Now showing 1 - 4 of 4
  • Publication
    Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature
    ( 2022) ; ; ;
    Le Guyon, Valerie
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    El-Rifai, Joumana
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    Angastiniotis, Nicos
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    Koutsokeras, Loukas
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    Duponchel, Benoît
    Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide (ZnO) , titanium dioxide (TiO2), aluminum oxide (Al2O3), and silicon dioxide (SiO2) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides.
      30  6
  • Publication
    High temperature spark plasma sintering, a fast and one step route to achieve dense and efficient SrTiO 3 -based thermoelectric ceramics
    ( 2022) ;
    Moitrier, Florence
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    Bourré, Thierry
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    Delorme, Fabian
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    Zaghrioui, Mustapha
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    Giovannelli, Fabien
    Sr0.95La0.05)0.95 0.05TiO3 ceramics were prepared by solid state reaction and sintered by spark plasma sintering at different temperatures ranging from 1473 to 1873 K for 10 min. The thermoelectric properties show that sintering at temperatures higher than 1773 K allows reaching high thermoelectric properties similar to the ones obtained after annealing at high temperatures in H2/N2 for several hours. The high temperature sintered samples exhibit highest power factor near room temperature, resulting in ZT values higher than 0.1. Therefore, the 10 min short SPS process at high temperatures described in this paper is an easy, cheap, fast, and one step route to obtain dense and efficient SrTiO3-based thermoelectric ceramics. However, SEM observations show that the samples are not pure perovskite phase but contain titanium oxide and lanthanum compound aggregates.
      39  9
  • Publication
    Investigation of the electrocaloric effect in BaTiO3 multilayers by pASC calorimetry
    ( 2021) ;
    Sahraoui, Abdelhak Hadj
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    Glorieux, Christ
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    Leys, Jan
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    Thoen, Jan
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    Longuemart, Stéphane
    The electrocaloric heat production in BaTiO3-based multilayer ceramic capacitors with Y5V specification was measured in a direct way by means of an adiabatic calorimeter setup. Applying an electric field of 30 MVm−1 is found to result in a heat release of 0.94 Jg−1 and an electrocaloric temperature change of 0.46 K, in good agreement with direct results in previous studies.
      31  2
  • Publication
    Ultra-low thermal conductivity in scheelite and A-deficient scheelite ceramics
    ( 2021) ;
    Fabian Delorme
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    Isabelle Monot-Laffez
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    Fabien Giovannelli
    Synthesis of scheelite-type oxides based on lanthanum and barium molybdate (BaMoO and LaMoO ceramics) were successfully prepared via conventional solid-state reaction method. Dense ceramics were obtained by conventional sintering. Structural, microstructural and thermal properties of both sintered ceramics were assessed to identify the impact of cation deficiency on thermal conductivity. BaMoO ceramic has shown a decrease in thermal conductivity from 0.8 W m K to 0.65 W m K from 400 K to 650 K. The deficient scheelite LaMoO compound was found to further reduce thermal conductivity. An ultra-low thermal conductivity constant value of about 0.59-0.62 W m K was calculated over the entire temperature range. This value is the lowest recorded value for oxides so far discovered and such materials may be promising ones for thermal insulating applications.
      17  2Scopus© Citations 4