Structure of NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 glasses and glass-ceramics

The crystallization of iron-containing sodium silicate phases holds particular importance, both in the management high-level nuclear wastes and in geosciences. Here, we study three asquenched glasses and their heat-treated chemical analogues, NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 (with nominal stoichiometries from feldspathoid, pyroxene, and feldspar mineral groups – i.e., Si/Fe = 1, 2, and 3 respectively) – using a variety of techniques. Phase analyses revealed that as-quenched NaFeSiO4 cannot accommodate all Fe in the glass phase (some Fe crystallizes as Fe3O4), whereas as-quenched NaFeSi2O6 and NaFeSi3O8 form amorphous glasses upon quenching. NaFeSi2O6 glass is the only composition that crystallizes into its respective isochemical crystalline polymorph, i.e. aegirine, upon isothermal heat-treatment. As revealed by Mössbauer spectroscopy, iron is predominantly present as 4-coordinated Fe3+ in all glasses, though it is present as 6-coordinated Fe3+ in the aegirine crystals (NaFeSi2O6), as expected from crystallography. Thus, Fe can form the crystalline phases in which it is octahedrally coordinated, even though it is mostly tetrahedrally coordinated in the parent glasses. Thermal behavior, magnetic properties, iron redox state (including Fe K-edge X-ray absorption), and vibrational properties (Raman spectra) of the above compositions are discussed

HAEMATOLOGY Smear microscopy revision Smear microscopy revision: propositions by the GFHC

Abstract Despite the development of automated haematology analysers for reliable blood counts, examining blood smears under the microscope is still indispensable for confirming results when the data the analyser obtains are qualitatively or quantitatively abnormal. Although most criteria that lead to blood smear examination are widely recognised and used in laboratories, a multicentre survey indicates that they are still highly heterogeneous. To contribute to the harmonisation and standardisation of essential cellular haematology practice within the context of laboratory accreditation, the GFHC reviewed in detail the criteria used within the CBC to generate blood smears and has decided on a number of minimum recommendations. The conclusions presented in this article are based on a 'strong professional consensus', defining threshold values and various situations in which the blood smear review is desirable. They are presented as minimum recommendations for technical verification and biological validation. All laboratories are free to use more restrictive thresholds based on their patient populations

Local structural characterization for electrochemical insertion-extraction of lithium into CoO with X-ray absorption spectroscopy

Cobalt oxide is known to exhibit a large capacity as a negative electrode in lithium-ion batteries. Here, Co K-edge X-ray absorption spectroscopy (XAS) was used to investigate variations in the local structure during the first electrochemical cycle of the insertion-extraction of lithium into CoO. The XANES and EXAFS spectra in LiyCoO (y: lithium content) varied markedly with the lithium content. The initial insertion of lithium leads to the reduction of Co2+ in the pristine CoO to the reduced metallic Co-0 state. The systematic variations observed in intensities of the peaks corresponding to the 1s --> 3d and 1s --> 4p transitions indicate that the mole ratio of Co to Co-0 increases gradually with the electrochemical insertion of lithium ions. Insertion of lithium causes the local structure around the Co atoms to become asymmetric. The systematic decrease in the magnitude of the Fourier transform (FT) with increasing amount of inserted lithium is closely related to an increase in static disorder due to the presence of two phases: Co-0 clusters and CoO. The small-sized Co particles evolve gradually with a well-separated distribution in the Li2O matrix. In the successive extraction of lithium, the reduced Co particles return reversibly to the high-temperature cubic phase of CoOclose595