Replacement Of Fe Atoms Research Articles

The impact of metal dopants on the properties of nZVI: a theoretical study

The substitution of Fe with metal dopants shows potential for enhancing the wastewater remediation performance of nanoscale zero-valent iron (nZVI). However, the specific roles and impacts of these dopants remain unclear. To address this knowledge gap, we employed density functional theory (DFT) to investigate metal-doped nZVI on stepped surfaces. Four widely used metal dopants (Ag, Cu, Ni, and Pd) were investigated by replacing Fe atoms at the edge of the stepped surface. Previous research has indicated that these Fe atoms exhibit chemical reactivity and are vulnerable to water oxidation. Our DFT calculations revealed that the replacement of Fe atoms on the edge of the stepped surface is energetically more favorable than that on the flat Fe(110) surface. Our results shed light on the effects of metal dopants on the surface properties of nZVI. Notably, the replacement of Fe atoms with a metal dopant generally led to weaker molecular and dissociated water adsorption across all systems. The results from this study enhance our understanding of the complex interplay between dopants and the surface properties of nZVI, offering theoretical guidance for the development and optimization of metal-doped nZVI for efficient and sustainable wastewater remediation applications.

Magnetization and Magnetostriction of LaFe<sub>11.2 – <i>х</i></sub>Mn<sub><i>x</i></sub>Co<sub>0.7</sub>Si<sub>1.1</sub> (<i>x</i> = 0.1, 0.2, 0.3) Alloys In Pulsed Magnetic Fields

Abstract—The magnetization and magnetostriction of polycrystalline alloys LaFe11.2 – хMnxCo0.7Si1.1 (x = = 0.1, 0.2, 0.3) were measured in pulsed magnetic fields up to 180 kOe in the temperature range 80–270 K. The replacement of Fe atoms by Mn atoms shifts the TC towards low temperatures and does not affect the value of saturation magnetization. The observed field dependence of the magnetization M(H) near the TC is characteristic of second-order phase transitions, while the temperature dependence of the magnetization M(T) above the TC in strong magnetic fields indicates a first-order magnetic phase transition. The magnetic volume effect ΔV/V reaches 0.81% in a field of 180 kOe. The asymmetry of magnetostriction relative to the temperature of the maximum effect, manifested in strong magnetic fields, and the magnetic field hysteresis of magnetostriction bear signs of a first-order phase transition

Effects of Ni-loading contents on dehydrogenation kinetics and reversibility of Mg2FeH6

Although Mg2FeH6 has drawn significant attention for storing hydrogen, its sluggish kinetics during hydrogenation and poor reversibility hinder practical uses. In this work, the replacement of Fe atoms in Mg2FeH6 with Ni atoms is attempted and the material properties are investigated. A detailed study of the de/rehydrogenation kinetics and reaction mechanisms of the Ni-doped Mg2FeH6 is carried out. The effects of Ni-loading contents on kinetic properties and behaviors as well as reversibility and reaction pathways are characterized. In addition, the crystal structure of a new Ni-substituted Mg2FeH6 phase is confirmed.

Effect of Annealing, Stoichiometry, and Surface on Magnetism of (Pr,Dy)FeCoB Microparticles Ensemble

AbstractMagnetic properties of powder (Pr,Dy)FeCoB ferrimagnetic alloys and effects of annealing, surface states were analyzed. X-ray photoelectron spectroscopy and Mössbauer spectra of powders indicate the effect of surface states on phase composition and magnetic properties of the studied powder, if particles average size is smaller than 10 μm. Effect of stoichiometry on magnetic anisotropy was found. Thermal stability of anisotropy field was proved by replacement of Fe atoms with Co atoms.

Coercitivity of (PrDy)(CoFe)B Microparticles Ensemble Controlled by Magnetic Dipole Interaction and Dry Friction

(DyPr)CoFeB microparticles are the building blocks of sintered magnets. The magnetic properties of powdered (DyPr)(CoFe)B microparticles and the effects of annealing, surface states, fixation of easy axis and magnetic dipole interaction on the magnetic hysteresis loop, and temperature dependencies of magnetization have been analyzed. Fixation of the annealed microparticles in polymer enhances the coercive field up to 11 times and the energy product up to six times. This fact indicates extraction of the true magnetic parameters from the magnetic measurements of powder. Thermal stability of the anisotropy field has been improved by the replacement of Fe atoms with Co atoms.

Replacement of Fe atoms by Ru in a carbidocarbonyl cluster [Fe6C(CO)16]2−. Structures of reaction products

The reaction of the carbidocarbonyl cluster [Fe6C(CO)16]2− with ruthenium(IV) hydroxochloride Ru(OH)Cl3 was studied. At 90–100 °C, the reaction gave products of replacement of Fe atoms by Ru in the [Fe6C(CO)16]2− cluster along with degradation products. Treatment of the replacement products with FeCl3 afforded the [Fe2.96Ru3.04C(CO)17] compound (1), which was characterized by X-ray diffraction analysis. The crystals of cluster 1 are composed of two types of octahedral molecules (1a and 1b) in a ratio of 2 : 1. Molecules 1a are in general positions, and molecules 1b are located on twofold axes. In both molecules, the Fe and Ru atoms are disordered over four of six positions.

Peculiarities of Forming of Magnetic Hardening in Sintered Nd15Fe76.2Ti1.0Al0.8B7 Permanent Magnet by Ageing

Variations of the intrinsic coercivity ( i H c ) with ageing (at 293 to 1173 K for 0.45 to 57.6 ks) of sintered Nd 15 Fe 76.2 Ti 1.0 Al 0.8 B 7 have been investigated. The tests indicated minimum and maximum of intrinsic coercivity ( i H min c and i H max c ) at temperatures 725 K and 1025 K, respectively. The observed behaviour of i H c has been compared with microhardness measurements and microstructure observations (SEM, EDAX, domain structure (DS) and room temperature Mossbauer spectroscopy). SEM and DS investigations gave hints to a change in microstructure. Fitting of the Mossbauer spectra of permanent magnets for different i H c has shown that the magnetic hyperfine field Bhf of 8j2 and 16k2 sites is reduced with increasing i H c which seems to be connected with the replacement of Fe atoms in their sites by Al atoms during ageing. Moreover the higher value of i H c corresponds to the higher value of the line width. The i H max c corresponds to the microhardness H max V for the Nd2 Fe 14 B grain phase. The results suggest that the coercivity of investigated permanent magnet increases during ageing not only by further diffusion of Al into Nd 2 Fe 14 B phase, but also by better distribution of elements in the main phase and especially in grain boundary phases and removing the stress between the phases of the permanent magnet.

Aluminum K-XANES spectra in minerals as a source of information on their local atomic structure

For Al containing compounds with different symmetry types of Al environment (from fourfold to 12-fold coordinated Al) it is revealed that Al K-XANES spectra are well reproduced by the XAFS code, based on the method of Hartree-Fock MT-potential generation, considering the photoelectron single-, double- and triple-scattering processes on approximately linear two- and three-atom chains, originated at the absorbing Al atom. The empirical `selection rules' for choosing these chains are obtained and the origins of features in spectra are interpreted using the SELCOMP code. The proposed EXAFS-like approach for Al K-XANES description is applied also to explain the differences in Al K-XANES spectra, caused by the replacement of Fe atoms by Al atoms in goethite (-FeOOH).

Computer simulation of the electronic structure of the Fe 4 − yAl yC carbide phase in its para- and ferromagnetic states

An understanding of the magnetic properties of the Fe 4 − y Al y C x carbide phase is important for cheap magnet production. A quantum-mechanical investigation of the Fe-Al-C electronic structure has been carried out using the Multiple-Scattering Waves method (SW-X α). Two clusters of the unit cell were chosen in its para- and ferromagnetic chemical arrangements. The total and atomic partial densities-of-states (DOS) were analyzed. Valence electron density maps have been plotted in the following crystallographic planes: (100), (110), (111). The strength of p- d bond hybridization resulting from the replacement of Fe atoms by Al atoms was found from the density distributions.