A sustainable reaction process for phase pure LiFeSi2O6 with goethite as an iron source

Lithium-iron methasilicate (LiFeSi$_{2}$O$_{6}$, LFS), a member of clinopyroxene family, is an attractive compound for its multiferroic properties and applicability in energy-related devices. Conventional preparative method requires heating at elevated temperatures for long periods of time, with inevitable severe grain growth. We demonstrate that α-FeO(OH) (goethite) is superior as an iron source toward phase pure LFS over conventional hematite, α-Fe$_{2}$O$_{3}$. The exact phase purity, i.e., no trace of iron containing reactant, is confirmed in the goethite-derived LFS by 57Fe Mössbauer spectroscopy. The grain growth of LFS during heating is suppressed to keep its crystallite size of 120 nm. Higher reactivity of goethite in comparison with hematite is mainly attributed to the dehydration of goethite, which in our case was accelerated by Li$_{2}$O. Related reaction mechanisms with the possible product pre-nucleation during mechanical activation are also mentioned. The magnetic properties of goethite-derived LFS are equivalent to those prepared via a laborious solid-state route. Thus, the presented preparative method offers a more sustainable route than conventional processing, and thus enables practical application of LFS

Disordered Gd6_{6}UO12−δ_{12-δ} with the cation antisite defects prepared by a combined mechanochemical−thermal method

The synthesis of the rhombohedral Gd$_{6}$UO$_{12-δ}$ is reported via mechanochemical processing of stoichiometric Gd$_{2}$O$_{3}$/UO$_{2}$ mixtures and their subsequent annealing. Rietveld refinement of XRD data reveals that the as-prepared material exhibits a remarkable degree of cation antisite disorder and oxygen deficiency. The simulations of intensities of the selected XRD superlattice reflections are performed for limiting states of Gd$_{6}$UO$_{12-δ}$ with its most extreme degrees of the cation antisite disorder. On the basis of the estimated bond lengths it can be stated that distorted geometry of structural units in the material is a consequence of its relatively large oxygen deficiency

Magnetite nanoparticles as-prepared and dispersed in Copaiba oil: Study using magnetic measurements and Mössbauer spectroscopy

Study of magnetite nanoparticles, as-prepared and dispersed in Copaiba oil as magnetic fluid, by means of magnetic measurement and Mössbauer spectroscopy at various temperatures demonstrated differences in the saturation magnetization and Mössbauer hyperfine parameters which were related to the interactions of Copaiba oil polar molecules with iron cations on magnetite nanoparticle's surface. © 2012 Springer Science+Business Media Dordrecht

Nanostructure and Magnetic Anomaly of Mechanosynthesized Ce1-xYxO2-δ (x ≤ 0.3) Solid Solutions

Electromagnetic properties of complex oxide solid solutions containing Ce and Y attract increasing interests due to their high application potential. Their properties are known to be dependent on many factors including grain size and crystal defects. Here we focus on unique features of nanocrystalline Ce1-xYxO2-δ (x ≤ 0.3) solid solutions prepared via a mechanosynthesis. Mechanically activated CeO2-δ and mechanosynthesized Ce1-xYxO2-δ exhibit room-temperature ferromagnetism. The saturation magnetization reaches maximum for the Ce0.9Y0.1O2-δ solid solution. XPS and Raman spectra show that Ce4+ ions are partially reduced to Ce3+, with simultaneous introduction of oxygen vacancies accumulated on surface of the solid solutions. An analysis of the experimental magnetization data and the determination of both the spin state and the concentration of magnetic carriers revealed that a small part of the Ce3+ spins (<1%) is responsible for the magnetic state of the Ce1-xYxO2-δ system. Existence of clusters with a short-range antiferromagnetic order is also suspected. © 2020 Elsevier LtdThe present work is supported by the APVV (project 19-0526 ), EUREKA (project E!9982 ) and the VEGA (project 2/0055/19 ). A. Ye. thanks the State Assignment (Theme “Magnit” No. АААА-А18-118020290129-5) for financial support. H.K., K.L.S. and M.S. are grateful to the National Scholarship Program of Slovakia ( SAIA, n. o.). V.Š. acknowledges the support by the DFG (project SE 1407/4-2 )

Bio-chemical methods in wasteprocessing

The mineral biotechnologies, the domain of which is primary raw material processing, are increasingly diversifying into some metallurgical areas. The presented results of the research carried out with metallurgical wastes from aluminium production, lead waste remaking and desulphurization zinc-ferrite-based sorbents regeneration prove the possibility of the use of bio-chemical methods. The results obtained and the proposed technologies applying bio-chemical processes enable a complex processing and use of waste sludge from aluminium production and the use of wastes from matte-based copper production for the production of hematite pigments. The use of microorganisms in the desulphurization sorbent regeneration processes allows to increase sorbent's efficiency and its repeated recycling

Bio-chemical methods in wasteprocessing

The mineral biotechnologies, the domain of which is primary raw material processing, are increasingly diversifying into some metallurgical areas. The presented results of the research carried out with metallurgical wastes from aluminium production, lead waste remaking and desulphurization zinc-ferrite-based sorbents regeneration prove the possibility of the use of bio-chemical methods. The results obtained and the proposed technologies applying bio-chemical processes enable a complex processing and use of waste sludge from aluminium production and the use of wastes from matte-based copper production for the production of hematite pigments. The use of microorganisms in the desulphurization sorbent regeneration processes allows to increase sorbent's efficiency and its repeated recycling

Mössbauer studies of the phase formation in the Fe-S system

The phase formation in the Fe-S system was investigated by differential thermal analysis and Mössbauer spectroscopy. It was found that the formation of FeS compound takes place after melting of sulphur in the temperature range from 490 to 590 K. Mössbauer parameters of the quenched samples allowed attributing the thermal peak at temperatures 590–620 K to formation of FeS2, which at the subsequent heating decomposes on peritectics at 1015 K. A full description of the alloys by DTA, XRPD, and Mössbauer studies allowed to make recommendations for the technology of preparation of multinary compounds with crystal structures of chalcopyrite CuFeS2, kesterite Cu2(Zn, Fe)SnS4, stannite Cu2FeSnS4, and compounds existing in the Cu-Fe-S system.Belarusian Republican Foundation for Fundamental Research (project F15MLD-025)