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Electrochemical nitrogen reduction reaction (NRR) is considered as an alternative to the industrial Haber-Bosch process for NH3 production due to both low energy consumption and environment friendliness. However, the major problem of electrochemical NRR is the unsatisfied efficiency and selectivity of electrocatalyst. As one group of the cheapest and most abundant transition metals, iron-group (Fe, Co, Ni and Cu) electrocatalysts show promising potential on cost and performance advantages as ideal substitute for traditional noble-metal catalysts. In this minireview, we summarize recent advances of iron-group-based materials (including their oxides, hydroxides, nitrides, sulfides and phosphides, etc.) as non-noble metal electrocatalysts towards ambient N2-to-NH3 conversion in aqueous media. Strategies to boost NRR performances and perspectives for future developments are discussed to provide guidance for the field of NRR studies.

Free iron leads to the formation of pro-oxidant reactive oxygen species (ROS). Humic acids (HAs) enhance permeability of cellular wall and act as a chelator through electron transferring. This study was designed to test chelator effect of HA on iron as well as its anti-oxidant effect against the iron-induced hepatotoxicity and cardiotoxicity. The rats used were randomly divided into four groups (n = 8/group): group I (the control group); group II (the HA group), humic acid (562 mg/kg) was given over 10 days by oral gavage; group III (the iron group), iron III hydroxide polymaltose (250 mg/kg) was given over 10 days by intraperitoneal route; and group IV (the HA plus iron group), received the iron (similar to group II) plus humic acid (similar to those in groups II and III) group. Blood and two tissue samples both from liver and heart were obtained for biochemical and histopathological evaluations. Iron deposition, the iron-induced hepatotoxicity, and cardiotoxicity were demonstrated by histopathological and biochemical manner. However, no significant differences were observed in the serum biochemical values and the histopathological results among the iron and the HA plus iron groups in the liver tissue but not in the heart tissue. The protective effects of humic acid against iron-induced cardiotoxicity were shown but not against hepatotoxicity in our study.

Based on the work of Wang et al. (Chin. Phys. Lett. 29:049701, 2012), we re-investigated electron capture on iron group nuclei in the outer crust of magnetars and studied magnetar evolution. Effects of ultra-strong magnetic field on electron capture rates for 57Co have been analyzed in the nuclear shell model and under the Landau-level-quantization approximation, and the electron capture rates and the neutrino energy loss rates on iron group nuclei in the outer crust of magnetar have been calculated. The results show that electron capture rates on 57Co are increase greatly in the ultra-strong magnetic field, and above 3 orders of magnitude generally; and the neutrino energy loss rates by electron capture on iron group nuclei increase above 3 orders of magnitude in the range from B=4.414×1013 G to B=4.414×1015 G. These conclusions play an important role in future studying the evolution of magnetar. Furthermore, we modify the expressions of the electron chemical potential (Fermi energy) and phase space factor by introducing Dirac δ-function, and select appropriate parameters of temperature T, magnetic field B and matter density ρ in the our crust, thus our results will be reliable than those of Wang et al.

Metal carbide ceramics offer potential as protective coatings for iron-group metals M (Fe, Co, and Ni) because of its favorable physical, chemical, and mechanical properties. We present a computational study to evaluate the adhesion of hafnium carbide coatings on iron-group metals substrates based on density functional theory. We consider the Fe(110)/HfC(100), Co(111)/HfC(100), and Ni(111)/HfC(100) interfaces and focus on the magnetism, adhesion, and bonding of C-site and Hf site interfaces. The C-site interfaces have the largest adhesion, forming polar covalent/ionic mixed bonds. The calculations reveal that the work of adhesion increases on passing from iron to nickel (Fe

The chemical abundances of the Ba stars are excellent information for setting constraints on models of s-processes nucleosynthesis. In this work, we adopt a new analysis approach to determine the relative contributions from individual neutron-capture processes to the elemental abundances of Ba stars. We find that the production of s-process elements should accompany by the production of Cu and Zn, the calculated results on Cu and Zn abundances are in quite good agreement with observed data. The observed [Cu, Zn/Fe]–[s/Fe] correlations of Ba stars can be explained by binary scenario in which Ba stars formed.

New three-body resonances appeared in the neutron scattering on two nuclei fixed in nodes of overdense crystalline lattice have been calculated for the iron group isotopes. These resonances are strongly dependent on the lattice parameters and characteristics of two-body resonances in neutron–nucleus subsystems. The effective forces created by the neutron resonance rescatterings supplement the Coulomb forces between nuclei of the crystalline lattice. These effective resonance interactions occur only at certain distances between nuclei and are accompanied by gamma radiation.

Samples of single-crystal silicon implanted with iron-group ions are investigated by electron paramagnetic resonance (EPR). The change in relative permittivity μr of the silicon layer modified by implanted nickel ions is found. The accumulation kinetics of paramagnetic centers of amorphous regions of silicon implanted with Co, Ni, and Fe are shown to be different. Magnetic hysteresis for both the wide EPR line due to implanted impurities and the EPR line due to dangling chemical silicon bonds is found.

Structuring has been examined for Cr-Cu composites under conditions of impregnation and subsequent liquid-phase sintering at 1200°C in a vacuum of (2–4) · 10−3 Pa with reduced and electrolytic chromium powders. The size distribution for the particles of the refractory component in the microstructure containing the reduced chromium on liquid-phase sintering for 60 min corresponds to a logarithmic normal distribution; the distribution parameters are sensitive to the volume fraction of refractory particles. The calculated values for the dihedral angle are close to one of the modes of the distribution for the dihedral angles in the microstructure for specimens made of electrolytic chromium (115°). At 1200°C, the equilibrium Crs-Cul system obeys the condition \(\frac{{\sigma _{sl} }}{{\sigma _{ss} }} \geqslant 0.5\). This indicates the probability of formation or preservation of framework structure elements during the liquid-phase sintering, which are observed by experiment in specimens containing reduced chromium.

Accurate theoretical data for the transition probabilities are highly demanding in astrophysics and in the study of plasma in astrophysical objects and fusion devices. Na-like highly stripped ions of iron group, specially NiXVIII is very important in this respect. A highly improved basis in a relativistic many-body coupled-cluster method (CCM) to include correlation properly is employed to calculate excitation energies, the electric quadrupole (E2) transition line strengths and transition probabilities for NiXVIII. The effect of correlation is studied thoroughly. The present improved data for different atomic/ionic properties are compared with the available theoretical and/or experimental data and they are in agreement. Some E2 transition data are reported for the first time.

The electrode kinetics of anomalous codeposition of iron group metals is interpreted by queuing theory applied to the recently proposed Zech–Podlaha–Landolt model which postulates an adsorbed mixed–metal species existing temporarily as an electrochemically activated complex. The complex acts as an intermediate in a consecutive reaction leading to enhanced deposition of the more electronegative metal. Numerical illustrations for the codeposition of iron and nickel, and cobalt and nickel from a sulphate electrolyte are provided.

A droplet flowing over onto a plate introduced from above has been used to study the kinetics of spreading and to describe the observable characteristics of spreading of tin on iron, cobalt, nickel, and the intermetallic compounds Ni3Sn, Ni3Sn2 under a vacuum of (2–4)·10−3 Pa at 400–1000°C, droplet mass 0.01–0.06 g. We show by a formal kinetic analysis of experimental data that in the low-temperature range (400–500°C) the kinetic regime dominates, and in the high-temperature range (600–1000°C) the inertial—kinetic regime dominates. In spreading of tin on iron, cobalt, nickel, and the intermetallic compounds Ni3Sn and Ni3Sn2, the nature of the interaction corresponds to the phase equilibrium in the studied systems. The results for the kinetics of spreading of tin on nickel and the intermetallic compound Ni3Sn showed that spreading of the main bulk is preceded by spreading of a precursor film.

The anomalous codeposition of the iron group metals was investigated using the rotating cylinder Hull (RCH) cell. Single metals and binary alloys of iron, nickel and cobalt were deposited in the RCH cell and the partial current densities were determined as a function of length by position sensitive X-ray fluorescence analysis. The measured overall polarization behaviour was used as a boundary condition for the numerical calculation of the potential distribution along the cylinder using the Laplace equation. By combining the results the partial current density potential curves were established. Experiments performed at different rotation rates confirmed the inhibiting effect of the less noble metal on the deposition of the more noble metal. The inhibiting effect of iron on nickel disappeared when iron reached the limiting current. Strong evidence was found that in binary alloy deposition of iron, cobalt and nickel the reaction rate of the less noble metal is promoted by the presence of the more noble component.

To select reliable information from the literature on the enthalpies of formation of iron, cobalt, and nickel phosphides, use has been made of linear correlation of the enthalpies of atomization for the phosphides and the enthalpies of sublimation of the phosphide-forming metals, which is implied by thermodynamic laws. Reliable values have been derived for the enthalpies of formation and atomization of iron-group metal phosphides.

Electrodeposition of Ni-Mo and Fe-Mo alloy coatings from acid citrate electrolyte was investigated over a wide range of cathode potentials and under various hydrodynamic conditions. Such alloys had been found to be deposited with substantial depolarization against iron group metals. With the same electrodeposition conditions, the molybdenum percentage in Fe-Mo coatings is much higher than in Ni-Mo. The molybdenum presence results in a lower overvoltage of hydrogen evolution, so that these alloys are deposited with a current efficiency much lower than that in the separate reduction of iron group metals. For a Ni-Mo system, the Mo percentage in the coating is increased together with increase of the transport rate of ions towards the cathode and with decrease of the cathode potential value being reduced; while for Fe-Mo alloy an inverse relation is observed. When passing from the Ni-Mo to the Fe-Mo system, the control of the molybdenum reduction reaction is changed. In codeposition with nickel it shows a diffusion control, while in discharging with iron its control is of the activation type. The Ni-Mo coatings obtained contained from 1.5–6% molybdenum whereas Fe-Mo deposits contained from 12–40% depending on electrolysis conditions. The quality of the coatings containing more than 20% Mo deteriorated and in these deposits some nonmetallic inclusions were present.

Composites suitable for triboengineering applications have been obtained by self-propagating high-temperature synthesis. X-ray structure investigations have been made of the phases arising from process combustion of a powder mixture of titanium and carbon in the presence of copper and metals of the iron group.

The differential thermal analysis method is used to detect a new phase transition in iron group ferromagnetics. Assuming that this transition is caused by relativistic interactions, a thermodynamic theory is constructed to describe the transition.

Sediment samples at 10 locations in the mainstem of the Yellow River were taken in 1994. Five forms (exchangeable, carbonate, organic, Fe/Mn oxide and residual) of metals were extracted by the Tessier method. The total contents and contents of the five forms of 16 metal elements (Li, Na, K, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Al) were determined by ICP-AES. In sediments of the Yellow River, except for Na, mobile elements (such as K, Ca) do not show a negative correlation with the immobile elements. Alkaline metals (Li, Na, and K), Ti, and Al exist mainly in the residual form. The exchangeable forms of alkaline-earth elements (Ca, Sr, and Ba) are the highest, and their residual forms go up with the increase of the period in the periodic table of elements. Half of Mn exists in the residual form, and its non-residual forms exist mainly in carbonate and oxide forms. Except Mn, the iron group elements (Fe, Co, Ni, V, Cr) mainly exist in the residual and oxide forms. High carbonate content of Ca does not cause high contents of other elements in carbonate form, showing that chemical weathering is not strong in the area.

The electrical conductivity of a number of the semiconducting alloys of iron disilicide with the iron group transition metals and some elements of Vb group have been investigated in detail. Wide temperature regions of linear temperature dependence of resistance were found. The temperature coefficient of resistance (TCR) in these regions is low enough. There is an opportunity of varying the resistivity of these alloys by means of modification of the alloy composition.

Conflicting opinions exist over the optimal amount of iron that low birth weight infants (LBW)should receive and for how long they should receive iron post discharge from hospital. Further,little information is available on the effect of poor iron nutrition on the neurodevelopmental outcome of LBW infants. We have previously demonstrated(CMAJ 1990:143;733-37)that 33% of LBW infants at 9 months of age fed an iron supplemented formula(12mg/l)for 6 months,had ferritin levels indicative of depleted iron stores. To investigate the effect of increased iron intakes on neurodevelopment, we randomly assigned infants at 2000g weight to receive either a formula with 12mg iron/l(iron) or 21 mg/l(high iron). The infants received either formula for a period of one year. At baseline, 3 months of age and 9 months of age the following measurements were taken: weight, hemoglobin, malondialdehyde (MDA), ferritin, and Griffiths Mental Develoment Scales. Statistical analysis between groups was with unpaired t-test using the Bonferonni correction for multiple comparisons. There were no statistical differences demonstrated between groups for any variables. There were no difference in birth weight or gestation between groups(bw=1432g ±390, gestation=31.5wks±2.3, N=29,iron group, N=31,high iron group). All statistics are reported as mean±sd. Table

Elemental abundances of the VH group of cosmic radiation have been measured in the energy interval 250–550 MeV nucl−1 in a balloon exposure at Sioux Falls (South Dakota) of a plastic detector LeXAN stack. The so obtained abundances have been extrapolated to the sources in the frame of the homogeneous model correcting for energy loss. After taking into account solar modulation, the best fit to model values has led to a escape mean free path λe = 5E−0.4 g cm−2, whereE is the energy in GeV nucl−1, forE>1 GeV nucl−1, and a constant λe = 5 g cm−2 forE≤1 GeV nucl−1. When turning to the diffusion model, also including an energy loss term, a diffusion coefficientD=3×1028 cm2 s−1 has been estimated.

The experimental results of a study of the characteristic absorption of x-rays by metals of the iron group in a number of their alloys and compounds with metalloids are described. On the basis of the results obtained and previous investigations, a conclusion is formulated on the specific features of the absorption curves for these atomic structures for the corresponding nature of the interatomic bond.

The wave function of the extended method of calculation is used as a correction to the wave function of the ordinary method of calculation for the d-electrons of atoms and ions of the iron group elements, under the extended method of calculation being understood the use of radial orbitals equal in number to the number of electrons in the shell. The method of expressing the energy in terms of radial integrals in the extended method of calculation is characterized. Some numerical results are presented and discussed.

This article examines results of x-ray emission spectroscopy and x-ray diffractometry of amorphous and crystalline layers of certain germanides of iron-group transition metals. Combined analysis of the K- and L-bands of Me and Ge in Me2 (Fe, Co, Ni)Ge and data from model interpretation of radial distribution functions of atoms in amorphous layers are used to make conclusions on the character of the chemical bond and the structure of the short-range order in the materials studied. It was established that there is no significant change in the character of the chemical bond in germanides Me2(Fe, Co, Ni)Ge in the transition from the crystalline to the amorphous state. It was also found that short-range order in the investigated amorphous layers can be described by a complex “poly-structural” atom distribution, i.e. it is characterized by a complex, microscopically nonuniform model of the type Me2Ge+Me.

The flux growth of crystals of a number of new rare-earth and transition metal compounds is reported. The following empirical formulae were in good agreement with electron probe microanalysis (EPMA): (Ba, Gd)TiO3, R4Ba6(BO3)9(R = Ho to La), Ni3Nb2O8, Ni8NbB3O15, Ni2V2PbO8, Ta2Co4O9 and PbCr2.3Ti2.3O9. X-ray powder pattern data are given. The growth of crystals of GdVO3, Pb2CrO5 and Ni3V2O8, which have previously been prepared only as powders, is also reported.

The methods of radioactive labelling the sea water and the conditions for reaching the equivalence of physico-chemical states of radiotracers and corresponding stable nuclides in sea water are analyzed. The process of bioassimilation, the uptake and release of radionuclides by plankton organisms, is considered as the way of fast stabilization of physicochemical forms of radiotracers in sea water. The data are presented on the sorption of iron, cobalt, nickel and manganese by typical ocean bottom sediments (deep-water red clay, diatomic coze, carbonate deposit).

1. A study was made of the effects of small additions (0.05–1.0 wt.%) of the iron-group metals upon the sintering of niobium and of some properties of the resultant alloys. 2. The hypothesis is advanced that Fe, Co, and Ni additions activate the sintering of niobium by bringing about localization of the free electrons of the niobium atoms in the 3d states, as a result of which the amount of free energy stored in the system niobium-addition metal diminishes. Nickel — the metal whose 3d level has the highest acceptor capacity — exerts the strongest activating influence.

The metal-insulator transition in 3d transition metal oxides such as the ternary perovskite oxides as well as the binary oxides both as a function of composition and temperature are reviewed. The description of metallisation in terms of a change in sign of the temperature coefficient of resistance as well as conductivity at 0 K are considered in terms of modern theories based on localisation. It is pointed out that there may be grounds to believe that in the high temperature limit a resistivity less than ≈10−1 ohm cm may be associated with metallic properties despite a negative temperature coefficient of resistance. The correlation between magnetic and electrical properties have also been examined.

Oscillator strengths are calculated by the STF method for selected transitions of Mn i. The results, applied to the analysis of solar spectra, support the ‘high’ solar photospheric abundance of manganese recently obtained on the basis of experimental gf-values.

A model has been obtained from a strict expression of crystal energy by introducing S and valence approximations. The Mulliken approximation has been used for double-centered exchange and three-center integrals. The calculations have been carried out for Slater type atomic orbitals, varying the screening parameters. The bond energy has been represented as a sum of the energy for forming partial differential electronic densities, EA, the interatomic interaction energy EIA, and the correlation energy of atomic states in the crystal, E S . The computed bond energies for four oxides of alkaline-earth metals and six oxides of transition (iron group) metals are in good agreement with experimental data.

Relative abundances for the VH group of Cosmic Radiation (20≤Z≤28) at energiesE≤600 MeV nucl−1 have been measured by means of plastic detector LEXAN. The stack was exposed to cosmic rays during a 82 hr balloon flight at Sioux Falls (South Dakota) at an average altitude equivalent to 4 g cm−2 of residual atmosphere. A total number of 1058 events have been analyzed, out of which 675 have been unambiguously identified. Two different discrimination methods have been applied in order to test their influence on final spectra.

Hartree-Fock variational procedure was carried out for the iron group atoms in singly ionized and neutral states to optimize the 3d orbital in a two exponential form. For the inner orbitals a simplified description was given and they were assumed to be fixed during the variational procedure. The analytic wave functions presented here are proposed first of all for use in molecular and solid state physics applications.

Moderately accurate oscillator strengths are obtained by application of systematic corrections to Warner's-log(gf) for the once ionized elements of the iron group. Corrections are derived by comparison of Warner's values with those of Kurucz-Peytremann (Scii, Tiii,Vii, Crii, Mnii, Coii, and Niii) and Kurucz (Feii).K−P andK derived log(gf) by semi-empirical methods for many transitions using scaled Thomas-Fermi-Dirac potentials for the atoms of the elements from B to Ni. Although their individual values may be seriously in error, it has been shown that their mean scales are acceptable, being affected at most by rather small errors. It is known, for example, that when interacting terms are not properly accounted for in the semi-empirical method, very small values are derived for log(gf); these were dropped away in calculating mean corrections as they exhibited gross deviations.

Mossbauer spectroscopy has been remarkably useful in understanding several properties of the mixed oxides. The investigations relating to spin arrangements form an important part of the successful applications of this method. In mixed spinel ferrites and garnets, Mossbauer spectroscopy unambiguously showed the non-collinearity of spins in the same sublattice in several cases. The detailed investigations showed features predicted by the localized canting model (LCM), viz., the simultaneous presence of non-collinearity at the two non-equivalent sites in certain cases, ’spin reversal’ of ions without magnetic ions on the nearest non-equivalent sites. However, it has not been possible to observe other details of the model. Another striking result obtained is that non-collinearity decreases rapidly as the temperature increases, disappears at temperatures below 80 K. These studies have not, however, succeeded in determining the exchange constants unambiguously. In orthoferrites, the complications due to the variations in the environments of ions in the same sublattice are not present. Consequently, studies of spin reorientations (SR) relative to the crystal axes and other magnetic properties have provided accurate results, ideal for theoretical analyses. SR is due to the anisotropic-symmetric and antisymmetric exchange interactions between the rare earths and iron group ions, which are much smaller than the isotropic part of the exchange interaction. Thus, a detailed theoretical analysis expresses SR parameters in terms of these smaller interactions and the external magnetic field, if present. The number of parameters involved is, however, large. Analyses of the experimental data are made using a simpler two-sublattice model involving a smaller number of parameters. This, nevertheless, makes comparison between similar orthoferrites possible. There are other oxides as well which show SRs due to changes in the signs and magnitudes of the crystal field anisotropic constants. Such studies are useful for investigating crystal field interactions.

The kinetics of He/sup 4/ burning at a constant temperature T> 10/sup 9/ /sup 0/K and a density rho> 10/sup 5/ g/cm/sup 3/ is considered. The regions of formation of iron group elements and lighter nuclides during He/sup 4/ burning are indicated in the rho, T plane. The dependence of the mean atomic number of the nuclides formed on the temperature and the density is determined. For the temperature T greater than or equal to4.10/sup 9/ /sup 0/K a ''neutron flash'' is found, which can lead to a change in the isotopic composition of the r- and s-process elements present. The range of rho and T in which the formation of an excess number of the elements beyond the iron peak is found.

The spectrum of the peculiar Bp star HD 36916 has been studied on plates with dispersion 9.7 A/mm and compared with those of η Aur, B3V andi And, B8V. A comparison of the observed contours of Hβ, Hγ and of the Balmer discontinuity D with those computed by Mihalas gives the following results: HD 36916: θe=0.347, logg=3.8;i And: θe=0.383, logg=3.2; η Aur: θe=0.302, logg=3.6. HD 36916 presents the characteristics of the Si-λ4200 stars: strong deficiency in helium and probably also in oxygen and nitrogen, strong excess of silicon and strontium; 3984 Hgii is present. Moreover this star also has characteristics which are not common to Si-λ4200 stars but rather to Mn stars: excess by a factor of ten of the elements of the iron group and an excess larger, probably of the order of 100, for manganese. The star is a member of the Sword subgroup of the Orion association.

A qualitative study was made of sintered materials containing titanium nitride and Fe, Co, Ni, Mo, or W. Their microhardness, microstructure, and strength characteristics were examined.

1. A study was made of the influence of iron-group metal additions on the sinterability of tungsten powder at temperatures of 1000–2000°C. It is shown that the activating effect of these additions increases in the sequence Fe → Co → Ni. 2. It is demonstrated that the method of introducing an addition has no effect on the course of sintering of tungsten powder. 3. An explanation, based on the model of configurational localization of the valence electrons of atoms, is proposed for the mechanism of activated sintering of tungsten.

1. A study was made of the hot pressing of oxides of the iron group metals in powder form, and the effects were determined of temperature, process time, and applied pressure on their relative density. 2. It is shown that the densification of powders of these oxides can be described within the frame-work of the theory of volume viscous flow of porous solids. 3. It was established that the deformation rate of particles of these oxide powders in hot pressing obeys the law έ∼σ, i.e., is proportional to the applied pressure. 4. The energy of activation for the creep of oxide powder particles in hot pressing and the micro-hardness of oxide specimens produced by this method were determined.

The question of the relative arrangement of the crystalline terms is considered, within the framework of crystal field theory, as a function of the location of the impurity atom in the silicon. The results of the corresponding calculations are found to agree with the experimental data.

Schemes for the analysis of the Iron group are reviewed. The advantages of the Midlands Association scheme are discussed.

1. The question of the interaction of iron with various chemical elements has been considered from the point of view of the formation of continuous, limited solid solutions, based on itsα -andγ modifications, and metallic compounds. 2. Elements, which form continuous solid solutions with iron, are situated in or near Group VIII and have a crystal structure isomorphous with iron. 3. As the elements of the periodic system become further removed from the iron group and the difference in the chemical properties of the atoms increases, the solubility of the elements in iron decreases, and a tendency toward formation of metallic compounds begins to develop. 4. It has been established that, of the total number of elements in the periodic system, iron can interact with 65; it forms solid solutions with most of them. 5. Proceeding from the possibility of simultaneous solution of many elements in theα- andγ -modifications of iron, routes and methods of synthesis of multicomponent iron alloys have been shown, and questions of equilibrium among phases in such complex systems also have been considered.