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Fragipan is a compacted but non-cemented subsurface horizon, considered as a pedogenic horizon, but the mechanism of its formation is not well understood. The main hydro-consolidation hypothesis involves a collapse of soil structure when it is loaded and wet, resulting a reorganisation of pore space. Soils with fragipan never have been marked in Russian soil maps. In the South Karelia, located in Eastern Fennoscandia (34.50921 E and 61.33186 N, 110 m asl) we studied a soil profile of Albic Fragic Retisol (Cutanic), developed in the glacial till of Last Glaciation with flat subhorizontal topography under an aspen-spruce forest. The aim of this study was to demonstrate how the fragic horizon was formed in the Retisol located in South Karelia. Observations were made in each soil horizon using micromorphological method, particle size analysis and the study of mineralogical composition of clay fraction by X-ray diffraction. The analysis of the morphological description combined with the laboratory data have led us to the conclusion that the consolidation of the fragipan occurred after the textural differentiation of the profile, following the Atlantic Optimum, and does not depend on the presence of swelling clay minerals. The well-developed argic horizon was probably formed around 6000 years ago, under climatic conditions more favourable for clay illuviation than in present time. Fragipan is supposed to be developed during the Sub-Boreal cooling. [ABSTRACT FROM AUTHOR]

Neutron and X-ray powder diffraction have been used to investigate the differences between the crystal growth of ferrite magnetic nanoparticles (MFe2O4 with M = Mn, Fe, Co, Ni, Zn) by two methodologies: microwave radiation and thermal decomposition routes. Rietveld refinement has been used to extract the cationic distribution, the microstructure and magnetic information. Results for the nanoparticles produced by the two procedures evidence similar cationic distribution, microstructure and magnetic properties: complete cationic disorder for M = Mn and Co, crystal size around/below 10 nm etc. It is thus proven that microwave-assisted growth is a promising eco-friendly synthetic technique for the generation of high-quality nanocrystals with comparable structure and properties to those produced by the thermal methodology, even though the microwave route needs a shorter time and lower annealing temperature to obtain the final crystal nanoparticles. [ABSTRACT FROM AUTHOR]

A detailed analysis of the thermal decomposition of yttrium trifluoroacetate under different atmospheres is presented. Thermogravimetry, differential thermal analysis, and evolved gas analysis have been used for this in situ analysis. Solid residues at different stages have been characterized by means of X-ray diffraction, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The first decomposition stage (310 °C) is exothermic and involves the complete removal of carbon (organic part) and the formation of yttrium fluoride. This process is characterized by a fast mass loss rate. Afterwards, yttria (YO) is formed at 1200 °C through a slow process controlled by the out diffusion of fluorine that involves the formation of yttrium oxyfluoride as an intermediate. The evolution of the mass during the decomposition and the structure of the yttria particles is not affected by the presence of oxygen or water. However, when the oxygen (water) partial pressure is as low as 0.02% (<0.002%), the kinetics and final particle structure are strongly affected. [ABSTRACT FROM AUTHOR]

Valencianite has been described as a variety of K-feldspar (adularia) from La Valenciana mine, Guanajuato, Mexico, from which three samples were used for this study. We present new major and trace element analysis, X-ray powder diffraction with Rietveld refinement, and single-crystal 40Ar/39Ar ages of this classical mineral. A detailed review of major works on feldspars and relevant papers from adularia shows that the structure of this mineral has monoclinic and triclinic domains with variable degrees of Al/Si order that we have been only able to model by powder X-ray diffraction assuming the presence of monoclinic (~50%) plus triclinic (~50%) K-feldspar. The literature data show some extreme structural states for adularia obtained in the pre-Rietveld refinement era; these data are dubious and need to be reanalyzed. A triangular diagram using the relative development of {110}, {010} and {001} faces is proposed. The temperature of formation, the Na/K ratio, and the growth kinetics seem to be the main factors controlling the morphological changes in K-feldspar crystals. The geochemistry of valencianite shows an almost pure orthoclase composition, as is common in most adularia crystals, although compositions up to Or90Ab10 have been found. Measurement of thallium in adularia can be an exploration guide for ore deposits. The weighted mean of 15 40Ar/39Ar analyses of one valencianite from La Valenciana mine gave an age of 30.43 ± 0.27 Ma (2 standard deviations). It is discussed whether valencianite can be considered a new mineral. [ABSTRACT FROM AUTHOR]

Maya blue is a well-known pre-Hispanic pigment, composed of palygorskite or sepiolite and indigo blue, which was used by various Mesoamerican cultures for centuries. There has been limited research about its continued use during the Viceroyalty period; therefore, the sixteenth century is the perfect period through which to study the continuity of pre-Hispanic traditions. The fact that the indigenous people were active participants in the construction and decoration of convents makes their wall paintings a good sampling material. X-ray fluorescence (XRF), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed in samples of blue found in convents across Puebla, Tlaxcala and Morelos in order to identify whether the numerous hues of blue were achieved with Maya blue or with other pigments. We found no copper (Cu) or cobalt (Co) with the XRF, so several pigments, such as azurite, smalt or verdigris, were discarded. With SEM, we discovered that the micromorphology of certain blues was clearly needle-shaped, suggesting the presence of palygorskite or sepiolite. In addition, we found silicon (Si), magnesium (Mg) and aluminum (Al) by using energy-dispersive X-ray spectroscopy (EDS) in all blue samples, which also suggests the presence of these magnesium-rich clay minerals. With the XRD samples, we verified that the blues were produced with these two clay minerals, thus confirming that several wall paintings were manufactured with Maya blue. These findings confirm that this particular manmade pre-Hispanic pigment, Maya blue, was an important pigment prior to the Viceroyal period. [ABSTRACT FROM AUTHOR]

We report size-dependent strain in epitaxial gadolinium doped ceria nanoislands, which was determined by synchrotron x-ray diffraction. Reciprocal space sections of symmetric, (004) and asymmetric, (224) reflections are approximated by a model assuming size-dependent strain of the islands using real-space size distribution obtained by atomic force microscopy. We show that the islands smaller than 40 nm are subjected to a high level of lateral tensile strain and normal compression. The lateral to normal strain ratio determined from the reciprocal map analysis suggests that lateral tension is the primary stress generator, possibly due to oxygen vacancy ordering on the island-substrate interface. [ABSTRACT FROM AUTHOR]

The mineralogy of surface crusts and efflorescent salts of two old abandoned tailings (Xochula and Remedios) of the mining district of Taxco, Guerrero, was studied by short-wave infrared spectroscopy (SWIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The chemistry of the selected samples was studied with induced coupled plasma mass spectrometry (ICP–MS). Principal mineralogy is composed of hydrated sulfates of iron (di-trivalent), other less-soluble sulfates such as gypsum and jarosite, and oxides–hydroxides of iron, all of which are the result of the weathering of sulfides (mainly pyrite) accumulated in mining waste. Using quantitative X-ray diffraction (Rietveld method) and the spatial distribution of secondary minerals, two main zones (lateral and central) have been established in both tailings. The genetic model for their formation shows that the secondary iron minerals (sulfates, oxides, and hydroxides) in these deposits have been formed at least in three different stages, mainly by oxidation, dissolution, and precipitation processes in combination with dehydration and primary sulfides neutralization reactions. The chemical analyses of some salts confirm the presence of potentially toxic elements (PTE) in their structure and therefore indicate that the dissolution of the efflorescences in these deposits is a potential source of contamination during the wet season. [ABSTRACT FROM AUTHOR]

The detailed mineralogical, physical and chemical characterization of nine samples of imported cosmetic talc and of two samples of talc from currently non-productive Mexican ore deposits (Oaxaca and Puebla States) is presented. The imported cosmetic talc was classified into two groups, considering whether they are packed in the country of origin or in Mexico and considering their price. X-ray diffraction, infrared short wave, thermogravimetric analysis and scanning electron microscopy were used for mineralogical characterization. For the physical characterization, colorimetry and laser granulometry were used. The chemical composition (major, trace elements) was studied by ICP-MS. It was concluded that only the highest priced and imported in packaged form talcs meet the specific purity requirements for a talc of cosmetic type. The talcs that are packed in Mexico and the talc of the studied Mexican deposits present mineralogical and chemical impurities that make their use difficult in the manufacture of high-quality cosmetic talc. The low-price talc should not be sold as cosmetic talc, and the regulations in Mexico on this subject should be reviewed and updated. [ABSTRACT FROM AUTHOR]

The crystallization process and physical properties of different functional oxide thin films (Ce0.9Zr0.1O2-y, LaNiO3, Ba0.8Sr0.2TiO3, and La0.7Sr0.3MnO3) on single crystal substrates (Y2O3:ZrO2, LaAlO3, and SrTiO3) are studied by pulsed laser annealing (PLA). A Nd:YAG laser source (λ = 266 nm, 10 Hz and τ ∼ 3 ns) is employed to crystallize chemical solution deposited (CSD) amorphous/nanocrystalline films under atmospheric conditions. We provide new insight on the influence of photochemical and photothermal interactions on the epitaxial crystallization kinetics of oxide thin films during the transformation from amorphous/polycrystalline material (i.e., atomic diffusion, epitaxial growth rates, and activation energies of nucleation and crystallization). The epitaxial growth is investigated by varying the laser fluence and the applied number of pulses. The morphology, structure, and epitaxial evolution of films are evaluated by means of atomic force and transmission electron microscopies and X-ray diffraction. Highly epitaxial oriented films of 20-40 nm in thickness are obtained by PLA. The crystallization kinetics of laser treatments is determined to be orders of magnitude faster than thermal treatments with similar activation energies (1.5-4.1 eV), mainly due to the large temperature gradients inducing modified atomic diffusion mechanisms derived mainly from photothermal interactions, as well as a minor contribution of photochemical effects. The fast heating rates achieved by PLA also contribute to the fast epitaxial growth due to reduced coarsening of polycrystalline material. The measurement of the physical properties (electrical resistivity and magnetism) of laser processed CSD films has revealed significantly good functionalities, close to those of thermally grown films, but with much shorter processing times. [ABSTRACT FROM AUTHOR]