Tiriana Segato

• X-ray diffraction (XRD)
• X-ray fluorescence (XRF)
• thermal analysis (STA, TGA, DTA and DSC)
• Fourier transform infrared spectroscopy (FTIR)

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• Supervision of BA2, MA1 Projects and Master Thesis

Articles dans des revues avec comité de lecture

A paraître

Morphotropic phase boundary in the BNT-BT-BKT system

2020

Hydrogen chloride removal from hydrogen gas by adsorption on hydrated ion-exchanged zeolites

Hydrogen chloride is found in important hydrogen gas streams of the chemical industry and needs to be removed for safety and environmental concerns. Here, a systematic study is presented on HCl removal from hydrogen gas by adsorption on zeolites, including cation free and high cation loaded materials, as well as ion-exchanged zeolites (with alkali, alkaline earth and transition metal ions). The HCl removal performance was studied by a fixed-bed breakthrough method under high gas velocities (>0.3 m/s), at high pressures (30 bar) and at room temperature, and with low HCl concentrations (<200 ppm). The zeolite screening indicated that the 13X zeolite outperforms the other tested materials. The ion-exchanged X zeolites were extensively characterized via SEM-EDX, XRD, ATR-FTIR, TGA and argon adsorption isotherms. The results revealed that the ion-exchange was successfully achieved with expected tendencies in XRD and ATR-FTIR spectra, and porosities. The breakthrough experiments demonstrated that the hydration of the zeolite prior HCl adsorption improves the hydrogen gas purification performance. The characterization after HCl adsorption supports the hypothesis that HCl is taken up by the material by forming salt molecules within the zeolite cavities by reaction with the cations and, which is, moreover, enhanced by the presence of pre-adsorbed water. The type of cation present in the zeolite framework structure notably affected the HCl removal adsorption capacity as well as uptake rate. Among the ion-exchanged zeolite samples, the Zn2+ form exhibited the highest adsorption capacity at saturation, attributed to the over-exchange of the zeolite cations. The investigation revealed important parameters such as cation radius, atomic mass and electronegativity, which played a noteworthy role in defining the HCl removal performance of ion-exchanged zeolites.

2019

Improving the atmospheric plasma deposition of crystalline inorganic coatings

Improving the atmospheric plasma deposition of crystalline inorganic coatings

The deposition of good quality crystalline inorganic coatings by atmospheric pressure dielectric barrier discharge remains a challenge. Thanks to an original coupling of a substrate heating device based on an inductive current loop and located under the dielectric and an atmospheric pressure dielectric barrier discharge, we show that one can deposit in one step crystalline vanadium oxide and titanium oxide, with grain sizes bigger than those achieved by post-deposition annealing.

Influence de la substitution d'argile par des déchets sédimentaires dans des briques en terre crue comprimée (BTCC) sur la résistance à l'abrasion

Grands émetteurs de gaz à effet de serre à la production, les matériaux de construction issus des filières thermiques peuvent être, dans certains cas, substitués par des « éco-matériaux ». L'économie circulaire pousse de plus en plus à intégrer des déchets dans les chaînes de production. Ce travail analyse la possibilité d'intégration de déchets urbains tel que des résidus fins de boues sédimentaires de dragage (BSD) pour partiellement remplacer la terre crue dans la production de briques en terre crue comprimée (BTCC). Les BSD ont été caractérisées par diffraction des rayons X, fluorescence X et analyse thermique. La présence de métaux lourds et composés organiques polluants a été quantifiée. Des pastilles de différentes teneurs en eau et compositions (mixte BSD et terres crues) ont été réalisées. Leur tenue à l'abrasion a été étudiée sur l'essai standardisé du pion-disque. Les pastilles contenant de la BSD dont les organiques ont été éliminés thermiquement, ont une faible tenue à l'abrasion. Cette performance est améliorée par l'ajout de 5 % de ciment, qui permet d'augmenter la cohésion du matériau.

Highly Robust MOF Polymeric Beads with a Controllable Size for Molecular Separations

Shaping metal-organic frameworks (MOFs) into robust particles with a controllable size is of large interest to the field of adsorption. Therefore, a method is presented here to produce robust MOF beads of different sizes, ranging from 250 μm to several millimeters, which, moreover, preserve the adsorption properties of the unformulated MOF. A simple, mild, and flexible method is demonstrated with the zeolitic imidazolate framework-8 (ZIF-8)/polyvinyl formal composite material. The properties of the composite material are determined via optical imaging, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, X-ray diffraction, mercury intrusion, argon porosimetry and pycnometry as well as thermogravimetric analysis/differential scanning calorimetry, crush strength tests, and immersion experiments. The proposed method allows the production of resistant particles with a high MOF loading (up to 85 wt %) and remarkable structural and textural properties required for adsorptive separation processes, including a preserved ZIF-8 crystalline structure, microporosity, and a narrow macropore size distribution (1.27 μm average). The particles show a spherical shape with an average aspect ratio of 0.85. The stability tests demonstrated that the composite MOF material exhibits a high mechanical strength (3.09 N/Pc crushing strength) almost equivalent to that of a widely used commercial zeolite material. Furthermore, the material remains stable up to 200 °C and in most solvents. The adsorption properties are explored via static and dynamic experiments in the vapor and liquid phases. The results show that the adsorption capacities are only reduced in proportion to the binder content compared with the pristine material, indicating no binder intrusion in the ZIF-8 pores. Fixed-bed experiments demonstrate the remarkable separation performance in the vapor phase, whereas mass transfer limitations arise in the liquid phase with increasing flow rate. The mass transfer limitations are attributed to the diffusion in the macropores or through the ZIF-8 crystal outer layer.

2018

Severe corrosion of steel and copper by strontium bromide in thermochemical heat storage reactors

Thermochemical heat storage exploits thermal solar energy to produce sustainable residential heating, obtained by exothermal reaction between bromides and water vapour. A protocol to test the corrosion of surrounding materials is discussed in the case of SrBr2 contacting copper or steel. Corrosion depth >1 mm y−1 is found for steel in conditions where the salt remains mostly solid, due to a reaction between SrBr2 and atmospheric CO2 that produces HBr. Temperature and the dissolution of the salt (deliquescence) also play a key role. Potentiodynamic tests, the limitations of which are discussed, corroborate the salt degradation in the case of steel.

Waste Management of Discarded Cell Phones and Proposal of Material Recovery Techniques

The treatment of end-of-Life products is one of the key steps for progression towards a circular economy. In this context, mobile phone recycling has attracted considerable attention in recent years due to the high metal concentrations in printed circuit assemblies (PCAs). Contrary to precious metals, the recycling technologies for tantalum and rare earths are less well established despite their high importance for future sustainable technologies. In this study, mobile phone samples were manually dismantled into their main constituents and the qualitative distribution of elements in the PCA was determined. Tantalum capacitors can be visually distinguished from other components, whereas neodymium was detected in easily separable non-magnetic components sized between 0.5 and 1.5 mm. From tantalum capacitors, a tantalum rich-powder with a grade of 50% was obtained via a leaching process followed by an oxidizing heat treatment, while neodymium-rich fractions (4 to 14%) were obtained by sieving, magnetic and density separations.

Electrochemical synthesis of copper(I) dicyanamide thin films

The electrochemical behaviour of Cu(II) ions has been investigated in acidic aqueous solutions in the presence ofdicyanamide (dca), an anion frequently used as bridging agent in coordination polymers. The cyclic voltammogramsrecorded at a gold electrode have revealed two consecutive one electron transfer processes indicatingthat Cu(I) is stabilized by the dicyanamide anion at the electrode surface. The formation of an insoluble film afterreduction of Cu(II) to Cu(I) was evidenced by EQCM measurements and imaged by scanning electron microscopy.XRD and infrared reflection spectroscopy data have confirmed the formation of a Cu(I)-dca film.

Affordable Process for the Production of Strontium Bromide Used in Low Grade Heat Recovery Applications

Strontium bromide, SrBr2, has a strong potential for the recovery, storage and controlled release of low grade heat (<100 °C). SrBr2 is currently only produced at lab scale, making it unaffordable for large scale application. In this paper, a route for cost-effective industrial scale production of SrBr2, of a potentially lower purity but still fit-for-purpose, is sought by modifying and simplifying existing processes. Based on literature, one such modified process is proposed and experimentally investigated. It is based on the Soda Ash method of producing strontium carbonate, SrCO3, from celestine ores (SrSO4) available in Spain. The process generates a valuable by-product, ammonium sulfate. It is found that SrBr2 of up to 97.6% purity could be produced using HBr. If NaBr brine is available, the use of expensive HBr can be avoided, thanks to the high solubility of SrBr2 in ethanol. Projected prices lie in the range 0.09-0.28 €/kWh of heat stored based on purified NaBr brines. A simplified LCA based on the SrBr2 production indicates a climate change contribution of SrBr2 to the heat storage of ∼0.052 kg CO2 eq./kWh stored. These encouraging results show that hygroscopic salts are a promising sustainable solution for the recovery of solar and/or excess industrial heat.

2016

Growth and characterization of WSe2 single crystals usingTeCl4 as transport agent

The growth of WSe2 single crystals, using TeCl4 as transport agent was performed successfully from slowly cooled polycrystalline powders as precursors. The resulting single crystals were characterized by X-ray diffraction (XRD) and their surfaces examined by scanning electron microscopy (SEM) presented fewer defects than single crystals prepared from air-quenched polycrystalline powders. Energy Dispersive X-ray microanalysis (EDX), inductively coupled plasma (ICP) spectroscopy and X-ray photoelectron spectroscopy (XPS) revealed that the single crystals are homogeneous and stoichiometric. Electrical conductivity and photocurrent measurements have confirmed the semiconducting character of the single crystals and a photocurrent of 75 mA cm^(-2) has been reached. In addition, single crystals with areas in the 25-100 mm2 range can be obtained under the reported growth conditions.

2014

Corrosion product identification at the cut edge of aluminum-rich metal-coated steel

The formation of corrosion product at the cut edge of aluminum-rich metalcoated steel is reported in the present work. Painted metal-coated steel samples with different amounts of Al in the metal coating, were immersed in a 0.05M NaCl solution. The ex situ analysis of the corrosion products formed was carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), Raman and Fourier transform infrared (FT-IR) spectroscopy. The role of these products is discussed along with the influence of Al content in the metal coating. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2013

Growth and characterization of large, high quality MoSe2 single crystals

MoSe2 single crystals were grown by chemical vapor transport using TeCl4 as transport agents in the temperature gradient 1020-980°C. They were characterized by scanning electron microscopy (SEM), optical microscopy, image analysis coupled with SEM, microanalysis by SEM-EDX, X-ray fluorescence, inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS) and electrical conductivity. The characterizations showed that single crystals are perfectly homogeneous, stoichiometric and have very few defects and clean surfaces with areas in the range of 35-100 mm2. Single crystals grown by TeCl4 showed a high electrical conductivity. Their properties were highly dependent on the quality of the polycrystalline powders used for the growth. © 2012 Elsevier B.V. All rights reserved.

2008

The structure of niobium-doped MoSe2 and WSe2

Polycryst. niobium-doped molybdenum and tungsten diselenides were synthesized in silica tubes sealed under secondary vacuum. They were characterized by SEM, electron diffraction, X-ray diffraction, chem. compn. and EDX analyses. The morphol. of niobium-doped molybdenum solid solns. was shown to depend strongly on the conditions of synthesis, whereas the structural characterization did not.

2006

Study of copper nitrate-based patinas

Artificial patination is mostly based on empirical recipes for which the result is difficult to forecast. Little is known about the final corrosion compound formed on the patinated object. Therefore, different patinas based on copper nitrate - an ingredient recurrent in numerous references - were realized according to traditional recipes. Their characteristics of morphology and molecular composition were studied using various methods such as scanning electron microscopy (SEM)-energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and Raman spectroscopy (RS). A better understanding of artificial patinas will not only allow developing appropriate methods of conservation and restoration, but also differentiating between natural and artificial patinas. An example of a patina present on an ancient artifact is discussed and compared with the studied artificial patinas. Copyright © 2006 John Wiley & Sons, Ltd.

2004

AES analysis of nitride layers on steel with target factor analysis

Industrially nitrided steel samples are analysed with AES. The aim of this work is to optimize the quantification of nitrogen and to extract the chemical information hidden in the shape of the measured Auger peaks with Target Factor Analysis (TFA). To optimize the use of TFA, reference samples of pure components are necessary. These components are made in a laboratory reactor in which pure iron is nitrided. The resulting nitride layer is identified with X-Ray Diffraction (XRD). Afterwards their AES spectra are takers as input for the TFA of the industrial layers. In this paper, the preparation and the characterization of a γ′ -Fe4N standard is discussed, as well as the correction of the sensitivity factors used for the quantification of nitrogen. Finally, the application of TFA on art industrial nitride layer is discussed. Copyright © 2004 John Wiley & Sons, Ltd.

Synthesis and characterisation of LiNi1-x-yCoxAlyO2 cathodes for lithium-ion batteries by the PVA precursor method

Polycrystalline powders of LiNi1-xCoxO2 and LiNi1-x-yCoxAlyO2 were synthesized at 720 °C from the nitrate-PVA precursor method. The water was removed by two different processes: (i) evaporation-drying at 110 °C, (ii) spray-drying at 150 °C. In both cases a gel is obtained wherein LiNO3 crystallizes in evaporated-dried samples but not in spray-dried samples which are more amorphous. All precursors give single phase powders with micronic well-shaped grains. The best electrochemical performances are obtained from evaporated samples with a capacity remaining higher than 160 mAh/g for LiNi0.82Co0.18O2 and 140 mAh/g for LiNi0.82Co0.13Al0.05 O2 after 20 cycles. The lower performances of the spray-dried samples seem to be related to Li2CO3 formation with subsequent non-stoichiometry as a consequence of the improved homogeneous distribution of the constituent cations in the polymer. © 2003 Elsevier Ltd. All rights reserved.

Synthesis and characterization of LiNi1-x-yCoxAlyO2 cathode materials for Li-ion batteries by the PVA precursor method

1996

Formation of MgO films by ultrasonic spray pyrolysis from β-diketonate

Chemical vapor deposition (CVD) from an aerosol generated by ultrasonic atomization was used to grow magnesium oxide films on alumina polycrystalline substrates. The precursor was a solution of magnesium acetylacetonate (Mg(acac)2) in isopropanol. The decomposition of the salt was studied to determine the CVD temperature range. Thermal analysis of the salt by thermogravimetry, differential scanning calorimetry and IR and mass spectrometry enabled a decomposition model of the salt to be determined. Above the melting temperature at 265 °C, Mg(acac)2 is no longer stable. The molecule splits giving, on the one hand, a gaseous organic residue and, on the other, a liquid (MgC5H6O2) which in turn gives rise to MgO at 450 °C. The film presents a smooth microstructure and a highly preferentially oriented structure with the (200) planes parallel to the substrate surface at a deposition temperature of about 400 °C. The thickness obtained reaches 10 μm, which represents an effective diffusion barrier on alumina for the deposition of thick films containing alkaline earth elements.

Formation of MgO films by ultrasonic pyrolysis from beta-diketonate

Communications publiées lors de congrès ou colloques nationaux et internationaux

2016

Apport des analyses élémentaires et structurales à l'interprétation des dispositifs pariétaux de la grotte d'El Castillo (Cantabrie).

2013

Les structures de combustion du Tiène des Maulins (Province de Namur, Belgique). Regards croisés.

2007

Morphotropic phase boundary in the BNT-BT-BKT system

1996

Synthesis of dense YBaCuO thick films on alumina substrates coated with MgO and ZrO2

1995

ZrO2 deposition by ultrasonic spray pyrolysis