Magnetic characterization techniques and micromagnetic simulations of magnetic nanostructures: from zero to three dimensions.

The investigation of the magnetic characteristics of magnetic nanostructures (MNs) in various dimensions is a crucial direction of research in nanomagnetism, with MNs belonging to various dimensions exhibiting magnetic properties related to their geometry. A better understanding of these magnetic properties is required for MN manipulation. The primary tools for researching MNs are magnetic characterisation techniques with great spatial resolution and spin sensitivity. Micromagnetic simulation is another technique that minimises experimental costs, while providing information on the magnetic structure and magnetic behaviour, and has enormous potential for predicting, validating, and extending the magnetic characterisation results. This review first looks at the progress of research into quantitatively characterising the magnetic properties of low-dimensional (including 0D, 1D, and 2D) and 3D MNs in two directions: magnetic characterisation techniques and micromagnetic simulations, with a particular emphasis on the potential for future applications of these techniques. Single magnetic characterization techniques, single micromagnetic simulations, or a mix of both are utilised in these research studies to investigate MNs in a variety of dimensions. How the magnetic characterisation techniques and micromagnetic simulations can be better applied to MNs in various dimensions is then outlined. This discussion has significant application potential for low-dimensional and 3D MNs.

Extending Ag Nanoparticles as Colorimetric Sensor to Industrial Zinc Electrolyte for Cobalt Ion Detection.

The direct and rapid determination of trace cobalt ion (Co2+) in the electrolyte of zinc smelting plants is urgently needed but is impeded by the severe interference of extremely high-concentration zinc ions in the solution. Herein, colorimetric detection of Co2+ by the polyvinylpyrrolidone functionalized silver nanoparticles (PVP-AgNPs) is realized in solutions with the Zn/Co ratio being high, up to (0.8-5) × 104, which is located within the ratio range in industrial solution. The high concentration of Zn2+ induces a strong attenuation of Co2+-related signals in ultraviolet-visible (UV-vis) extinction spectra; nevertheless, a good linear range for detecting 1-6 mg/L Co2+ in 50 g/L Zn2+ solution is still acquired. The strong anti-interference toward other metal ions and the mechanism understanding for trace Co2+ detection in such a high-concentration Zn2+ solution are also revealed by systematic analysis techniques. The results extend the AgNPs as colorimetric sensors to industrial solutions, providing a new strategy for detecting trace-metal ions in industrial plants.

Mechanistic study on calcium ion diffusion into fayalite: A step toward sustainable management of copper slag.

Copper slag, which contains Fe-rich fayalite (Fe2SiO4), is a valuable solid waste that warrants further research in order to recover iron. Calcium oxide (CaO) can significantly enhance iron recovery from copper slag; however, the associated mechanism has not yet been explored. In this study, we investigated the interaction between CaO and Fe2SiO4 to obtain detailed understanding of the role of CaO in enhancing iron recovery. The presence of CaO was found to accelerate the decomposition of Fe2SiO4 via an ion-exchange-like process. Specifically, CaO dissociated into Ca(II) and a Ca-deficient Ca1-yO species at high temperatures. The Fe(II) ion at the M2 site of Fe2SiO4 was substituted by the released Ca(II) ion, resulting in the formation of [(Fe(2-x)Cax)SiO4]∙xFe(II). Subsequently, the substituted Fe(II) occupied the Ca vacancy in Ca1-yO to form (Ca(1-y)Fe(II)y)O. The disproportionation of Fe(II) and the combination reaction between CaO and the SiO2 separated from Fe2SiO4 led to the generation of the final products, viz. Fe2O3, Fe3O4, and CaSiO3. This study explains the specific role of CaO in decomposing Fe2SiO4. It would not only provide theoretical guidance for iron recovery from copper slag but also present a new perspective on the recycling of valuable resources from many other smelting slags (e.g., iron slag, lead slag, and nickel slag).

Isothermal Coal-Based Reduction Kinetics of Fayalite in Copper Slag.

The coal-based reduction of fayalite was characterized using thermogravimetric (TG) and differential TG methods with reduction temperatures from 1123 to 1273 K. The results of fayalite isothermal reduction indicate that the reduction process is divided two stages. The corresponding apparent activation energy E was gained using the isoconversional and model-fitting methods. At the first stage, the effect of temperature on the reduction degree was not clear, and the phase boundary chemical reaction was the controlling step, with an apparent activation energy E value of 175.32-202.37 kJ·mol-1. At the second stage, when the temperature was more than 1123 K, the conversion degree and the reaction rate increased nonlinearly with increasing temperature, and two-dimensional diffusion, three-dimensional diffusion, one-dimensional diffusion, and phase boundary-controlled reaction were the controlling stages, with an apparent activation energy E ranging from 194.81 to 248.96 kJ·mol-1. For the whole reduction process, the average activation energy E and pre-exponential factor A were 185.07-225.67 kJ·mol-1 and 0.796-0.797 min-1, respectively.

Engineering SrCuxO composition to tailor the degradation activity toward organic pollutant under dark ambient conditions.

The composition of SrCuxO mixed metal oxides (MMOs) was engineered via varying the amount of copper relative to strontium. As-synthesized SrCuxO were highly active for degrading methyl orange (MO) pollutant at dark ambient conditions without the aid of other reagents. The catalytic activity of SrCuxO demonstrated a reverse-volcano relationship with copper content. Copper-rich MMOs (SrCu2O) exhibited the highest degradation activity for MO by far and degraded ca. 96% MO within 25 min. MO degradation over SrCu2O was a surface-catalytic reaction and fitted pseudo-first-order reaction kinetics. The contact between MO molecules and catalyst surface initiated the reaction via the catalytic-active phase (Cu+/Cu2+ redox pair), which serves as an electron-transfer shuttle ([Formula: see text]) from MO to dissolved O2, inducing the consecutive generation of reactive oxygen species, which resulted in MO degradation as evidenced by radical trapping experiment. XPS and XRD analysis revealed that active phases in SrCu2O materials underwent irreversible transformation after reaction, contributing to the observed deactivation in the cycling experiment. The observations in this study demonstrate the significance of chemical composition tailoring in catalyst synthesis for environmental remediation under dark ambient conditions. Graphical abstract.