Cinzia Cristiani

Università degli Studi di Genova, Genova, Liguria, Italy

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Publications (62)101.26 Total impact

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    ABSTRACT: Coating is the most widely used technique for the preparation of structured catalysts. This paper reviews the main methods reported in the open literature for depositing catalytic layers onto metallic substrates, specifically focusing on the coating of metallic honeycomb monoliths and open-cell foams. All the relevant steps, including substrate pre-treatments, means for catalytic activation and thermal treatments, are discussed.
    Catal. Sci. Technol. 08/2014; 4(9).
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    ABSTRACT: Gas diffusion medium (GDM) is a crucial carbon-based component for water management in polymer electrolyte membrane fuel cells (PEMFCs). GDM consists of a macro-porous substrate, which is usually a carbon cloth or carbon paper, coated with a thin micro-porous layer (MPL). Traditionally, PTFE is used as hydrophobic agent and binder. In this work, three different GDMs were prepared using fluorinated polymers (polytetrafluoroethylene-co-hexafluoro-propylene (FEP), polytetrafluoroethylene-co-perfluoroalcoxy vinyl ether (PFA) and a fluorinated polyurethane based on perfluoropolyether blocks (PFPE)) in order to replace conventional PTFE as hydrophobic agent, which was used as reference. Inks composition and rheological behaviour were fixed in order to apply the blade coating technique for MPL deposition. These polymers allowed to decrease temperature during thermal treatments with respect to the one necessary for treating PTFE-based MPLs. Moreover, superhydrophobic layers were obtained for all the samples and the final electrical performances of the whole fuel cell system were improved with respect to the ones reached with PTFE-based samples. In particular, FEP allowed to reduce significantly mass transfer resistances in the operating conditions of the fuel cell.
    Progress in Organic Coatings 07/2014; · 2.30 Impact Factor
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    ABSTRACT: This work presents the application of FT IR spectroscopy to study the thermal evolution of PEG-based nanocomposites prepared using montmorillonite STx intercalated with polyethylene-oxides PEG 1500 and PEG 4000 and polyethylene oxide Brij. The effect of different polymer molecular weight and polymer loadings has been evaluated by means of diagnostic mid-IR bands. PEG fragmentation through the cleavage of the C-O bond appears to be the main reaction step, leading to the formation of short chain carbonyl adsorbed species (such as acetaldehyde), alcohols (ethanol and methanol) and, to a lesser extent, esters species, characterized by the frequency of the carbonyl stretching band. The detection of carbonyl band evidenced the formation of partial oxidation products as first step of the thermal degradation. Increasing polymer loadings, as well as increasing polymer molecular weight leads to lower temperature of formation of the first oxidation products. No clear indication of the effect of the chemical nature for the intercalated polymers can be obtained. BRIJ thermal decomposition seems to be mainly driven by the PEG-like moiety chemistry. CH stretching bands detected at 450-500 °C for the samples intercalated with PEG samples indicated the formation of residual organic compounds resisting oxidation, possibly char species preserved from further oxidation by the interlayer galleries.
    Vibrational Spectroscopy 03/2014; · 1.75 Impact Factor
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    ABSTRACT: A 2D isothermal axisymmetric model of an anode-supported solid oxide fuel cell has been developed. The model, which is based on finite element approach, comprises electronic and ionic charge balance, Butler–Volmer charge transfer kinetic, flow distribution and gas phase mass balance in both channels and porous electrodes. The model has been validated using available experimental data coming from a single anode-supported cell comprising Ni–YSZ/YSZ/LSM–YSZ as anode, electrolyte and cathode, respectively. Hydrogen and steam were used as fuel inlet and air as an oxidant. The validation has been carried out at 1 atm, 1,500 ml min–1 air flow rate and three different operating conditions of temperature and fuel flow rate: 1,073 K and 400 ml min–1, 1,073 K and 500 ml min–1, and 1,003 K and 400 ml min–1. The polarization and power density versus current density curves show a good agreement with the experimental data. A parametric analysis has been carried out to highlight which parameters have main effect on the overall cell performance as measured by polarization curve, especially focusing on the influence of two geometrical characteristics, temperature and some effective material properties.
    Fuel Cells 02/2014; · 1.55 Impact Factor
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    ABSTRACT: press as: Pelosato R, et al. Electrical characterization of co-precipitated LaBaCo 2 O 5+δ and YBaCo 2 O 5+δ oxides. J Eur Ceram Soc (2014), Abstract REBaCo 2 O 5+δ layered perovskite oxides (RE = Rare Earth) are promising cathodes for IT-SOFCs. In this work, a simple co-precipitation synthesis in aqueous medium was applied to prepare LaBaCo 2 O 5+δ (LBC) and YBaCo 2 O 5+δ (YBC) cathodes. The chemical and electrochemical properties of both materials were characterized via XRD, SEM, TPO, TG–DTA, 4-probe conductivity measurement, and EIS tests on symmetric cells. The coprecipitation synthesis revealed a promising preparation route: the measured ASR values of both materials were well comparable with the literature ones. A kinetic investigation of the O 2 reduction process was performed on LBC (600–800 • C, 5–100% O 2 , v/v), whose results were analyzed with equivalent circuits. The main steps were identified (oxygen diffusion and charge transfer at high frequency, O 2 chemisorption at medium frequency), and their activation energy and reaction order were quantified. Aging tests (500 h time on stream, 500–800 • C) revealed quick deactivation for YBC and good stability for LBC.
    Journal of the European Ceramic Society 01/2014; · 2.36 Impact Factor
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    ABSTRACT: A series of four compounds (LaMnO3, La0.70Sr0.30MnO3−δ, La0.80Sr0.20FeO3−δ and La0.75Sr0.25Cr0.50Mn0.50O3−δ) of interest as electrode materials in intermediate temperature solid oxide fuel cells have been prepared using a carbonate co-precipitation route in aqueous medium. LaMnO3, La0.70Sr0.30MnO3−δ, and La0.75Sr0.25Cr0.50Mn0.50O3−δ have been obtained as a pure phase, while La0.80Sr0.20FeO3−δ retained an impurity phase; fine microstructures with sub-micron sized particles can be obtained in all cases at the proper calcinations temperature, except for LaMnO3. The precipitation yield of the single metal ions have been experimentally determined in the mother liquors and in the final powders; the results have been evaluated also in comparison with expected yields calculated from thermodynamics of the precipitation process using the software Medusa. pH higher than 7.5 are suggested to avoid ion losses for all cations. Structural and microstructural properties and TPO/TPR behaviour suggest that materials prepared via co-precipitation, especially LSCM, could be suited as electrode materials in solid oxide fuel cells.
    International Journal of Hydrogen Energy 01/2013; 38(1):480-491. · 3.55 Impact Factor
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    ABSTRACT: In this work we investigate the effect of ceria and other rare earths (La, Pr, Tb) on Pd–PdO transformation, which is strongly related to the catalytic activity of Pd-based catalysts for the combustion of methane at high temperature. Also the behavior of Pd on ZrO2 and on yttria-stabilized zirconia is considered for comparison. The catalysts are characterized by XRD and BET surface area measurements. Pd–PdO transformation is studied by means of temperature programmed oxidation measurements and thermogravimetric analysis. Temperature programmed combustion experiments have been carried out in order to compare catalytic activity of different catalysts. The results show that rare earth oxides promote the onset of Pd re-oxidation upon cooling, that for ceria doped sample is reflected in an improvement in the catalytic activity.
    Catalysis Today 01/2012; 180:124. · 3.31 Impact Factor
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    ABSTRACT: Preparation of active washcoats of Ni/MgAl2O4 steam-reforming catalysts on FeCrAlloy foams is reported in this work. The MgAl2O4 powdered support was prepared via co-precipitation method, and Ni/MgAl2O4 was obtained via dry impregnation of 10% (w/w) of Ni. After full characterization of the powders, the deposition of the catalyst over the foams was performed by percolation followed by air-blowing (percolation-blowing). The resulting washcoat layers were quite homogeneous, uniform, and well adherent to the metallic support. Prototype catalytic foam samples, tested at the lab-scale, were found to be active in the steam reforming process.
    Catalysis Today 01/2012; · 3.31 Impact Factor
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    ABSTRACT: The intercalation of organic polymers molecules (i.e., PEGs and BRIJ) into a standard Ca-montmorillonite has been studied by XRD, TG, and IR spectroscopy. The polymer intercalation is confirmed by the increasing of the d(001) in XRD spectra as well as by the complex multisteps thermal decomposition behavior of the organo-clay materials. Mid-IR and diffuse reflectance near-IR spectra of the intercalated materials show the polymer diagnostic bands (CH stretching and deformation mode), shifted or changed in shape by the interaction with the clay matrix. Both PEG 1500 and PEG 4000 based materials are likely intercalated in an extended configuration, similar to the amorphous polymer form. BRIJ intercalated polymer spectra suggest the disordered conformation of the alkilic chain in a prevailing "gauche", poorly packed, conformation. Host montmorillonite IR bands, mainly OH and water stretching and deformation fundamentals, combination, and overtone bands, are reduced in intensity by polymer intercalation, pointing out an interaction, likely through H-bonding and/or a possible substitution of cations hydration water molecules.
    The Journal of Physical Chemistry A 06/2011; 115(26):7484-93. · 2.77 Impact Factor
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    ABSTRACT: In the present work, preliminary results of different hydrophobic surface treatments for gas diffusion layer (GDL) for PEM fuel cells are presented. This hydrophobic coating consists of new perfluoropolyether (PFPE) derivatives, in comparison to standard polytetrafluoroethylene (PTFE) dispersions. Experimental conditions for an efficient coating of fluoropolymers onto carbon clothes were explored by wet chemical methods.The GDLs obtained were tested in a single fuel cell at the lab scale. The cell testing was run at two temperatures (60°C and 80°C) with a relative humidity (RH) of the feeding gases of 80/100%, hydrogen/air respectively.The new PFPE coatings measurably improve the cell performances, and this effect is more evident at 60°C with respect to 80°C.
    Lancet. 01/2011; 196(18):7645-7648.
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    ABSTRACT: A simple and inexpensive co-precipitation route in aqueous medium is proposed to prepare La0.8Sr0.2Ga0.8Mg02O3−δ ionic conductor (LSGM). Different synthetic procedures and operating parameters (i.e. nature and amount of the precipitating agents, HNO3 addition and temperature) have been evaluated in order to underline their influence on the composition and microstructure of the final phase. Intermediate and final products were characterized by Thermal-Gravimetry, IR-spectroscopy, X-ray Powder Diffraction, Rietveld analysis and Scanning Electron Microscopy. The electrical properties were measured by Impedance Spectroscopy in the temperature range 250–800 °C. Slight variations of the synthetic procedure (such as precipitating agent amount or no HNO3 addition) have a considerable and detrimental effect on the ions losses and the subsequent achievement of the final phase. The use NH4OH as an alternative precipitating agent is dramatically disadvantageous. Ions losses during precipitation must be controlled (i) to avoid understoichiometry in the LSGM phase and (ii) to prevent the formation of large amounts of secondary phases. In fact, both affect the total electrical conductivity.The use of large excess of (NH4)2CO3 precipitating agent and the addition of HNO3 lead to the best material characterized by a rhombohedral structure, small amount of side phases, a relative density of 98% and a total conductivity of 6.44 × 10−2 S cm−1 at 800 °C and 1.13 × 10−2 S cm−1 at 600 °C.
    Journal of Power Sources 12/2010; 195(24):8116–8123. · 5.26 Impact Factor
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    ABSTRACT: A multi-wall carbon nanotubes (MWCNTs)-based gas diffusion medium (GDM) was prepared, where carbon black was partially substituted by carbon nanotube (CNT) in the formulation of the micro-porous layer (MPL). A rheological analysis of the ink used to coat the gas diffusion layer (GDL) was previously performed to correlate viscosities with the slurry composition. Shear thinning inks with viscosity of 0.4 (Pa s–1) were obtained for a composition containing 10 wt.-% of CNT and 12 wt.-% of fluorinated polymer. Using the doctor-blade technique, a coating thickness of about 100–150 μm was obtained.Moreover, electrochemical performance of a single cell assembled with the CNT-based GDM was compared with that obtained with a sample without CNTs. In order to better understand the role of CNTs, electrochemical impedance spectroscopy (EIS) of the running fuel cell (FC) was also performed. As a result, it was found that the addition of CNTs sensibly improves single cell performances.
    Fuel Cells 03/2010; 10(2):270 - 277. · 1.55 Impact Factor
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    ABSTRACT: The objective of the present research was to investigate the intercalation of three different polymer-based surfactants, namely polyethylene-glycol 1500 and 4000 (PEG 1500 and PEG 4000) and polyethylene-oxide (BRIJ 78), inside the interlayer of STx-1 montmorillonite. The effect of three parameters, such as time (30, 60, 90min), temperature (30 and 60°C) and initial concentrations in solution (45, 90, and 180mM) was studied. A full microstructural characterization of the synthesized organoclays by XRD, FT-IR, and TG-DTA was performed. The quantification of polymer intercalated was estimated by COD (Chemical Oxygen Demand) analysis of the residual amount in solution.The intercalation was successful, as showed by the basal expansions detected by XRD, and confirmed by FT-IR, showing the typical C–H-stretching bands in the spectra of the synthesized clays. TG-DTA was not a reliable technique for the quantification of polymer intercalated, while COD correctly quantified such amounts.The role of temperature and time appeared to be uninfluent for intercalating the polymer inside the interlayer of STx-1 montmorillonite, while the driving parameter ruling the amount of intercalated polymer was the initial concentration in solution.
    Applied Clay Science 03/2010; 48(1):97-102. · 2.34 Impact Factor
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    ABSTRACT: The present research investigated the intercalation of three different polymers, namely polyethylene-glycol (PEG) 1500 and 4000, and BRIJ78 into STx-1 montmorillonite. Samples of modified montmorillonite were prepared starting from different initial concentrations in solution (C0) ranging from 20 to 180 mM. The basal spacing of the modified clay minerals was related to the amounts of polymer intercalated, estimated by COD (Chemical Oxygen Demand) analysis of the residual amounts in solution. The correlation between the basal spacings of the modified montmorillonites and the amounts of polymers intercalated allowed properly modulating the microstructural characteristics of organo-clay minerals prepared with polymers.Research Highlights►Quantification of intercalated PEOs and BRIJ78 in montmorillonite by COD. ►Use of monomeric units to compare intercalation of PEOs with different molar mass. ►Correlation between d001 and intercalated PEOs. ►A priori” modulation of the interlayer-space size.
    Applied Clay Science 01/2010; 50(2):266-270. · 2.34 Impact Factor
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    ABSTRACT: A new method to deposit active washcoats of Ni/MgAl2O4 steam-reforming catalysts over FeCrAlloy foams is reported in this work. The MgAl2O4 powdered support was prepared via a co-precipitation method, and Ni was dry-impregnated on it. The deposition of the catalyst over the foams was performed by dip-coating followed by air-blowing (dip-blowing). The resulting washcoat layers were quite homogeneous and uniform, and well adherent to the metallic support. Prototype catalyst samples, tested at the lab-scale, were found to be active and selective in the steam reforming process.
    Studies in Surface Science and Catalysis - STUD SURF SCI CATAL. 01/2010; 175:653-656.
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    ABSTRACT: Export Date: 26 February 2014, Source: Scopus
    ECS Transactions; 09/2009
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    ABSTRACT: The rheology of microporous layer (MPL) inks for polymer electrolyte membrane fuel cell (PEM-FC) applications was investigated, and its effect on thickness and morphology of final layer, prepared via doctor-blade technique, was examined. The effect of the carbon black (CB) on slurry viscosity was studied in the range CB/water=0.11/0.17 (g/g) as well as the effect of surfactant and PTFE (Teflon®) addition. Slurry viscosity is mainly determined by the CB/water and CB/surfactant ratios, while PTFE addition has minor influence. Viscosities in the range 0.05–0.06Pas (at shear rate 100s−1) were found to be appropriate for coating deposition. Two substrates of different morphology, a carbon cloth (CC) and a woven non-woven (WNW), were coated with slurries of different composition but showing the same rheology. Notwithstanding the use of slurries with the same rheological behavior, different MPL coating thicknesses were obtained. This suggested that the substrate morphology has a non-negligible influence on the final MPL thickness. The MPL layer definitely increased the hydrophobicity, and in some samples the region of superhydrophobicity (contact angle >150°) was reached. In-plane electrical resistance of gas diffusion layers (GDLs), i.e. substrate coated with MPL, was measured and it was found that the two different substrates have no influence on it (about 0.8Ω). FCs assembling different GDLs showed different electrochemical performances in terms of I–V curves: MPLs coated onto WNW gave somewhat higher power densities (0.40W/cm2 at 0.5V).
    Catalysis Today 09/2009; 147. · 3.31 Impact Factor
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    ABSTRACT: A carbonate coprecipitation synthesis, simple and easily scalable to industrial level, has been successfully applied to produce Sr- and Mg-doped LaGaO3. The thermal evolution shows that the main perovskite phase crystallizes already at 1000 °C. Samples sintered at 1400 °C for 10 h have a relative density of 93% and an electrical conductivity of 7.7∙10−2 S cm−1 at 800 °C, similar to the one reported for solid state synthesis. The presence of small amounts of secondary phases (about 17%) such as LaSrGaO4 and LaSrGa3O7 does not seem to deeply affect the electrical properties of the final material.
    Materials Letters 08/2009; 63(21):1892-1894. · 2.27 Impact Factor
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    ABSTRACT: The influence of two different washcoats deposited on ceramic honeycombs (alumina and carbon) on the catalytic and mechanical properties of catalysts are examined in this work. A series of carbon and alumina washcoated samples was prepared through a dip-coating method and subsequently cured and treated to reach a suitable chemistry surface. Carbon-coated monoliths present a high washcoat homogeneity, high integrity and a suitable chemistry surface that favour NO reduction at low temperatures. The carbon washcoat was bonded perfectly to the ceramic monoliths. The high adherence between both materials, checked by vibrational tests, provides higher resistance indexes against axial compression and prevents crack propagation. Both facts are a consequence of the high mechanical strength of the catalyst.On the other hand, alumina coatings present better temperature resistance, although their adherence to ceramic monoliths is not as good as in carbon-coated samples. The properties of alumina coatings are strongly dependent on the slurry viscosities, which influence the integrity of the washcoat, mechanical properties and even NO conversion. Both series of catalysts have shown a good NO conversion under on-board conditions, although the key parameters of each washcoat are completely different.
    Chemical Engineering Journal 07/2009; · 3.47 Impact Factor
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    ABSTRACT: The effects on the slurry rheology of the chemical composition of suspensions representative of those typically adopted for the washcoating of structured supports have been studied in this work, with the purpose of rationalizing the process conditions used in the preparation of structured catalysts. It has been found that the viscosity of the suspensions can be easily predicted and controlled by knowing the pore volume and the nature of the surface of the dispersed powders. In order to prepare suspensions, containing different powders, with the same rheology, water content has to be modulated considering the pore volume, while the dispersant (nitric acid) amount has to be proportional to the quantity required by the complete charging of the surface of the dispersed powders. Obtained results clarify some fundamentals of the washcoating processes and allow a dramatic reduction of the number of experimental tests typically performed to washcoat a structured support starting from a new catalytic material.
    Catalysis Today 01/2009; 147. · 3.31 Impact Factor