Direct Recycling of Nd-Fe-B Magnets Based on the Recovery of Nd2 Fe14 B Grains by Acid-free Electrochemical Etching.

Recycling of end-of-life Nd-Fe-B magnets is an important strategy for reducing the environmental dangers associated with rare-earth mining and overcoming the supply risks associated with the rare-earth elements. In this study, a novel concept for recycling of sintered Nd-Fe-B magnets by directly recovering the matrix Nd2 Fe14 B grains is presented. The procedure is based on the anodic etching of sintered Nd-Fe-B magnets in a nonaqueous dimethylformamide (DMF)/0.3 mol L-1 FeCl2 bath. Selective recovery of Nd2 Fe14 B grains was realized within the applied current density <5 mA cm-2 based on the etching priority of phases: metallic Nd > intergranular NdFe4 B4 > matrix Nd2 Fe14 B. The total energy consumption of the proposed recycling route is estimated to be 2.99 kWh kg-1 , which is comparable to the state-of-the-art methods. However, the proposed recycling route is currently the only procedure that enables repeated recycling of sintered Nd-Fe-B magnets in a closed-loop system.

Controlling the radical-induced redox chemistry inside a liquid-cell TEM.

With Liquid-Cell Transmission Electron Microscopy (LCTEM) we can observe the kinetic processes taking place in nanoscale materials that are in a solvated environment. However, the beam-driven solvent radiolysis, which results from the microscope's high-energy electron beam, can dramatically influence the dynamics of the system. Recent research suggests that radical-induced redox chemistry can be used to investigate the various redox-driven dynamics for a wide range of functional nanomaterials. In view of this, the interplay between the formation of various highly reactive radiolysis species and the nanomaterials under investigation needs to be quantified in order to formulate new strategies for nanomaterials research. We have developed a comprehensive radiolysis model by using the electron-dose rate, the temperature of the solvent, the H2 and O2 gas saturation concentrations and the pH values as the key variables. These improved kinetic models make it possible to simulate the material's specific radical-induced redox reactions. As in the case of the Au model system, the kinetic models are presented using Temperature/Dose-rate Redox potential (TDR) diagrams, which indicate the equilibrium [Au0]/[Au+] concentration ratios that are directly related to the temperature-/dose-rate-dependent precipitation or dissolution regions of the Au nanoparticles. Our radiolysis and radical-induced redox models were successfully verified using previously reported data from low-dose experiments with γ radiation and experimentally via TDR-dependent LCTEM. The presented study represents a holistic approach to the radical-induced redox chemistry in LCTEM, including the complex kinetics of the radiolysis species and their influence on the redox chemistry of the materials under investigation, which are represented here by Au nanoparticles.

Dual purpose laser ablation-inductively coupled plasma mass spectrometry for pulsed laser deposition and diagnostics of thin film fabrication: preliminary study.

PLD (pulsed laser deposition) is an attractive technique to fabricate thin films with a stoichiometry reflecting that of the target material. Conventional PLD instruments are more or less black boxes in which PLD is performed virtually "blind", i.e. without having great control on the important PLD parameters. In this preliminary study, for the first time, a 213 nm Nd-YAG commercial laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS) intended for microanalysis work was used for PLD under atmospheric pressure and in and ex situ ICPMS analysis for diagnostics of the thin film fabrication process. A PLD demonstration experiment in a He atmosphere was performed with a Sm(13.8)Fe(82.2)Ta(4.0) target-Ta-coated silicon wafer substrate (contraption with defined geometry in the laser ablation chamber) to transfer the permanent magnetic properties of the target to the film. Although this paper is not dealing with the magnetic properties of the film, elemental analysis was applied as a means of depicting the PLD process. It was shown that in situ ICPMS monitoring of the ablation plume as a function of the laser fluence, beam diameter and repetition rate may be used to ensure the absence of large particles (normally having a stoichiometry somewhat different from the target). Furthermore, ex situ microanalysis of the deposited particles on the substrate, using the LA-ICPMS as an elemental mapping tool, allowed for the investigation of PLD parameters critical in the fabrication of a thin film with appropriate density, homogeneity and stoichiometry.