Imanol de Pedro - Academia.edu (original) (raw)
Papers by Imanol de Pedro
Chemical Engineering Journal, 2021
The slow kinetics in the photocatalytic reduction of CO2, as well as the low quantum efficiencies... more The slow kinetics in the photocatalytic reduction of CO2, as well as the low quantum efficiencies achieved, directly related to the photocatalyst and reactor configuration applied, limit the widespread use of this technology. In light of this, the main objective of this work is to evaluate the continuous photocatalytic conversion of CO2 into methanol in an optofluidic microreactor (with enhanced mass transport, large volume/active area ratio and uniform light distribution) using Cu nanoparticles synthesized in the hydrophilic 3-methyl-n-butylimidazolium tetrafluoroborate (BMIm.BF4) ionic liquid and embedded in TiO2 (P25). The ionic liquid not only acts as a template to control the size of the nanoparticles but also as a stabilizing agent. The analysis includes the effect of structural parameters of the photoactive layer such as Cu content (from 0.8 to 6.8 wt.%) and photocatalyst loading (0.5-3 mg•cm-2), as well as operating variables such as UV and visible light intensities (2.5-10 mW•cm-2) and cell configuration (i.e. one or two compartments). The maximum methanol yield reached from the continuous transformation of CO2 is r = 230.3 µmol•g-1 •h-1 at 2 wt.% Cu content, photocatalyst loading of 2 mg•cm-2 , UV light intensity of 10 mW•cm-2 and a two-compartment microreactor configuration. This result outperforms the values previously reported for Cu/TiO2-based systems using optofluidic microreactors, as well as most of those in common CO2 photoreactors.
Journal of Molecular Liquids, 2021
Abstract A new imidazolium-based halometallate complex with formula (trimim)[FeBr4] (trimim: 1,2,... more Abstract A new imidazolium-based halometallate complex with formula (trimim)[FeBr4] (trimim: 1,2,3-trimethylimidazolium) has been synthesized and characterized as a function of the temperature. The structural phase transitions, magnetic properties and magnetic structure of this compound have been thoroughly studied. The crystal structure evolution from 1.8 to 400 K has been investigated by a combination of synchrotron X-ray and neutron powder diffraction, as well as single crystal X-ray and neutron diffraction. Four different phases were found: phase I, from 400 to 350 K, with the orthorhombic Cmc21 space group; phase II, from 350 to 160 K, which was modelled with the monoclinic P21/m space group; and phase III, stable down to 13 K and showing the monoclinic Cm space group. The transition from phase III to II involves the appearance of disorder in the organic cations. Magnetometry measurements indicate a long-range magnetic order below 13 K, which was confirmed by single crystal and powder neutron X-ray diffraction analyses. The occurrence of new reflections that were not possible to index with the phase III unit cell suggests a symmetry breaking, giving rise to the phase IV. A joint refinement (single-crystal and powder data) revealed that the latter phase exhibits the magnetic Shubnikov Ccc space group. This model consists of a strictly antiferromagnetic structure with ferromagnetic interactions within the unit cell, which is compatible with the magnetometry results.
![Research paper thumbnail of Correction: Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]](https://attachments.academia-assets.com/98939478/thumbnails/1.jpg)
](RSC Advances, 2020
Correction for ‘Crystal structure, magneto-structural correlation, thermal and electrical studies... more Correction for ‘Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]’ by Palmerina González-Izquierdo et al., RSC Adv., 2020, 10, 11200–11209. DOI: 10.1039/D0RA00245C.
![Research paper thumbnail of Incommensurate crystal structure, thermal expansion study and magnetic properties of (dimethylimidazolium)2[Fe2Cl6(μ-O)]](https://attachments.academia-assets.com/98939480/thumbnails/1.jpg)
](Journal of Physics: Materials, 2019
A thorough characterization of the title compound, (dimim)2[Fe2Cl6(μ-O)], consisting of a (μ-oxid... more A thorough characterization of the title compound, (dimim)2[Fe2Cl6(μ-O)], consisting of a (μ-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group P 1 ¯ (/α/β/γ)0 with modulation vector q = 0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (μ-oxido)-bridged binuclear iron(III) complex, ...
Applied Catalysis B: Environmental, 2019
The functionalization of silica-coated, magnetic Fe3O4 nanoparticles, with an ironcontaining ioni... more The functionalization of silica-coated, magnetic Fe3O4 nanoparticles, with an ironcontaining ionic liquid, allows for the synthesis of a Fe3O4@SiO2@(mim)[FeCl4] system that can be employed as a magnetically recoverable nanocatalyst. Herein, we present the use of Fe3O4@SiO2@(mim)[FeCl4] for the glycolysis of PET into BHET under conventional heating. The catalyst achieved nearly 100% yield and selectivity over twelve consecutive reaction cycles at 180 °C and was efficiently recovered without tedious work-up or purification processes. Additional analyses revealed that the amount of catalyst lost after each cycle was negligible and no trace of Fe was found in the purified BHET product.
ChemPlusChem, 2019
Supporting Information for this article is given via a link at the end of the document.
Physical chemistry chemical physics : PCCP, Jan 18, 2018
We report on a simple preparation of extremely small diameter (ca. 2 nm) Ni-Ir-based NPs using Ni... more We report on a simple preparation of extremely small diameter (ca. 2 nm) Ni-Ir-based NPs using Ni(COD)2 and [Ir(COD)OCH3]2 in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm·NTf2). The prepared NPs had either core-shell-like or alloy-like structures with the presence of Ni,Ir-oxides, depending on the synthetic approach. X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and magnetic measurements are combined to describe the influence of nanostructure on the magnetic behavior of these nanosystems. The present findings reveal that the alloy NPs display a disordered magnetic state, similar to a spin glass (SG)-like system (Tf = 7.2 K). Core-shell NPs are formed by a magnetically blocked/unblocked core with a magnetically disordered shell as deduced from the two magnetic responses peaking at TB = 75 K ...
CrystEngComm, 2017
The nucleophilic attack of a series of nucleobase derivatives on [(η6-p-cymene)RuCl(μ-Cl)]2 dinuc... more The nucleophilic attack of a series of nucleobase derivatives on [(η6-p-cymene)RuCl(μ-Cl)]2 dinuclear entity has yielded four mononuclear complexes with the general formula [Ru(η6-p-cymene)(L)Cl2], in which L stands for cytosine (1),...
Inorganic chemistry, Jan 13, 2016
The present work provides two new examples of supramolecular metal-organic frameworks consisting ... more The present work provides two new examples of supramolecular metal-organic frameworks consisting of three-dimensional extended noncovalent assemblies of wheel-shaped heptanuclear [Cu7(μ-H2O)6(μ3-OH)6(μ-adeninato-κN3:κN9)6](2+) entities. The heptanuclear entity consists of a central [Cu(OH)6](4-) core connected to six additional copper(II) metal centers in a radial and planar arrangement through the hydroxides. It generates a wheel-shaped entity in which water molecules and μ-κN3:κN9 adeninato ligands bridge the peripheral copper atoms. The magnetic characterization indicates the central copper(II) center is anti-ferromagnetically coupled to external copper(II) centers, which are ferromagnetically coupled among them leading to an S = 5/2 ground state. The packing of these entities is sustained by π-π stacking interactions between the adenine nucleobases and by hydrogen bonds established among the hydroxide ligands, sulfate anions, and adenine nucleobases. The sum of both types of sup...
Munibe Antropologia-Arkeologia, 2014
Although techniques for the characterisation of archaeological material enjoy a long tradition in... more Although techniques for the characterisation of archaeological material enjoy a long tradition in Europe, they have been less influential in Spain, particularly in the Cantabrian region. This may be one reason why, in this region, the traditional approach to the study of prehistoric pottery has prevailed over the use of new methodologies, which require the application of technological (mineralogical, geochemical etc.) and functional analytical techniques (for example, gas chromatography) or the study of post-depositional alterations. However, an integral study of this kind of evidence is able not only to approach an understanding of ceramic assemblages but also to propose interpretative hypotheses contributing to the formulation and development of new research projects. In the present study, pottery is seen as a product within a sequence of operations transforming raw material into the final recipient. In this process, the final product may possess very different physical-chemical properties from the original material. In accordance with this approach, the technological, morphological and functional study of the pottery assemblage from Cueva 3167 in Seldesuto (Matienzo, Cantabria) applied different methods, from macroscopic description to techniques of mineralogical (petrography and X-ray diffraction) and functional characterisation (gas chromatography). The study succeeded in determining a series of characteristics of the storage urns, a pottery type widely documented in Cantabria from the third millennium cal BC. It covers such aspects as the raw materials used to make the urns, the way the fabric was prepared and the firing conditions and temperature, as well as the age determination of one of the urns and information about how the archaeological record formed. This site is located practically at the summit of the ridge between the valleys of Matienzo and Arredondo in eastern Cantabria, at 673m above sea level. It is a small cave where several groups of sherds were located in the first twelve metres of the passage, which is less than a metre high. The main concentration consisted of pottery fragments in situ, just as the recipient had been abandoned, upside down in the middle of the passage. The base of the vessel was not recovered, which may indicate that the urn had been placed in an inverted position because the base had already been lost. Macroscopic observation of the sherds determined that they belonged to a minimum of four recipients, differentiated by their technological, morphological and decorative traits. Thin section observation of the fabric revealed that it had been mostly tempered with grog between 0.5 and 1.5mm in size. X-ray Diffraction analysis showed the high proportion of illite in the clay fabric. The recipients were fired at a low temperature, possibly lower than 800ºC. The presence of idiomorphic quartz, epidotes and even gypsum in one of the samples suggests that the raw materials were related to Triassic deposits, the nearest of which are located several kilometres from the cave site. A thermoluminescence determination established a chronology of 2832-1820 BC for the main urn, which is coherent with the ages obtained for similar vessels in the same area. RESUMEN Los estudios tecnológicos de manufacturas cerámicas prehistóricas constituyen una clara excepción dentro del marco general de la investigación en la región a pesar de su larga trayectoria en la investigación arqueológica europea. Sin embargo, el estudio integral de este tipo de evidencias permite no sólo realizar una aproximación a los conjuntos cerámicos sino también proponer hipótesis interpretativas que contribuyan al planteamiento y desarrollo de nuevos proyectos de investigación. En este artículo se presenta el estudio tecnológico, morfológico y funcional del conjunto cerámico procedente de la cueva 3167 de Seldesuto (Matienzo, Cantabria), en el cual se han aplicado distintas aproximaciones que abarcan desde un análisis macroscópico a las técnicas de caracterización mineralógicas (petrografía y difracción de rayos X). El análisis realizado nos ha permitido reconocer una serie de características de los recipientes tipo "orza" ampliamente documentados en el ámbito de Cantabria desde el III milenio cal BC. Se apuntan aspectos relacionados con las materias primas empleadas en su elaboración, el método de preparación de la pasta, las condiciones y temperaturas de cocción, así como los resultados obtenidos de la datación directa del recipiente cerámico y la información sobre la formación del depósito arqueológico.
Journal of Materials Chemistry C, 2015
The onset of the exchange bias effect in air-oxidized Ni@NiO nanoparticles is mainly driven by th... more The onset of the exchange bias effect in air-oxidized Ni@NiO nanoparticles is mainly driven by the properties of the magnetically disordered NiO shell, and less dependent on the size of the metallic Ni core.
Inorganic chemistry, Jan 18, 2014
We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays ... more We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays a three-dimensional (3D) magnetic ordering below the Néel temperature, TN = 7.7 K. In this material, called Dimim[FeBr4], an exhaustive and systematic study involving structural and physical characterization (synchrotron X-ray, neutron powder diffraction, direct current and alternating current magnetic susceptibility, magnetization, heat capacity, Raman and Mössbauer measurements) as well as first-principles analysis (density functional theory (DFT) simulation) was performed. The crystal structure, solved by Patterson-function direct methods, reveals a monoclinic phase (P21 symmetry) at room temperature with a = 6.745(3) Å, b = 14.364(3) Å, c = 6.759(3) Å, and β = 90.80(2)°. Its framework, projected along the b direction, is characterized by layers of cations [Dimim](+) and anions [FeBr4](-) that change the orientation from layer to layer, with Fe···Fe distances larger than 6.7 Å. Magnet...
Trabajos de Prehistoria, 2012
La tecnología cerámica de los niveles IV y III en el yacimiento de Kobaederra (Cortézubi, Bizkaia... more La tecnología cerámica de los niveles IV y III en el yacimiento de Kobaederra (Cortézubi, Bizkaia). Aprovisionamiento y modificación de las materias primas Pottery technology of levels IV and III in Kobaederra site (Cortézubi, Bizkaia). Supply and modifi cation of raw materials Miriam Cubas (*) Manuel García-Heras (**
![Research paper thumbnail of Pressure Effects on Emim[FeCl4], a Magnetic Ionic Liquid with Three-Dimensional Magnetic Ordering](https://attachments.academia-assets.com/98939601/thumbnails/1.jpg)
](The Journal of Physical Chemistry B, 2013
Physical Review B, 2012
Combining different experimental techniques, investigations in hexagonal P 6 3 /mmc Er 2 Fe 17 sh... more Combining different experimental techniques, investigations in hexagonal P 6 3 /mmc Er 2 Fe 17 show remarkable magnetovolume anomalies below the Curie temperature, T C. The spontaneous magnetostriction reaches 1.6 × 10 −2 at 5 K and falls to zero well above T C , owing to short-range magnetic correlations. Moreover, Er 2 Fe 17 exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy S M , and adiabatic temperature T ad changes [ S M ∼ −4.7 J(kgK) −1 and T ad ∼ 2.5 K near the T C , and S M ∼ 1.3 J(kgK) −1 and T ad ∼ −0.6 K at 40 K for H = 80 kOe, respectively, determined from magnetization measurements]. The existence of an inverse MCE seems to be related to a crystalline electric field-level crossover in the Er sublattice and the ferrimagnetic arrangement between the magnetic moments of the Er and Fe sublattice. The main trends found experimentally for the temperature dependence of S M and T ad as well as for the atomic magnetic moments are qualitatively well described considering a mean-field Hamiltonian that incorporates both crystalline electric field and exchange interactions. S M (T) and T ad (T) curves are essentially zero at ∼150 K, the temperature where the transition from direct to inverse MCE occurs. A possible interplay between the MCE and the magnetovolume anomalies is also discussed.
![Research paper thumbnail of Ammonium–cobalt–nickel phosphates, NH4[Co1−xNixPO4]·H2O](https://attachments.academia-assets.com/98939603/thumbnails/1.jpg)
](Journal of Solid State Chemistry, 2013
Journal of Physics: Conference Series, 2010
The isostructural Co1.5Cu0.5(OH)(XO4) (X = P, As) phases have been prepared from hydrothermal syn... more The isostructural Co1.5Cu0.5(OH)(XO4) (X = P, As) phases have been prepared from hydrothermal synthesis and characterized from powder X-ray diffraction. The structure consists of a three-dimensional framework in which M(1)O5-trigonal bipyramid dimers and M(2)O6-octahedral chains M = (Cu and Co) are simultaneously present. Magnetization measurements of Co1.5Cu0.5(OH)(PO4) show the presence of one maxima at ca. 60 K attributed to a
Chemical Engineering Journal, 2021
The slow kinetics in the photocatalytic reduction of CO2, as well as the low quantum efficiencies... more The slow kinetics in the photocatalytic reduction of CO2, as well as the low quantum efficiencies achieved, directly related to the photocatalyst and reactor configuration applied, limit the widespread use of this technology. In light of this, the main objective of this work is to evaluate the continuous photocatalytic conversion of CO2 into methanol in an optofluidic microreactor (with enhanced mass transport, large volume/active area ratio and uniform light distribution) using Cu nanoparticles synthesized in the hydrophilic 3-methyl-n-butylimidazolium tetrafluoroborate (BMIm.BF4) ionic liquid and embedded in TiO2 (P25). The ionic liquid not only acts as a template to control the size of the nanoparticles but also as a stabilizing agent. The analysis includes the effect of structural parameters of the photoactive layer such as Cu content (from 0.8 to 6.8 wt.%) and photocatalyst loading (0.5-3 mg•cm-2), as well as operating variables such as UV and visible light intensities (2.5-10 mW•cm-2) and cell configuration (i.e. one or two compartments). The maximum methanol yield reached from the continuous transformation of CO2 is r = 230.3 µmol•g-1 •h-1 at 2 wt.% Cu content, photocatalyst loading of 2 mg•cm-2 , UV light intensity of 10 mW•cm-2 and a two-compartment microreactor configuration. This result outperforms the values previously reported for Cu/TiO2-based systems using optofluidic microreactors, as well as most of those in common CO2 photoreactors.
Journal of Molecular Liquids, 2021
Abstract A new imidazolium-based halometallate complex with formula (trimim)[FeBr4] (trimim: 1,2,... more Abstract A new imidazolium-based halometallate complex with formula (trimim)[FeBr4] (trimim: 1,2,3-trimethylimidazolium) has been synthesized and characterized as a function of the temperature. The structural phase transitions, magnetic properties and magnetic structure of this compound have been thoroughly studied. The crystal structure evolution from 1.8 to 400 K has been investigated by a combination of synchrotron X-ray and neutron powder diffraction, as well as single crystal X-ray and neutron diffraction. Four different phases were found: phase I, from 400 to 350 K, with the orthorhombic Cmc21 space group; phase II, from 350 to 160 K, which was modelled with the monoclinic P21/m space group; and phase III, stable down to 13 K and showing the monoclinic Cm space group. The transition from phase III to II involves the appearance of disorder in the organic cations. Magnetometry measurements indicate a long-range magnetic order below 13 K, which was confirmed by single crystal and powder neutron X-ray diffraction analyses. The occurrence of new reflections that were not possible to index with the phase III unit cell suggests a symmetry breaking, giving rise to the phase IV. A joint refinement (single-crystal and powder data) revealed that the latter phase exhibits the magnetic Shubnikov Ccc space group. This model consists of a strictly antiferromagnetic structure with ferromagnetic interactions within the unit cell, which is compatible with the magnetometry results.
RSC Advances, 2020
Correction for ‘Crystal structure, magneto-structural correlation, thermal and electrical studies... more Correction for ‘Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]’ by Palmerina González-Izquierdo et al., RSC Adv., 2020, 10, 11200–11209. DOI: 10.1039/D0RA00245C.
Journal of Physics: Materials, 2019
A thorough characterization of the title compound, (dimim)2[Fe2Cl6(μ-O)], consisting of a (μ-oxid... more A thorough characterization of the title compound, (dimim)2[Fe2Cl6(μ-O)], consisting of a (μ-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group P 1 ¯ (/α/β/γ)0 with modulation vector q = 0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (μ-oxido)-bridged binuclear iron(III) complex, ...
Applied Catalysis B: Environmental, 2019
The functionalization of silica-coated, magnetic Fe3O4 nanoparticles, with an ironcontaining ioni... more The functionalization of silica-coated, magnetic Fe3O4 nanoparticles, with an ironcontaining ionic liquid, allows for the synthesis of a Fe3O4@SiO2@(mim)[FeCl4] system that can be employed as a magnetically recoverable nanocatalyst. Herein, we present the use of Fe3O4@SiO2@(mim)[FeCl4] for the glycolysis of PET into BHET under conventional heating. The catalyst achieved nearly 100% yield and selectivity over twelve consecutive reaction cycles at 180 °C and was efficiently recovered without tedious work-up or purification processes. Additional analyses revealed that the amount of catalyst lost after each cycle was negligible and no trace of Fe was found in the purified BHET product.
ChemPlusChem, 2019
Supporting Information for this article is given via a link at the end of the document.
Physical chemistry chemical physics : PCCP, Jan 18, 2018
We report on a simple preparation of extremely small diameter (ca. 2 nm) Ni-Ir-based NPs using Ni... more We report on a simple preparation of extremely small diameter (ca. 2 nm) Ni-Ir-based NPs using Ni(COD)2 and [Ir(COD)OCH3]2 in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm·NTf2). The prepared NPs had either core-shell-like or alloy-like structures with the presence of Ni,Ir-oxides, depending on the synthetic approach. X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and magnetic measurements are combined to describe the influence of nanostructure on the magnetic behavior of these nanosystems. The present findings reveal that the alloy NPs display a disordered magnetic state, similar to a spin glass (SG)-like system (Tf = 7.2 K). Core-shell NPs are formed by a magnetically blocked/unblocked core with a magnetically disordered shell as deduced from the two magnetic responses peaking at TB = 75 K ...
CrystEngComm, 2017
The nucleophilic attack of a series of nucleobase derivatives on [(η6-p-cymene)RuCl(μ-Cl)]2 dinuc... more The nucleophilic attack of a series of nucleobase derivatives on [(η6-p-cymene)RuCl(μ-Cl)]2 dinuclear entity has yielded four mononuclear complexes with the general formula [Ru(η6-p-cymene)(L)Cl2], in which L stands for cytosine (1),...
Inorganic chemistry, Jan 13, 2016
The present work provides two new examples of supramolecular metal-organic frameworks consisting ... more The present work provides two new examples of supramolecular metal-organic frameworks consisting of three-dimensional extended noncovalent assemblies of wheel-shaped heptanuclear [Cu7(μ-H2O)6(μ3-OH)6(μ-adeninato-κN3:κN9)6](2+) entities. The heptanuclear entity consists of a central [Cu(OH)6](4-) core connected to six additional copper(II) metal centers in a radial and planar arrangement through the hydroxides. It generates a wheel-shaped entity in which water molecules and μ-κN3:κN9 adeninato ligands bridge the peripheral copper atoms. The magnetic characterization indicates the central copper(II) center is anti-ferromagnetically coupled to external copper(II) centers, which are ferromagnetically coupled among them leading to an S = 5/2 ground state. The packing of these entities is sustained by π-π stacking interactions between the adenine nucleobases and by hydrogen bonds established among the hydroxide ligands, sulfate anions, and adenine nucleobases. The sum of both types of sup...
Munibe Antropologia-Arkeologia, 2014
Although techniques for the characterisation of archaeological material enjoy a long tradition in... more Although techniques for the characterisation of archaeological material enjoy a long tradition in Europe, they have been less influential in Spain, particularly in the Cantabrian region. This may be one reason why, in this region, the traditional approach to the study of prehistoric pottery has prevailed over the use of new methodologies, which require the application of technological (mineralogical, geochemical etc.) and functional analytical techniques (for example, gas chromatography) or the study of post-depositional alterations. However, an integral study of this kind of evidence is able not only to approach an understanding of ceramic assemblages but also to propose interpretative hypotheses contributing to the formulation and development of new research projects. In the present study, pottery is seen as a product within a sequence of operations transforming raw material into the final recipient. In this process, the final product may possess very different physical-chemical properties from the original material. In accordance with this approach, the technological, morphological and functional study of the pottery assemblage from Cueva 3167 in Seldesuto (Matienzo, Cantabria) applied different methods, from macroscopic description to techniques of mineralogical (petrography and X-ray diffraction) and functional characterisation (gas chromatography). The study succeeded in determining a series of characteristics of the storage urns, a pottery type widely documented in Cantabria from the third millennium cal BC. It covers such aspects as the raw materials used to make the urns, the way the fabric was prepared and the firing conditions and temperature, as well as the age determination of one of the urns and information about how the archaeological record formed. This site is located practically at the summit of the ridge between the valleys of Matienzo and Arredondo in eastern Cantabria, at 673m above sea level. It is a small cave where several groups of sherds were located in the first twelve metres of the passage, which is less than a metre high. The main concentration consisted of pottery fragments in situ, just as the recipient had been abandoned, upside down in the middle of the passage. The base of the vessel was not recovered, which may indicate that the urn had been placed in an inverted position because the base had already been lost. Macroscopic observation of the sherds determined that they belonged to a minimum of four recipients, differentiated by their technological, morphological and decorative traits. Thin section observation of the fabric revealed that it had been mostly tempered with grog between 0.5 and 1.5mm in size. X-ray Diffraction analysis showed the high proportion of illite in the clay fabric. The recipients were fired at a low temperature, possibly lower than 800ºC. The presence of idiomorphic quartz, epidotes and even gypsum in one of the samples suggests that the raw materials were related to Triassic deposits, the nearest of which are located several kilometres from the cave site. A thermoluminescence determination established a chronology of 2832-1820 BC for the main urn, which is coherent with the ages obtained for similar vessels in the same area. RESUMEN Los estudios tecnológicos de manufacturas cerámicas prehistóricas constituyen una clara excepción dentro del marco general de la investigación en la región a pesar de su larga trayectoria en la investigación arqueológica europea. Sin embargo, el estudio integral de este tipo de evidencias permite no sólo realizar una aproximación a los conjuntos cerámicos sino también proponer hipótesis interpretativas que contribuyan al planteamiento y desarrollo de nuevos proyectos de investigación. En este artículo se presenta el estudio tecnológico, morfológico y funcional del conjunto cerámico procedente de la cueva 3167 de Seldesuto (Matienzo, Cantabria), en el cual se han aplicado distintas aproximaciones que abarcan desde un análisis macroscópico a las técnicas de caracterización mineralógicas (petrografía y difracción de rayos X). El análisis realizado nos ha permitido reconocer una serie de características de los recipientes tipo "orza" ampliamente documentados en el ámbito de Cantabria desde el III milenio cal BC. Se apuntan aspectos relacionados con las materias primas empleadas en su elaboración, el método de preparación de la pasta, las condiciones y temperaturas de cocción, así como los resultados obtenidos de la datación directa del recipiente cerámico y la información sobre la formación del depósito arqueológico.
Journal of Materials Chemistry C, 2015
The onset of the exchange bias effect in air-oxidized Ni@NiO nanoparticles is mainly driven by th... more The onset of the exchange bias effect in air-oxidized Ni@NiO nanoparticles is mainly driven by the properties of the magnetically disordered NiO shell, and less dependent on the size of the metallic Ni core.
Inorganic chemistry, Jan 18, 2014
We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays ... more We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays a three-dimensional (3D) magnetic ordering below the Néel temperature, TN = 7.7 K. In this material, called Dimim[FeBr4], an exhaustive and systematic study involving structural and physical characterization (synchrotron X-ray, neutron powder diffraction, direct current and alternating current magnetic susceptibility, magnetization, heat capacity, Raman and Mössbauer measurements) as well as first-principles analysis (density functional theory (DFT) simulation) was performed. The crystal structure, solved by Patterson-function direct methods, reveals a monoclinic phase (P21 symmetry) at room temperature with a = 6.745(3) Å, b = 14.364(3) Å, c = 6.759(3) Å, and β = 90.80(2)°. Its framework, projected along the b direction, is characterized by layers of cations [Dimim](+) and anions [FeBr4](-) that change the orientation from layer to layer, with Fe···Fe distances larger than 6.7 Å. Magnet...
Trabajos de Prehistoria, 2012
La tecnología cerámica de los niveles IV y III en el yacimiento de Kobaederra (Cortézubi, Bizkaia... more La tecnología cerámica de los niveles IV y III en el yacimiento de Kobaederra (Cortézubi, Bizkaia). Aprovisionamiento y modificación de las materias primas Pottery technology of levels IV and III in Kobaederra site (Cortézubi, Bizkaia). Supply and modifi cation of raw materials Miriam Cubas (*) Manuel García-Heras (**
The Journal of Physical Chemistry B, 2013
Physical Review B, 2012
Combining different experimental techniques, investigations in hexagonal P 6 3 /mmc Er 2 Fe 17 sh... more Combining different experimental techniques, investigations in hexagonal P 6 3 /mmc Er 2 Fe 17 show remarkable magnetovolume anomalies below the Curie temperature, T C. The spontaneous magnetostriction reaches 1.6 × 10 −2 at 5 K and falls to zero well above T C , owing to short-range magnetic correlations. Moreover, Er 2 Fe 17 exhibits direct and inverse magnetocaloric effects (MCE) with moderate isothermal magnetic entropy S M , and adiabatic temperature T ad changes [ S M ∼ −4.7 J(kgK) −1 and T ad ∼ 2.5 K near the T C , and S M ∼ 1.3 J(kgK) −1 and T ad ∼ −0.6 K at 40 K for H = 80 kOe, respectively, determined from magnetization measurements]. The existence of an inverse MCE seems to be related to a crystalline electric field-level crossover in the Er sublattice and the ferrimagnetic arrangement between the magnetic moments of the Er and Fe sublattice. The main trends found experimentally for the temperature dependence of S M and T ad as well as for the atomic magnetic moments are qualitatively well described considering a mean-field Hamiltonian that incorporates both crystalline electric field and exchange interactions. S M (T) and T ad (T) curves are essentially zero at ∼150 K, the temperature where the transition from direct to inverse MCE occurs. A possible interplay between the MCE and the magnetovolume anomalies is also discussed.
Journal of Solid State Chemistry, 2013
Journal of Physics: Conference Series, 2010
The isostructural Co1.5Cu0.5(OH)(XO4) (X = P, As) phases have been prepared from hydrothermal syn... more The isostructural Co1.5Cu0.5(OH)(XO4) (X = P, As) phases have been prepared from hydrothermal synthesis and characterized from powder X-ray diffraction. The structure consists of a three-dimensional framework in which M(1)O5-trigonal bipyramid dimers and M(2)O6-octahedral chains M = (Cu and Co) are simultaneously present. Magnetization measurements of Co1.5Cu0.5(OH)(PO4) show the presence of one maxima at ca. 60 K attributed to a