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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

The mechanochemical process denoted as a mechanically induced self-sustaining reaction was successfully applied in obtaining Mn-doped ZnS samples with Mn content between 0 and 5 mol%. The process consists in milling Zn/Mn/S powder elemental mixtures with the appropriate stoichiometry, which promotes after approximately 80 min the induction of a combustion reaction. The doping level was properly adjusted by controlling the atomic ratio of the starting mixture. A complete characterization of samples was carried out, including X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, diffuse reflectance UV–Vis spectroscopy and emission and excitation photoluminescence measurements. A wurtzite structure, in which Mn2+ replaces Zn2+, was obtained with a nanometric character. The photoluminescence of samples showed the characteristic Mn2+ 4T1–6A1 emission that was highly dependent on the doping level. The maximum luminescence efficiency through the ZnS excitation was found for a doping value of 1 mol%. The photoluminescence showed virtually no contribution from the host emission, which confirmed that samples were properly doped.

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.

The complete ZnSxSe1−x solid solution was successfully obtained by the mechanochemical process denoted as a mechanically induced self-sustaining reaction. Excellent control of the chemical stoichiometry of the solid solution was possible by adjusting the atomic ratio of the starting Zn/S/Se elemental mixture subjected to milling. A mixture of both wurtzite-2H (hexagonal) and zinc blende (cubic) structures was always obtained, although for a similar milling time the proportion of the zinc blende structure increased with the Se content in the solid solution. However, wurtzite was the major phase for S-rich compositions when milling was stopped just after ignition. It was demonstrated that milling induces the wurtzite-to-zinc blende phase transition. The 8H hexagonal polytype was also observed in samples subjected to long milling times. Variation of the lattice parameters for both structures with the x value in the solid solution presented an excellent linearity, confirming the validity of Vegard’s law. However, variation of the band-gap energy (Eg) with x was not perfectly linear, and a small bowing parameter of 0.34 was obtained. It was possible to tune the Eg value between those of the end members of the solid solution in a continuous manner by adjusting the stoichiometry of the solid solution. The morphology and crystalline domain size can also be controlled by adjusting, in this case, the postignition milling time of the mechanochemical process.

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.

The identification of archaeological amber has been used in Iberian prehistory to evidence long-distance exchanges and engage Iberia in networks that connect western Europe with central and northern Europe, the emergence of social complexity, and the consolidation of trade networks. However, until now, no comprehensive analytical study of the Iberian amber has been produced to support any of the interpretive models currently in use. This paper approaches the analysis of Iberian Peninsula amber artefacts by considering their provenance (based on FTIR characterization), chronology, and spatial relationship with other exotica. Our work increases the number of analyzed artefacts to 156 (24%), out of the c. 647 currently known for the Iberian Peninsula. Based on these new data and a review of Murillo-Barroso and Martinón-Torres (2012), this overview outlines amber consumption patterns from the 6th to 2nd millennia BCE and demonstrates long-distance amber exchange connecting Iberia with the Mediterranean region from the Neolithic period onwards.

El objeto de la invención es una composición que contiene como principio activo ácido monocloroacético (MCA), en disolución con etanol (50% en volumen), preparado según un procedimiento que se describe, empleado para el tratamiento químico sistemático de la verruga plantar (papilomavirus humano plantar), sin cirugía, produciendo su cauterización química.

High energy planetary ball milling has been used to synthesize pseudo-cubic highly-pure LaGaO in one hour from its oxide components in an air atmosphere. Calcination at different temperatures led to the crystallization of lanthanum gallate in an orthorhombic structure with its local lanthanum coordination number environment changing from 12 to 7 when the temperature was increased. This change was attributed to the thermal expansion of the Ga-O bonds that varied non-monotonically inducing GaO tilting. Rietveld analysis, Raman spectroscopy, and transmission electron microscopy were used to elucidate the LaGaO structures at different temperatures.

El objeto de la invención es una composición que contiene como principio activo ácido monocloroacético (MCA), en disolución con etanol (50% en volumen), preparado según un procedimiento que se describe, empleado para el tratamiento químico sistemático de la verruga plantar (papilomavirus humano plantar), sin cirugía, produciendo su cauterización química.

Cermets based on Ti(C,N) have interesting properties, such as high wear resistance, high chemical stability and good mechanical strength at high temperature, but to become a viable alternative to cemented carbides, the fracture toughness and damage tolerance must be significantly improved. Complete solid-solution cermets (CSCs) have been proposed to further improve the mechanical properties of these materials. However, to develop this family of cermets with a high level of quality and reliability, using pre-fabricated complex carbonitrides is necessary instead of unalloyed mixtures as the raw ceramic material. A mechanochemical process called mechanically induced self-sustaining reaction (MSR) is suitable to obtain these complex carbonitrides with high stoichiometric control. On the other hand, high entropy alloys (HEAs), which can also be obtained by mechanochemical processes, are a good candidate to replace the current binder phase in cermets because they exhibit high strength and ductility at high temperature and good resistance to both wear and corrosion. In this work, a new family of CSCs based on (Ti,Ta,Nb)CxN1 − x with HEAs belonging to the Fe-Co-Ni-Cr-Mn-V system as the binder phase is developed by mechanochemical processes. With only two constituent phases, these cermets have a simple microstructure but a high compositional complexity because both the ceramic and binder phases are complex solid solutions with at least five components.

Beads and pendants from the Castillejo del Bonete (Terrinches, Ciudad Real) and Cerro Ortega (Villanueva de la Fuente, Ciudad Real) burials were analysed using XRD, micro-Raman and XRF in order to contribute to the current distribution map of green bead body ornament pieces on the Iberian Peninsula which, so far, remain undetailed for many regions. XRD, micro-Raman and XRF analyses showed that most of the beads from Castillejo del Bonete (Late 3rd millennium cal. BC) were made from variscite or green phyllosilicates, while Cerro Ortega's (Late 4th millennium cal. BC) beads were made out of fossil wood or Clinochlore. Significantly enough, while XRD pointed to variscite as the main crystallo-graphic phase, the elemental composition did not match any elemental compositions of known and characterised sources, thus suggesting an unknown south-eastern source or an extra-peninsular origin of these ornamental pieces.

The synthesis of (Ti1-xZrx)B2-Al2O3, (Ti1-xHfx)B2-Al2O3 and (Zr1-xHfx)B2-Al2O3 (x=0, 0.5 and 1) powder nanocomposites via a mechanochemical method using TiO2, ZrO2, HfO2, HBO2 and Al as the raw materials was investigated. The formation of the nanocomposites proceeds via a mechanically-induced self-sustaining reaction (MSR) process that involves several simultaneous reactions. The aluminothermic reductions of the TMO2 and HBO2 produce Al2O3 and transition metal and boron elements, which in turn react to yield the diboride phase. The ignition of the complex combustion reaction occurred after a short milling time (15-30min), instantly transforming most of the reactants into products. The sample composition was marked by the stoichiometry of the combustion reaction, and the resulting nanocomposites were analysed using XRD, ED, SEM, TEM and EDX techniques. The X-ray results confirmed the biphasic character of the prepared composite powder (TMB2 and Al2O3 structures); minor amounts of the Zr and Hf oxides were also observed. The achieved microstructure was characterised by the agglomeration of Al2O3 nanocrystallites and diboride crystals with a diffraction domain size ranging between 100 and 300nm

The synthesis of (Ti1-xZrx)B2-Al2O3, (Ti1-xHfx)B2-Al2O3 and (Zr1-xHfx)B2-Al2O3 (x=0, 0.5 and 1) powder nanocomposites via a mechanochemical method using TiO2, ZrO2, HfO2, HBO2 and Al as the raw materials was investigated. The formation of the nanocomposites proceeds via a mechanically-induced self-sustaining reaction (MSR) process that involves several simultaneous reactions. The aluminothermic reductions of the TMO2 and HBO2 produce Al2O3 and transition metal and boron elements, which in turn react to yield the diboride phase. The ignition of the complex combustion reaction occurred after a short milling time (15-30min), instantly transforming most of the reactants into products. The sample composition was marked by the stoichiometry of the combustion reaction, and the resulting nanocomposites were analysed using XRD, ED, SEM, TEM and EDX techniques. The X-ray results confirmed the biphasic character of the prepared composite powder (TMB2 and Al2O3 structures); minor amounts of the Zr and Hf oxides were also observed. The achieved microstructure was characterised by the agglomeration of Al2O3 nanocrystallites and diboride crystals with a diffraction domain size ranging between 100 and 300nm. © 2014 Elsevier B.V.

TiC xN 1-x-15 wt.%Co cermets were obtained by a mechanically induced self-sustaining reaction (MSR) and sintered by spark plasma sintering (SPS) technique at different temperatures (1200-1400°C) for 1 min in vacuum under a uniaxial load of 80 MPa. The evolution of microstructure and mechanical properties was investigated. SPS allowed high densification with limited grain growth at a relatively low temperature. Material sintered at 1300°C showed a good combination of mechanical properties with Vickers hardness of 17.1 ± 0.5 GPa, fracture toughness of 5.51 ± 0.29 MPa m 1/2 and bending strength of 904 ± 12 MPa. Lower sintering temperature resulted in a decrease in bending strength due to poor cohesion between the ceramic and binder phases. An increase in sintering temperature would allow tailoring the cermet microstructure and, therefore, adjusting the Vickers hardness/fracture toughness relation. Crown Copyright © 2012 Published by Elsevier Ltd. All rights reserved.

The complete range of Ti5Si3–Ti5Ge3 solid solutions was synthesised from elemental mixtures of Ti, Si, and Ge under an inert atmosphere via mechanically induced self-sustaining reactions (MSR). The stoichiometry of Ti5Si3−xGex solid solutions was controlled by adjusting the Si/Ge ratio of the initial mixture. The chemical composition and lattice parameters of the materials confirmed that Ti5Si3–Ti5Ge3 solid solutions with good chemical homogeneity could be produced via MSR.

The plastic flow of TiCxN1-x-CoTi cermets has been investigated by uniaxial compression tests carried out in argon atmosphere at temperatures between 1100 and 1200°C. Two different cermets, with 5wt.% W or WC content as sintering additives, have been explored to assess the influence of the sintering additives on creep. The microstructural observations of deformed samples and the mechanical results indicate that the hard phase (ceramic grains) controls the plastic deformation. The stress exponent changes from 1 to 2 with increasing strain rate, suggesting a transition in the deformation mechanism from diffusional creep to grain boundary sliding; both with similar activation energy values of about 400kJ/mol. This value of activation energy agrees with C diffusion in the carbonitride grains as the strain rate controlling mechanism. © 2010 Elsevier Ltd.

High-purity, nanometer-sized titanium carbonitride powders, TiyNb1−yCxN1−x, were obtained with a mechanically induced self-sustaining reaction (MSR) in a high-energy planetary ball mill from a mixture of titanium and different carbon precursors under a nitrogen atmosphere. A promising method for developing dense TiCxN1−x materials is the coupling of MSR with the spark plasma sintering (SPS) technique. The powders were sintered at different temperatures to provide a completely dense monolithic ceramic (>99% theoretical density). In this work, the influence of the carbon precursor and SPS treatment on the material microstructures were studied, and the main mechanical properties of the end material were evaluated.

[EN]: In this work high purity and nanometer character titanium carbonitride TiCxN1-x powders were obtained by mechanically induced self sustaining reaction (MSR) in a high-energy planetary ball mill, from a mixture of titanium with graphite or carbon nanofiber (CNFs) in a nitrogen atmosphere. A promising method for developing these materials is the coupling of the MSR with SPS sintering technique. The product is sintered at 1400 ºC and 1700 ºC, obtaining a completely dense monolithic ceramic (>99% t.d). In this work, the influence of SPS treatment and carbon precursor on material microstructures was studied and the main mechanical properties of the end material were evaluated., [ES]: En el presente trabajo se han obtenido carbonitruros de titanio TiCxN1-x de alta pureza y con carácter nanométrico, por molienda reactiva (MSR) de alta energía en un molino planetario, a partir de la mezcla de titanio con grafito o nanofibras de carbono (CNFs) en una atmósfera de nitrógeno. Una metodología prometedora para el desarrollo de estos materiales consiste en el acoplamiento de la técnica MSR con el sinterizado por SPS. El producto obtenido se ha sinterizado a 1400 ºC y 1700 ºC, obteniéndose una cerámica monolítica totalmente densa (>99% d.t). En este trabajo se analizan las distintas microestructuras obtenidas en función del precursor de carbono y el tratamiento de SPS, evaluando las principales propiedades mecánicas de los materiales resultantes.

The creep behavior of a TiCxN1-x-Co-Mo2C cermet has been investigated at temperatures between 1100-1200°C in an inert atmosphere to assess the one step mechanically induced self-sustaining reaction synthesis and pressureless sintering process, and the influence of the Mo 2C additive in the high temperature mechanical properties of this cermet. The samples deform plastically at the chosen temperatures, and values of the stress exponent (n=1.7±0.6) and activation energy (Q= 4.3±0.5 eV) have been estimated from uniaxial compression tests. No significant grain growth has been detected after deformation. The reproducibility of the creep tests compared to other compositions indicates that the Mo2C addition contributes to increase notably the resistance to high temperature oxidation of the samples, so that the plastic behavior is not affected by oxidation when deformation experiments are performed in an inert atmosphere.

The low temperature of decomposition of some calcium carbonates and the bending of the TG curves of hydrated cement between 500 and 800°C suggested the presence of some complex compound(s), which needed complementary investigation (XRD, TG). Stepwise transformation of portlandite (and/or lime) into calcium carbonate, with intermediate steps of calcium carbonate hydroxide hydrates (CCH-1 to CCH-5), was indicated by the previous study of two OPC. This was checked here on four cements ground for t g=15, 20, 25 and 30 min and hydrated either in water vapour, successively at RH=1.0, 0.95 and 0.5 for 2 weeks each (WR1, WR2 and WR3, respectively) or as mortars in liquid water (1m), followed by WR as above. The d[001] spacing of portlandite was confirmed to vary: here between the lowest and the highest standard values. The diffractograms of n=32 different samples were analyzed for presence of standard CCH peaks, generally slightly displaced. These were: CCH-1 [Ca 3(CO3)2(OH)2]: N=11 peaks, of three different d[hkl] spacings, CCH-2 [Ca6(CO2.65) 2(OH657)7(H2O)2]: N=10 for two d[hkl], CCH-3 [Ca3(CO3)2(OH) 2•1.5H2O]: N=14 for five d[hkl], CCH-4, ikaite [CaCO3(H2O)6]: N=13 for six d[hkl], CCH-5[CaCO3(H2O)]: N=15 for five d[hkl]. Thus the most probable is the presence of the last three. The stepwise transformation of Ca(OH)2 into CaCO3 was confirmed: portlandite (varying d[001])→CCH-1→CCH-2→CCH-3→CCH-4→CCH-5→CaCO 3 The content of CCH was the highest at t gr=15 min, decreasing down to t gr=25 min and increasing slightly at 30 min, as inferred from the number of the peaks observed. After cement powder hydration at RH=1.0 (WR1) peak number increased gradually from CCH-1 to CCH-5, whereas in the hydrated mortar (1m) the peak number decreased from CCH-1 to CCH-5, indicating the respective progress of the carbonation reaction. © Springer-Verlag 2007.

[ES] En este trabajo se presentan y discuten los resultados de la caracterización arqueométrica realizada sobre un conjunto representativo de figurillas cerámicas del Clásico Tardío procedentes de las excavaciones arqueológicas efectuadas en la ciudad maya de Calakmul (Campeche, México). Los objetivos principales han sido recabar información sobre la tecnología de manufactura de estas cerámicas y evaluar su posible procedencia. La caracterización arqueométrica se ha llevado a cabo mediante las siguientes técnicas complementarias: microscopía óptica convencional (MO), difracción de rayos X (DRX) de polvo, espectroscopía infrarroja por Transformada de Fourier (FT-IR) y fluorescencia de rayos X (FRX). Con el fin de aislar grupos cerámicos con un perfil químico similar, los datos obtenidos con FRX se han analizado también con técnicas exploratorias de análisis estadístico multivariante. Los resultados indican que la mayoría de las figurillas se manufacturaron localmente con una materia prima arcillosa rica en carbonato de calcio (calcita). También se ha identificado un pequeño grupo de cerámicas rico en carbonatos mixtos de calcio y magnesio (dolomita), que podría ser foráneo o procedente de otra zona de la región de Calakmul. Estos datos sugieren que la producción de figurillas cerámicas pudo estar asociada a talleres ligados al monopolio sobre la producción cerámica que el poder centralizado de la ciudad de Calakmul ejerció en este período., [EN] The results derived from an archaeometric characterization study undertaken on a representative ensemble of Late Classic ceramic figurines coming from the archaeological field work carried out in the Mayan town of Calakmul (Campeche, México) are reported and discussed in this paper. The main goals of the research were to gather some information on the technology of manufacture of these ceramics and provide some insights into their probable provenance. The archaeometric characterization was accomplished through the following complementary techniques: conventional optical microscopy (OM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray fluorescence (XRF). In order to isolate ceramic groups with a similar chemical profile, XRF data were also analyzed by exploratory multivariate statistical techniques. The resulting data indicate that most of the figurines were locally manufactured from a calcium carbonate (calcite)-rich clay raw material. A small ceramic group containing mixed calcium and magnesium carbonates (dolomite), which could be foreign or from other area of the Calakmul region, was also identified. These data suggest that the production of ceramic figurines could be associated to workshops linked to the monopoly on ceramic production performed by the centralized power of the town of Calakmul during this period.

Desde su creación en el año 1986, en el Instituto de Ciencia de Materiales de Sevilla se viene desarrollando una línea de investigación denominada “síntesis y preparación de nuevos materiales a partir de silicatos naturales”. Dentro de este campo específico se enmarca la presente Tesis Doctoral, en la que se realiza un estudio sobre la síntesis de materiales cerámicos avanzados mediante la reducción carbotérmica de vermiculita.Se consideranmateriales cerámicos avanzados aquellos compuestos inorgánicos policristalinos, no metálicos, consolidados mediante tratamiento térmico a alta temperatura y que poseen excelentes propiedades mecánicas, eléctricas, magnéticas, ópticas, o bien, excepcional resistencia a altas temperaturas y ambientes corrosivos.Lareduccióncarbotérmica es uno de los métodos de preparación de materiales cerámicos avanzados más utilizados en la industria y consiste en el tratamiento de un compuesto oxidado a alta temperatura, generalmente entre 1300 ºC y 1700 ºC, en una atmósfera controlada y en presencia de un reductor. Existen numerosos ejemplos en la bibliografía en los que se utiliza este métodos, utilizando como materiales primas sílice, alúmina o silicatos.La presente Tesis Doctoral tiene como objetivo el estudio del proceso de la reducción carbotérmica devermiculita, la cual no se había usado con anterioridad en este tipo de reacciones.Teniendo en cuenta la composición de la vermiculita, como se ha mencionado formada por silicio, aluminio, magnesio, hierro, oxígeno e hidrógeno, los productos que cabe esperar se obtengan al final del proceso son:nitruros de silicio, nitruros de aluminio, oxinitruros de silicio y aluminio (sialones) y carburos de silicio. De estos compuestos, así como de la vermiculita y del poliacrilonitrilo, se ha realizado una minuciosa revisión bibliográfica, con anterioridad al desarrollo del trabajo experimental, con el propósito de tener una base a partir de la cual avanzar en las investigaciones objeto de la Tesis.De acuer

Non destructive physical methods have been applied to the characterization of granites. Reflectance spectra, recorder using the FT_IR, microscope, was used to identify the individual minerals and its distrbution in the surface. The grazing-incide X-Ray diffraction allows the analysis of very thin layers of the materials, being applied to the study of the first steps of the alteration propcesses.