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  • Publication
    Influence of the early-age length change of alkali-activated slag mortars on the corrosion of embedded steel
    (Informa UK Limited, 2023-12-14) Shagñay Pucha, Segundo Manuel; Bautista Arija, María Asunción; Velasco López, Francisco Javier; Ramón Álvarez, Irene; Torres Carrasco, Manuel; Ministerio de Ciencia, Innovación y Universidades (España); Comunidad de Madrid
  • Publication
    Versatile graphene-alumina nanofibers for microwave absorption and EMI shielding
    (Elsevier Ltd., 2023-06-15) Shamshirgar, Ali Saffar; Fernández Álvarez, María; Del Campo, Adolfo; Fernandez, José Francisco; Rojas-Hernandez, Rocío E.; Ivanov, Roman; Rosen, Johanna; Hussainova, Irina
    Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer structure with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 ± 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 °C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the obtained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of -25 dB at ~11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption characteristics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.
  • Publication
    Carbonation of alkali-activated and hybrid mortars manufactured from slag: confocal Raman microscopy and impact on wear performance= Carbonatación de morteros de escoria activados alcalinamente e híbridos: estudio mediante microscopía Raman Confocal y la repercusión en las prestaciones de desgaste
    (Elsevier España, 2023-10-20) Shagñay Pucha, Segundo Manuel; Bautista Arija, María Asunción; Velasco López, Francisco Javier; Torres Carrasco, Manuel
    This work aims to contribute to reducing environmental damage caused by the manufacturing of Portland cements (PC), through in-depth exploration into the durability of two mortars manufactured from blast furnace slag: an alkaline-activated one (AAS) and a hybrid cement (HS) with less than 20% clinker. The carbonation resistance of these eco-friendly mortars is compared to that of a mortar based on Portland IV cement. From a mineralogical point of view, DTA-TG and confocal Raman microscopy (CRM) tests have been carried out, along with measurement of pH changes, compression strength and total porosity. Böhme tests have been performed to evaluate changes due to carbonation in the wear behavior of the mortars under study. Using the CRM technique, it has been possible to establish a relationship between the carbonation of the systems with the unbound carbon content, as well as identify the different polymorphic phases of CaCO3 formed. The results obtained reveal that alternative AAS and HS mortars are more difficult to carbonate than Portland cement mortars, and that the effect of this process on the porosity depends on the nature of the hydroxides previously present in the pore solution. The carbonation of the surfaces also improves the abrasive wear resistance of the mortars under study.
  • Publication
    Electrodes based on carbon aerogels partially graphitized by doping with transition metals for oxygen reduction reaction
    (MDPI, 2018-01-01) Abdelwahab, A.; Castelo-Quibén,; Vivo Vilches, José Francisco; Pérez-Cadenas, M.; Ministerio de Economía y Competitividad (España)
    A series of carbon aerogels doped with iron, cobalt and nickel have been prepared. Metal nanoparticles very well dispersed into the carbon matrix catalyze the formation of graphitic clusters around them. Samples with different Ni content are obtained to test the influence of the metal loading. All aerogels have been characterized to analyze their textural properties, surface chemistry and crystal structures. These metal-doped aerogels have a very well-developed porosity, making their mesoporosity remarkable. Ni-doped aerogels are the ones with the largest surface area and the smallest graphitization. They also present larger mesopore volumes than Co- and Fe-doped aerogels. These materials are tested as electro-catalysts for the oxygen reduction reaction. Results show a clear and strong influence of the carbonaceous structure on the whole electro-catalytic behavior of the aerogels. Regarding the type of metal doping, aerogel doped with Co is the most active one, followed by Ni- and Fe-doped aerogels, respectively. As the Ni content is larger, the kinetic current densities increase. Comparatively, among the different doping metals, the results obtained with Ni are especially remarkable. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.
  • Publication
    Environmentally Friendly Plasma Activation of Acrylonitrile-Butadiene-Styrene and Polydimethylsiloxane Surfaces to Improve Paint Adhesion
    (2018-12-26) Martínez Casanova, Miguel Ángel; Abenojar Buendía, Juana; López de Armentia Hernández, Sara
    Generally, polymeric materials present an issue related to their low surface energy: low painting ability. The main aim of this work is to improve the adhesion between polymeric surfaces (polydimethylsiloxane (PDMS), and acrylonitrile-butadiene-styrene (ABS)) and paints (epoxy (EP), and polyurethane (PU)-based). In order to increase adhesion, hydrophilic modification of surfaces by atmospheric pressure plasma torch treatment (APPT) was proposed. Furthermore, it can permit dissimilar joints, i.e., ABS with a metal joined by a silicone (based PDMS), to be painted. The surface modifications were characterized by measurements of surface energy and roughness. In addition, the effectiveness of the pre-treatment on improving paint adhesion was confirmed by scratch, cross-cut, and adhesion tests. Results showed the possibility of coating both ABS and PDMS with a PU-based paint when treated with plasma. As a novel result, polymer and metal panels joined by silicone were able to be painted with the PU paint.
  • Publication
    Evaluation of the Bioaccumulation Capacity of Buddleja Species in Soils Contaminated with Total Chromium in Tannery Effluents in Arequipa (Peru)
    (MDPI, 2023-04-02) Almirón, Jonathan; Arosquipa Pachari, Karen Rocio; Huillcañahui Taco, Cintia; Huarsaya Huillca, Jamilet Ariana; Mamani Quispe, Jose; Ortiz-Valdivia, Yosheff; Velasco López, Francisco Javier; Tupayachy-Quispe, Danny
    The main purpose of this study is to evaluate the Buddleja species bioaccumulation capacity for the phytoremediation of soils contaminated with chromium produced by tannery effluents. The soils evaluated were collected from the A¿shuayco stream, located in Arequipa region. The soil samples were collected from four different locations, in order to determine the presence of total chromium through the Environmental Protection Agency analytical technique, method 3050B acid digestion of sediment, sludge and soil. Three soil samples were analyzed for each collected location. Additionally, two non-contaminated soil samples (control group) were also analyzed. A Buddleja species seedling was placed in each sample to be monitored monthly for up to 90 days. Then, the plant tissue analysis was carried out by the analytical method of atomic absorption spectrophotometry in order to determine the amount of bioaccumulated total chromium. As a result, the Buddleja species bioaccumulated 30.45%, 24.19%, 34.55% and 40.72% of total chromium per each soil sample location in a period of 90 days. Therefore, the Buddleja species can be considered as an alternative to remediate soils contaminated with total chromium that comes from tannery effluents.
  • Publication
    Experimental and computational optimization of eco-friendly mortar blocks for high temperature thermal energy storage of concentrated solar power plants
    (Elsevier, 2023-11-01) Ramón Álvarez, Irene; Sánchez Delgado, Sergio; Peralta, Ignacio; Caggiano, Antonio; Torres Carrasco, Manuel; Ministerio de Ciencia e Innovación (España)
    New avenues for thermal energy storage (TES) need to be investigated due to the lack of competitiveness of concentrated solar power (CSP) technologies. Solutions must be found to replace molten salt tanks which have a major economic impact and are difficult to maintain due to corrosion problems. In this sense, concrete represented an attractive candidate by proving excellent sensible TES in CSP. However, its main phase, made of Portland cement (PC), has significant environmental consequences. The production of PC is known to emit high levels of polluting gases, particularly the CO2. It is estimated to be responsible for between 5% and 7% of the world's CO2 emissions, making it a major contributor to climate change. This work presents greener cementitious materials, made of alkaline cements and hybrids cements, to be used as alternative eco-friendly TES media in CSP plants. An experimental campaign is presented which shows that these eco-efficient materials can have better mechanical properties, than the ordinary PC mortar, when exposed to high temperatures, in addition, can offer improvements of their thermal properties (thermal conductivity or specific heat). Second part of the work is devoted to Finite Element simulations, with the aim to find the best configuration, in terms of selection of materials and geometry, which are more efficient as TES system. The work is showing the following advancements in CSP technology by using alternative eco-friendly binders: the installation volume can be reduced by 17%, compared to a molten salt tank, while the heat exchanger's surface area can be resized by 29%, compared to the reference system using PC. These improvements enable wider variations in CSP operational efficiency and dynamic capabilities and represent important progress towards developing more efficient and sustainable CSP technologies.
  • Publication
    Experimental and numerical studies of polyamide 11 and 12 surfaces modified by atmospheric pressure plasma treatment
    (Elsevier, 2022-08) Bahrami, Mohsen; Lavayen Farfan, D.; Martínez Casanova, Miguel Ángel; Abenojar Buendía, Juana
    Polyamide 11 and 12 (PA11 and PA12) have been applicable in various industries, including automotive, oil and gas, and sporting goods, over the past 70 years. Although they have good dyeability, their adhesion to other materials is limited due to relatively poor surface properties, which can be promoted by good wettability and high surface energy. This study aims to improve the surface properties of PA11 and PA12 by employing the advanced method of Atmospheric Pressure Plasma Torch (APPT) treatment. In this regard, the adhesion strengths of four commercially available adhesives were evaluated with the pull-off test on PAs plates before and after APPT treatment. The numerical simulation of this test was carried out in commercial finite element software using a cohesive zone model (CZM) to predict the fracture of adhesively bonded joints. Moreover, the modified PAs were analyzed using XPS, DSC, ATR-FTIR, optical profilometer and surface energy measurement. The results indicated that the surface properties, including wettability, polar surface energy and adhesion bonding, improved by employing the plasma treatment on PAs surfaces. The numerical simulation outcomes showed that the pull-off test might be a viable alternative to determine the CZM laws for fracture mode I.
  • Publication
    Thermal characterization and diffusivity of two mono-component epoxies for transformer insulation
    (Elsevier, 2020-12) Abenojar Buendía, Juana; Enciso Ramos, María Belén; Pantoja Ruiz, Mariola; Velasco López, Francisco Javier; Martínez Casanova, Miguel Ángel; European Commission
    The main aim of this study is the thermal characterization of an organic insulation. This insulation is a compound of two mono-component epoxy resins: Epoxylite® primer and Elmotherm® varnish. A mono-component epoxy resin usually needs a high temperature to cure; through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), non-isothermal curves are obtained, allowing the estimation of activation energies of curing and decomposition processes respectively. If Model Free Kinetic (MFK) is used from DSC curves, it is possible to simulate isothermal curves at different temperatures and times, plotting activation energy as a function of the conversion degree. The simulation from TGA curves can be used to estimate lifetime of the resins and compare them following the Toop method. DSC also allows measurement of thermal conductivity, the melting peak of metallic gallium being used for this measurement. Finally, water diffusion in resins is studied. Currently, the Materials Performance research group of UC3M is working on the European project named "Essial", where this organic insulation is used to protect the windings and the whole transformer from the environment. The results obtained will be used to determinate the optimal operating range for this insulator, demonstrating that both epoxies are required to achieve the insulating performance of the transformer and long curing times are required for full curing of Epoxylite®.
  • Publication
    Novel application of a thermoplastic composite with improved matrix-fiber interface
    (Elsevier, 2019-11-01) López de Armentia Hernández, Sara; Enciso Ramos, María Belén; Mokry López, Guillermo; Abenojar Buendía, Juana; Martínez Sánchez, Manuel; European Commission
    Ornamental materials are widely used in many fields such as construction. However, they have a main issue: up to 60% of processed marble pieces break due to their low toughness. In this work, an externally bonded reinforcement which can cope with this problem is presented. It must absorb the shock energy when marble is subjected to an impact without increasing severely the production cost. A thermoplastic polymer matrix composite is proposed due to its high toughness compared with conventional thermoset polymer matrix composites. However, thermoplastics present an issue related to the adhesion with the reinforcement, therefore fibers must be treated to solve this matter. Atmospheric pressure plasma torch offers a time saving and environmental friendly solution for improving adhesion between the fibers and the matrix. Finally, when marble is reinforced with the composite an important increase in absorbed energy is found in both, Charpy and drop tower test.
  • Publication
    Influence of the cold working induced martensite on the electrochemical behavior of AISI 304 stainless steel surfaces
    (Elsevier, 2019-03-01) Monrrabal Márquez, Gleidys; Bautista Arija, María Asunción; Gúzman Fernández, Susana; Gutierrez, Cristina; Velasco López, Francisco Javier
    It is clear that the corrosion resistance of carbon steels decreases as cold working amount increases, but for austenitic stainless steels, the relation between cold-working and corrosion performance is not clear. The electrochemical behavior of AISI 304 stainless steel with 3 different cold working amounts is characterized by Mott-Schottky analysis, OCP records, EIS and cyclic polarization curves. An innovative cell with gel electrolyte is used for an easy study of the deformed surfaces without modifying them. After the polarization tests, the influence of the deformation on the amount of pits and on their morphological characteristics is also analyzed. The microstructural changes caused by cold rolling are studied, and the residual stresses are determined by XRD using the sin(2) psi method. It is proved that AISI 304 stainless steel decreases its pitting resistance in a medium with chlorides when it is subjected to moderate cold rolling, but heavy thickness reduction causes a subsequent recovery of corrosion resistance. The results obtained suggest that this trend is related to changes in the magnitude and type of the stresses (tensile or compressive) on the surface of the material.
  • Publication
    Dynamic characterisation of interlaminar fracture toughness in carbon fibre epoxy composite laminates
    (Elsevier, 2019-11-01) Riezzo, M.A.; Simmons, M.; Russell, B.; Sket, F.; Martínez León, Víctor; González, C.; European Commission
    In this work, the rate dependence of mode I interlaminar fracture toughness for two different materials systems, IM7/8552 and IM7/M91, both unidirectional UD carbon-fibre epoxy composite laminates have been examined over a wide range of loading rates from 0.5 mm/min up to 2000 mm/s at room temperature. Quasi-static fracture tests were performed using a DCB (double-cantilever beam) method with a screw-driven testing machine, while the dynamic tests were carried out using a WIF (wedge-insert fracture) specimen loaded dynamically in a hydraulic system. For performing the tests at high displacement rates, a special setup was designed and manufactured which allowed the insertion of the wedge within the DCB specimens at different cross-head displacement rates. The experimental technique used a pair of strain gauges attached to the bending surface of one of the arms of the cantilever beams and far from the initial crack tip. The peak values of the recorded strain were used to determine the fracture toughness under dynamic conditions through use of the compliance calibration method. A finite element model was developed to check the consistency of the measurements and validate the data reduction method used. The results exhibited rate insensitive behaviour in the case of the IM7/8552 laminates while IM7/M91 showed the contrary behaviour with maximum peak at 500 mm/s of displacement rate, with a toughness increase of 95% with respect to the quasi-static conditions.
  • Publication
    Effect of APPT treatment on mechanical properties and durability of green composites with woven flax
    (MDPI, 2020-11) Enciso Ramos, María Belén; Abenojar Buendía, Juana; Martínez Casanova, Miguel Ángel
    Through this study, two different natural fibres green composites were characterised from the point of view of mechanical properties and durability. These green polymers allow manufacturing with a respectful life cycle due to their biodegradable or recyclable character. Composite materials were prepared in a hot plates press with two biopolymeric matrices, green low density polyethylene (GPE) and polybutylene succinate (PBS). As reinforcement, Atmospheric Pressure Plasma Torch (APPT) treated and untreated unidirectional woven flax were used. Mechanical properties were evaluated by tensile tests and the adhesion between matrices and reinforcement by peeling tests. The durability of each composite was analysed by water absorption measurements, Fourier Transform Infrared Spectroscopy (FTIR) analysis and tensile tests, during several aging times, up to 60 days, under high temperature and humidity conditions. The influence of the Atmospheric Pressure Plasma Torch treatment (APPT) was evaluated in all studies. It was found that GPE composites present better durability against aging conditions than PBS materials, due to the tendency of polyester to hydrolyse compared to the good resistance to humidity of polyolefins. The adhesion between matrices and reinforcement improves with APPT treatment. This improvement is more evident by avoiding the absorption of water than in the mechanical properties results, where only a slightly improvement is shown.
  • Publication
    Recent progress in hybrid biocomposites: Mechanical properties, water absorption, and flame retardancy
    (MDPI, 2020-11-02) Bahrami, Mohsen; Abenojar Buendía, Juana; Martínez Casanova, Miguel Ángel
    Bio-based composites are reinforced polymeric materials in which one of the matrix and reinforcement components or both are from bio-based origins. The biocomposite industry has recently drawn great attention for diverse applications, from household articles to automobiles.This is owing to their low cost, biodegradability, being lightweight, availability, and environmental concerns over synthetic and nonrenewable materials derived from limited resources like fossil fuel. The focus has slowly shifted from traditional biocomposite systems, including thermoplastic polymers reinforced with natural fibers, to more advanced systems called hybrid biocomposites. Hybridization of bio-based fibers/matrices and synthetic ones offers a new strategy to overcome the shortcomings of purely natural fibers or matrices. By incorporating two or more reinforcement types into a single composite, it is possible to not only maintain the advantages of both types but also alleviate somedisadvantages of one type of reinforcement by another one. This approach leads to improvement of the mechanical and physical properties of biocomposites for extensive applications. The present review article intends to provide a general overview of selecting the materials to manufacture hybrid biocomposite systems with improved strength properties, water, and burning resistance in recent years.
  • Publication
    Reuse of Carbon Fibers and a Mechanically Recycled CFRP as Rod-like Fillers for New Composites: Optimization and Process Development
    (MDPI, 2023-02-01) Butenegro García, José Antonio; Bahrami, Mohsen; Martínez Casanova, Miguel Ángel; Abenojar Buendía, Juana
    The rising amount of carbon fiber reinforced polymer (CFRP) composite waste requires new processes for reintroducing waste into the production cycle. In the present research, the objective is the design and study of a reuse process for carbon fibers and CFRP by mechanical recycling consisting of length and width reduction, obtaining rods and reintegrating them as fillers into a polymeric matrix. Preliminary studies are carried out with continuous and discontinuous unidirectional fibers of various lengths. The processing conditions are then optimized, including the length of the reinforcement, the need for a plasma surface treatment and/or for resin post-curing. The resin is thermally characterized by differential scanning calorimetry (DSC), while the composites are mechanically characterized by tensile strength tests, completed by a factorial design. In addition, the composites tested are observed by scanning electron microscopy (SEM) to study the fracture mechanics. Optimal processing conditions have been found to reduce the reinforcement length to 40 mm while maintaining the mechanical properties of continuous reinforcement. Furthermore, the post-curing of the epoxy resin used as matrix is required, but a low-pressure plasma treatment (LPPT) is not recommended on the reinforcement.
  • Publication
    Mechanical performance after high-temperature exposure and Life Cycle Assessment (LCA) according to unit of stored energy of alternative mortars to Portland cement
    (Elsevier, 2023-02-15) Ramón Álvarez, Irene; Batuecas Fernández, Esperanza; Sánchez Delgado, Sergio; Torres Carrasco, Manuel; Comunidad de Madrid; Ministerio de Ciencia, Innovación y Universidades (España)
    Decoupling energy demand has led to the importance of energy storage for increasing the capacity of renewable energy power plants. In this field, Portland cement (PC) concrete is proving to be a promising way to store energy as it can be used as sensible thermal energy storage (TES) medium in concentrated solar power (CSP) technology. However, the high energy and water consumption involved in the PC manufacturing process makes it necessary to develop new alternatives. Thus, alkali-activated materials (AAM) and hybrid materials (HM) were manufactured using blast furnace slag and glass waste (GW) to replace the PC and the sand in concretes respectively in order to study their feasibility as TES media in parabolic through CSP systems. The viability of these proposed new systems was tested from a mechanical point of view, while taking into account the environmental aspect using Life Cycle Assessment (LCA) methodology to study carbon and water footprints. The new systems were exposed to high temperature (up to 500 °C), showing better performance than the ordinary PC under high temperatures, and their mechanical properties were not affected at all. After thermal treatment the alternatives show improvements of up to 79% compared to the PC reference sample. Furthermore, in terms of LCA analysis, it was concluded that TES systems with partial (HM) or total (AAM) substitution of PC by using by-products improve water use up to 40% when an AAM material includes GW as a recycled aggregate in its composition. Results likewise revealed a more than 100% reduction in the carbon footprint. These results open a new gate for the study of materials as TES since the alternatives to PC are more promising from an operational and environmental point of view.
  • Publication
    Effect of BaCO3 reactivity and mixing procedure on sulfate-resistant cement performance
    (Elsevier, 2021-07) Carmona Quiroga, P. M.; Mota Heredia, C.; Torres Carrasco, Manuel; Fernández, J. F.; Blanco Varela, M. T.; Ministerio de Economía y Competitividad (España); Ministerio de Ciencia e Innovación (España)
    The present study focuses on exploring the effects of reactivity and degree of dispersion of BaCO3 additions in the manufacture of sulfate-resistant OPC cements. A new electrochemical deposition method is attempted to effectively disperse BaCO3 particles (studying two different materials with particle size: D50 = 11.45 and 2.37 mum) on cement to enhance their reactivity and favour sulfate immobilisation in the form of BaSO4. The barium carbonate additions, particularly the finest, activate cement hydration to a greater extent. Electrodeposition is also observed to improve early age reactivity (2 d-7 d) in fine BaCO3. Cement paste bearing 15 wt % BaCO3 is more resistant to sulfate attack by a 5% (w/v) solution of Na2SO4 (180 d at 23 ºC) than a commercial sulfate-resistant cement, although secondary ettringite and gypsum precipitated in all cases.
  • Publication
    Magnetic cork particles as reinforcement in an epoxy resin: effect of size and amount on thermal properties
    (Springer, 2023-03) Abenojar Buendía, Juana; López de Armentia, Sara; Barbosa, A. Q.; Martínez Casanova, Miguel Ángel; Del Real, J. C.; Da Silva, L. F. M.; Velasco López, Francisco Javier
    Natural brightness of epoxy adhesives can be reduced by adding cork. Besides, when cork was magnetized, it was possible to move them depending on the properties required in each section of the adhesive bond (PAT354/2019). The main objective of this work was to study possible changes in the thermal properties of the adhesive due to the addition of magnetic cork particles. If changes were significant, the use of magnetic cork particles would be compromised. To this end, natural cork particles and magnetic cork particles, with two different particle size (53–38 and 250–125 μm) and percentage (1 and 5 v/v%), were compared as reinforcement material. Magnetic cork was obtained by co-precipitated coating, according to patent number WO2019025651. The thermal properties studied by Differential Scanning Calorimetry were activation energy of curing reaction, glass transition temperature (Tg) and thermal conductivity. Two different hardeners were studied and a factorial design (2k with k = 4) was carried out. It allowed to determine which variable or combination of variables had most impact on thermal properties. Results showed that the main parameter affecting thermal properties was the hardener, regardless of the kind of particle used. However, the presence of magnetic cork highlights further the differences found between hardeners. The conclusion of this study was that magnetic cork particles can be used as fillers in epoxy resin to make graded joints, since they do not affect the thermal properties of the resin.
  • Publication
    Polymerization kinetics of acrylic photopolymer loaded with graphene-based nanomaterials for additive manufacturing
    (MDPI, 2022-12-02) Lopez de Armentia, Sara; Abenojar Buendía, Juana; Ballesteros, Yolanda; Del Real, Juan Carlos; Dunne, Nicholas; Paz, Eva
    Graphene-based nanomaterials (GBN) can provide attractive properties to photocurable resins used in 3D printing technologies such as improved mechanical properties, electrical and thermal conductivity, and biological capabilities. However, the presence of GBN can affect the printing process (e.g., polymerization, dimensional stability, or accuracy), as well as compromising the quality of structures. In this study an acrylic photocurable resin was reinforced with GBN, using methyl methacrylate (MMA) to favor homogenous dispersion of the nanomaterials. The objective was to investigate the influence that the incorporation of GBN and MMA has on polymerization kinetics by Differential Scanning Calorimetry using Model Free Kinetics, ultra-violet (UV) and thermal triggered polymerization. It was found that MMA catalyzed polymerization reaction by increasing the chain's mobility. In the case of GBNs, graphene demonstrated to inhibit both, thermally and UV triggered polymerization, whilst graphene oxide showed a double effect: it chemically inhibited the polymerization reaction during the initialization stage, but during the propagation stage it promoted the reaction. This study demonstrated that MMA can be used to achieve photocurable nanocomposites with homogenously dispersed GBN, and that the presence of GBN significantly modified the polymerization mechanism while an adaptation of the printing parameters is necessary in order to allow the printability of these nanocomposites.
  • Publication
    V2O5 encapsulated MWCNTs in 2D surface architecture: Complete solid-state bendable highly stabilized energy efficient supercapacitor device
    (Nature Research, 2017-03-03) Pandit, Bidhan; Dubal, Deepak P.; Gomez-Romero, Pedro; Kale, Bharat B.; Sankapal, Babasaheb R.; Ministerio de Economía y Competitividad (España)
    A simple and scalable approach has been reported for V2O5 encapsulation over interconnected multi-walled carbon nanotubes (MWCNTs) network using chemical bath deposition method. Chemically synthesized V2O5/MWCNTs electrode exhibited excellent charge-discharge capability with extraordinary cycling retention of 93% over 4000 cycles in liquid-electrolyte. Electrochemical investigations have been performed to evaluate the origin of capacitive behavior from dual contribution of surface-controlled and diffusion-controlled charge components. Furthermore, a complete flexible solid-state, flexible symmetric supercapacitor (FSS-SSC) device was assembled with V2O5/MWCNTs electrodes which yield remarkable values of specific power and energy densities along with enhanced cyclic stability over liquid configuration. As a practical demonstration, the constructed device was used to lit the VNIT acronym assembled using 21 LEDs.