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Intensive characterization studies of iron ore slime carried out by X-ray diffraction spectroscope (XRD), scanning electron microscope (SEM-EDS), field emission scanning electron microscope (FESEM), and quantitative mineralogical evaluation by scanning electron microscope (QEMSCAN) are discussed. In slimes, mineral phases like hematite, goethite, gibbsite, kaolinite, and quartz are present in a complex and intricate way. SEM-EDS and QEMSCAN studies indicate that significant amounts of aluminum are associated with both ochreous and vitreous goethite. Hematite and goethite phases are contaminated with some amount of alumina and silica. The liberation of hematite in the coarser fraction (+500 µm) is only 20.6% compared to 40% in the finer fraction (−500 µm) size. A flow sheet, comprising of hydrocyclone and magnetic separation techniques, has been developed to produce an iron concentrate containing ∼63% Fe with 70.7% weight recovery from a feed sample containing 56.8% Fe, 5.1% SiO2, and 6.4% Al2O3. [ABSTRACT FROM PUBLISHER]

Abstract: We have observed good ferroelectric loops at room temperature in hexagonal HoMnO3 (HMO) bulk ceramics sintered at 1250°C. Microstructure and ferroelectric hysteresis loops are observed to be dependent on sintering temperature. It is observed that with an increase of sintering temperature, hexagonal a-axis is compressed and c-axis is marginally dilated with overall contraction of the hexagonal unit-cell volume. We explain the origin of ferroelectricity through relative movement of Ho ion and Mn ion within its unit-cell volume, resulting in the distortion of unit-cell volume. We argue that ferroelectric origin of hexagonal HMO at room temperature may be due to the marginal displacement of Ho ion along a-axis, that influences the exchange interaction among the Mn3+ and Ho3+ ions, causing magnetically induced ferroelectricity at room temperature. [Copyright &y& Elsevier]

Abstract: The thermal behavior of hafnium dioxide fiber has been investigated with the aid of time differential perturbed angular correlation (TDPAC) technique along with XRD and SEM measurements. This study has proved a good thermal stability of the fibrous material up to 1173K and the fiber loses its crystallinity to a meager extent at 1673K. No phase transition has been observed up to 1673K in this fiber. TDPAC parameters for the HfO2 fiber annealed at 1173K are ω Q =124.6 (3) Mrad/s and η=0.36 (1). These values remain unaltered for the HfO2 fiber annealed even at 1673K. Electronic structure calculations based on the density functional theory (DFT) for HfO2 doped with tantalum impurity have been performed and the calculated EFG parameters are in reasonable agreement with the experimental values. [Copyright &y& Elsevier]

Abstract: A clean signature of room temperature multiferroicity in Bi1.2Gd0.1Fe0.8O3 ceramics is observed. Samples were prepared by slow step sintering technique at 850°C. Impurity peaks normally present in original BiFeO3 are completely suppressed with the increase of Bi concentration. Apart from this, structural transformation took place from R3 C to Pn21 a space group and a clear orthorhombic grain growth habit is seen by SEM microstructure. Suppression of impurity phases favors the reduction of mobile oxygen vacancies and hence reduces leakage current for which ferroelectric properties of Bi1.2Gd0.1Fe0.8O3 are enhanced. We argue that the addition of Gd is likely to suppress the spiral spin modulation and at the same time increase the canting angle which favors the enhanced ferromagnetism. Excess Bi is expected to act as point defects and occupy interstitial positions which in turn surrounded by oxygen vacancies and is likely to promote defect driven ferromagnetism with enhanced spin and electric polarization. This finding encourages further revaluation of long-discounted BiFeO3 for multiferroics research. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on multiferroic properties of Ho substituted BiFeO3 (Bi1−x Ho x FeO3) ceramics. It is observed that for x=0.15, a prominent ferroelectric loop is seen at 300K even if the system remains in rhombohedral (R3c) phase without appearance of any observable impurity phases. A well shaped M–H loop is observed at 10K for x=0.15. However it showed ferromagnetism, confirming the contribution of Ho3+ towards enhancement of ferromagnetic properties of BiFeO3 at 300K. Suppression of impurity phases of pure BiFeO3 bulk ceramic favors the reduction of mobile oxygen vacancies and reduces leakage current, due to which ferroelectric properties of BiFeO3 is enhanced. We argue that Ho substitution at Bi site is likely to suppress the spiral spin modulation and at the same time increase the canting angle, which favors enhanced multiferroic properties. XRD, SEM, magnetization, polarization and chemical bonding analysis measurements were carried out to explain the multiferroic behavior. [ABSTRACT FROM AUTHOR]

Abstract: Pure and Sr-doped LaGaO3, LaFeO3 and LaCoO3 and Sr,Mg-doped LaGaO3 were synthesized by various wet chemical routes, namely combustion, co-precipitation and citrate-gel methods. The effect of the various process parameters on the phase purity, particle size and surface area and morphology of the synthesized powders were determined by XRD, simultaneous TG-DTA, laser light scattering, BET and scanning electron microscopy. The stability of the synthesized pure phases in oxidizing and reducing atmosphere was also studied by thermogravimetry. It was observed that pure and Sr-doped single perovskite phases of lanthanum ferrite, cobaltite and gallate and Sr,Mg-doped lanthanum gallate could be synthesized by combustion and citrate-gel methods under suitable process conditions. Synthesis using the co-precipitation method yielded incomplete reaction irrespective of the calcination temperature adopted. The citrate-gel method yielded better powder properties in terms of particle size and morphology and surface area compared to combustion synthesis. It was found that pure and Sr-doped lanthanum ferrite, lanthanum cobaltite, lanthanum gallate and Sr,Mg-doped lanthanum gallate were stable in the oxidizing atmosphere. In the reducing atmosphere, pure and Sr-doped lanthanum ferrite and Sr,Mg-doped lanthanum gallate was found to be stable at least during the timeframe of the thermogravimetric experiment whereas pure and Sr-doped lanthanum cobaltite was partially reduced in hydrogen atmosphere. [Copyright &y& Elsevier]

Abstract: Mechanically activated granulated blast furnace slag (GBFS) was used in the range of 50–95% to replace clinker in portland slag cement (PSC). The slag and clinker were activated separately using an attrition mill and mixed to prepare cement formulations. Use of activated slag resulted in a remarkable increase in strength vis-à-vis commercial slag cement. Both 1-day and 28-day strength were found to increase with an increase in slag content up to 70%. The strength of the sample containing 80–85% slag was comparable to the commercial cement used as a reference. It was observed that mechanical activation of slag was more critical from the point of view of strength development. The hydrated cement samples were characterised using powder X-ray diffraction (XRD), scanning electron microscopy with X-ray microanalysis (SEM-EDS) and simultaneous thermogravimetry and differential thermal analysis (TG/DTA). It is established that microstructural changes resulting from enhanced reactivity of slag and densification are related with the improvement in cement strength. [Copyright &y& Elsevier]