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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. European Commission RYC-2013-12437

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. Fondo Europeo de Desarrollo Regional (FEDER) y Ministerio de Ciencia e Innovación español (Programa Ramón y Cajal)-RYC-2013-12437

[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., Este trabajo ha sido realizado con cargo al proyecto MCYT MAT2002-02549, financiado en parte con fondos FEDER.

5 páginas, 8 figuras, 2 tablas., 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., This work was financially supported by the National Plan projects MAT2006-01783 and MAT2006-04911.