Technical University MadridMadrid

Solar, Spain

Technical University MadridMadrid

Solar, Spain
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Yue H.,IMDEA Madrid Institute for Advanced Studies | Reguero V.,IMDEA Madrid Institute for Advanced Studies | Senokos E.,IMDEA Madrid Institute for Advanced Studies | Senokos E.,Technical University MadridMadrid | And 5 more authors.
Carbon | Year: 2017

Macroscopic fibres of carbon nanotubes are hierarchical structures combining long building blocks preferentially oriented along the fibre axis and a large porosity arising from the imperfect packing of bundles. Synchrotron small-angle X-ray scattering (SAXS) measurements show that such structure is a surface fractal with fractal dimension (Ds) of 2.5 for MWCNT fibres and 2.8 for SWCNT fibres. N2 adsorption measurements give similar values of 2.54 and 2.50, respectively. The fractal dimension and deviation from Porod's law are related to density fluctuations associated with the wide distribution of separations between CNTs. These fluctuations are also evident as diffuse wide-angle X-ray scattering (WAXS) from CNTs at distances above turbostratic separation. The structure of CNT fibres produced at different draw ratios is compared in terms of degree of orientation and characteristic lengths parallel and perpendicular to the fibre. Drawing not only increases alignment but also the fraction of graphitic planes forming coherent domains capable of taking part in stress transfer by shear; thus increasing both tensile modulus and strength. The invariant-normalized intensity of the (002) equatorial reflection thus takes the form of a degree of crystallinity closely related to tensile properties. © 2017 Elsevier Ltd

Cenis J.L.,Instituto Murciano Of Investigacion Y Desarrollo Agrario Y Alimentario | Madurga R.,Technical University of Madrid | Madurga R.,Technical University MadridMadrid | Aznar-Cervantes S.D.,Instituto Murciano Of Investigacion Y Desarrollo Agrario Y Alimentario | And 13 more authors.
Soft Matter | Year: 2015

High performance silk fibers were produced directly from the silk glands of silkworms (Bombyx mori) following an alternative route to natural spinning. This route is based on a traditional procedure that consists of soaking the silk glands in a vinegar solution and stretching them by hand leading to the so called silkworm guts. Here we present, to the authors' best knowledge, the first comprehensive study on the formation, properties and microstructure of silkworm gut fibers. Comparison of the tensile properties and microstructural organization of the silkworm guts with those of naturally spun fibers allows gain of a deeper insight into the mechanisms that lead to the formation of the fiber, as well as the relationship between the microstructure and properties of these materials. In this regard, it is proved that an acidic environment and subsequent application of tensile stress in the range of 1000 kPa are sufficient conditions for the formation of a silk fiber. © The Royal Society of Chemistry.

Cruz-Izquierdo A.,University of the Basque Country | Cruz-Izquierdo A.,University of Bath | Pico E.A.,University of the Basque Country | Lopez C.,University of the Basque Country | And 4 more authors.
PLoS ONE | Year: 2014

Enzyme-catalyzed production of biodiesel is the object of extensive research due to the global shortage of fossil fuels and increased environmental concerns. Herein we report the preparation and main characteristics of a novel biocatalyst consisting of Cross-Linked Enzyme Aggregates (CLEAs) of Candida antarctica lipase B (CALB) which are covalently bound to magnetic nanoparticles, and tackle its use for the synthesis of biodiesel from non-edible vegetable and waste frying oils. For this purpose, insolubilized CALB was covalently cross-linked to magnetic nanoparticles of magnetite which the surface was functionalized with -NH2 groups. The resulting biocatalyst combines the relevant catalytic properties of CLEAs (as great stability and feasibility for their reutilization) and the magnetic character, and thus the final product (mCLEAs) are superparamagnetic particles of a robust catalyst which is more stable than the free enzyme, easily recoverable from the reaction medium and reusable for new catalytic cycles. We have studied the main properties of this biocatalyst and we have assessed its utility to catalyze transesterification reactions to obtain biodiesel from non-edible vegetable oils including unrefined soybean, jatropha and cameline, as well as waste frying oil. Using 1% mCLEAs (w/w of oil) conversions near 80% were routinely obtained at 30°C after 24 h of reaction, this value rising to 92% after 72 h. Moreover, the magnetic biocatalyst can be easily recovered from the reaction mixture and reused for at least ten consecutive cycles of 24 h without apparent loss of activity. The obtained results suggest that mCLEAs prepared from CALB can become a powerful biocatalyst for application at industrial scale with better performance than those currently available. © 2014 Cruz-Izquierdo et al.

Ruiz-Gomez S.,University Complutense Of Madridmadrid | Ruiz-Gomez S.,Technical University MadridMadrid | Bosca A.,Technical University MadridMadrid | Bosca A.,Universidad Politécnica de Ingeniería | And 7 more authors.
Diamond and Related Materials | Year: 2015

Abstract The need of new systems for the storage and conversion of renewable energy sources is fueling the research in supercapacitors. In this work, we propose a low temperature route for the synthesis of electrodes for these supercapacitors: electrodeposition of a transition metal hydroxide-Ni(OH)2 on a graphene foam. This electrode combines the superior mechanical and electrical properties of graphene, the large specific surface area of the foam and the large pseudocapacitance of Ni(OH)2. We report a specific capacitance up to 900 F/g as well as specific power and energy comparable to active carbon electrodes. These electrodes are potential candidates for their use in energy applications. © 2015 Elsevier B.V.

Suarez P.,DAEDALUS - Data, Decisions and Language | Gonzalez J.C.,DAEDALUS - Data, Decisions and Language | Gonzalez J.C.,Technical University MadridMadrid | Villena-Roman J.,DAEDALUS - Data, Decisions and Language | Villena-Roman J.,Charles III University of Madrid
CEUR Workshop Proceedings | Year: 2010

In this paper, we describe the algorithm that has been used to carry out our plagiarism detection within the context of PAN10 competition. Our system is based on the LempelZiv distance, which is applied to extract structural information from texts. Then the algorithm tries to find outliers in the vector of distances between each fragment of the text and the whole document itself.

Datas A.,Technical University MadridMadrid
Solar Energy Materials and Solar Cells | Year: 2015

The choice of the optimum semiconductor for manufacturing thermophotovoltaic (TPV) cells is not straightforward. In contrast to conventional solar photovoltaics (PV) where the optimum semiconductor bandgap is determined solely by the spectrum (and eventually the irradiance) of the incident solar light, in a TPV converter it depends on the emitter temperature and on the spectral control elements determining the net spectral power flux between the TPV cell and the emitter. Additionally, in TPV converters there is a tradeoff between power density and conversion efficiency that does not exist in conventional solar PV systems. Thus, the choice of the proper semiconductor compound in TPV converters requires a thorough analysis that has not been presented so far. This paper presents the optimum semiconductor bandgaps leading to the maximum efficiency and power density in TPV converters using both single junction and multijunction TPV cells. These results were obtained within the framework of the detailed balance theory and assuming only radiative recombination. Optimal bandgaps are provided as a function of the emitter and cell temperature, as well as the degree of spectral control. I show that multijunction TPV cells are excellent candidates to maximize both the efficiency and the power density simultaneously, eliminating the historical tradeoff between efficiency and power density of TPV converters. Finally, multijunction TPV cells are less sensitive to photon recycling losses, which suggest that they can be combined with relatively simple cut-off spectral control systems to provide practically-viable high performing TPV devices. © 2014 Elsevier B.V.All rights reserved.

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