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Miguel E.K.,FAE
Electronic Products | Year: 2013

ICs with on-board oscillators requiring low-frequency fundamental crystals are commonplace, but now IC frequency multipliers require the higher frequencies of third overtone crystals. Compared to its fundamental implementation however, the third-overtone (3OT) crystal oscillator is more complex, with different crystal characteristics plus additional reactive elements and higher gain. Most crystals use the fundamental thickness-shear vibration mode of AT-cut quartz. The practical upper limit of fundamental operation is around 50 MHz because the fundamental resonant frequency is inversely proportional to thickness. The 3OT is a crystal mode that resonates at three times its fundamental frequency. There are in fact an infinite number of odd harmonics that exist on the same quartz plate. Source

Pulgarin-Agudelo F.A.,National Autonomous University of Mexico | Lopez-Marino S.,Catalonia Institute for Energy Research IREC | Fairbrother A.,Catalonia Institute for Energy Research IREC | Placidi M.,Catalonia Institute for Energy Research IREC | And 7 more authors.
Journal of Renewable and Sustainable Energy | Year: 2013

In this work we present an alternative thermal route for the synthesis of CuInSe2 light absorber films for photovoltaic applications from printed CuO/In2O3 nanoparticle-based inks. We demonstrate the possibility of substituting highly toxic (H2Se) and explosive (H2) gases for the processing of this type of precursors, using more environmental friendly gases (elemental Se and Ar/H2 mixtures). We show that by using Ar/H2 mixtures with low H2 concentration, it is possible to reduce the oxide nanoparticles to their metallic form, thus priming the film for subsequent selenization. This reactive thermal process seems to be the critical step to obtain large CuInSe2 grains with photovoltaic activity. Optimizing the proposed thermal route, based on less toxic, safer, and more eco-friendly gases, we obtain a very promising 2.4% efficiency solar cell based on CuInSe2 films as the absorber layer. © 2013 AIP Publishing LLC. Source

Pulgarin-Agudelo F.A.,National Autonomous University of Mexico | Placidi M.,Catalonia Institute for Energy Research IREC | Fairbrother A.,Catalonia Institute for Energy Research IREC | Fontane X.,Catalonia Institute for Energy Research IREC | And 7 more authors.
International Journal of Nanotechnology | Year: 2013

CuInSe2 (CISe) nanopowders were synthesised using the innovative microwave assisted solvothermal method. We studied the impact of the synthesis temperature as well as the precursor composition on the morphological, compositional, and structural properties of the nanopowders. We have found that for the synthesis of stoichiometric CISe particulates with chalcopyrite phase structure, temperatures equal to 230°C and In concentration in excess in the reaction solution with respect to Cu are required. At lower temperatures (200°C) and In excess, the presence of binary phases such as CuxSe and In2Se3 is clearly detected indicating a inadequate In incorporation. At intermediate temperatures (215°C), CISe is mainly formed but preferentially with the Cu-Au polytype structure. The method presented here may be very interesting for the possible mass production of CISe nanopowders due to the facile temperature control, the fast reaction process, and the easy scalability. Copyright © 2013 Inderscience Enterprises Ltd. Source

Ramos F.M.,FAE | Blanes M.,FAE | Amell A.,FAE | Rodriguez R.,FAE | Diaz L.A.,University of Oviedo
5th World Tribology Congress, WTC 2013 | Year: 2014

Ceramic-graphitic C/C-SiC composite materials have been synthesized by a novel two step method: Tape Casting and Spark Plasma Sintering. Several processing conditions and raw materials have been tested. The composites have been synthesized with different raw materials such as micro and nano-SiC powders, carbon nanofibers and short carbon fibers. The addition of sintering additives to the SiC matrix has been also studied. Several materials have been sintered with carbon/silicon carbide ratio for this purpose. Mechanical and tribological study was carried out to monitor the performance of these novel C/C-SiC nanocomposites. © Shell International Petroleum Company 2013. Source

Nazarpour S.,INRS - Institute National de la Recherche Scientifique | Lopez-Gandara C.,University of Barcelona | Ramos F.M.,FAE | Zamani C.,University of Barcelona | And 2 more authors.
Ceramics International | Year: 2012

Short and long term thermal stability of YSZ was studied considering the equilibrium and non-equilibrium phase transformation of YSZ. To improve the long term thermal stability of YSZ, electrical treatment was introduced. Electrical treatment consists of applying electric field into YSZ at high temperatures under a reducing atmosphere. By optimizing the conditions of treatment, electrical resistivity reduced around 40% and thermal stability improved dramatically. These improvements are due to the generation of tetragonal metastable phases. Arguments are put forth to show that electrical treatment induces a relaxation in the lattice. This relaxation is associated with a reduction in lattice tetragonality and replaces the tetragonal grains of YSZ with domain of metastable phases. High resistance of metastable phase to creep deformation and lower electrical resistivity of domains of metastable phases in comparison with tetragonal grains brings about these improvements. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source

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