Cecilia Granados-Miralles

Cecilia Granados-Miralles
Institute of Ceramics and Glass | ICV

PhD in Nanoscience

About

39
Publications
5,216
Reads
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524
Citations
Citations since 2017
33 Research Items
513 Citations
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2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140
Additional affiliations
January 2020 - present
Institute of Ceramics and Glass
Position
  • Juan de la Cierva Postdoctoral Fellow
February 2018 - December 2019
Institute of Ceramics and Glass
Position
  • Postdoctoral Researcher
May 2017 - December 2017
Aarhus University
Position
  • Postdoctoral Researcher
Education
February 2013 - January 2015
Aarhus University
Field of study
  • Chemistry
September 2006 - September 2015

Publications

Publications (39)
Article
We show here for the first time the use of a cold sintering process (CSP) to sinter CoSb3-based thermoelectric materials. CSP at 150 ºC for 90 min under a uniaxial pressure of 750 MPa yields pieces with a relative density of 86%, which is increased to around 92% after a post-annealing at temperatures ≥500 ºC in Ar atmosphere. The reported CSP produ...
Article
Full-text available
Powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD) have been used to investigate the crystal structure of CoFe 2 O 4 nanoparticles prepared via different hydrothermal synthesis routes, with particular attention given to accurately determining the spinel inversion degrees. The study is divided into four parts. In the first part, th...
Article
Full-text available
We have monitored the Verwey transition in micrometer-wide, nanometer-thick magnetite islands on epitaxial Ru films on Al2O3(0001) using Raman spectroscopy. The islands have been grown by high-temperature oxygen-assisted molecular beam epitaxy. Below 100 K and for thicknesses above 20 nm, the Raman spectra correspond to those observed in bulk cryst...
Article
Full-text available
The use of rare-earth-based permanent magnets is one of the critical points for the development of the current technology. On the one hand, industry of the rare-earths is highly polluting due to the negative environmental impact of their extraction and, on the other hand, the sector is potentially dependent on China. Therefore, investigation is req...
Preprint
Full-text available
We have monitored the Verwey transition in micrometer-wide, nanometer-thick magnetite islands on epitaxial Ru films on Al2O3(0001) using Raman spectroscopy. The islands have been grown by high-temperature oxygen-assisted molecular beam epitaxy. Below 100 K and for thicknesses above 20 nm the Raman spectra correspond to those observed in bulk crysta...
Article
Full-text available
Fe 3 C/few-layered graphene core/shell nanoparticles embedded in a carbon matrix are synthesized by a novel two-step surfactant sol-gel strategy, where the processes of hydrolysis, polycondensation and drying take place in a one-pot. The present approach is based on the combined action of oleic acid and oleylamine, which act sterically on the precu...
Article
Full-text available
Fe3C/few-layered graphene core/shell nanoparticles embedded in a carbon matrix are synthesized by a novel two-step surfactant sol-gel strategy, where the processes of hydrolysis, polycondensation and drying take place in a one-pot. The present approach is based on the combined action of oleic acid and oleylamine, which act sterically on the precurs...
Article
Full-text available
In this work we have investigated the effect of the solvent during the processing of SrFe12O19 platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190-270 °C, under pressures of...
Article
Full-text available
With an annual production amounting to 800 kilotons, ferrite magnets constitute the largest family of permanent magnets in volume, a demand that will only increase as a consequence of the rare-earth crisis. With the global goal of building a climate-resilient future, strategies towards a greener manufacturing of ferrite magnets are of great interes...
Article
Full-text available
The incessant technological pursuit towards a more sustainable and green future depends strongly on permanent magnets. At present, their use is widespread, making it imperative to develop new processing methods that generate highly competitive magnetic properties reducing the fabrication temperatures and costs. Herein, a novel strategy for developi...
Article
Full-text available
A plethora of modern technologies rely on permanent magnets for their operation, including many related to the transition towards a sustainable future, such as wind turbines or electric vehicles. Despite the overwhelming superiority of magnets based on rare-earth elements in terms of the magnetic performance, the harmful environmental impact of the...
Article
Composites of magnetically hard and soft phases are present in multiple and diverse applications, ranging from bulk permanent magnets in motors and generators to state-of-the-art recording media devices. The nature of the magnetic coupling between the hard and soft phases is of great technological relevance, as the macroscopic properties of the fun...
Article
In order to obtain competitive strontium ferrite sintered magnets, SiO2 and CaO are added to avoid exaggerated grain growth. Besides favoring proper densification, these additives prevent the collapse of coercivity associated to grain growth. However, these additives may lead to slight decreases in density and the formation of paramagnetic α-Fe2O3...
Article
Strontium hexaferrite nanocrystalline powders were synthesized using a citrate combustion method and subsequently subjected to post-synthesis processing with the aim of tuning the micro-nanostructure to improve the magnetic properties. Firstly, the synthesis thermal treatments were optimized in order to minimize the formation of secondary phases, m...
Article
Full-text available
Due to the issues associated with rare-earth elements, there arises a strong need for magnets with properties between those of ferrites and rare-earth magnets that could substitute the latter in selected applications. Here, we produce a high remanent magnetization composite bonded magnet by mixing FeCo nanowire powders with hexaferrite particles. I...
Article
Several M-type SrFe12O19 nanoparticle samples with different morphologies have been synthesized by different hydrothermal and sol-gel synthesis methods. Combined Rietveld refinements of neutron and X-ray powder diffraction data with a constrained structural model reveal a clear correlation between crystallite size and long-range magnetic order, whi...
Article
In situ neutron powder diffraction (NPD) was employed for investigating gram-scale reduction of hard magnetic CoFe2O4 (spinel) nanoparticles into CoFe2O4/CoFe2 exchange-spring nanocomposites via H2 partial reduction. Time-resolved structural information was extracted from Rietveld refinements of the NPD data, revealing significant changes in the re...
Article
Full-text available
CoFe2O4/Co–Fe magnetic composites are usually prepared through partial reduction of CoFe2O4, which often yields monoxides (i.e., FeO, CoO) as secondary phases. Since these compounds are paramagnetic at ambient conditions, the presence of a small amount of monoxide is generally downplayed in the literature, and the possible effects on the magnetic p...
Preprint
Full-text available
SrFe$_{12}$O$_{19}$ (SFO) films grown on Si (100) substrates by radio-frequency magnetron sputtering have been characterized in terms of composition, structural and magnetic properties by a combination of microscopy, diffraction and spectroscopy techniques. M\"ossbauer spectroscopy was used to determine the orientation of the films magnetization, w...
Patent
La presente invención se refiere a un procedimiento de obtención de un imán permanente de cerámica que comprende una etapa de mezclar micro-y/o nano- partículas magnéticas duras o blandas con un solvente orgánico básico o ácido, una etapa de compactación, una etapa de calentamiento bajo presión, una etapa de enfriamiento y una etapa de sintonizació...
Article
Cobalt aluminate spinel compounds prepared by different methods were characterized in terms of crystalline structure, morphology, textural properties and acidity, and evaluated as catalysts for diesel soot combustion in NOx/O2 mixtures. The activation of commercial CoAl2O4 microparticles by ball milling reduced the onset temperature of this materia...
Article
Full-text available
We show that it is possible to tune the Néel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the de...
Preprint
We show that it is possible to tune the Néel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the de...
Article
The magnetic properties of spinel ferrites (MFe2O4, M=Mn, Fe, Co, Ni, Zn, etc.) are largely determined by the type of divalent cation, M²⁺ and cation distribution between the tetrahedral and octahedral sites in the structure. Partial substitution of Zn²⁺ into the thermodynamically preferred tetrahedral coordination in ferrites produces an increase...
Article
Full-text available
Exchange-coupled hard-soft biphase magnets are technologically relevant systems in that they enable tailoring the magnetization reversal process. Here, exchange-spring behavior is observed in CoFe2O4/FeCo bilayers for soft thicknesses as thin as 2 nm, at least four times below the exchange length of the system. This result is in contrast with the a...
Article
Magnetic materials are ubiquitous in electric devices and motors making them indispensable for modern-day society. The hexaferrites currently constitute the most widely used permanent magnets (PMs), accounting for 85% (by weight) of the PMs global sales. This work presents a complete bottom-up nanostructuring protocol for preparation of magneticall...
Article
Magnetic spinel ferrite MFe2O4 (M=Mn, Co, Ni, Zn) nanoparticles have been prepared via simple, green and scalable hydrothermal synthesis pathways utilizing sub- and supercritical conditions to attain specific product characteristics. The crystal-, magnetic- and micro-structures of the prepared crystallites have been elucidated through meticulous ch...
Article
Full-text available
During the last decade, CoFe2O4 (hard)/Co Fe alloy (soft) magnetic nanocomposites have been routinely prepared by partial reduction of CoFe2O4 nanoparticles. Monoxide (i.e., FeO or CoO) has often been detected as a byproduct of the reduction, although it remains unclear whether the formation of this phase occurs during the reduction itself or at a...
Article
The formation of CoFe2O4 nanoparticles has been investigated via three hydrothermal synthesis routes with substantially different heating rates. The syntheses were conducted at various temperatures in the interval 100-390 °C using three different rector setups: 1) conventional Teflon lined steel autoclave, 2) custom-designed spiral reactor and 3) c...
Article
Platelet-shaped nano-crystallites of SrFe12O19 were hydrothermally synthesised and compacted into bulk magnets using Spark Plasma Sintering (SPS). Pellets were obtained with densities >90% of the theoretical crystallographic density. Compaction of the as-synthesised powders at 950 °C for 2 minutes causes improved alignment of the crystallites withi...
Article
Full-text available
The hydrothermal synthesis of magnetic strontium hexaferrite (SrFe12O19) nanocrystallites was followed in situ using synchrotron powder X-ray diffraction. For all the studied temperatures, the formation of SrFe12O19 happened through an intermediate crystalline phase, identified as the so-called six-line ferrihydrite (FeOOH). The presence of FeOOH h...
Article
Full-text available
A novel approach to incorporate cobalt atoms into a magnetite single crystal is demonstrated by a combination of x-ray spectro-microscopy, low-energy electron diffraction, and density-functional theory calculations. Co is deposited at room temperature on the reconstructed magnetite (001) surface filling first the subsurface octahedral vacancies and...
Article
Ferrite-based, hard-soft magnetic nanocomposites with the composition (100%−x)SrFe12O19–xCoFe2O4, where x = 5, 10, and 15 wt%, were prepared by mixing the constituent powders, followed by spark plasma sintering. In order to control the particle size of the constituent materials, the SrFe12O19 and CoFe2O4 powders were synthesized using the hydrother...
Article
Full-text available
Magnetically soft zinc-substituted cobalt ferrite ZnxCo1-xFe2O4 (x = 0.4, 0.5 and 0.6) nanocrystallites were successfully synthesized from cheap, abundant materials, using a mild, scalable hydrothermal route. The partial substitution of zinc by cobalt was generally observed to reduce the resulting crystallite sizes and the saturation magnetization....
Article
Full-text available
Interfacial exchange coupling is known to improve the permanent magnetic performance (i.e., maximal energy product) in composites of magnetically hard and soft particles. The prevailing strategy, employed in a plethora of compositions, consists in maximizing the coupling between the hard and soft phases and optimizing material parameters such as pa...
Article
Full-text available
The influence of synthesis and compaction parameters is investigated with regards to formation of high performance SrFe12O19 bulk magnets. The produced magnets consist of highly aligned, single-magnetic domain nanoplatelets of SrFe12O19. The relationship between the magnetic performance of the samples and their structural features is established th...

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Projects

Projects (3)
Project
The INSPIRES project aims at recovering and supplying Rare-Earths within the EU through radical innovations in the recycling of permanent magnets, focusing on one of the most readily available sources: home appliances. INSPIRES will optimize methods at industrial scale for sustainable extraction and recycling and use of recycled magnets in new motors.
Project
Fabrication of multifunctional nano/micromaterials by non-conventional methodologies with active interfaces tailoring the final response for diverse applications.
Project
To develop up-scalable and cost-efficient methods for manufacturing improved rare earth free permanent magnets. We aim at producing permanent magnets with an enhanced performance with respect to already existing rare earth free magnets; and making them more enduring and sustainable. AMPHIBIAN is a Research and Innovation project funded by the European Commission. Grant agreement H2020-NMBP-2016-720853. http://amphibianproject.eu/