INSTITUTO DE CIENCIA DE MATERIALES DE SEVILLA

(Consejo Superior de Investigaciones Científicas – Universidad de Sevilla)

icms-conferences

2019

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Plasma treatments had emerged as a useful technique to improve seed germination. In this work we investigate the influence of different irrigation conditions and plasma treatments on the germination of nasturtium seeds. During plasma treatment, seeds experience a progressive weight loss as a function of treatment time that has been associated to water release, a process that is more pronounced after longer plasma treatment times. Seeds treated for short times (<30 s) are able to germinate more efficiently than untreated specimen under hydric stress (drought conditions), while plasma treatments for longer times (up to 300 s) impaired germination independently on irrigation conditions. Characterization analysis of plasma treated seeds by FTIR-ATR, SEM/EDX and XPS showed that plasma treatment affected the chemical state of pericarp while, simultaneously, induced a considerable increase in the seeds water uptake capacity. The decrease in germination efficiency found after plasma treatment for long times, or for short times under optimum irrigation conditions, has been attributed to that the excess of water accumulated in the pericarp hampers the diffusion up to the embryo of other agents like oxygen which are deemed essential for germination.

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The reaction mechanism of the reverse water–gas shift (RWGS) reaction was investigated using two commercial gold-based catalysts supported on Al2O3 and TiO2. The surface species formed during the reaction and reaction mechanisms were elucidated by transient and steady-state operando DRIFTS studies. It was revealed that RWGS reaction over Au/Al2O3 proceeds through the formation of formate intermediates that are reduced to CO. In the case of the Au/TiO2 catalyst, the reaction goes through a redox mechanism with the suggested formation of hydroxycarbonyl intermediates, which further decompose to CO and water. The Ti3+ species, the surface hydroxyls, and oxygen vacancies jointly participate. The absence of carbonyl species adsorbed on gold particles during the reaction for both catalysts indicates that the reaction pathway involving dissociative adsorption of CO2 on Au particles can be discarded. To complete the study, operandoultraviolet–visible spectroscopy was successfully applied to confirm the presence of Ti3+ and to understand the role of the oxygen vacancies of TiO2 support in activating CO2 and thus the subsequent RWGS reaction.

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The graphene family comprises not only single layer graphene but also graphene-based nanomaterials (GBN), with remarkably different number of layers, lateral dimension and price. In this work, two of these GBN, namely graphene nanoplatelets (GNP) with n∼15–30 layers and few-layer graphene (FLG) with n < 3 layers have been evaluated as fillers in 3 mol% yttria stabilized tetragonal zirconia (3YTZP) ceramic composites. Composites with 10 and 20 vol% GNP or FLG have been fabricated by wet powder processing and spark plasma sintering (SPS) and the influence of the content and number of layers of the graphene-based filler has been assessed. For both graphene-based fillers, an intermediate zirconia oxycarbide has been detected in the grain boundaries. The lower stacking degree and much more homogeneous distribution of the FLG, revealed by transmission electron microscopy (TEM), can improve load transfer between the GBNs and the ceramic matrix. However, high FLG contents lower densification of the composites, due partly to the larger FLG interplanar spacing also estimated by TEM. The hardness (both Vickers and nanoindentation) and the elastic modulus decrease with increased GBN content and with improved graphene dispersion. The FLG greatly inhibit the crack propagation that occur perpendicular to their preferential orientation plane. The composites with thinner FLG have higher electrical conductivity than those with GNP. The highest electrical conductivity is achieved by composites with 20 vol% FLG in the direction perpendicular to the compression axis during sintering, σ = 3400 ± 500 Sm-1.

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This paper reports a new methodology for the coloring of glazed ceramic tiles consisting of the near infrared pulsed laser processing of copper containing oxide coatings prepared by magnetron sputtering. As a second approach, the employ for the same purpose of a novel laser furnace technique is also described. Changing the laser parameters and using the laser furnace to treat the tiles at high temperature during irradiation has resulted in a wide color palette. The optical characterization of the modified tiles by UV‐Vis spectroscopy has been complemented with their microstructural and compositional analysis by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Time Of Flight Secondary Ion Mass Spectrometry (TOF‐SIMS). The chemical composition of the surface was obtained by X‐ray Photoemission Spectroscopy (XPS) and its structure determined by X?ray diffraction (XRD). The chemical resistance was characterized by several tests following the norm ISO 10545‐13. Color changes have been attributed to surface microstructural and chemical transformations that have been accounted for by simple models involving different ablation, melting, diffusion, and segregation/agglomeration phenomena depending on the laser treatments employed.

May 21st
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Active and selective structured RuO2/Al2O3 catalysts for CO methanation using a flow simulating CO2-rich reformate gases from WGS and PROX units (H2 excess, CO2 presence and 300 ppm CO concentration) were prepared. Both, the RuO2/Al2O3 powder and the slurry prepared from it for its structuration by washcoating of the metallic micromonolithic structure, were also active and selective. Both the slurry (S-RuAl) and micromonoliths (M-RuAl) were able to completely and selectively methanate CO at much lower temperatures than the parent RuAl powder. The optimal working temperature in which the CO conversion is maximum and the CO2 conversion is minimized was determined to be from 149 °C to 239 °C for S-RuAl and from 165 °C to 232 °C for M-RuAl, whilst it was from 217 °C to 226 °C for RuAl powder. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity for CO methanation among the considered catalysts can be related with modifications in the surface particle size of ruthenium and its reducibility. These were ascribed to the metallic substrate, the presence of PVA and colloidal alumina in the slurry preparation, the aqueous and acidic media and the thermal treatment used, resulting in a more active and selective catalysts than the parent powder.

September 17th | 10.00 h (Seminario cicCartuja2J
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The influence of one dimensional substrate patterns on the nanocolumnar growth of thin films deposited by magnetron sputtering at oblique angles is theoretically and experimentally studied. A well‐established growth model has been used to study the interplay between the substrate topography and the thin film morphology. A critical thickness has been defined, below which the columnar growth is modulated by the substrate topography, while for thicknesses above, the impact of substrate features is progressively lost in two stages; first columns grown on taller features take over neighboring ones, and later the film morphology evolves independently of substrate features. These results have been experimentally tested by analyzing the nanocolumnar growth of SiO2 thin films on ion‐induced patterned substrates.

October 8th | 10.00 h (Seminario cicCartuja2J
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Graphical abstract: Phase-pure BiFeO3 produced by reaction flash-sintering of Bi2O3 and Fe2O3

Mixed powders of Bi2O3 and Fe2O3 are shown to yield single-phase, dense nanostructured polycrystals of BiFeO3 in reaction flash sintering experiments, carried out by applying a field of 50 V cm−1 and with the current limit set to 35 mA mm−2. The furnace was heated at a constant rate with the reaction sintering taking place abruptly upon reaching 625 °C. Remarkably, an intermediate bismuth-rich phase of the oxide that forms just before reaching the flash temperature transforms, and at the same time sinters, into single-phase BiFeO3 within a few seconds after the onset of the flash. The BiFeO3 so produced is electrically insulating, a property that is critical to its applications. This one-step synthesis of single-phase polycrystals of complex oxides from their basic constituents, by reaction flash sintering, is a significant development in the processing of complex oxides, which are normally difficult to sinter by conventional methods.

October 22th | 10.00 h (Seminario cicCartuja2J
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Figure 1

Until recently, superhydrophobicity was considered as a hint to predict surface icephobicity, an association of concepts that is by no means universal and that has been proven to depend on different experimental factors and material properties, including the actual morphology and chemical state of surfaces. This work presents a systematic study of the wetting and freezing properties of aluminum Al6061, a common material widely used in aviation, after being subjected to nanosecond pulsed IR laser treatments to modify its surface roughness and morphology. All treated samples, independent of their surface finishing state, presented initially an unstable hydrophilic wetting behavior that naturally evolved with time to reach hydrophobicity or even superhydrophobicity. To stabilize the surface state and to bestow the samples with a permanent and stable hydrophobic character, laser-treated surfaces were covered with a thin layer of CFx prepared by plasma-enhanced chemical vapor deposition. A systematic comparison between freezing delay (FD) and wetting properties of water droplets onto these plasma-/polymer-modified laser-treated surfaces that, under conditions where a heterogeneous nucleation mechanism prevails, surface morphology rather than the actual value of the surface roughness parameter the key feature for long FD times. In particular, it is found that surface morphologies rendering a Cassie–Baxter wetting regime longer FDs than those characterized by a Wenzel-like wetting state. It is that laser treatment, with or without additional coverage with thin CFx coatings, affects wetting and ice formation behaviors and might be an efficient procedure to mitigate icing problems on metal surfaces.

 

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Figure 1

A series of CexZr1–xO2 supports with different Ce/Zr molar ratios were utilized for the preparation of gold catalyst used in the selective oxidation of 5-hydroxymethyl-2-furfural to 2,5-furandicarboxylic acid. The used method of gold deposition allows the preparation of gold particles with homogeneous size and shape distribution, a formulation very useful for studies dedicated to revealing the support participation in the reaction. The supports are characterized by Fourier transform infrared spectroscopy using CO as probe molecule, and the sample catalytic activity is thereafter correlated to the support acid site distribution. The possible participation of its Lewis/Brønsted acidity in the reaction mechanism is also proposed.

 

November 19th | 10.00 h (Seminario cicCartuja2J
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A group of beads from the artificial cave of La Molina (Lora de Estepa, Sevilla) and Cova del Gegant (Sitges, Barcelona) were made from a biogenic raw material and intentionally covered by a layer of resin. This is the first time this type of treatment has been documented on elements of adornment in the Late Prehistory of the Iberian Peninsula. The composition and nature of the coatings are analysed and the symbolic role of such alterations and imitations of prehistoric adornments is discussed.

December 10th | 10.00 h (Seminario cicCartuja2J
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Unlabelled Image

In this work, bacterial behavior on dense and porous titanium substrates is discussed. Porous titanium was fabricated by a space holder technique (using 50 vol%, NH4HCO3 with particle sizes between 250 and 355 μm). These substrates were coated by sulfonated PEEK (termed SPEEK). Characterization of the porous substrate was carried out using the Archimedes Method, Image Analysis, and three-dimensional X-ray Micro-Computed Tomography (including total and interconnected porosity, equivalent diameter, and pore shape factor), as well as mechanical characterization (specifically stiffness and yield strength). A detailed study was performed here to investigate the influence of substrate porosity on the adhesion and proliferation of E. coliMRSA, and P. aeruginosa (common causes of orthopedic device-associated infections). Bacterial colonization was examined in terms of the initial bacterial concentration, as well as bacterial adherence to and growth on the surface and inside the pores. Results suggest that fully dense titanium supported the least bacterial colonization, while the porous titanium promoted bacterial growth in the medium and inside the cavities. Furthermore, the SPEEK coating deposited onto the samples inhibited bacteria growth inside the porous materials. In this manner, this study showed for the first time that SPEEK could have potential antibacterial properties to offset the increase in bacteria growth commonly observed in porous materials.

 

March 13th

Flash Sintering of Ceramics

Prof. Rishi Raj
Universidad de Colorado en Boulder

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Flash sintering is a novel densification technology for ceramics, which allows a dramatic reduction of processing time and temperature. It represents a promising sintering route to reduce economic, energetic and environmental costs associated to firing. Moreover, it allows to develop peculiar and out-of-equilibrium microstructures.
The flash process is complex and unusual, including different simultaneous physical and chemical phenomena and their understanding, explanation and implementation require an interdisciplinary approach from physics, to chemistry and engineering. In spite of the intensive work of several researchers, there is still a wide debate as for the predominant mechanisms responsible for flash sintering process.
This talk will include an overview of the original research that led to the discovery of the technique by Prof. Raj, as well as an analysis of the most significant mechanisms proposed for explaining the “flash” event. It will also include future scientific activities and potential technological implementations.

Biografía:
Prof. Rishi Raj pursued his Ph.D. in 1965 at Harvard. He graduated in 1970 with a Ph. D. in Engineering and Applied Sciences, under the tutelage of Mike Ashby and David Turnbull. After graduating he worked from 1971-1972 as a Staff Scientist at Chase Brass and Copper Company in Cleveland, OH. He returned to Academia in 1972 when he became an Assistant Professor of Mechanical Engineering, University of Colorado at Boulder, CO (1972-1975). In 1975, Raj accepted a position as Professor of Materials Science and Engineering at Cornell University, Ithaca, NY. He worked at Cornell for 21 years from 1975-1996. In 1996, he moved back to Boulder and is currently employed as Professor of Mechanical Engineering, University of Colorado at Boulder, CO.
Prof. Raj has studied oxides and non-oxides to understand a wide range of behavior phenomena, including high-temperature creep, superplasticity, interfaces and amorphous phases and their role in sintering and creep, sintering mechanisms, and polymer-derived amorphous materials. Most recently, he has turned his attention to understanding electric field effects on sintering and defect chemistry, also called “flash sintering.”
Through his career, he has published more than 450 peer reviewed articles in refereed International Journals, with over 20,000 citations of his work on Google Scholar.
He has been named a 2015 Distinguished Life Member by The American Ceramic Society, the highest honor accorded to members of the scientific and technical organization—recognizes an individual’s eminent contribution to the ceramic and glass profession.

July 4th

Colour Engineering: from nature to applications

Dr. Silvia Vignolini
University of Cambridge

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The most brilliant colours in nature are obtained by structuring transparent materials on the scale of the wavelength of visible light. By controlling/designing the dimensions of such nanostructures, it is possible to achieve extremely intense colourations over the entire visible spectrum without using pigments or colorants. Colour obtained through structure, namely structural colour, is widespread in the animal and plant kingdom [1]. Such natural photonic nanostructures are generally synthesised in ambient conditions using a limited range of biopolymers. Given these limitations, an amazing range of optical structures exists: from very ordered photonic structures [2], to partially disordered [3], to completely random ones [4].
In this seminar, I will introduce some striking example of natural photonic structures [2-4] and review our recent advances to fabricate bio-mimetic photonic structures using the same material as nature. Biomimetic with cellulose-based architectures enables us to fabricate novel photonic structures using low cost materials in ambient conditions [6-7]. Importantly, it also allows us to understand the biological processes at work during the growth of these structures in plants.

[1] Kinoshita, S. et al. (2008). Physics of structural colors. Rep. Prog. Phys. 71(7), 076401.
[2] Vignolini, S. et al. (2012). Pointillist structural color in Pollia fruit. PNAS 109, 15712-15716.
[3] Moyroud, E. et al. (2017). Disorder in convergent floral nanostructures enhances signalling to bees. Nature 550, 469.
[4] Burresi M. et al. (2014) Bright-White Beetle Scales Optimise Multiple Scattering of Light. Sci.Rep. 4, 727
[5] Parker R. et al. (2018) The Self-Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance. Adv Mat 30, 1704477
[6] Parker R. et al. (2016). Hierarchical Self-Assembly of Cellulose Nanocrystals in a Confined Geometry. ACS Nano, 10 (9), 8443–8449
[7] Liang H-L. et al. (2018). Roll-to-roll fabrication of touch-responsive cellulose photonic laminates, Nat Com 9, 4632

Seminario cicCartuja2 / Salón de Grados cicCartuja2

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Americo Vespucio 49
Isla de la Cartuja
Sevilla
, 41092 España
Teléfono: 954489500

Instituto de Ciencia de Materiales de Sevilla

Centro de Investigaciones Científicas Isla de la Cartuja. C/Américo Vespucio, 49 – 41092 Sevilla (España)
Tel.: (+34) 954489527 | Fax: (+34) 954460165 | se.ci1566378088sc.es1566378088mci@n1566378088ozub1566378088