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2021


Reactividad de Sólidos

Calcination under low CO2 pressure enhances the calcium Looping performance of limestone for thermochemical energy storage

Sarrion, B; Perejon, A; Sanchez-Jimenez, PE; Amghar, N; Chacartegui, R; Valverde, JM; Perez-Maqueda, LA
Chemical Engineering Journal, 417 (2021) 127922

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The Calcium Looping performance of limestone for thermochemical energy storage has been investigated under novel favorable conditions, which involve calcination at moderate temperatures under CO2 at low pressure (0.01 and 0.1 bar) and carbonation at high temperature under CO2 at atmospheric pressure. Calcining at low CO2 pressures allows to substantially reduce the temperature to achieve full calcination in short residence times. Moreover, it notably enhances CaO multicycle conversion. The highest values of conversion are obtained for limestone samples calcined under 0.01 bar CO2 at 765 degrees C. Under these conditions, the residual conversion is increased by a factor of 10 as compared to conditions involving calcination under CO2 at atmospheric pressure. The enhancement of CaO conversion is correlated to the microstructure of the CaO samples obtained after calcination. As seen from SEM, BET surface and XRD analysis, calcination under low CO2 pressure leads to a remarkable decrease of pore volume and CaO crystallite size. Consequently, CaO surface area available for carbonation in the fast reaction-controlled regime and therefore reactivity in short residence times is promoted.


Agosto, 2021 | DOI: 10.1016/j.cej.2020.127922

Reactividad de Sólidos

Mechanochemical synthesis of ternary chalcogenide chalcostibite CuSbS2 and its characterization

Dutkova, E; Sayagues, MJ; Fabian, M; Kovac, J; Kovat, J; Balaz, M; Stahorsky, M
Journal of Materials Science-Materials in Electronics (2021)

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In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from copper, antimony, and sulfur precursors by high-energy milling for only 30 min in a planetary mill is reported. XRD confirmed the orthorhombic crystal structure of CuSbS2. The crystallite size of CuSbS2 calculated by LeBail refinement of the X-ray powder diffraction data was 25 nm. The nanocrystalline chalcostibite CuSbS2 was also confirmed by transmission electron microscopy. The purity of CuSbS2 was verified by Raman spectroscopy. The synthesized chalcostibite exhibits the specific surface area value of 2.4 m(2)g(-1). UV-Vis spectroscopy showed the optical bandgap of CuSbS2 as 1.54 eV with wide range of absorption in visible region. Photoresponse of CuSbS2 was confirmed by I-V measurements under dark and light illumination. The proposed mechanochemical synthesis provides an alternative approach to prepare also other ternary semiconductor nanomaterials. CuSbS2 semiconductor nanocrystals have the potential to be used as light absorbers in photovoltaics.


Agosto, 2021 | DOI: 10.1007/s10854-021-06767-9

Nanotecnología en Superficies y Plasma - Materiales Ópticos Multifuncionales

One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR

Castillo-Seoane, J; Gil-Rostra, J; Lopez-Flores, V; Lozano, G; Ferrer, FJ; Espinos, JP; Ostrikov, K; Yubero, F; Gonzalez-Elipe, AR; Barranco, A; Sanchez-Valencia, JR; Borras, A
Nanoscale, 13 (2021) 13882-13895

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The eventual exploitation of one-dimensional nanomaterials needs the development of scalable, high yield, homogeneous and environmentally friendly methods capable of meeting the requirements for fabrication of functional nanomaterials with properties on demand. In this article, we demonstrate a vacuum and plasma one-reactor approach for the synthesis of fundamental common elements in solar energy and optoelectronics, i.e. the transparent conducting electrode but in the form of nanotube and nanotree architectures. Although the process is generic and can be used for a variety of TCOs and wide-bandgap semiconductors, we focus herein on indium doped tin oxide (ITO) as the most previously researched in previous applications. This protocol combines widely applied deposition techniques such as thermal evaporation for the formation of organic nanowires serving as 1D and 3D soft templates, deposition of polycrystalline layers by magnetron sputtering, and removal of the templates by simply annealing under mild vacuum conditions. The process variables are tuned to control the stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees. Four-probe characterization reveals the improved lateral connectivity of the ITO nanotrees and applied on individual nanotubes shows resistivities as low as 3.5 +/- 0.9 x 10(-4) omega cm, a value comparable to that of single-crystalline counterparts. The assessment of diffuse reflectance and transmittance in the UV-Vis range confirms the viability of the supported ITO nanotubes as random optical media working as strong scattering layers. Their further ability to form ITO nanotrees opens a path for practical applications as ultra-broadband absorbers in the NIR. The demonstrated low resistivity and optical properties of these ITO nanostructures open a way for their use in LEDs, IR shields, energy harvesting, nanosensors, and photoelectrochemical applications.


Agosto, 2021 | DOI: 10.1039/d1nr01937f

Reactividad de Sólidos

Tuning the excitation wavelength of luminescent Mn2+-doped ZnSxSe1-x obtained by mechanically induced self-sustaining reaction

Aviles, MA; Gotor, FJ
Optical Materials, 117 (2021) 111121

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Mn2+-doped ZnSxSe1-x solid solution samples (Mn:ZnSxSe1-x) were synthesized by the mechanochemical process denoted as mechanically-induced self-sustaining reaction from Mn/Zn/S/Se powder elemental mixtures. The samples were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance UV-Vis spectroscopy and emission and excitation photoluminescence measurements. The band-gap energy of samples was controlled by changing the stoichiometry, x, of the solid solution. All samples showed the characteristic Mn2+ 4T1-6A1 emission at -588 nm when exciting the host material, so it was possible to tune the excitation wavelength from 349 nm to 467 nm. However, an efficiency loss was observed with increasing Se content, probably due to the overlap between the absorption and emission spectra that induced self-absorption and emission quenching.


Julio, 2021 | DOI: 10.1016/j.optmat.2021.111121

Archeometric characterization (physical-chemical and microstructural) of tiles in the Mudejar Palace of the Royal Alcazar of Seville using non-invasive quantitative chemical methods

Perez-Rodriguez, JL; Robador, MD; Castaing, J; de Viguerie, L; Garrote, MA; Pleguezuelo, A
Boletin de la Sociedad Española de Ceramica y Vidrio, 60 (2021) 211-228

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The Palaces in the Alcazar of Seville, Spain, are famous for their ceramic decoration. The technique of tessellation was used extensively in all rooms in the Mudejar Palace, dated in the fourteenth century. These glazed ceramics have been analysed in situ using noninvasive quantitative chemical methods of X-ray fluorescence and diffraction (XRF and XRD). Micro-samples were taken to prepare cross-sections and analysed by optical and electronic microscopy. The composition of these ceramics, their manufacturing technique and the time of application in the different areas of the Palace have been characterized in this work. Five colours have been found in the glazed ceramics: green, black, molasses, white and blue. Fe, Co, Cu, Mn and Sn are the main chemical elements responsible for the colour of the glass phase of these ceramics. Wollastonite, quartz, bustamite and feldspars inclusions have been found in the glass phase. Casiterite and Malayaite have been also characterized by XRD. The ceramic paste used for manufacturing was calcic and was heated at about 900 degrees C. Thenardite, gypsum, sodium chloride and nitrogen compounds have been characterized in the ceramic and are responsible for their alteration. The information obtained in the 24 zones studied shows that there is no homogeneity in the ceramics due to the different times in which the tiles were placed and the restorations carried out over time. There are 3 main groups of ceramics: a) probably from 14th century, b), probably from 15-16th centuries and c) from 19-20th centuries and recent restorations. 


Julio, 2021 | DOI: 10.1016/j.bsecv.2020.03.001

 

 

 

 

 

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