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Terbium orthoferrite (TbFeO3) perovskite demonstrates specific magnetic properties which are object of interest. Aggregated granular nanopowder of TbFeO3 particles of 85.6 nm were obtained by direct solution combustion method. The orthorhombic perovskite structure (space group Pbnm) of the terbium orthoferrite was confirmed by powder X-ray diffraction, Raman spectroscopy and 57Fe Mössbauer spectroscopy. The unusual granular morphology and mesoporous structure of the nanopowder were investigated by scanning electron microscopy and adsorption-structural analysis via low-temperature (77 K) adsorption-desorption of nitrogen with a total porosity of 0.0145 cm³/g and average pore width of 12 nm. The magnetic properties of TbFeO3 nanoparticles were thoughtfully studied, M = 34.2 emu/g at T = 10 K, Hc = 300 Oe. The onset of reorientation of the Fe3+ spin system at T ~ 18 K and the antiferromagnetic ordering of Tb3+ ions at T ~ 4 K were observed by vibrational magnetometry. Obtained results confirm the flexible paramagnetic to antiferromagnetic behavior of granular TbFeO3 nanopowder. Highlight: Granular nanopowder of TbFeO3 was obtain by direct solution combustion method. Aggregated granular morphology of perovskite TbFeO3 was confirmed. Magnetization of TbFeO3 granules is in pronounced dependence of temperature. [ABSTRACT FROM AUTHOR]

The features of the formation of nanocrystals in the BiFeO3–CaFeO3 system via glycine-nitrate combustion were studied. The crystallite size of the bismuth orthoferrite-based solid solutions (20–45 nm), as well as their particle size, were found to depend on the calcium content. The formation processes were activated in the temperature range corresponding to the melting of the surface (nonautonomous) phase. [ABSTRACT FROM AUTHOR]

The paper describes magnetic core-shell nanoparticles (Fe3O4/SiO2) synthesis that is an important stage of the manufacturing of smart material for targeted drug delivery based on the construction of the composite system mesoporous silica (MCM-41) - magnetite nanoparticles (Fe3O4) - immune cells (macrophages) for targeted drug delivery. The synthetic procedure for the fabrication of core-shell nanoparticles is modified in order to produce core-shell nanoparticles of the composition Fe3O4@SiO2 in the superparamagnetic state. This is confirmed by the studies of phase composition and magnetic properties of this material. The dependence of the particles size of magnetite sol on initial concentration of iron chlorides is established. The conditions for the fabrication of core-shell Fe3O4@SiO2 particles that are aggregatively stable in water are determined. Structural investigations of the samples demonstrate that the sizes of Fe3O4@SiO2 particles lie in the range 30 - 50 nm. [ABSTRACT FROM AUTHOR]

A series of tellurides FexTi1− x Te1.65 ( x = 0, 0.1, 0.2 ..., 1.0) synthesized at 850°C were studied by X-ray phase and X-ray fluorescent analysis and Møssbauer spectroscopy on 57Fe. In this series two solid solutions are formed: phases I and II with homogeneity regions within the limits of 0 ≤ x ≤ 0.3 and 0.9 ≤ x ≤ 1.0, respectively. Iron in this series exists in two various states: Fe2+ sym and Fe2+ asym as differentiated from the series of tellurides FexTi1− x Te1.45 where three states of iron Fe2+ sym, Fe2+ asym, and Fe0 were found. On passing from FexTi1− x Te1.45 to FexTi1− x Te1.65 the number of formed phases decreases, and phase relations become simpler. The absence of Fe0 from phase I of tellurides FexTi1− x Te1.65 can point to the fact that TiTe1.45 and TiTe1.65 belong to different homogeneity regions. [ABSTRACT FROM AUTHOR]

A series of tellurides FexTi1− x Te1.65 ( x = 0, 0.1, 0.2 ..., 1.0) synthesized at 850°C were studied by X-ray phase and X-ray fluorescent analysis and Møssbauer spectroscopy on 57Fe. In this series two solid solutions are formed: phases I and II with homogeneity regions within the limits of 0 ≤ x ≤ 0.3 and 0.9 ≤ x ≤ 1.0, respectively. Iron in this series exists in two various states: Fe2+ sym and Fe2+ asym as differentiated from the series of tellurides FexTi1− x Te1.45 where three states of iron Fe2+ sym, Fe2+ asym, and Fe0 were found. On passing from FexTi1− x Te1.45 to FexTi1− x Te1.65 the number of formed phases decreases, and phase relations become simpler. The absence of Fe0 from phase I of tellurides FexTi1− x Te1.65 can point to the fact that TiTe1.45 and TiTe1.65 belong to different homogeneity regions. [ABSTRACT FROM AUTHOR]

When it comes to address quantitative analysis in complex mixtures, Partial Least Squares (PLS) is often referred to as a standard first-order multivariate calibration method. The set of samples used to build the PLS regression model should ideally be large and representative to produce reliable predictions. In practice, however, the large number of calibration samples is not always affordable and the choice of these samples should be handled with care as it can significantly affect the accuracy of the predictive model. Correlation constrained multivariate curve resolution (CC-MCR) is an alternative regression method for first-order datasets where, unlike PLS, calibration and prediction stages are performed iteratively and optimized under constraints until the decomposition meets the convergence criterion. Both calibration and test samples are fitted into a unique bilinear model so that the number of calibration samples is no longer a critical issue. In this paper we demonstrate that under certain conditions CC-MCR models can provide for reasonable predictions in quantitative analysis of complex mixtures even when only three calibration samples are employed. The latter are defined as samples having the minimum, the maximum and the average concentration, providing for a simple and rapid strategy to build reliable calibration model. The feasibility of three-point multivariate calibration approach was assessed with several case studies featuring mixtures of different analytes in presence of interfering species. Satisfactory predictions with relative errors in the range 3-15% were achieved and good agreement with classical PLS models built from a larger set of calibration samples was observed., (Copyright © 2016 Elsevier B.V. All rights reserved.)