Examinando por Autor "Casado, Eva"

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    Synthesis and characterization of Ce/SiOC nanocomposites through the polymer derived ceramic method and evaluation of their catalytic activity
    (2019-09-13) García, Beatriz; Casado, Eva; Tamayo, Aitana
    Cerium oxide and silicon oxycarbide (Ce/SiOC) porous nanocomposites have been synthesized through the polymer derived ceramic route. In the synthesis of the preceramic precursors, the addition of urea facilitates the deposition of Cerium atoms on the surface of SiO2 nanoparticles since it prevents the SiO2 from agglomeration. Both Ce and urea affects the structural and textural parameters of the obtained ceramics. Less crosslinked structures are formed when the urea concentration increases and it also provokes a reduction of the carbon crystallite size. Cerium, on the other hand, induces an increase of the carbon size as well as the number of SiOC units. Pore anisotropy and smoothness of the surface are also dependent on the composition of the material. As expected, the better thermocatalytic behavior against CO2 decomposition is found at the largest Ce amounts but also, smooth surfaces and low pore anisotropies favor the accessibility of the gases to the thermocatalytic centers.
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    Synthesis and characterization of Sr1-xLaxMnO3/SiOC nanocomposites decorated with 1D nanostructures for high temperature CO2 splitting
    (2018-10-15) Casado, Eva; García, Beatriz; Tamayo, Aitana
    1D nanostructures of Lanthanum Strontium Manganite (LSM) are tested as thermochemical catalyst for CO2 splitting. The manganite precursors were incorporated into a ceramic silicon oxycarbide (SiOC) matrix at two different stages during its synthesis to form the nanocomposites. As a result, the LSM nanostructures decorate the large-size pores of the SiOC matrix in form of 1D nanofibers and nanowires. At the same time, the formation of the SiOC units decreases because of the incorporation of these LSM. Moreover, the synthetic strategy strongly affects the surface parameter related to apolar interactions. It turns out that the surface fractal constant of the nanocomposite determines the reactivity of the LSM materials towards CO2. This reactivity has been verified by collecting the spectra of the gases involved in the thermochemical reactions and determining the relative CO2 concentration as a function of the temperature.