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Pascual L.,Institute Catalisis y Petroquimica CSIC
Minerals | Year: 2016

Although there are many studies on biomineralization processes, most of them focus on the role of prokaryotes. As fungi play an important role in different geological and biogeochemical processes, it was considered of interest to evaluate their role in a natural extreme acidic environment, Río Tinto, which has a high level of fungal diversity and a high concentration of metals. In this work we report, for the first time, the generation of iron oxyhydroxide minerals by the fungal community in a specific location of the Tinto basin. Using Transmission Electron Microscopy (TEM) and High Angle Angular Dark Field coupled with Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy-Dispersive X-ray Spectroscopy (EDX), we observed fungal structures involved in the formation of iron oxyhydroxide minerals in mineralized sediment samples from the Río Tinto basin. Although Río Tinto waters are supersaturated in these minerals, they do not precipitate due to their slow precipitation kinetics. The presence of fungi, which simply provide charged surfaces for metal binding, favors the precipitation of Fe oxyhydroxides by overcoming these kinetic barriers. These results prove that the fungal community of Río Tinto participates very actively in the geochemical processes that take place there. © 2016 by the authors; licensee MDPI, Basel, Switzerland.


Mascaraque N.,CSIC - Institute of Ceramics and Glass | Fierro J.L.G.,Institute Catalisis y Petroquimica CSIC | Munoz F.,CSIC - Institute of Ceramics and Glass | Duran A.,CSIC - Institute of Ceramics and Glass | And 6 more authors.
Journal of Materials Research | Year: 2015

Lithium thio-phosphorus oxynitride glasses, LiPOSN, have been prepared by mechanical milling process from the mixture of Li2S and LiPON glass. The anionic substitution of oxygen by sulphur and nitrogen in the phosphate glass structure has been confirmed by 1D 31P solid state nuclear magnetic resonance and x-ray photoelectron spectroscopy. The study of thermal and electrical properties reveals a decrease in the glass transition temperature, likely due to the depolymerization of glass network by the decrease of bridging oxygens and sulphurs, along with a sharp increase in the ionic conductivity when lithium sulphide is incorporated into the oxynitride glasses. The improvement of chemical durability by the introduction of nitrogen, together with the increase in ionic conductivity up to values closed to the value of commercial LiPON thin film electrolyte, suggests that these LiPOSN glasses could be good candidates as solid electrolytes for lithium microbatteries. © Materials Research Society 2015.


Mascaraque N.,CSIC - Institute of Ceramics and Glass | Takebe H.,Ehime University | Tricot G.,Lille University of Science and Technology | Fierro J.L.G.,Institute Catalisis y Petroquimica CSIC | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2014

For the first time, a thio-phosphorus oxynitride glass containing nitrogen and sulfur, LiPOSN, has been prepared by a melting process in two steps and its manipulation is possible in air without any decomposition. The anionic substitution of oxygen by sulfur and nitrogen in the phosphate glass structure has been confirmed by 1D 31P solid state NMR and XPS. The 2D 31P DQ-SQ experiment indicates that S bearing phosphate groups are integrated into the global phosphate network and do not form clusters. Through the study of the properties of this glass, it was verified a decrease of the glass transition temperature, due to the depolymerization of the phosphate network when lithium sulfide is introduced into the oxynitride glass, along with a pronounced increase of the ionic conductivity, that suggest that this glass can be considered as a new highly conductive and corrosion resistant glass electrolyte. © 2014 Elsevier B.V.


Mascaraque N.,CSIC - Institute of Ceramics and Glass | Fierro J.L.G.,Institute Catalisis y Petroquimica CSIC | Duran A.,CSIC - Institute of Ceramics and Glass | Munoz F.,CSIC - Institute of Ceramics and Glass
Solid State Ionics | Year: 2013

The influence of nitrogen in the mechanism of ionic conduction has been studied in lithium phosphorus oxynitride glasses with composition xLi 2O.(100 - x)P2O5 (x = 38-60 mol%). A correlation between glass structure and ionic conductivity has been established for explaining the conduction mechanism. The change of glass structure during nitridation has been studied as a function of lithium and nitrogen contents. Raman spectra confirm the increase of P2O7 4 - groups with increasing lithium and the presence of nitrogen, as also shown by X-Ray Photoelectron Spectroscopy. The O1s core-level XPS spectra allow determining the variation of the bridging (BO) to non-bridging (NBO) oxygen ratio, observing that its decrease is directly linked to an increase of ionic conductivity. The ionic conductivity of oxynitride glasses is higher than that of their parent phosphate glasses, although this increase also depends on the lithium content. Furthermore, it has been demonstrated that the influence of nitrogen is higher in glasses with smaller amount of lithium. These findings will contribute to the design of glasses with lower lithium contents and high ionic conductivity for their application as solid electrolytes in lithium rechargeable batteries. © 2013 Elsevier B.V.

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