Li+ distribution into V2O5 films resulting from electrochemical intercalation reactions

We studied interface effects of thin film V2O5 electrodes on top of indium tin oxide (ITO) glass for Li intercalation by means of a combination of methods: depth-profiling by secondary ion mass spectroscopy (SIMS), electrochemical insertion-extraction of lithium ions by slow-scan cyclic voltammetry (SSCV) and by potentiostatic intermittent titration technique (PITT). We show that the Li+ distribution inside the oxide film is always far from homogeneous, and that different diffusion paths (parallel to interfaces as well as perpendicular to them) have to be considered in experiments with electrodes having areas of few cm². The exposed edge formed when cutting out coupons from the coated glass plate supporting the V2O5 electrode plays a significant role in the process, because it exposes the V2O5-ITO interface to the electrolyte.Estudamos os efeitos de interface de filmes finos de eletrodos de V2O5 sobre vidros com óxido de índio-estanho (ITO) para intercalação de Li utilizando combinações de métodos: perfil de profundidade por espectrometria de massas de íons secundários (SIMS), inserção-extração eletroquímica de íons lítio por voltametria cíclica de varredura lenta (SSCV) e por técnica de titulação potenciostática intermitente (PITT). Nós demonstramos que a distribuição de Li+ no interior do filme de óxido é sempre distante de ser considerada homogênea e que diferentes etapas de difusão (paralelas às interfaces e bem como perpendiculares a elas) são consideradas por conter áreas de alguns cm² em experimentos com eletrodos. A margem exposta pelo corte da placa de vidro revestida com ITO e recoberta com V2O5 desempenha um papel importante no processo, pelo fato de expor a interface V2O5-ITO ao eletrólito.66767

Use of Potabilized Water Sludge in the Production of Low-Energy Blended Calcium Sulfoaluminate Cements

Ordinary Portland cement (OPC) manufacture determines about 8% of the global anthropogenic CO2 emissions. This has led to both the cement producers and the scientific community to develop new cementitious materials with a reduced carbon footprint. Calcium sulfoaluminate (CSA) cements are special hydraulic binders from non-Portland clinkers; they represent an important alternative to OPC due to their peculiar composition and significantly lower impact on the environment. CSA cements contain less limestone and require lower synthesis temperatures, which means a reduced kiln thermal energy demand and lower CO2 emissions. CSA cements can also be mixed with supplementary cementitious materials (SCMs) which further reduce the carbon footprint. This article was aimed at evaluating the possibility of using different amounts (20 and 35% by mass) of water potabilization sludges (WPSs) as SCM in CSA-blended cements. WPSs were treated thermally (TT) at 700° in order to obtain an industrial pozzolanic material. The hydration properties and the technical behavior of two different CSA-blended cements were investigated using differential thermal–thermogravimetric and X-ray diffraction analyses, mercury intrusion porosimetry, shrinkage/expansion and compressive strength measurements. The results showed that CSA binders containing 20% by mass of TTWPSs exhibited technological properties similar to those relating to plain CSA cement and were characterized by more pronounced ecofriendly features

Oxyfuel Combustion Residues as Supplementary Cementitious Materials for the Production of Blended Portland Cements

Oxyfuel combustion represents one of the most interesting processes aimed at CO2 capture and storage to mitigate greenhouse effects ascribable to the process industry. In a different technical area, searching for new processes aimed at producing low-CO2 cements has comparable relevance, due to the huge generation of greenhouse gases related to cement production. This paper proposes an integration of these two aspects, with an approach new in the pertinent literature. The possibility of reusing ashes, issued by a pilot plant fluidized bed oxyfuel combustion process, as a source of material in the production of low-CO2 cements is investigated. Ashes were tested as substitutes for natural pozzolan in blended cements. They were mixed with an industrial Portland clinker and natural gypsum in order to evaluate their hydraulic behavior at different curing temperatures (20–40°C) and times (2–28 days). Pozzolanicity tests together with differential thermal–thermogravimetric and X-ray diffraction analyses were employed to explore the hydration behavior of oxyfuel ashes-based blended cements

Construction and Demolition Waste as Raw Materials for sustainable Cements

In 2014 about four billion tonnes of cement were produced [CEMBUREAU, 2014]. The use of industrial by-products, as a source of raw materials in the manufacture of portland and blended cements, is a research theme of significant relevance to the construction industry. Such industrial by-products can be employed as constituents of the final product or components of the raw feed in a cement kiln. Due to their hydraulic and/or pozzolanic activity, industrial by-products are utilized worldwide. Such by-products also increase durability and reduce costs for producing blended cements. The use of such by-products as raw mixture component for the cement production has received comparatively little attention by researchers and engineers. There is currently an increasing interest towards searching for new categories of by-products, which would be able to provide reactive calcium, silicon, aluminum, and/or iron oxides, for portland cement clinker manufacture. In this regard, construction and demolition waste (C&DW) is worthy of consideration because, when obtained from a properly selective demolition process, they could be employed as alternative raw material for portland clinker production. The present study deals with the use of two different kinds of C&DW, namely concrete waste (CW) and masonry waste (MW). In this study, C&DW is proposed to be employed as partial or total substitute for limestone and clay, respectively, in the portland clinker generating raw mixture. Four ternary mixtures containing limestone, as well as CW and MW, were subjected to laboratory tests in order to evaluate the clinker raw mixture produced and the performance of the related portland cement. A binary mixture, composed of limestone and clay, was used as a reference. All of these different cements displayed similar hydration behavior. Detailed results are presented and discussed

Use of Fluidized Bed Combustion Residues and Alumina Powder as Components of Ettringite-Based Aerated Building Elements

The use of industrial wastes and by-products for making construction materials unequivocally gives a pronounced environment-friendly character to their manufacturing process. Two binary (M1, M2) and one ternary (M3) mixtures, based on alumina powder, fluidized bed coal combustion fly- and/or bottom-ash were submitted to hydrothermal treatments in order to generate aerated building elements based on ettringite (6CaO·Al2O3·3SO3·32H2O); ettringite is a compound characterized by low density, water insolubility, high fire resistance and significant mechanical strength. The M1 – M3 systems were hydrated in a thermostatic bath (100 % R.H) at 55 °C and 70 °C for aging periods ranging from 2 h to 28 d; the hydrated samples were submitted to both differential thermal–thermogravimetric and X-ray diffraction analyses for assessing the formation of the hydration products. In this regard, the ettringite generation, being also dependent on the operating temperatures and times, was observed within all the investigated systems. Furthermore, the best results in terms of both ettringite concentration and formation rate were exhibited by the M2 system at 70 °C after 2 d of curing

Solar-driven production of lime for ordinary Portland cement formulation

Cement production is an energy-intensive manufacturing process with potentially large environmental burdens. Among the others, it is one of the largest industrial sources of CO2 emission. Limestone calcination is the stage responsible for most of CO2 emissions and energy requirement. This article aims at supporting the use of solar energy as non-carbogenic renewable source to sustain limestone calcination, with advantages on both the economic and environmental aspects of the process. A directly irradiated Fluidised Bed (FB) reactor was used as limestone precalciner for clinker production. Concentrated solar radiation was simulated with an array of three short-arc Xe-lamps of 4 kWel each, coupled with elliptical reflectors, capable of producing a peak flux of about 3 MW m−2 at the centre of the reactor. The total irradiated power is of approximately 3.2 kWth. Thermocouples and an IR camera were used for the analysis of the FB thermal profiles. Calcination was carried out at a nominal bulk bed temperature of 950 °C, in an atmosphere containing about 70% CO2. The reactivity of lime generated by the solar-driven calcination process has been characterised. Lime produced by the solar-driven process was used together with commercial clay as kiln feed components for the formulation of Portland cement samples. A binary mixture composed by fresh limestone and the same clay as above was employed as a reference. The key focus of the investigation was the assessment of the reactivity of the solar-generated lime toward the main clay components in the clinker production process, as compared to lime from ordinary calcination. An aspect that is specifically scrutinised is whether the different, and possibly more severe, thermal history to which limestone particles undergo during solar-driven calcination in directly irradiated FB reactors may compromise lime reactivity. Portland clinkers were produced by burning the raw meals at 1500 °C for 15 min. Clinkers were mixed with 5% natural gypsum to prepare the related Portland cements, which were then paste hydrated for times ranging from 2 to 28 days (water/cement mass ratio = 0.5, 20 °C, 95% relative humidity). Parameters as lime saturation factor, burnability, phase composition of clinkers and hydration behaviour of cement pastes were taken into consideration. Techniques as X-ray fluorescence and diffraction, and simultaneous differential thermal–thermogravimetry were used to study the materials

Influence of Li intercalation on thin films of V2O5 deposited by atomic layer deposition (ALD) : XPS, UPS and electrochemical studies

Abstract 4-A-0

Rutile microtubes assembly from nanostructures obtained by ultra-short laser ablation of titanium in liquid

Pulsed laser ablation of a titanium target in water was performed by an ultra-short laser source (Ti:sapphire, @=800nm, 1kHz, 100fs). The obtained structures were characterized by Atomic Force Microscopy, Scanning Electron Microscopy, X-Ray Photoelectron Spectroscopy, micro-Raman spectroscopy and X-ray Diffraction, revealing the presence of non-stoichiometric titanium oxide nanoparticles with a certain amount of crystalline rutile phase. Upon remaining in water the ablated species, the formation of a lamellar phase has been observed. This lamellar phase rolls up to microtubes by remaining in water for a month, through a self-assembling process. The formed microtubes, with an inner diameter of about 2 um and an outer diameter of 4 um are characterized by a smooth interior surface and aggregation of nanoparticles on the outer surface

Characterisation of helical structure in AFM micrographs of a trimer of the peptide sequence (ValGlyGlyValGly)

Studies by atomic force microscopy of a set of helical fibres formed within the same period of time from the amyloidogenic peptide, (VGGVG)3 show that there is a characteristic increment in diameter, suggesting that the helices are formed from multiple layers. Measurement of the height to pitch ratio suggests that each succeeding layer forms on top of the previous winding and does not fit into the gap between the turns. Dimensions are given for the increment per layer and for the pitch of the helices