Lluís Yedra

Lluís Yedra
CentraleSupélec | ECP

PhD

About

54
Publications
11,417
Reads
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966
Citations
Citations since 2017
20 Research Items
706 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
Additional affiliations
July 2014 - December 2014
Luxembourg Institute of Science and Technology (LIST)
Position
  • PostDoc Position

Publications

Publications (54)
Article
Electrolyte-cathode interfaces are critical regions of solid oxide fuel cells where important degradation phenomena are localized due to cation interdiffusion and reactivity. State-of-the-art barrier layers deposited by screen-printing are not fully blocking, resulting in the formation of insulating phases such as SrZrO3. This article is the contin...
Article
Full-text available
BiFeO3 is the model multiferroic material widely considered as nanoparticles for its potential photocatalytic activity. In this work, we study the influence of annealing temperature on the structural, morphological and optical properties of BiFeO3 nanoparticles prepared by a facile chemical route and, the resulting photodegradation of Eosin B dye....
Article
Full-text available
During additive manufacturing of alloys, just after local heat-matter interactions, a molten material undergoes rapid solidification. Then, for the rest of the building time, it is subjected to cooling/heating cycles in the solid-state i.e., solid-state thermal cycling. The thermo-mechanical forces generated during solid-state thermal cycling can t...
Article
Diffusion bonding with Au, Cu and Sn is a technique that can be used to manufacture printed circuit boards. The mechanisms of reactive diffusion and Kirkendall void formation were studied in the Cu–Au–Sn–Cu sandwich system. The initial thickness of the Au and Sn layers was a few micrometers, corresponding to 57 mol.% Au and 43 mol.% Sn. The experim...
Article
Full-text available
Precipitates in an austenitic stainless steel fabricated via any Additive Manufacturing (AM), or 3D printing, technique have been widely reported to be only Mn-Si-rich oxides. However, via Transmission Electron Microscopy (TEM) studies on a 316L stainless steel, we show that non-oxide precipitates (intermetallics, sulfides, phosphides and carbides)...
Preprint
Full-text available
Precipitates in an austenitic stainless steel fabricated via any Additive Manufacturing (AM), or 3D printing, technique have been widely reported to be only Mn-Si-rich oxides. However, via Transmission Electron Microscopy (TEM) studies on a 316L stainless steel, we show that non-oxide precipitates (intermetallics, sulfides, phosphides and carbides)...
Article
Full-text available
The study demonstrates a new method to quantify Secondary Ion Mass Spectrometry (SIMS) data by using a synergetic combination of Energy Dispersive X-ray spectroscopy (EDX) and SIMS. The novelty of this approach lies in using a diffusion couple to produce a continuum of concentration variation to cover a large portion of the composition space (100 a...
Article
PbTiO_{3}/SrRuO_{3} superlattices deposited on SrTiO_{3} substrates are studied using a combination of x-ray diffraction, piezoresponse force microscopy, scanning transmission electron microscopy, transport measurements, and impedance spectroscopy. The superlattices are found to have two inequivalent interfaces resulting from differences in the gro...
Article
Full-text available
Degradation mechanisms in LiV3O8 cathode films (~500 nm) with different initial microstructures i.e., globular nanocrystals in amorphous matrix and needle-like nanocrystals, synthesized by annealing the cathodes at 150 °C and 300 °C for 6 h are studied by Transmission Electron Microscopy (TEM) and Auger Electron Spectroscopy (AES). In addition, a u...
Article
Full-text available
Ultrathin Hf1-x Zr x O2 films have attracted tremendous interest since they show ferroelectric behavior at the nanoscale, where other ferroelectrics fail to stabilize the polar state. Their promise to revolutionize the electronics landscape comes from the well-known Si compatibility of HfO2 and ZrO2, which (in amorphous form) are already used as g...
Preprint
Ultra-thin Hf1-xZrxO2 films have attracted tremendous interest owing to their Si-compatible ferroelectricity arising from polar polymorphs. While these phases have been grown on Si as polycrystalline films, epitaxial growth was only achieved on non-Si substrates. Here we report direct epitaxy of polar phases on Si using pulsed laser deposition enab...
Article
Full-text available
The development of advanced materials relies crucially on the availability of suitable high-resolution analytical characterization techniques. In this review, we discuss correlative microscopy methods combining Transmission Electron Microscopy (TEM) and Secondary Ion Mass Spectrometry (SIMS) for high-resolution high-sensitivity analysis. We review...
Article
Full-text available
In Situ Correlative Microscopy Combining Transmission Electron Microscopy and Secondary Ion Mass Spectrometry - Volume 24 Supplement - Santhana Eswara, Lluis Yedra, Alisa Pshenova, Varun Sarbada, Jean-Nicolas Audinot, Robert Hull, Tom Wirtz
Article
HIM-SIMS: Correlative SE/Chemical Imaging at the Limits of Resolution. - Volume 23 Issue S1 - D. Dowsett, T. Wirtz, L. Yedra
Article
Secondary Ion Mass Spectrometry in the TEM: Isotope Specific High Resolution Correlative Imaging. - Volume 23 Issue S1 - L. Yedra, S. Eswara, D. Dowsett, H. Q. Hoang, T. Wirtz
Conference Paper
Despite having superior spatial resolution, the analytical capabilities of Transmission Electron Microscopy (TEM), either Energy Dispersive X-ray Spectroscopy (EDS) or Electron Energy-Loss Spectroscopy (EELS) [1], are fundamentally limited in terms of isotopic analysis. Moreover, the analysis of light elements still remains out of reach. However, t...
Conference Paper
Development and innovations of modern high-performance materials rely crucially on the repertoire of characterization methods available. While individual techniques provide information on a specific aspect of the investigated material, a comprehensive understanding requires a correlative approach in which complementary information are needed from e...
Patent
Full-text available
Precession Illumination in Transmission Electron Microscopes of electro-transparent specimens makes their emitted analytical X_Ray and Electron Energy Loss signals less sensitive to channeling effects and, thereby, increase reliability of the atomic ratios calculated in the multielemental volume probed in the specimen by the incoming beam.
Article
The physicochemical properties used in numerous advanced nanostructured devices are directly controlled by the oxidation states of their constituents. In this work we combine electron energy-loss spectroscopy, blind source separation and computed tomography to reconstruct in three dimensions the distribution of Fe2+ and Fe3+ ions in a FeO/Fe3O4 cor...
Conference Paper
div class="title">Distinguishing Isotopes in the Electron Microscope: In-situ TEM-SIMS Correlative Analysis - Volume 22 Issue S3 - Lluís Yedra, Santhana Eswara, David Dowsett, Tom Wirtz
Article
Full-text available
Isotopic analysis is of paramount importance across the entire gamut of scientific research. To advance the frontiers of knowledge, a technique for nanoscale isotopic analysis is indispensable. Secondary Ion Mass Spectrometry (SIMS) is a well-established technique for analyzing isotopes, but its spatial-resolution is fundamentally limited. Transmis...
Article
Electron energy-loss spectroscopy-spectrum image (EELS-SI) tomography is a powerful tool to investigate the three dimensional chemical configuration in nanostructures. Here, we demonstrate, for the first time, the possibility to characterize the spatial distribution of Fe and Co cations in a complex FexCo(3-x)O4/Co3O4 ordered mesoporous system. Thi...
Article
We investigated the hydrogen distribution and desorption behavior in an electrochemically hydrogen- charged binary Ni-Nb model alloy to study the role of d phase in hydrogen embrittlement of alloy 718. We focus on two aspects, namely, (1) mapping the hydrogen distribution with spatial resolution enabling the observation of the relations between des...
Conference Paper
Full-text available
div class="title">Parallel Ion Electron Spectrometry (PIES): A New Paradigm for High-Resolution High-Sensitivity Characterization based on integrated TEM-SIMS - Volume 21 Issue S3 - S. Eswara Moorthy, D. Dowsett, L. Yedra, T. Wirtz
Article
Anisotropic and branched gold nanoparticles have great potential in optical, chemical and biomedical applications. However their syntheses involve multi-step protocols and the use of cytotoxic agents. Here, we report a novel one-step method for the preparation of gold nanostructures using only Hantzsch 1,4-dihydropyridines as mild reducing agents....
Article
Ordered mesoporous metal oxides were prepared from a silica hard template. Two stabilization approaches for preparing high temperature ordered mesoporous structures were presented and their functionality as electrodes for intermediate temperature solid oxide fuel cells (IT-SOFCs) was proven. Firstly, nickel based mesoporous cermets were synthesized...
Article
The effects of beam precession on the Electron Energy Loss Spectroscopy (EELS) signal of the carbon K edge in a 2 monolayer graphene sheet are studied. In a previous work, we demonstrated the use of precession to compensate for the channeling-induced reduction of EELS signal when in zone axis. In the case of graphene, no enhancement of EELS signal...
Article
Full-text available
Electron Energy Loss Spectroscopy (EELS) in a transmission electron microscope offers the possibility of extracting high accuracy maps of composition and electronic properties through EELS spectrum images (EELS-SI). Acquiring EELS-SI for different tilt angles, a 3D tomographic reconstruction of EELS information can be achieved. In the present work...
Article
Full-text available
Physicochemical properties of transition metal oxides are directly determined by the oxidation state of the metallic cations. To address the increasing need to accurately evaluate the oxidation states of transition metal oxide systems at the nanoscale, here we present "Oxide Wizard." This script for Digital Micrograph characterizes the energy-loss...
Article
The collapse of nanostructures at high temperature is one of the main drawbacks for the implementation of nanomaterials in some energy applications. An exciting virtual non-degradation up to 1000 °C is presented here for ordered mesoporous gadolinia doped ceria. By using the nanocasting method based on the KIT-6 template, the long-term stability of...
Article
Full-text available
The controlled filling of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic FexCo3-xO4 nanolayers is presented as a proof-of-concept toward the integration of nanosized units in highly ordered, heterostructured 3D architectures. Antiferromagnetic (AFM) Co3O4 mesostructures are obtained as negative replicas o...
Article
Full-text available
The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique way of engineering the magnetic response by modifying the strength of the dipolar interactions between particles. Here we report on an experimental and theoretical analysis of magnetic hyperther...
Article
High temperature stable ordered mesoporous nickel–gadolinium-doped ceria cermets were prepared from a silica hard template (KIT-6), by a multistep impregnation process. The resulting cermet consists of an intimately mixed composite at the nanoscale with highly connected nickel and ceria percolation networks that ensure good electronic conductivity...
Article
Nanoparticles of strontium titanate (SrTiO3) have been synthesized in the 15 nm to 1 μm size range and studied using a combination of dielectric, Raman, x-ray, and neutron measurements. When diminishing the grain size, a strong reduction of dielectric permittivity, an enhancement of (normally forbidden) Raman polar modes and a progressive decouplin...
Chapter
Electron tomography is nowadays a well established technique for recovering three dimensional information of nanostructures. While somewhat linked with the chemistry of the sample, imaging techniques such as bright-field in biomedical samples and high angle annular dark field in materials science are the most widely spread techniques, basically off...
Article
Electron tomography is a widely spread technique for recovering the three dimensional (3D) shape of nanostructured materials. Using a spectroscopic signal to achieve a reconstruction adds a fourth chemical dimension to the 3D structure. Up to date, energy filtering of the images in the transmission electron microscope (EFTEM) is the usual spectrosc...
Article
Full-text available
The successful combination of electron beam precession and bright field electron tomography for 3D reconstruction is reported. Beam precession is demonstrated to be a powerful technique to reduce the contrast artifacts due to diffraction and curvature in thin foils. Taking advantage of these benefits, Precession assisted electron tomography has bee...
Article
Full-text available
If one solves the Scrödinger equation for an electron in a crystalline potential, the resulting wavefunctions are Bloch waves. When a number of Bragg beams are excited, the same number of Bloch waves propagate in the crystal. In the most simple case, in the two beam condition, two Bloch waves are present: one that is peaked at the specimen atoms (t...

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Project (1)
Project
Horizon 2020. FCH 2 JU The overall goal of ECo is to develop and validate a highly efficient co-electrolysis process for conversion of excess renewable electricity into distributable and storable hydrocarbons via simultaneous electrolysis of steam and CO2 through SOEC (Solid Oxide Electrolysis Cells) thus moving the technology from technology readiness level (TRL) 3 to 5. In relation to the work program, ECo will specifically: • Develop and prove improved solid oxide cells (SOEC) based on novel cell structure including electrode backbone structures and infiltration and design of electrolyte/electrode interfaces to achieve high performances and high efficiencies at ~100 oC lower operating temperatures than state-of-the-art in order to reduce thermally activated degradation processes, to improve integration with hydrocarbon production, and to reduce overall costs. • Investigate durability under realistic co-electrolysis operating conditions that include dynamic electricity input from fluctuating sources with the aim to achieve degradation rates below 1%/1000 h at stack level under relevant operating conditions. • Design a plant to integrate the co-electrolysis with fluctuating electricity input and catalytic processes for hydrocarbon production, with special emphasis on methanation (considering both external and internal) and perform selected validation tests under the thus needed operating conditions. • Test a co-electrolysis system under realistic conditions for final validation of the obtained results at larger scale. • Demonstrate economic viability for overall process efficiencies exceeding 60% using results obtained in the project for the case of storage media such as methane and compare to traditional technologies with the aim to identify critical performance parameters that have to be improved. • Perform a life cycle assessment with CO2 from different sources (cement industry or biogas) and electricity from preferably renewable sources to prove the recycling potential of the concept