magnetic characteristics and high porosity, and it has been tested as carrier for targeted drug delivery studying loading and release of a model drug (doxorubicin). Developed systems can associate therapeutics and diagnostics properties with possible relevant impact for theranostic and personalized patient treatment. Furthermore, the material properties make them excellent candidates for several other applications such as catalysis, sensing, and selective sequestration processes. © 2018 American Chemical Society
The effect of chemical composition on high temperature behaviour of Fe and Cu doped Mn-Co spinels
No full textMixed Mn-Co spinels are currently studied as protective coating materials for Solid Oxide Fuel Cells interconnects. Compositional changes in manganese cobaltites lead to modifications in the materials properties, such as sintering behaviour, thermal expansion and electrical conductivity, with advantages in the technological application. In this work, the effect of Fe, Cu and simultaneous Fe+Cu doping of Mn-Co spinels has been studied. Different oxide powder mixtures were prepared with a High Energy Ball Milling (HEBM) treatment, obtaining highly reactive oxides that easily form single spinel phase compounds by moderate heating. The effect of the composition is observed on high temperature stability of the spinel phase and on densification behaviour of the powders, greatly enhanced by copper addition. Analyses carried out on sintered pellets allow to observe simple relations among dopant concentration, thermal expansion and electrical conductivity. The combined effect is obtained in case of the simultaneous addition of multiple dopants. An appropriate composition can be therefore designed to obtain a material characterized by enhanced sintering behaviour, high electrical conductivity and tailored thermal expansion to fulfil the application requirements. © 2016 Elsevier Ltd and Techna Group S.r.l
Mechanochemical synthesis of manganese cobalt spinel as interconnector protective coating material. First experimental findings.
No full textIn the frame of an activity oriented on the development and characterization of cells and stacks for the integration in a micro- CHP system, synthesis, formulation and optimization of manganese cobalt spinel for the deposition of protective coatings on interconnector plates have been performed. A description of the process is given. Characterization of spray coated interconnector samples and discussion of the experimental findings are reported. © The Electrochemical Society
Liquid-assisted mechanochemical synthesis of an iron carboxylate Metal Organic Framework and its evaluation in diesel fuel desulfurization
No full textAn iron (III) carboxylate Metal Organic Framework isostructural with MIL-100(Fe) was synthesized through a mechanochemical route. The material, rapidly obtained by liquid-assisted grinding at room temperature, was characterized by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, thermal gravimetry, nitrogen physisorption and adsorption microcalorimetry of ammonia. For comparison, the features of a commercial iron trimesate produced via electrochemical route were investigated as well. The ball-milled sample showed better crystallinity, associated with good thermal stability, higher surface area and pore volume. The adsorption performance of both the ball-milled and commercial samples for the ambient-temperature removal of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from 4,6-DMDBT)/n-heptane solutions simulating a diesel fuel was also investigated. The maximum adsorption capacity for the ball-milled sample resulted twice as big as that for the commercial one. An interpretation of the different adsorption behavior is proposed. © 2015 Elsevier Inc. All rights reserved
Cu-Mn-Co oxides as protective materials in SOFC technology: The effect of chemical composition on mechanochemical synthesis, sintering behaviour, thermal expansion and electrical conductivity
No full textTo study the effect of the composition on the physico-chemical properties of mixed Cu-Mn-Co oxides as SOFC interconnects coating materials, different compounds have been obtained through a High Energy Ball Milling (HEBM) process. The mechanochemical treatment produces highly activated multi-phase powders that easily react at intermediate temperature to form the equilibrium products. Thermogravimetric, dilatometric and in-situ high temperature analyses allowed to show that Copper addition promotes cubic spinel stability at low temperature and enhances sintering behaviour. Dilatometric and conductivity analysis carried out on sintered pellets allowed to obtain simple relations between the materials properties and the composition. Coefficient of Thermal Expansion (CTE) and electrical conductivity are increased by Copper doping and high Co:Mn ratios. These findings suggest that the materials characteristics can be opportunely tuned through appropriate composition design, to simultaneously obtain enhanced sintering behaviour, high electrical conductivity and CTE adapted to match the substrate. © 2016 Elsevier Lt
Hydrogen production by the sodium manganese ferrite thermochemical cycle-experimental rate and modeling
No full textThe sodium manganese ferrite thermochemical cycle for hydrogen production by water splitting can successfully operate in a relatively low temperature range (1023-1073 K) and has a high potential for coupling with the solar source using conventional structural materials. With the aim of implementing the cycle in a solar reactor, the hydrogen evolution rate from the reactive mixture measured in laboratory apparatus has been modeled by using a shrinking-core model. Such a model proved to adequately describe the rate of hydrogen production in the studied temperature and water concentration range. The model was extended to predict the behavior of the reactive mixture subjected to different experimental conditions. © 2014 American Chemical Society
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