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  • Publication
    Fractal-like kinetics for adsorption of Pb (II) on graphene oxide/hydrous zirconium oxide/crosslinked starch bio-composite: Application of Taguchi approach for optimization
    (Elsevier, 2023-07-01) Rahman, Nafisur; Raheem, Abdur; Al-Kahtani, Abdullah A.; Pandit, Bidhan; Ubaidullah, Mohd
    This study deals with the decontamination of Pb (II) from aqueous environment using graphene oxide/hydrous zirconium oxide/crosslinked starch bio-composite (GZS-BC). Various instrumental techniques were used to characterize the GZS-BC. The main factors of Pb (II) sorption were optimized by Taguchi method. Under optimum conditions, (adsorbent dose: 40 mg, contact time: 180 min and initial Pb (II) concentration: 50 mg/L) maximum removal efficiency (98.50%) was achieved at pH 6. Various isotherm models were tested to fit the adsorption data and Freundlich isotherm model was the best fit model with high R2 values (0.9977–0.9983) and low values of χ2 (0.01–0.02) and APE (0.90–1.14). The kinetic data were investigated using classical and fractal-like kinetic equations. The fractal-like mixed 1,2-order kinetic model was the best fit model which pointed towards heterogeneous surface of GZS-BC with more than one type of sorption sites. Thermodynamic study shows that Pb (II) sorption onto GZS-BC was spontaneous and endothermic in nature. The values of ΔG° indicated that physisorption together with chemisorption was responsible for uptake of Pb (II).
  • Publication
    Evanescent wave sensor for potassium ion detection with special reference to agricultural application
    (Elsevier, 2023-07-01) Potdar, Revati P.; Khollam, Yogesh; Shaikh, Shoyebmohamad F.; Raut, Rajesh W.; Pandit, Bidhan; More, Pravin S.
    We are introducing 4 & PRIME;-aminodibenzo-18-crown-6 ether (A2BC) modification of gold nanoparticles coated optical fiber as a new sensor for evanescent wave trapping on the polymer optical fiber to detect low-level potassium ions. We characterized these gold nanoparticles by X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Nanoparticle tracking analysis (NTA), Field Emission scanning electron microscopes (FE-SEM), and UV-Visible spectroscopy. In the present study, we modified the gold nanoparticles with A2BC for selective sensing of potassium (K+) ions. The interaction between A2BC and K+ ions leads to the temporary formation of a sandwich structure as crown ethers form steady complexes with metal ions. This sandwich structure leads to potassium detection. In our implementation, related operational parameters such as cladding length, roughness, and concentration of A2BC and gold nanoparticles, were optimized to achieve a detection threshold of 1 ppm. Additionally, we optimized the optical fiber sensor to increase its detection sensitivity from the μV range to the mV range. The sensor demonstrates a fast response time (10 s) and high sensitivity, selectivity, and stability, which cause a wide linear range (1-100 ppm) and a low limit of detection (LOD = 0.14 ppm). Lastly, we tested the sensor for a soil-sensing application.
  • Publication
    High performance NASICON ceramic electrolytes produced by tape-casting and low-temperature hot-pressing: Towards sustainable all-solid-state sodium batteries operating at room temperature
    (Elsevier, 2023-09) Naranjo Balseca, Johanna-Monserrath; Martínez Cisneros, Cynthia Susana; Pandit, Bidhan; Lumbier Álvarez, Alejandro; Agencia Estatal de Investigación (España); Comunidad de Madrid; European Commission; Universidad Carlos III de Madrid
    In this work, we propose a processing methodology, based on the combination of tape-casting and low temperature hot-pressing, to develop ceramic NASICON electrolytes with formula Na3.16Zr1.84Y0.16Si2PO12 towards the attainment of solid-state sodium batteries operating at room temperature. Solid-state NASICON electrolytes with very good mechanical properties and high ionic conductivity are successfully tested in terms of electrochemical behavior by using the cell configuration: Na/NASICON/FePO4. Following charge-discharge cycles, an unusual redox pair of FePO4 is found, indicating that the all-solid-state battery with the Na metal anode may be effectively operated at room temperature. At a charge/discharge current density of C/20, the solid-state battery has an initial reversible discharge capacity of 85 mAh/g. Because of its relatively high ionic conductivity and thermostability, when in contact with the Na anode and the FePO4 cathode, the NASICON ceramic electrolyte is a viable option for attaining reliable, safer and sustainable all-solid-state batteries operating at room temperature.
  • Publication
    Highly integrated autonomous lab-on-a-chip device for on-line and in situ determination of environmental chemical parameters
    (Royal Society of Chemistry, 2018-07-01) Martínez Cisneros, Cynthia Susana; Da Rocha, Zaira; Seabra, Antonio; Alonso Chamarro, Julián; Valdés, Francisco; Ministerio de Economía y Competitividad (España)
    The successful integration of sample pretreatment stages, sensors, actuators and electronics in microfluidic devices enables the attainment of complete micro total analysis systems, also known as lab-on-a-chip devices. In this work, we present a novel monolithic autonomous microanalyzer that integrates microfluidics, electronics, a highly sensitive photometric detection system and a sample pretreatment stage consisting on an embedded microcolumn, all in the same device, for on-line determination of relevant environmental parameters. The microcolumn can be filled/emptied with any resin or powder substrate whenever required, paving the way for its application to several analytical processes: separation, pre-concentration or ionic-exchange. To promote its autonomous operation, avoiding issues caused by bubbles in photometric detection systems, an efficient monolithic bubble removal structure was also integrated. To demonstrate its feasibility, the microanalyzer was successfully used to determine nitrate and nitrite in continuous flow conditions, providing real time and continuous information.
  • Publication
    Flexible solvent-free polymer electrolytes for solid-state Na batteries
    (Elsevier, 2023-03-01) Martínez Cisneros, Cynthia Susana; Pandit, Bidhan; Levenfeld Laredo, Belén; Lumbier Álvarez, Alejandro; Sánchez, Jean Yves
    Post-lithium batteries, based on alkaline and alkaline earth elements, are cheaper technologies with the potential to produce disruptive changes in the transition towards cleaner and sustainable energy sources less dependent on fossil fuels. This contribution deals with the development and characterization of sodium-conducting solvent-free polymer electrolytes towards the attainment of Sodium Polymer Batteries. Obtained via the polycondensation of α, ω-dihydroxy-oligo(oxyethylene) with an unsaturated dihalide, whose further curing leads to amorphous networked electrolyte films. Using NaClO4 and NaCF3SO3 at different O/Na ratios, the best polymer electrolyte reaches a cationic conductivity (σ+) exceeding 1 mS cm−1 at 90 °C whereas maintaining mechanical integrity up to at least 120 °C.
  • Publication
    Chemical regeneration of thermally conditioned basalt fibres
    (MDPI, 2020-10-01) Lilli, Matteo; Sarasini, Fabrizio; Di Fausto, Lorenzo; González, Carlos; Fernández Gorgojo, Andrea; Lópes, Claudio Saúl; Tirillò, Jacopo
    The disposal of fibre reinforced composite materials is a problem widely debated in the literature. This work explores the ability to restore the mechanical properties of thermally conditioned basalt fibres through chemical treatments. Inorganic acid (HF) and alkaline (NaOH) treatments proved to be effective in regenerating the mechanical strength of recycled basalt fibres, with up to 94% recovery of the strength on treatment with NaOH. In particular, HF treatment proved to be less effective compared to NaOH, therefore pointing towards a more environmentally sustainable approach considering the disposal issues linked to the use of HF. Moreover, the strength regeneration was found to be dependent on the level of temperature experienced during the thermal treatment process, with decreasing effectiveness as a function of increasing temperature. SEM analysis of the fibres' lateral surfaces suggests that surface defects removal induced by the etching reaction is the mechanism controlling recovery of fibre mechanical properties. In addition, studies on the fracture toughness of the regenerated single fibres were carried out, using focussed ion beam (FIB) milling technique, to investigate whether any structural change in the bulk fibre occurred after thermal exposure and chemical regeneration. A significant increase in the fracture toughness for the regenerated fibres, in comparison with the as-received and heat-treated basalt ones, was measured.
  • Publication
    Using Metal-Organic Framework HKUST-1 for the Preparation of High-Conductive Hybrid Membranes Based on Multiblock Copolymers for Fuel Cells
    (MDPI, 2023-01-08) Gorban, Ivan; Ureña Torres, María de las Nieves; Pérez Prior, María Teresa; Varez, Alejandro; Levenfeld Laredo, Belén; Rio, Carmen del; Soldatov, Mikhail; Comunidad de Madrid; Universidad Carlos III de Madrid; Agencia Estatal de Investigación (España)
    Novel proton-conducting hybrid membranes consisting of sulfonated multiblock copolymer of polysulfone and polyphenylsulfone (SPES) reinforced with a HKUST-1 metal-organic framework (MOF) (5, 10, and 20 wt. %) were prepared and characterized for fuel cell applications. The presence of the MOF in the copolymer was confirmed by means of FE-SEM and EDS. The hybrid membranes show a lower contact angle value than the pure SPES, in agreement with the water uptake (WU%), i.e., by adding 5 wt. % of the MOF, this parameter increases by 20% and 40% at 30 °C and 60 °C, respectively. Additionally, the presence of the MOF increases the ion exchange capacity (IEC) from 1.62 to 1.93 mequivH+ g−1. Thermogravimetric analysis reveals that the hybrid membranes demonstrate high thermal stability in the fuel cell operation temperature range ( 85 MPa in the Na+ form). Proton conductivity was analyzed using EIS, achieving the highest value with a 5 wt. % load of the HKUST-1. This value is lower than that observed for the HKUST-1/Nafion system. However, polarization and power density curves show a remarkably better performance of the hybrid membranes in comparison to both the pure SPES and the pure Nafion membranes
  • Publication
    Layer shape LiFePO4 obtained by powder extrusion molding as solid boosters for ferro/ferricyanide catholyte in semisolid redox flow battery: Effect of porosity and shape
    (Wiley, 2022-07) Vivo Vilches, José Francisco; Vázquez Navalmoral, Álvaro; Torre Gamarra, Carmen de la; Cebollada, Jesús; Varez Álvarez, Alejandro; Levenfeld Laredo, Belén; Comunidad de Madrid; European Commission; Ministerio de Ciencia e Innovación (España); Universidad Carlos III de Madrid
    Powder extrusion molding is proposed to fabricate ceramic LiFePO4 layers (0.5-1.0 mm thickness) as solid booster for ferricyanide electrolyte in semisolid redox flow battery. In some extruded layers, the binder is partially decomposed, while in others it is completely removed and, afterwards, the material is sintered, so materials with different porosity and dimensions are obtained. After characterizing the materials, the kinetics for the reaction with ferricyanide is evaluated, being the binder-less materials the ones which react faster and reach larger degrees of oxidation. For the material with 1.0 mm thick comparable results to the ones already published are obtained (69 % capacity for LiFePO4 compared to the theoretical value). In the case of the 0.5 mm thick sintered solid, an outstanding performance is achieved, reaching almost the theoretical capacity (94 %) with a very high coulombic efficiency (>99 %) at 1 mA cm-2, results that were only obtained at much lower current densities in previous works.
  • Publication
    Effect of relaxations on the conductivity of La1/2+1/2xLi1/2-1/2 xTi1-xAlxO3 fast ion conductors
    (ACS Publications, 2022-06-28) Vezzù, Keti; García-González, Ester; Pagot, Gioele; Urones Garrote, Esteban; Sotomayor Lozano, María Eugenia; Varez, Alejandro; Noto, Vito Di; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España); Universidad Carlos III de Madrid
    Perovskite-type solid-state electrolytes, Li3xLa2/3–xTiO3 (LLTO), are considered among the most promising candidates for the development of all-solid-state batteries based on lithium metal. Their high bulk ionic conductivity can be modulated by substituting part of the atoms hosted in the A- or B-site of the LLTO structure. In this work, we investigate the crystal structure and the long-range charge migration processes characterizing a family of perovskites with the general formula La1/2+1/2xLi1/2–1/2xTi1–xAlxO3 (0 ≤ x ≤ 0.6), in which the charge balance and the nominal A-site vacancies (nA = 0) are preserved. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) investigations reveal the presence of a very complex nanostructure constituted by a mixture of two different ordered nanoregions of tetragonal P4/mmm and rhombohedral R3̅c symmetries. Broadband electrical spectroscopy studies confirm the presence of different crystalline domains and demonstrate that the structural fluctuations of the BO6 octahedra require to be intra- and intercell coupled, to enable the long-range diffusion of the lithium cation, in a similar way to the segmental mode that takes place in polymer-ion conductors. These hypotheses are corroborated by density functional theory (DFT) calculations and molecular dynamic simulations.
  • Publication
    Modeling the interplay between water capillary transport and species diffusion in gas diffusion layers of proton exchange fuel cells using a hybrid computational fluid dynamics formulation
    (Elsevier, 2022-02-01) Zapardiel, Diego; García-Salaberri, Pablo A.; Universidad Carlos III de Madrid; Agencia Estatal de Investigación (España)
    Improved modeling of the membrane electrode assembly (MEA) and operation is essential to optimize proton exchange fuel cells (PEFCs). In this work, a hybrid model, which includes a pore network formulation to describe water capillary transport and a continuum formulation to describe gas diffusion, is presented. The model is validated with previous data of carbon-paper gas diffusion layers (GDL), including capillary pressure curve, relative effective diffusivity, , and saturation profile. The model adequately captures the increase of capillary pressure with compression, the nearly cubic dependency of on average saturation, , and the shape of the saturation profile in conditions dominated by capillary fingering (e.g., running PEFC at low temperature). Subsequently, an analysis is presented in terms of the area fraction of water at the inlet and the outlet of the GDL, and , respectively. The results show that gas diffusion is severely hindered when is exceedingly high (¿80%), a situation that can arise due to the bottleneck created by flooded interfacial gaps. Furthermore, it is found that increases with , reducing the GDL effective diffusivity. Overall, the work shows the importance of an appropriate design of MEA porous media and interfaces in PEFCs.
  • Publication
    Modeling the Effect of Low Pt loading Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells. Part I: Model Formulation and Validation
    (IOP Science, 2021-12-30) Sánchez Ramos, Arturo; Gostick, Jeff T.; García-Salaberri, Pablo A.; Universidad Carlos III de Madrid; Agencia Estatal de Investigación (España)
    A model for the cathode catalyst layer (CL) is presented, which is validated with previous experimental data in terms of both performance and oxygen transport resistance. The model includes a 1D macroscopic description of proton, electron and oxygen transport across the CL thickness, which is locally coupled to a 1D microscopic model that describes oxygen transport toward Pt sites. Oxygen transport from the channel to the CL and ionic transport across the membrane are incorporated through integral boundary conditions. The model is complemented with data of effective transport and electrochemical properties extracted from multiple experimental works. The results show that the contribution of the thin ionomer film and Pt/ionomer interface increases with the inverse of the roughness factor. Whereas the contribution of the water film and the water/ionomer interface increases with the ratio between the geometric area and the surface area of active ionomer. Moreover, it is found that CLs diluted with bare carbon provide lower performance than non-diluted samples due to their lower electrochemical surface area and larger local oxygen transport resistance. Optimized design of non-diluted samples with a good distribution of the overall oxygen flux among Pt sites is critical to reduce mass transport losses at low Pt loading.
  • Publication
    Sulfonated Polysulfone/TiO2(B) Nanowires Composite Membranes as Polymer Electrolytes in Fuel Cells
    (MDPI, 2021-06-21) Martínez Morlanes, María José; Torre Gamarra, Carmen de la; Pérez Prior, María Teresa; Lara-Benito, Sara; Rio, Carmen del; Varez, Alejandro; Levenfeld Laredo, Belén; Comunidad de Madrid; Agencia Estatal de Investigación (España)
    New proton conducting membranes based on sulfonated polysulfone (sPSU) reinforced with TiO2 (B) nanowires (1, 2, 5 and 10 wt.%) were synthesized and characterized. TiO2 (B) nanowires were synthesized by means of a hydrothermal method by mixing TiO2 precursor in aqueous solution of NaOH as solvent. The presence of the TiO2 (B) nanowires into the polymer were confirmed by means of Field Emission Scanning Electron Microscopy, Fourier transform infrared and X-ray diffraction. The thermal study showed an increase of almost 20 ◦C in the maximum temperature of sPSU backbone decomposition due to the presence of 10 wt.% TiO2 (B) nanowires. Water uptake also is improved with the presence of hydrophilic TiO2 (B) nanowires. Proton conductivity of sPSU with 10 wt.% TiO2 (B) nanowires was 21 mS cm−1 (at 85 ◦C and 100% RH). Under these experimental conditions the power density was 350 mW cm−2 similar to the value obtained for Nafion 117. Considering all these obtained results, the composite membrane doped with 10 wt.% TiO2 (B) nanowires is a promising candidate as proton exchange electrolyte in fuel cells (PEMFCs), especially those operating at high temperatures.
  • Publication
    Characterization and Modeling of Free Volume and Ionic Conduction in Multiblock Copolymer Proton Exchange Membranes
    (MDPI AG, 2022-05-01) Gomaa, Mahmoud Mohammed; Sánchez Ramos, Arturo; Ureña Torres, María de las Nieves; Pérez Prior, María Teresa; Levenfeld Laredo, Belén; García-Salaberri, Pablo A.; Elsharkawy, Mohamed Rabeh Mohamed; Comunidad de Madrid; Ministerio de Ciencia, Innovación y Universidades (España); Universidad Carlos III de Madrid
    Free volume plays a key role on transport in proton exchange membranes (PEMs), including ionic conduction, species permeation, and diffusion. Positron annihilation lifetime spectroscopy and electrochemical impedance spectroscopy are used to characterize the pore size distribution and ionic conductivity of synthesized PEMs from polysulfone/polyphenylsulfone multiblock copolymers with different degrees of sulfonation (SPES). The experimental data are combined with a bundle-of-tubes model at the cluster-network scale to examine water uptake and proton conduction. The results show that the free pore size changes little with temperature in agreement with the good thermo-mechanical properties of SPES. However, the free volume is significantly lower than that of Nafion®, leading to lower ionic conductivity. This is explained by the reduction of the bulk space available for proton transfer where the activation free energy is lower, as well as an increase in the tortuosity of the ionic network.
  • Publication
    Enhanced morphological characterization of cellulose nano/microfibers through image skeleton analysis
    (MDPI, 2021-08) Sánchez Salvador, José Luis; Campano, Cristina; López Expósito, Patricio; Tarres, Quim; Mutje, Pere; Delgado Aguilar, Marc; Monte, M. Concepcion; Blanco, Angeles; Comunidad de Madrid; Ministerio de Economía y Competitividad (España)
    The present paper proposes a novel approach for the morphological characterization of cellulose nano and microfibers suspensions (CMF/CNFs) based on the analysis of eroded CMF/CNF microscopy images. This approach offers a detailed morphological characterization and quantifi-cation of the micro and nanofibers networks present in the product, which allows the mode of fibrillation associated to the different CMF/CNF extraction conditions to be discerned. This information is needed to control CMF/CNF quality during industrial production. Five cellulose raw materials, from wood and non-wood sources, were subjected to mechanical, enzymatic, and (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO)-mediated oxidative pre-treatments followed by different homogenization sequences to obtain products of different morphologies. Skeleton analysis of microscopy images provided in-depth morphological information of CMF/CNFs that, complemented with aspect ratio information, estimated from gel point data, allowed the quantification of: (i) fibers peeling after mechanical pretreatment; (ii) fibers shortening induced by enzymes, and (iii) CMF/CNF entanglement from TEMPO-mediated oxidation. Being mostly based on optical microscopy and image analysis, the present method is easy to implement at industrial scale as a tool to monitor and control CMF/CNF quality and homogeneity.
  • Publication
    New amphiphilic semi-interpenetrating networks based on polysulfone for anion-exchange membrane fuel cells with improved alkaline and mechanical stabilities
    (Elsevier, 2021-06-04) Levenfeld Laredo, Belén; Ureña Torres, María de las Nieves; Pérez Prior, María Teresa; Lumbier Álvarez, Alejandro; Del Rio, Carmen; Agencia Estatal de Investigación (España)
    As considerable advance has recently been made in enhancing the conductivity of anion-exchange membranes, durability has become the critical requirement in the development of fuel cells. Such properties often develop at the expense of the other. In this work, new amphiphilic semi-interpenetrating networks composed of free polysulfone and crosslinked polysulfone are synthesized for the first time. The same nature of both polymers makes them highly compatible. The free polymer provides the hydrophobic component, whereas the crosslinked polysulfone, functionalized with trimethylammonium, 1-methylimidazolium, or 1,2-dimethylimidazolium groups, is responsible for the ionic conductivity. The compatibility between both components in the blend, improves the mechanical properties, while unaffecting the transport properties. Thus, the obtained membranes exceed the mechanical behaviour of commercial materials, even in conditions of extreme humidity and temperature. The tensile strength of these synthesized membranes can reach to relatively high values, and when compared to the commercial PSU, the difference in tensile strength can be noted to be as low as 10%. Moreover, the tensile strength and the ductility values of the crosslinked PSU are higher than those obtained with non-crosslinked PSU. Furthermore, the membranes presented in this work show a great alkaline stability (e.g. semi-interpenetrating network containing 1,2-dimethylimidazolium maintains 87% of the ionic conductivity after 14 days of treatment). Thus, these membranes provide an improvement in the durability limiting factors, in comparison to functionalized polysulfones, fulfilling the requirements to be used as electrolytes in anion-exchange membrane fuel cells.
  • Publication
    Interplay between Conductivity, Matrix Relaxations and Composition of Ca-Polyoxyethylene Polymer Electrolytes
    (Wiley, 2021-07-01) Martínez Cisneros, Cynthia Susana; Pagot, Gioele; Vezzu, Keti; Antonelli, Claire; Levenfeld Laredo, Belén; Lumbier Álvarez, Alejandro; Sánchez, Jean Yves; Di Noto, Vito; European Commission
    In this report, the conductivity mechanism of Ca2+-ion in polyoxyethylene (POE) solid polymer electrolytes (SPEs) for calcium secondary batteries is investigated by broadband electrical spectroscopy studies. SPEs are obtained by dissolving into the POE hosting matrix three different calcium salts: CaTf2, Ca(TFSI)2 and CaI2. The investigation of the electric response of the synthetized SPEs reveals the presence in materials of two polarization phenomena and two dielectric relaxation events. It is demonstrated that the nature of the anion (i. e., steric hindrance, charge density and ability to act as coordination ligand) and the density of “dynamic crosslinks” of SPEs is fundamental in the establishment of ion-ion/ion-polymer interactions. The long-range charge migration processes occurring along the two revealed percolation pathways of the electrolytes are generally coupled with the polymer host dynamics and depend on the temperature and the anion nature. This study offers the needed tools for understanding Ca2+ conduction in POE-based electrolytes.
  • Publication
    Development of sodium hybrid quasi-solid electrolytes based on porous NASICON and ionic liquids
    (Elsevier, 2021-12) Martínez Cisneros, Cynthia Susana; Pandit, Bidhan; Antonelli, C.; Sánchez, Jean Yves; Levenfeld Laredo, Belén; Lumbier Álvarez, Alejandro; Comunidad de Madrid; Ministerio de Ciencia, Innovación y Universidades (España)
    Lithium-ion batteries are currently the alternative of choice to overcome the increasing demand of energy. However, besides the scarcity of lithium and limited geolocation, it is believed that such batteries have already reached their maximum maturity. Sodium batteries emerge as an alternative to produce the new, so called, post-lithium batteries. In this study, we explore (i) the effect of sodium content and sintering temperature in solid electrolytes based in NASICON-type compounds and (ii) the use of two methodologies to obtain porous NASICON samples: application of natural substances and organic materials as pore-formers and freeze casting. The main purpose is the attainment of hybrid quasi-solid state electrolytes, with enhanced room temperature conductivity, based on porous ceramic electrolyte layers infiltrated with ionic liquids. Using this approach, porous samples with different microstructure and porous morphology and distribution were achieved, providing an enhancement in conductivity (ranging from 0.45 to 0.96 mS cm−1 at 30 °C) of one order of magnitude for infiltrated samples respect to pore-free samples. According to these results the porous NASICON might be considered as a functional macroporous inorganic separator that can act as a Na+ reservoir.
  • Publication
    Non-woven polyaramid porous membranes as separators for Li-ion batteries?
    (Elsevier, 2021-09-10) Martínez Cisneros, Cynthia Susana; Antonelli, Claire; Levenfeld Laredo, Belén; Lumbier Álvarez, Alejandro; Perez-Flores, Juan Carlos; Santos-Mendez, Antonio; Kuhn, Alois; Sánchez, Jean Yves; Comunidad de Madrid; European Commission; Ministerio de Ciencia, Innovación y Universidades (España)
    Macroporous separators play a crucial role regarding safety in current Li-ion batteries. Most separators used in battery applications are based on polyolefin and present shrinkage and a decrease in mechanical properties when used at high temperatures, both detrimental in the battery performance. In search of more suitable alternatives that render to more stable and safer batteries, in this work, non-woven separators based on polyacrylonitrile blended with cellulose and para-aramid fibers are systematically investigated. This study has been carried out in terms of microstructure, mechanical properties, ionic conductivity and thermal and electrochemical stability (using Li4Ti5O12/LiCoO2 full cells with a nominal potential of ≈2.5 V). Although conductivity values of separators are somewhat modest, the electrochemical performance developed when used in Li4Ti5O12/LiCoO2 cells are, at moderate C rates, comparable to commercial Celgard©2400 separator. At high C rates, in particular at 2C, DwG40 exhibits much higher capacities than the whole of the separators, including Celgard®2400. This study responds to the continuous need reflected not only by the scientific community but also by the industrial one when new materials for electrolytes and electrodes should be tested, since there is a lack of reports characterizing such elements in the literature.
  • Publication
    LTCC microflow analyzers with monolithic integration of thermal control
    (Elsevier, 2007-07-20) Martínez Cisneros, Cynthia Susana; Ibáñez-García, Núria; Valdés, Francisco; Alonso, Julián
    Recently, the low temperature co-fired ceramics technology has shown to be an excellent alternative to silicon-based microfabrication techniques for the production of three-dimensional structures using a multi-layer approach. This enables the integration of several unitary operations of a classical analytical process and also the integration of sensors, actuators and electronics in the same substrate. In this work, we show the integration of the actuators and the sensors needed for the control of temperature inside a miniaturized fluidic device. The proposed device presents enough thermal accuracy to be used in chemical systems where temperature control is a crucial factor, such as enzyme reactions or polymerase chain reaction systems.
  • Publication
    Synthesis and characterization of novel anion exchange membranes based on semi-interpenetrating networks of functionalized polysulfone: Effect of ionic crosslinking
    (MDPI, 2021-03-02) Swaby Martínez, Sydonne Leonor; Ureña Torres, María de las Nieves; Pérez Prior, María Teresa; Lumbier Álvarez, Alejandro; Levenfeld Laredo, Belén; Comunidad de Madrid; Ministerio de Ciencia, Innovación y Universidades (España); Universidad Carlos III de Madrid
    In this work, anion exchange membranes based on polymer semi-interpenetrating networks were synthesized and characterized for the first time. The networks are composed of sulfonated polysulfone and 1-methylimidazolium-functionalized polysulfone crosslinked covalently with N,N,N′,N′-tetramethylethylenediamine (degree of crosslinking of 5%). In these membranes, sulfonic groups interact electrostatically with cationic groups to form an ionic crosslinking structure with improved alkaline stability. The effect of the ionic crosslinking on the thermal, chemical, mechanical, and electrochemical behavior of membranes was studied. These crosslinked membranes containing sulfonated polysulfone showed higher thermal stability, with a delay of around 20 °C in the onset decomposition temperature value of the functional groups than the crosslinked membranes containing free polysulfone. The tensile strength values were maintained above 44 MPa in all membranes with a degree of chloromethylation (DC) below 100%. The maximum ionic conductivity value is reached with the membrane with the highest degree of chloromethylation. The chemical stability in alkaline medium of the conducting membranes also improved. Thus, the ionic conductivity variation of the membranes after 96 h in a 1 M potassium hydroxide (KOH) solution is less pronounced when polysulfone is replaced by sulfonated polysulfone. So, the ionic crosslinking which joins both components of the blends together, improves the material’s properties making progress in the development of new solid electrolyte for polymeric fuel cells.