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Placidi M.,IMB CNM | Perez-Tomas A.,IMB CNM | Zielinski M.,NOVASiC | Godignon P.,IMB CNM | And 4 more authors.
Journal of Micromechanics and Microengineering | Year: 2010

Here, we report on a comparison between two different insulated substrates, semi-insulated silicon (SIS) and silicon-on-insulator (SOI), used for the growth of 3C-SiC for electrostatic-based mechanical resonators able to operate at high temperatures. The epitaxial growth of monocrystalline 3C-SiC films in these starting materials is first described and the main encountered problems are discussed. Structural and morphological characterization of the SiC layers is then performed using an optical microscope, a scanning electron microscope, an atomic force microscope and x-ray diffraction. Raman spectroscopy is also used to study the residual stress. Then, innovative lateral electrostatic SiC resonators using these materials are fabricated and electrically tested. Globally, devices using a SOI substrate allowed electrical sensing without any associated circuitry. Temperature measurements of the electrical resonance up to 200 °C are also performed and demonstrate that SiC on SOI is a promising material for a new generation of a harsh-environment-resistant micro-electro-mechanical system. © 2010 IOP Publishing Ltd.

Dubal D.P.,Catalan Institute of Nanoscience and Nanotechnology | Suarez-Guevara J.,Catalan Institute of Nanoscience and Nanotechnology | Tonti D.,ICMAB | Enciso E.,Complutense University of Madrid | Gomez-Romero P.,Catalan Institute of Nanoscience and Nanotechnology
Journal of Materials Chemistry A | Year: 2015

In pursuit of high capacitance and high energy density storage devices, hybrid materials have quickly garnered well-deserved attention based on their power to merge complementary components and properties. Here, we report the fabrication of all-solid state symmetric supercapacitors (ASSSC) based on a double hybrid approach combining a hybrid electrode (reduced graphene oxide-phoshomolybdate, rGO-PMo12) and a hybrid electrolyte (hydroquinone doped gel-electrolyte). To begin with, a high-performance hybrid electrode based on H3PMo12O40 nanodots anchored onto rGO was prepared (rGO-PMo12). Later, an all-solid state symmetric cell based on these rGO-PMo12 electrodes, and making use of a polymer gel-electrolyte was assembled. This symmetric cell showed a significant improvement in cell performance. Indeed, it allowed for an extended potential window by 0.3 V that led to an energy density of 1.07 mW h cm-3. Finally, we combined these hybrid electrodes with a hybrid electrolyte incorporating an electroactive species. This is the first proof-of-design where a redox-active solid-state gel-electrolyte is applied to rGO-PMo12 hybrid supercapacitors to accomplish a significant enhancement in the capacitance. Strikingly, a further excellent increase in the device performance (energy density of 1.7 mW h cm-3) was realized with the hybrid electrode-hybrid electrolyte combination cell as compared to that of the conventional electrolyte cell. Thus, this unique symmetric device outclasses the high-voltage asymmetric counterparts under the same power and represents a noteworthy advance towards high energy density supercapacitors. © The Royal Society of Chemistry 2015.

Placidi M.,IMB CNM | Perez-Tomas A.,IMB CNM | Godignon P.,IMB CNM | Mestres N.,ICMAB | And 3 more authors.
Materials Science Forum | Year: 2010

In this study, a SiC on insulator growth is optimized, in order to electrically isolate the active structural layer towards the substrate. High quality single crystalline SiC was grown on SOI and SIS substrates. Smooth surface, low stress and bowing, confirmed by microscopy techniques, SEM, AFM, X-Ray diffraction and Raman spectroscopy, have been obtained. SiC electrostatic resonators on insulated substrates were also fabricated, and electrically driven. These results demonstrate that this material is very promising for MEMS application requiring isolation from the substrate and operation in harsh ambient. © (2010) Trans Tech Publications, Switzerland.

Lopez J.,Polytechnic University of Catalonia | Maynou R.,Polytechnic University of Catalonia | Granados X.,ICMAB | Grau J.,Polytechnic University of Catalonia | And 2 more authors.
Physics Procedia | Year: 2012

Multiple studies have reported information about the magnetization by pulses applied in YBCO superconducting pellets. "Electrical machines" is one of the areas where it is possible to take advantage of using superconducting magnetized pellets by the high magnetic trapped field. However, it is well known the strong dependence of the maximum value of remanence with temperature. The relaxation experienced by the HTS, once the pulse magnetization has finished, and the heat generated in the superconductor by the effect of the "supercritical" currents generated during the flux penetration, make the maximum trapped field lower than expected considering a critical state model. In this work we present simulations performed, with a commercial finite element program, about the resulting magnetization in the HTS superconducting pellets, taking into account the influence of temperature. ©2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.

Laukhin V.,Catalan Institution for Research and Advanced Studies | Laukhin V.,CIBER ISCIII | Lebedev V.,ICMAB | Laukhina E.,CIBER ISCIII | And 8 more authors.
2013 Transducers and Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013 | Year: 2013

The purpose of this paper is the development of devices for monitoring the intraocular pressure (IOP) variations in a non-invasive way. The importance of the problem is caused by the need of a glaucoma diagnostic by control of the IOP in patients. It has been shown [1] that monitoring of the IOP variations over 24 h may change the glaucoma management of patients. Here we present a new prototype of an IOP sensing device based on a commercial hybrid contact lens (HCL) that provides a greater comfort for patients. Although the HCL was equipped with the same sensing BL film as in [2], in the sensing lens fabrication, a new design approach has been used. This approach allowed the use of different parts of the same BL film gauge as the pressure sensor and temperature effect compensator. © 2013 IEEE.

Lazic Z.,HTS 110 | Chamritski V.,HTS 110 | Pooke D.,HTS 110 | Valvidares S.M.,ALBA Synchrotron Light Facility | And 4 more authors.
Journal of Physics: Conference Series | Year: 2013

Integrating UHV (ultra high vacuum) and superconducting magnets poses special challenges to the magnet designer. A range of HTS (High Temperature Superconducting) magnets have been developed for UHV synchrotron beamline applications providing users with compact powerful cryogen-free solutions. Recent examples include HTS magnets for LARIAT (Large Area Rapid Imaging Analytical Tool) [8.5 T with 110 mm warm bore], X-ray scattering experiments at BESSY and LNLS [5-6 T with 110 degrees scattering angle aperture], X-ray magnetic circular dichroism, and resonant scattering experiments at ALBA. This paper will focus on the in-UHV HTS magnet installed at ALBA. © Published under licence by IOP Publishing Ltd.

Robert C.,CNRS Foton Laboratory | Cornet C.,CNRS Foton Laboratory | Thanh T.N.,CNRS Foton Laboratory | Nestoklon M.O.,RAS Ioffe Physical - Technical Institute | And 21 more authors.
Conference Proceedings - International Conference on Indium Phosphide and Related Materials | Year: 2014

The nature of the ground optical transition in (In, Ga)As/GaP quantum dots is thoroughly investigated through k·p calculations and a supercell tight-binding simulation. Quantum dot morphology is deduced from scanning-tunneling-microscopy images. The strain field has a strong influence on the conduction band states. Indeed, for a pure GaAs QD, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a tensile strain region, having mainly Xz character. Time resolved and hydrostatic pressure photoluminescence experiments strongly support the theoretical conclusions. Promising results from the literature on (In, Ga)As/GaP quantum dot will be reviewed. © 2014 IEEE.

Camara N.,IMB CNM | Tiberj A.,Montpellier University | Jouault B.,Montpellier University | Caboni A.,IMB CNM | And 4 more authors.
Journal of Physics D: Applied Physics | Year: 2010

The current status of long, self-organized, epitaxial graphene ribbons grown on the (0 0 0-1) face of 6H-SiC substrates is reviewed. First, starting from the early stage of growth it is shown that on the C face of 6H-SiC substrates the sublimation process is not homogeneous. Most of the time it starts from defective sites, dislocations or point defects, that define nearly circular flakes surrounded by bare SiC. These flakes have a volcano-like shape with a graphite chimney at the centre, where the original defect was located. At higher temperatures a complete conversion occurs, which is not yet homogeneous on the whole sample. This growth process can be modified by covering the sample with a graphite cap. It changes the physics of the surface reconstruction during the Si-sublimation process and, on the C face, makes more efficient the reconstruction of few selected terraces with respect to the others. The net result is the formation of strongly step-bunched areas with, in between, long and large reconstructed terraces covered by graphitic material. Despite the low intrinsic optical absorption of a few graphene layers on SiC, micro-transmission experiments, complemented by micro-Raman spectroscopy, demonstrate that most of this graphitic coverage is made of one or two homogeneous graphene layers. We show also that most of the thermal stress between the graphene layer and the 6H-SiC substrate is relaxed by pleats or wrinkles which are clearly visible on the AFM images. Finally, the results of transport experiments performed on the graphitic ribbons reveal the p-type character of the ribbons. © 2010 IOP Publishing Ltd.

Soika R.,Nexans Deutschland GmbH | Garcia X.G.,ICMAB | Nogales S.C.,Endesa
IEEE Transactions on Applied Superconductivity | Year: 2011

Nexans, ICMAB-CSIC, Tecnalia and UAB have collaborated on the ENDESA Supercable, a 30 m long, medium-voltage superconducting ac power cable. The cable was developed and manufactured within the framework of the ENDESA Novare program. With a rated current of 3200 A, a 3-phase system based on this cable is able to transmit 138 MVA at its envisioned operating voltage of 25 kV. While the cable was designed for 25 kV, the terminations available for cable testing were rated for the 20-kV class. Consequently the high voltage tests were carried out at the levels appropriate for 20 kV cable systems. The cable has successfully passed all high voltage and load cycle tests. The load cycles consisted of ten 24-hour cycles during which, with a voltage of 2 · UO applied for the full duration of the 10 test cycles, the rated current of 3200 A was applied for 8 hours. The ac losses of the cable were also measured. The successful prototype testing of the cable confirmed the design, manufacturing, and performance of this high transmission capacity cable: To our knowledge, it is the highest ampacity power cable so far that has passed the rigorous load cycle test protocol of a similarly rated conventional cable. © 2011 IEEE.

Ponrouch A.,ICMAB | Ponrouch A.,Alistore European Research Institute | Palacin M.R.,ICMAB | Palacin M.R.,Alistore European Research Institute
ECS Transactions | Year: 2013

Carbon coating on battery electrode active material powders is currently achieved through chemical procedures involving dispersing the powder in a liquid medium with a carbon precursor followed by thermolysis at high temperatures (ca. 700°C). This procedure has the drawback of not being applicable to materials which may decompose or reduce under such conditions. We present herein an alternative procedure based on physical deposition of carbon, carried out at room temperature under dry conditions, hence avoiding the limitations mentioned above and being generally applicable to any electrode active material. Homogeneous conformal coating was achieved and results are herein presented regarding improved electronic conductivity and limited side reactions recorded upon oxidation and reduction for carbon coated powder active materials in Li cells. © 2014 The Electrochemical Society.

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