Role of humic substances in the formation of nanosized particles of iron corrosion products

Particle size distribution during a corrosion reactionRole of humic substances in the formation of nanosized particles of iron corrosion products. Pankratov D.A., Anuchina M.M. //Russian Journal of Physical Chemistry A. 2017. V.91. №2. P.233-239.Search the full text below. Ищи полный текст ниже.

The corrosion of metallic iron in aqueous solutions of humic substances (HS) with limited access to air is studied. The HS are found to exhibit multiple functions. Acid–base, redox, and surfactant properties, along with the ability to form complexes with iron in solution, are displayed in the corrosion process. Partial reduction of the HS during the corrosion reaction and their adsorption onto the main corrosion product (Fe3O4 nanoparticles) are observed.

Synthesis of nanohydroxyapatite in the presence of iron (III) ions

Room-temperature Mössbauer spectra of the 2-x samples, models for their description (left panels), and the corresponding quadrupole splitting probability distribution functions (right panels)Synthesis of nanohydroxyapatite in the presence of iron (III) ions. Severin A.V., Pankratov D.A. //Russian Journal of Inorganic Chemistry. 2016. V.61. №3. P.265-272.Search the full text below. Ищи полный текст ниже.

The effect of small amounts of iron (III) ions on the morphology, phase composition, and structure of the products of the hydroxyapatite (HAP) synthesis has been studied by electron microscopy, X-ray powder diffraction, and Mossbauer spectroscopy methods. It has been demonstrated that the introduction of dopant iron (III) ions into the reaction mixture at different stages of HAP formation makes it possible to control crystal growth, morphology, and phase composition. The iron ions are not incorporated into the HAP crystal structure; rather, they form their proper nanophase, as well as adsorption clusters on the HAP surface.

Properties of Iron-Containing Nanohydroxyapatite-Based Composites

EPR spectra of the (a) N-a and (b) N-c samplesProperties of Iron-Containing Nanohydroxyapatite-Based Composites. Pankratov D.A., Dolzhenko V.D., Ovchenkov E.A., Anuchina M.M., Severin A.V. //Inorganic Materials. 2017. V.53. №1. P.89-98.Search the full text below. Ищи полный текст ниже.

The paramagnetic properties of compounds resulting from the synthesis of nanohydroxyapatite in the presence of Fe(III) ions have been studied by electron paramagnetic resonance, Mössbauer spectroscopy, and magnetochemistry. Based on the obtained results on the mechanism of the reaction between an orthophosphoric acid solution and an aqueous calcium hydroxide suspension, we have found conditions for incorporating Fe(III) impurity ions into hydroxyapatite. We have studied samples differing in the sequence in which reagents were mixed and in hydroxyapatite crystallite formation conditions. It has been shown that, in all instances, the composition and properties of the iron-containing phases in the composites depend significantly on both synthesis and heat treatment conditions.

Sorption of humic substances on a weakly basic anion-exchange resin: Relationship with the adsorbate structure

Experimental data on the sorption of HS on ANS anion-exchange resin and respective theoretical isotherms in terms of (1) the BET and (2–7) Langmuir models: (solid lines) commercial preparations (1) CHS, (3) LH, and (5) CHP and (dashed lines) desalted samples (2) CHA-SH, (4) LHA, (6) PHF, and (7) PHASorption of humic substances on a weakly basic anion-exchange resin: Relationship with the adsorbate structure. Pankratov D.A., Anuchina M.M., Borisova E.M., Volikov A.B., Konstantinov A.I., Perminova I.V. //Russian Journal of Physical Chemistry A. 2017. V.91. №6. P.1109-1115.Search the full text below. Ищи полный текст ниже.

Adsorption of a broad range of humic substances (HS) of different origins and fractional compositions on a macroporous weakly basic anion-exchange resin is studied. It is found that the nature of the humic substances has a substantial effect on both the efficiency of sorption and the mechanism of interaction with the adsorbent. The dependence of the determined thermodynamic parameters of sorption on the humic substances origin, composition, and structure is shown for a broad range of humic substances. It is concluded that the results can be used to predict the sorption properties of weakly basic anion-exchange resins with respect to humic substances of known origin and structural group composition.

Synthesis and magnetic properties of cobalt ferrite nanoparticles in polycarbosilane ceramic matrix

Mössbauer spectra of the sample comprised of cobalt ferrite nanoparticles in a ceramic matrix after sintering in argon.Synthesis and magnetic properties of cobalt ferrite nanoparticles in polycarbosilane ceramic matrix. Yurkov G.Y., Shashkeev K.A., Kondrashov S.V., Popkov O.V., Shcherbakova G.I., Zhigalov D.V., Pankratov D.A., Ovchenkov E.A., Koksharov Yu.A. //Journal of Alloys and Compounds. 2016. V.686. P.421–430

Composite materials comprised of a ceramic matrix with metal-containing nanoparticles were prepared by sintering a blend of cobalt ferrite nanoparticles and polycarbosilane. Sintering process was performed either in air or argon, resulting in different material composition. The air-sintering materials consist mainly of oxide phases (silica matrix and cobalt ferrite nanoparticles). The process of sintering in argon leads to partial reduction of oxides and formation of α-Fe, carbide and silicate phases. The prepared samples were characterized by the SEM, TEM, XRD and EMR techniques and the Mössbauer spectroscopy. Static magnetic properties were also studied. All samples were found to be soft magnetic. Sintering, especially in argon, increases remnant magnetization of resulting composite products.

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