Cinzia Cristiani

Politecnico di Milano, Milano, Lombardy, Italy

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Publications (71)180.7 Total impact

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    ABSTRACT: Free access until 11 october at: http://authors.elsevier.com/a/1RaWW1M7w07aO2
    Journal of Power Sources 12/2015; 298:46-67. DOI:10.1016/j.jpowsour.2015.08.034 · 6.22 Impact Factor
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    ABSTRACT: Currently, Gas Diffusion Media for Polymer Electrolyte Membrane Fuel Cells are made hydrophobic by using mainly PTFE. In this work, PTFE was replaced with a less conventionally employed polymer (i.e. fluorinated ethylene propylene, FEP) and carbon nanotubes partially substituted carbon black in the formulation for preparing MPLs. Three inks with variable CNTs concentration were prepared. The presence of FEP allowed to decrease the treatment temperature (260 °C) with respect to the one necessary with GDMs based on PTFE (350 °C). Performances of the cells assembled with FEP-based samples were better than those obtained with conventional GDMs. GDM containing the highest amount of CNTs (10% wt) showed the best results in terms of output power density and cell efficiency. Durability of such a sample was also assessed. Both chemical and mechanical ad-hoc accelerated stress tests were developed. Such tests showed that the main degradation for MPL is due to mechanical stresses, which led to detachment of part of the micro-porous surface and this caused a dramatic mass transfer resistance increase which means a reduction of capability of managing water. Whereas, chemical AST did not show substantial changes in GDMs surface resulting in more restrained diffusion resistance increases.
    International Journal of Hydrogen Energy 06/2015; DOI:10.1016/j.ijhydene.2015.05.100 · 2.93 Impact Factor
  • S. Latorrata · P. Gallo Stampino · C. Cristiani · G. Dotelli
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    ABSTRACT: In this paper the effect of the addition of carboxymethylcellulose (CMC) to microporous layers (MPLs) formulation is reported and the rheological, morphological and electrical properties of the so-obtained MPLs are assessed. Two different PTFE/carbon black ratios are considered, with and without CMC in the ink formulation. CMC addition results in a better homogeneity and stability of the inks. Moreover, the presence of CMC leads to a better shear thinning behaviour and to a general increase in viscosity that makes these slurries more appropriate for coating deposition via doctor blade technique. The presence of CMC in MPL formulation also affects the electrochemical performances in terms of I–V curves and impedance spectra. CMC-containing MPLs show the best performances in terms of generated power at high temperature (80 °C) and low cathodic relative humidity (RH 60 %). Ohmic resistances too, in presence of CMC, are lower than those exhibited by CMC-free MPLs.
    Fuel Cells 04/2015; 15(3). DOI:10.1002/fuce.201400054 · 2.08 Impact Factor
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    Renato Pelosato · Alessandro Donazzi · Giovanni Dotelli · Cinzia Cristiani · Isabella Natali Sora · Mario Mariani
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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 12/2014; 34(16). DOI:10.1016/j.jeurceramsoc.2014.07.005 · 2.95 Impact Factor
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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.
    08/2014; 4(9). DOI:10.1039/C4CY00179F
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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; 78. DOI:10.1016/j.porgcoat.2014.05.028 · 2.36 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 04/2014; 14(2). DOI:10.1002/fuce.201300235 · 2.08 Impact Factor
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    ABSTRACT: Microporous layers (MPLs) obtained from inks containing three fluorinated polymers (perfluoroalcoxy, fluorinated ethylene propylene and a fluorinated polyurethane based on perfluoropolyether blocks) replacing conventional PTFE were prepared. Inks composition and rheological behaviour were fixed in order to apply the blade coating technique for MPL deposition. Superhydrophobic layers were obtained since contact angles higher than 150 degrees were measured. The samples, tested in a single fuel cell at lab scale, at 60 degrees C and different relative humidity (RH 80/100 and 80/60, hydrogen/air) evidenced that new polymers are able to improve electrical performances reaching maximum power density values higher than those showed by conventional MPLs based fuel cells. Electrochemical impedance spectroscopy (EIS) was also carried out on the running cell using a Frequency Response Analyzer to assess the different dissipation phenomena and related losses. Copyright
    International Journal of Hydrogen Energy 03/2014; 39(10):5350-5357. DOI:10.1016/j.ijhydene.2013.12.199 · 2.93 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; 71. DOI:10.1016/j.vibspec.2013.12.010 · 1.55 Impact Factor
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    ABSTRACT: A very simple, cost-effective, chloride- and alkali-free, carbonate co-precipitation synthesis in aqueous medium was applied in the preparation of perovskite-type lanthanum manganese oxide-based powders, i.e. La0.70Sr0.30MnO3−δ (LSM) and La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCrM). The precursors so obtained yielded nano-structured perovskite oxides when treated at 900°C and 800°C, respectively. The measured BET surface areas were in the low-end range for high temperature oxides (4 m2 g−1 and 10 m2 g−1) but the X-ray crystallite size was as low as 50 nm for LSCrM and 90 nm for LSM.
    Chemical Papers- Slovak Academy of Sciences 05/2013; 67(5). DOI:10.2478/s11696-013-0306-z · 1.19 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. DOI:10.1016/j.ijhydene.2012.09.063 · 2.93 Impact Factor
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    ABSTRACT: Inks formulation to deposit microporous layers (MPL) for polymer electrolyte membrane fuel cells (PEM-FCs) application were studied. The effect of the addition of carboxymethylcellulose (CMC) on slurry rheological behaviour and on final morphological, electrical and wettability properties of the so-obtained MPLs were assessed. For this purpose different formulation, namely with and without CMC, were compared. The presence of CMC resulted in a general increase of slurry viscosity and stability. Wettability analyses for surface characterization were performed by means of contact angle measurements applying the sessile drops technique. Static contact angles and contact angle hysteresis were evaluated at ambient temperature, at 60 degrees C and at 80 degrees C. Drop evaporation at the three temperatures was also evaluated. The presence of residual amounts of CMC, not fully decomposed upon MPL thermal treatment, affected negatively the final MPL characteristics in terms of hydrophobicity. Fuel cell assemblies using MPLs with and without CMC showed different electrochemical performances in terms of I-V curves and impedance spectra. CMC-containing MPLs showed electrochemical performances that were influenced by the CMC content: more CMC induced a decrease in power density. However, CMC-based MPLs exhibited lower ohmic resistances.
    11th International Conference on Chemical and Process Engineering; 01/2013
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    ABSTRACT: In the present work two different hydrophobic agents (i. e. a Perfluoropolyether derivative, PFPE, and a Polytetrafluoroethylene, PTFE) were used to treat the surface of a carbon cloth gas diffusion layer (GDL). Commercially available products were used in both cases, namely Fluorolink (R) P56 (supplied by Solvay Solexis s.p.a., Italy) for PPFE and Algoflon (R) D 1214X (supplied by Solvay Solexis s. p. a., Italy) for PTFE. The behaviour of the PFPE-based hydrophobic coating was compared with that of a standard PTFE one. The properties of a GDL coated with about 1 % wt of PFPE were analysed and compared with those of a 10 % wt PTFE coated GDL. Wettability of the PFPE- and PTFE-based surfaces were analysed by means of contact angle measurement. A simplified axisymmetric drop shape analysis technique was used on sessile drops. Static contact angles and contact angle hysteresis were evaluated at ambient temperature, at 60 degrees C and at 80 degrees C. Drop evaporation at the three temperatures was also evaluated. Both the surfaces were found to be highly hydrophobic. The obtained GDLs were used in a single fuel cell and tested in a lab scale. The cell testing was run at two temperatures (60 degrees C and 80 degrees C) with a relative humidity (RH) of the feeding gases of 80/100 %, Hydrogen/Air, respectively. The new PFPE coating sensibly improved the cell performances, and this effect was more evident at 60 degrees C than 80 degrees C.
    11th International Conference on Chemical and Process Engineering; 01/2013
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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 12/2012; DOI:10.1016/j.cattod.2012.09.003 · 3.31 Impact Factor
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    ABSTRACT: Formulations of carbon-based inks for doctor blade applications were considered and the use of Carboxymethylcellulose (CMC) as rheology modifier and suspension stabilizer was proposed. Rheological measurement evidenced that CMC addition guarantees a good dispersion of the carbon powder which results in a higher stability of the ink. The electrical performances of Gas Diffusion Layer (GDL) coated with Micro-Porous Layers (MPLs) prepared with and without CMC were compared. A single PEMFC was used to assess the properties of these GDLs: electrochemical performances were tested in terms of I–V curves and of AC Electrochemical Impedance Spectroscopy (EIS) of the running cell. CMC-containing GDLs showed improved performances when the cell was operated at 80 °C and RH 80–60. Analysis of the EIS spectra demonstrated that, at high Current Density (CD), the CMC-based GDLs suffer for water management. Such a behavior was ascribed to a hydrophilic character of the GDL due to residual amounts of CMC in MPL coating.
    Solid State Ionics 05/2012; 216:73–77. DOI:10.1016/j.ssi.2012.03.030 · 2.11 Impact Factor
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    ABSTRACT: Two polyethylene-glycols (PEG), having different molecular weight (i.e. PEG 1500 and PEG 4000) were intercalated inside the interlayer space of a STx montmorillonite. The microstructure of the intercalated clay mineral was investigated by thermogravimetry (TG) and in situ high temperature-XRD, in order to assess the evolution of the interlayer space upon temperature. Data were collected over a temperature range of 25–1000 °C and 25–850 °C for TG and thermo-XRD, respectively. Decomposition of the intercalated polymers was very different compared to the one of the pure surfactants, as detected by TG and FT IR spectroscopy. In situ high temperature-XRD data showed the formation of a high-temperature phase, detected at 250 °C, independently from the molecular weight of the PEG intercalated. This phase showed to be stable when the temperature was decreased to 25 °C and was raised again to 250 °C. An irregularly interstratified phase was observed when the modified clay minerals were heated at 200 °C.
    Applied Clay Science 05/2012; s 59–60:140–147. DOI:10.1016/j.clay.2012.02.015 · 2.70 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(1):124. DOI:10.1016/j.cattod.2011.03.021 · 3.31 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.
    Journal of Power Sources 09/2011; 196(18):7645-7648. DOI:10.1016/j.jpowsour.2011.04.039 · 6.22 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. DOI:10.1021/jp200845e · 2.78 Impact Factor
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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. DOI:10.1016/j.jpowsour.2010.07.046 · 6.22 Impact Factor

Publication Stats

1k Citations
180.70 Total Impact Points

Institutions

  • 1993–2014
    • Politecnico di Milano
      • • Department of Energy
      • • Department of Chemistry, Materials and Chemical Engineering "Giulio Natta"
      Milano, Lombardy, Italy
  • 2003
    • CMIC
      Cranbury, New Jersey, United States
  • 1997
    • University of Milan
      Milano, Lombardy, Italy