Characterization and Thermal Behaviour of Garnets from Almandine–Pyrope Series at 1200°C

Hyperfine Interactions - The natural garnets from almandine (Fe3Al2Si3O12)–pyrope (Mg3Al2Si3O12) series with the iron to magnesium atomic ratio ranging from 0.2 to 1 were characterised and...     

Magnetically modified bentonite as a possible contrast agent in MRI of gastrointestinal tract

A composite of iron oxide nanoparticles and mineral matrix has been studied by XRD, Mössbauer spectroscopy, and TEM. Magnetite and superparamagnetic magnetite have been identified by Mössbauer spectroscopy in the nanocomposite. A relationship between the hyperfine parameters and iron oxide particle size has been confirmed by TEM. The optimal concentration of “magnetite—bentonite” composite, when the MRI signal is fully reduced, was found for using this composite as a negative contrast agent.     

Mössbauer Study of the Thermal Behaviour of Garnets Used in High-Energy Water Jet Technologies

A high-energy water jet combined with silicate garnets as abrasives has been proven to be a powerful tool for disintegration of hard materials. Thermal heating of the garnets is one way for structure improvement of the abrasive material. Room-temperature Mössbauer spectra of initial powdered almandine samples are characterised by one doublet corresponding to Fe²⁺ in dodecahedral position 24c. Almandine garnet, industrial product Barton HP 80 as reference material in all experiments, has a second doublet corresponding to Fe³⁺ in octahedral position 16a. In room-temperature spectra of heated almandine garnet samples from locality Ktí and Mdnec (heated under temperatures 200–1000°C by 100 degrees for 1 hour in air) a new doublet originating from -Fe₂O₃ nanoparticles appeared. Under a heating temperature of higher than 800°C, the broad sextets of -Fe₂O₃ and -Fe₂O₃ in spectra were discovered. No additional doublets or sextets appeared in room-temperature Mössbauer spectra of reference material of almandine garnet Barton HP 80 heated under each temperature.     

Improving detector signal processing with pulse height analysis in Mössbauer spectrometers

A plenty of different programming techniques and instrument solutions are used in the development of Mössbauer spectrometers. Each of them should provide a faster spectrum accumulation process, increased productivity of measurements, decreased nonlinearity of the velocity scale, etc. The well known virtual instrumentation programming method has been used to design a computer-based Mössbauer spectrometer. Hardware solution was based on two commercially-available PCI modules produced by National Instruments Co. Virtual Mössbauer spectrometer is implemented by the graphical programming language LabVIEW 7 Express. This design environment allows to emulate the multichannel analyzer on the digital oscilloscope platform. This is a novel method based on Waveform Peak Detection function which allows detailed analysis of the acquired signal. The optimal treatment of the detector signal from various detector types is achieved by mathematical processing only. As a result, the possibility of an increase of signal/noise ratio is presented.     

Cubic β-Fe2O3 as the product of the thermal decomposition of Fe2(SO4)3

Hyperfine Interactions - The thermal decomposition of Fe2(SO4)3 in air has been investigated using transmission Mössbauer spectroscopy, CEMS and X-ray powder diffraction. The hexagonal...     

A new fast type of Mössbauer spectrometer for the rapid determination of iron-bearing minerals used in the paint industry

A new miniaturised Mössbauer spectrometer has been developed for laboratory and industrial application. Equipped with a YAIO₃:Ce crystal fast scintillation detector unit and mini transducer for the energy modulation of gamma rays, the unique mechanical design enhances protection from radiation and prevents disturbance by mechanical vibrations. It can be used with various types of cryostat and furnace.Supported by the LabVIEW graphical programming environment and by the new algorithm for the quantification of iron-components, the spectrometer can be used as a single-purpose instrument for the rapid determination of the Fe²⁺/Fe³⁺ ratio in ilmenite and Morin transition temperature of hematite. It can also be used to monitor the manufacturing processes for titanium white and copperas red.     

Preparation and Properties of Iron and Iron Oxide Nanocrystals in MgO Matrix

We have prepared α-iron and magnetite (Fe₃O₄) nanoparticles in MgO matrix from a mixture of nanocrystalline Fe₂O₃ with Mg(H,O) powders calcinated in hydrogen. This procedure yielded spherical magnetic nanoparticles embedded in MgO. Transmission electron microscopy and Mössbauer spectroscopy were used for structure and phase analysis. The measurements of magnetic properties showed increased coercivity of the nanocomposite samples.     

Thermal decomposition of almandine garnet: Mössbauer study

The thermal decomposition of almandine garnet from Zoltye Vody, Ukraine, has been studied using⁵⁷Fe Mössbauer spectroscopy. Room temperature Mössbauer spectrum of the initial powdered sample is characterised by one doublet corresponding to Fe²⁺ in dodecahedral position 24c. In the room temperature spectra of all heated almandine samples, a doublet corresponding to γ-Fe₂O₃ nanoparticles appeared. Depending on experimental conditions (heating temperature and time), the additional spectral lines of α-Fe₂O₃ and ε-Fe₂O₃ were observed in Mössbauer spectra. It is obvious that the thermal transformation of almandine garnet in air is related to the primary formation of γ-Fe₂O₃ superparamagnetic nanoparticles. γ-Fe₂O₃ nanoparticles are transformed into ε-Fe₂O₃ and consequently into α-Fe₂O₃ at higher temperatures. The mechanism and kinetics of the individual structural transformations depend on experimental conditions — mainly on the heating temperature and size of the particles.     

Fe-lactate mediated formation of ZnO sols and self-organized nanorod assemblies

Hot ethanolic mixtures of hydrated Zn(II)- and Fe(II)-carboxylates (acetate and lactate) react to form yellow-orange colored Fe(III)_xZn_yO_zOH_w heteroclusters showing pronounced electronic resonances in the optical UV absorption spectra. On the addition of LiOH to these polymolecular sols, stable nanoparticulate Fe(III)–ZnO colloids are formed. During colloidal growth, 2–4 nm sized weakly crystallized Wurtzite nanoparticles are exclusively formed even in the presence of high Fe content up to 20 at.%. The presence of Fe(III) in the ZnO condensation process retards the nanoparticle growth and blocks the thermal crystallization and size enhancement up to 250 °C. The produced 0.5 M Fe(III)–ZnO sols are useful for film formation processes. From atomic force microscopy-AFM, scanning electron microscopy-SEM and X-ray diffraction-XRD studies, we note important differences in shape and morphology of the thermally annealed Fe(III)–ZnO layers depending on the iron carboxylate employed. Surprisingly, Fe(II)-lactate derived coatings are carrying vertically oriented cone-shaped aggregates composed of 60–120 nm long primary nanorods. Contrary, Fe(II)-acetate based synthesis gave sand-dune like film morphologies containing spherical 12 nm sized nanocrystallites. All film samples possess mesoporosity with pore size ranging between 5 and 20 nm.     

Fast Determination of Fe2+/Fe3+ Ratio in Ilmenite

Ilmenite (FeTiO₃) is an initial raw material in titanium white manufacture. The Fe²⁺/Fe³⁺ ratio in ilmenite is measured before the sulphate technological process is started. The possibility of fast measurements of this ratio could help to control the manufacture process. A single-purpose Mössbauer effect analyser for the fast determination of Fe²⁺/Fe³⁺ ratio in ilmenite was built. The fast algorithm based on the calculation of a Fe²⁺/Fe³⁺ ratio from heights of spectral lines allowed to reduce the time of one analysis to ten minutes.