The effect of an external magnetic field on the activation energy (E*) of carbon monoxide interaction with hematite under isothermal conditions in the temperature range of 250 to 350 degrees C has been studied using in situ magnetometry. The dependence of E* of the reaction of magnetite formation on the magnetic field strength in the field strength range from 60 Oe to 3 kOe is shown for hematite nanoparticle samples deposited on 20 nm silica gel. An extreme field dependence of E* was observed. The effect of an external magnetic field on the activation energy (E*) of carbon monoxide interaction with hematite under isothermal conditions in the temperature range of 250 to 350 degrees C has been studied using in situ magnetometry.

The Fe/MgAl2O4 catalysts modified with In were prepared by joint impregnation of aluminum–magnesium spinel with solutions of metal nitrate salts. Data on the adsorptive and reductive properties of the catalysts obtained by the in situ magnetic method, XPS, thermolysis, and IR spectroscopy of adsorbed CO are compared. It was established that the presence of indium in the catalyst inhibits the reduction of iron oxides to magnetite, as well as the stage of water removal from the catalysts and the decomposition of metal nitrates. It was shown by IR spectroscopy that the main adsorption sites are the structures that include Fe2+ cations.

Cobalt nanoparticles embedded in a carbon matrix were obtained by thermolysis of glucose deposited on Co3O4/SiO2. The magnetic characteristics of the obtained nanoparticles were measured. This process formed single-domain (d < 20 nm) carbon-coated Co nanoparticles. The average size and the size distribution of Co nanoparticles depend on the amount of glucose used for the preparation. The use of a relatively small amount of glucose (glucose/cobalt < 1 mol/mol) leads to the formation of carbon shells enveloping Co nanoparticles, which are resistant to oxidation in air up to 200°C. In contrast, the use of a larger amount of glucose leads to the formation of an amorphous carbon layer with metal particles enclosed in it. Thus, the resulting nanoparticles are more susceptible to oxidation, and approximately half of the deposited cobalt is oxidized to CoO within a few days of exposure to air.

Cobalt-based Amorphous Metal Alloys (AMA) can be used as soft magnetic materials in various magnetic devices due to the low value of the natural crystalline magnetic anisotropy. The addition of non-metallic components (Si, B) does not adversely affect the magnetic properties. On the contrary, AMA have high magnetic permeability at low values of coercive force and greater resistance to corrosion compared to crystalline ones. The required important parameters for corrosion description are: the concentration of chloride-ions, the microstructure (especially surface heterogeneity) and the composition of the oxide layer [1]. It was determined that the initial AMA Co75Si15Fe5Cr4.5Al0.5 possesses the low coercive force 0.38 A/m. The modification of the alloy surface with nanostructures by anodizing at different current densities (i) and times in the BmimBF 4 ionic liquid (IL) does not affect the value of the coercive force, but its resistance to corrosion in a chloride solution increases. The coercive force increases after corrosion, which may be due to a change in surface morphology. The domain structures of the surface modified with nanostructures and initial alloys are different. After excerption at a constant (i) in IL, the domain structure of the surface consists of relatively large uniformly magnetized regions (Fig. 1a). The coercive force of the sample practically does not change compared to the initial sample. The surface domains after corrosion are broken into smaller ones, while the predominant orientation changes its direction (Fig.1 b). The change in the surface domain structure is accompanied by a significant increase in the coercive force (by a factor of 10), although the maximum magnetic permeability (the slope of the hysteresis loops) does not change. The EIS-tests (electrical impedance spectroscopy) were performed at -200 mV (Ag/AgCl) in the frequency range of 50,000 to 0.01 Hz and an oscillation amplitude of 20 mA in Ringer's solution (Fig.1 c, d) to compare the charge transfer kinetics for modified with nanostructures and initial samples. The simulated equivalent circuit included the values of the solution resistance Rs (22 Ω), the value of the constant phase element CPE associated with the double layer capacity, including the capacitance of the modified surface layer, and Rp is the charge transfer resistance across the interface. The capacity of the double layer is higher for the modified sample (4.28*10 -5 Ohm -1 *c N vs. 1.88*10 -5 Ом -1 *с N ) and the resistance value of the material has hardly changed (18000±13.5% Ohm for modified and 15500±3.5% Ohm for unmodified). The values of the phase angle (0.78 - modified and 0.88 - unmodified) indicate a greater heterogeneity of the charge distribution at the boundaries of the double layer for the modified surface of the alloy. So, surface modification affects the corrosion resistance, while it has little effect on the parameters of hysteresis loops, what is very important in practical applications. Nyby, C., Guo, X., Saal, J. E., Chien, S.-C., Gerard, A. Y., Ke, H., Frankel, G. S. (2021). Electrochemical metrics for corrosion resistant alloys. Scientific Data, 8(1). doi:10.1038/s41597-021-00840-y Figure 1

In this work, an attempt was made to reveal and explain the influence of the process of formation of 2D nanostructures at the surface of an amorphous alloy (an alloy with the composition Co75Si15Fe5Cr4.5Al0.5 (in at.%) was used for this purpose) on the corrosion and magnetic properties of such an alloy. Two-dimensional nanostructures (nanocells of 100–150 nm in size, which were obtained by anodizing the initial sample in an ionic liquid) are essentially a pattern on the surface of the sample, and they cannot completely cover and block the surface from external effects. It was postulated that the presence of these nanostructures during corrosion and magnetic tests has no significant effect. However, a noticeable inhibition effect was observed during corrosion tests and a less noticeable (but still detectable) effect was observed during magnetic tests. The authors believe that the effect obtained, with a detailed study, can be used to increase the corrosion resistance and to improve the properties of traditional magnetic materials.

A hybrid electromagnetic nanomaterial, which is a matrix based on a conjugated polymer of poly-3-amine-7-methylamine-2-methylphenazine with dispersed magnetite nanoparticles immobilized on multi-walled carbon nanotubes, has been synthesized. In situ magnetometry was used to study the kinetics of the hydrogen reduction of Fe3O4 immobilized in the structure of a ternary nanocomposite in magnetic fields of different intensities. An increase in the magnetite reduction reaction rate with the formation of metallic iron nanoparticles at T=420∘C and at a magnetic field strength in the range of 60–3000 Oe was observed. The dependence of the degree of conversion of Fe3O4 on the magnetic field strength was established.

Fe-Co alloy nanoparticles with different sizes, supported by carbon derived from several polymers, namely polyacrylonitrile, polyvinyl alcohol and chitosan, have been synthesized by a one-pot method involving simultaneous metal nanoparticle formation and polymer carbonization. The method involves the joint dissolution of metal salts and a polymer, followed by annealing of the resulting dried film. Detailed XRD analysis confirmed the formation of Fe-Co alloy nanoparticles in each sample, regardless of the initial polymer used. Transmission electron microscopy images showed that the Fe-Co nanoparticles were all spherical, were homogeneously distributed within the carbon support and varied by size depending on the initial polymer nature and synthesis temperature. Fe-Co nanoparticles supported by polyacrylonitrile-derived carbon exhibited the smallest size (6–12 nm), whereas nanoparticles on chitosan-derived carbon support were characterized by the largest particle size (13–38 nm). The size dependence of magnetic properties were studied by a vibrating sample magnetometer at room temperature. For the first time, the critical particle size of Fe-Co alloy nanoparticles with equiatomic composition has been experimentally determined as 13 nm, indicating the transition of magnetic properties from ferromagnetic to superparamagnetic.

A study is performed of cobalt/MgAl 2 O 4 catalysts promoted with glucose at Co/C molar ratios of 16.5, 3.2, and 1.6 via sequential deposition and codeposition. Magnetometry and IR spectroscopy of adsorbed CO show that raising the content of carbon in the catalyst contributes to the reduction of cobalt, regardless of how Co is introduced. Infrared spectroscopy reveals the main adsorption sites are cobalt cations and metallic Co. A strong contribution from adsorption sites characteristic of large Co particles is observed in systems synthesized via codeposition. Adsorption sites attributed to Co 2+ and Co δ+ are structurally more homogeneous than ones attributed to metallic Co.

Novel ternary hybrid polyphenoxazine (PPOA)-derived nanocomposites involving Co-Fe particles and single-walled (SWCNTs) or multi-walled (MWCNTs) carbon nanotubes were prepared and investigated. An efficient one-pot method employing infrared (IR) heating enabled the formation of Co-Fe/CNT/PPOA nanocomposites. During this, the dehydrogenation of phenoxazine (POA) units led to the simultaneous reduction of metals by released hydrogen, yielding bimetallic Co-Fe particles with a size range from the nanoscale (5–30 nm) to the microscale (400–1400 nm). The synthesized Co-Fe/CNT/PPOA nanomaterials exhibited impressive thermal stability, demonstrating a half-weight loss at 640 °C and 563 °C in air for Co-Fe/SWCNT/PPOA and Co-Fe/MWCNT/PPOA, respectively. Although a slightly broader range of saturation magnetization values was obtained using MWCNTs, it was found that the type of carbon nanotube, whether an SWCNT (22.14–41.82 emu/g) or an MWCNT (20.93–44.33 emu/g), did not considerably affect the magnetic characteristics of the resulting nanomaterial. By contrast, saturation magnetization escalated with an increasing concentration of both cobalt and iron. These nanocomposites demonstrated a weak dependence of electrical conductivity on frequency. It is shown that the conductivity value for hybrid nanocomposites is higher compared to single-polymer materials and becomes higher with increasing CNT content.

The effect of N-layer-by-layer promotion (N = 0, 1, 5, 10 layers) of Co/MgAl2O4 catalysts (MgAl2O4 is aluminum-magnesium spinel with S-sp = 23 m(2)/g) with glucose on the textural and physicochemical properties of the catalyst was studied. For Co-supported catalysts, the dispersity of cobalt increased significantly after promotion of the MgAl2O4 support with glucose (N > 1). For cobalt catalysts prepared by impregnation of the support with both cobalt nitrate and glucose, the dispersity of cobalt did not change.

The influence of carbon on the genesis of the active phase of cobalt in aluminum–magnesium spinel supported catalysts on their catalytic properties in the synthesis of hydrocarbons from CO and H2 has been studied. Promotion with carbon was carried out by two independent methods: in the first one, carbon was deposited on a spinel support by thermolysis of glucose followed by the deposition of cobalt; in the second one, the catalyst was prepared by coimpregnation of the support with a solution of cobalt nitrate and glucose followed by thermolysis. The catalysts were characterized by simultaneous thermal analysis in combination with mass spectroscopy of evolved gases, in situ magnetic measurements, low-temperature nitrogen adsorption, and transmission electron microscopy. The modified catalysts showed a significantly higher CO conversion rate (turnover frequency) and selectivity for target liquid hydrocarbons compared to the unpromoted catalyst.

Intermetallic hydrides (IHs) are shown to be complex dynamic systems. Hydrogen desorption and dissociative adsorption on IHs are the rate-determining stages in the heterophase exchange of hydrogen of the gas phase and hydride. The oxidative treatment of IHs leads to surface enrichment with a more noble metal, which determines the unique catalytic properties of the system along with the heterophase exchange of hydrogen.

Carbon material (CM) based on shadbush CAm (Amelanchier) wood pulp and a mixture of CAm + AMS, where AMS is aluminum magnesium spinel, are used as a support for a Fe-containing catalyst promoted by Bi (0.6 wt %) for the hydrogenation of CO. The dynamics of the formation of iron carbides during the activation of iron oxides supported on the CM and CM–aluminum magnesium spinel mixture is studied, along with the effect bismuth has on this process. It is found that they already have nonzero magnetization at the stage of preparing the catalysts. It is shown that with Fe/CAm, only Hägg carbide forms in a medium of CO/H2 (1 : 1), while a mixture of Hägg carbides and ε'-Fe2.2C forms when using Fe/(CAm + AMS). The promotion of the Fe/(CAm + AMS) catalyst by bismuth substantially increases the amount of formed Hägg carbide and affects the amount of ε'-Fe2.2C negligibly.

This study is devoted to the reduction of Fe2O3 supported on silica gel in H-2 in the temperature range of 290-600 degrees C. A continuous magnetization measurement method was used to obtain the temperature programmed reduction (TPR) profile. The influence of the external magnetic field on the dynamics of the process is investigated. It was shown that the TPR profile depends both on the magnitude of the applied field and on the particle size of hematite.

Magnetic and calorimetric properties of a eutectic alloy of ZnSnAs 2 –MnAs system are studied depending on particle size in the range of magnetostructural transition temperatures of the ferromagnetic phase MnAs. The particle sizes are varied by using different cooling rates as measured by a temperature-control device. The cooling rate is ~0.05°C/s under ordinary conditions and ~90°C/s under quenching with salt systems having high heat conductivity. Simultaneous phase solidification, typical of eutectics, under high cooling rates yields nanosized (≤50 nm) MnAs grains. DSC curves for quenched samples, unlike for samples prepared under ordinary conditions, have no thermal feature associated with α–β-MnAs magnetostructural transformation. The magnetization and Curie temperature have considerably different values in quenched samples and in samples prepared in an ordinary manner. The Curie temperature rises to 337 K and the coercive force increases as the particle size increases.