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Asphaltene deposition from crude oil, induced by n-heptane and acetone flows in a microfluidic device, was studied by optical and FTIR spectroscopic imaging techniques in situ. It was found that n-heptane and acetone penetrate crude oil in completely different ways, which is responsible for the formation of deposits with different structures and chemical compositions. The contact of the n-heptane flow with crude oil leads to fast aggregation of asphaltenes at the interface, resulting in the formation of a compact deposit fixed to the surface. Subsequent slow diffusion of n-heptane into crude oil causes asphaltene aggregation and precipitation of loose deposits. In the case of acetone, the flocculant diffuses (faster than n-heptane) into crude oil, which results in removal of its soluble components and in the formation of deposits appearing as strips as well. The distribution of the functional groups (–OH(NH), CH2–CH3, C=O, C–O, S=O) in the deposits is spatially heterogeneous. The asphaltenes deposits formed at the flocculant-crude oil interface are richer in the functional groups than those formed during diffusion. No carbonyl groups were revealed in the deposits formed in the acetone flow, while oxygen-containing groups such as –OH(NH) and S=O were present, which was an unusual result. [ABSTRACT FROM AUTHOR]

In this work, step-by-step high-pressure high-temperature annealing of plastically deformed-type IaAB diamonds from the Istok placer has been performed and the behavior of characteristic centers has been investigated by infrared, electron paramagnetic resonance, and photoluminescence spectroscopies. A new paramagnetic center with one magnetically inequivalent position and hyperfine structure from one hydrogen atom has been found. This paramagnetic center can be assigned to the dangling carbon bond in the dislocation core, and the hydrogen hyperfine structure is due to the polarization of the electron shell of hydrogen forming the C–H bond. For this center and W7 center, the annealing temperatures have been determined. Spin relaxation was studied by pulse electron paramagnetic resonance technique at low temperatures. The spin–spin relaxation times for the W7 and 490.7 centers exclude exchange interactions between the paramagnetic centers. At the same time, the close spin–lattice relaxation times for these centers can be determined by the distorted structure near the dislocation core. [ABSTRACT FROM AUTHOR]

Asphaltene-containing deposits formed on the CaF2 window induced by n-heptane flow in a microfluidic device have been investigated using an IR microscope and an imaging macro chamber (IMAC) with FPA detection. This is the first example of the ex situ infrared imaging of the deposits from crude oil formed under dynamic conditions of flocculant flow. It has been shown that fast aggregation of asphaltenes in n-heptane flow leads to the formation of deposit rich in heteroatom-containing functional groups: (О–Н, N–H, C=O, C–O, and S=O). [ABSTRACT FROM AUTHOR]

Nuclear γ-resonance experiments with energy and time resolved detection are carried out with ϵ-F2O3 nanoparticles and a 57Co(Rh) laboratory Mössbauer source of γ radiation and a 14.4125 keV synchrotron radiation source on the ID18 beamline (ESRF) in the temperature range of 4–300 K. Both methods show a tremendous increase in the hyperfine field in tetrahedrally coordinated iron positions during the magnetic transition in the range of 80–150 K. As a result, the splitting of the quantum beat peaks in the nuclear scattering spectra is observed in the time interval of 20–170 ns with a periodicity of ∼ 30 ns. In addition, the first quantum beat is slightly shifted to shorter times. A correlation between the quadrupole shift and the orbital angular momentum of iron in ϵ-F2O3 nanoparticles is found. The magnetic transition leads to the rotation of the magnetic moment in the tetrahedral positions of iron around the axis of the electric field gradient by an angle of 44°. [ABSTRACT FROM AUTHOR]

Electron spin resonance in situ was applied to study the initial stages of ferrofluid formation in combination with the X-ray diffraction, high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy studies data. The ultrafine (d = 4 nm) magnetite in dimethylsulfoxide ferrofluid with a narrow size nanoparticles distribution was obtained in a single step at room temperature by admixing butylene oxide to a solution of iron (II) and (III) chlorides in dimethylsulfoxide. It has been shown that at the first step of the ferrofluid synthesis antiferromagnetically ordered iron containing phase is formed, which can be correlated with iron hydroxides. [ABSTRACT FROM AUTHOR]

The stability of a catalyst for partial H2S oxidation has been studied by the ferromagnetic resonance (FMR) technique combined with transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetostatic investigations. The ε-Fe2O3 iron oxide nanoparticles supported on silica have been examined for their stability under the selective H2S oxidation conditions. The combination of the physicochemical methods has been used to study the state of reacted catalysts. The ε-Fe2O3 phase has been found to remain stable under the selective H2S oxidation conditions at temperatures up to 300 °C. The active phase state during the catalytic reaction has been explored using in situ FMR experiments. It has been established that the ε-Fe2O3 nanoparticles retain their structure and magnetic properties in the presence of H2S at high temperatures. During the in situ FMR experiments, the ε-Fe2O3 sulfidation process has been studied. [ABSTRACT FROM AUTHOR]

Evolution of the local environment of Fe3+ ions in deposited Fe2O3/SiO2 nanoparticles formed in samples with different iron contents was investigated in order to establish the conditions for obtaining the stable ε-Fe2O3/SiO2 samples without impurities of other iron oxide polymorphs. Microstructure of the samples with an iron content of up to 16% is studied by high-resolution transmission electron microscopy, X-ray diffraction analysis, and Mössbauer spectroscopy, and their magnetic properties are examined. At iron concentrations below 6%, calcinations of iron-containing precursor nanoparticles in a silica gel matrix lead to the formation of the ε-Fe2O3 iron oxide polymorphic modification without foreign phase impurities, while at the iron concentration in the range of 6-12%, the hematite phase forms in the sample in the fraction of no more than 5%. It is concluded on the basis of the data obtained that the spatial stabilization of iron-containing particles is one of the main factors facilitating the formation of the ε-Fe2O3 phase in a silica gel matrix without other iron oxide polymorphs. It is demonstrated that the increase in the iron content leads to the formation of larger particles in the sample and gradual changes of the Fe3+ ion local environment during the phase transition ε-Fe2O3 → α-Fe2O3. [ABSTRACT FROM AUTHOR]

Evolution of the local environment of Fe3+ ions in deposited Fe2O3/SiO2 nanoparticles formed in samples with different iron contents was investigated in order to establish the conditions for obtaining the stable ε-Fe2O3/SiO2 samples without impurities of other iron oxide polymorphs. Microstructure of the samples with an iron content of up to 16% is studied by high-resolution transmission electron microscopy, X-ray diffraction analysis, and Mössbauer spectroscopy, and their magnetic properties are examined. At iron concentrations below 6%, calcinations of iron-containing precursor nanoparticles in a silica gel matrix lead to the formation of the ε-Fe2O3 iron oxide polymorphic modification without foreign phase impurities, while at the iron concentration in the range of 6-12%, the hematite phase forms in the sample in the fraction of no more than 5%. It is concluded on the basis of the data obtained that the spatial stabilization of iron-containing particles is one of the main factors facilitating the formation of the ε-Fe2O3 phase in a silica gel matrix without other iron oxide polymorphs. It is demonstrated that the increase in the iron content leads to the formation of larger particles in the sample and gradual changes of the Fe3+ ion local environment during the phase transition ε-Fe2O3 → α-Fe2O3. [ABSTRACT FROM AUTHOR]

A new metamaterial is obtained on the basis of ε-Fe2O3 nanoparticles immobilized in a xerogel matrix. Samples are synthesized by impregnating SiO2 hydrogel with iron (II) salts with subsequent drying and calcination. The structure and magnetic properties of the composites are probed using transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and static magnetic measurements. [ABSTRACT FROM AUTHOR]

The ferromagnetic resonance (FMR) method in situ is used to study the initial stages of the formation of ɛ iron oxide nanoparticles deposited on silica gel at temperatures up to 600°C. It is shown that at high-temperature treatment of starting samples obtained by impregnation with an iron(II) sulfate solution, supermagnetic ɛ-Fe 2O 3/SiO 2 nanoparticles form with a narrow size distribution. An analysis of the FMR data in comparison with the data of other methods enables the formulation of the formation conditions for systems of deposited ɛ-Fe 2O 3 nanoparticles without other polymorph impurities. [ABSTRACT FROM AUTHOR]

Erratum [ABSTRACT FROM AUTHOR]