Enhanced magnetization in highly crystalline and atomically mixed bcc Fe-Co nanoalloys prepared by hydrogen reduction of oxide composites

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe_1-xCo_x (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe₂O₄ and Fe₃O₄ phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe_0.25Co_0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (M_S) of the Fe_0.25Co_0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the M_S of the Fe_0.75Co_0.25 and Fe_0.50Co_0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing.

Micromixer: An Effective Tool for the Production of Sub-Nanosized Noble Metal Particles

This paper demonstrates the functionality of a simple and convenient microfluidic method in synthesizing a series of poly(vinylpyrrolidone) (PVP) stabilized nanoparticles (NPs) of various novel metals (Pt, Pd, Ru, Rh, Ag, and Au) with an average diameter of [Formula: see text]2 nm. In this method, the use of microfluidic mixture provided a homogenous mixing of the metal precursors and reducing agent nearly at the molecular level, that yield monodispersed sub-nanosize NPs. Core diameters of the produced NPs determined by transmission electron microscopy (TEM), were [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]nm for Pt, Pd, Ru, Rh, Ag and Au NPs, respectively. Of them, Pt NPs were detailed characterized. The obtained Pt NPs were found to have fcc crystal structure with 1.2 nm crystalline size which is very similar to the corresponding TEM result. The efficiency of the synthesis of NPs by micromixer was compared with batch/NaBH4 reduction method for the Pt NPs. It was found that in batch method the as-prepared NPs decreased the reducing ability of NaBH4 by catalytic degradation. In contrast, the micromixer could separate the produced metal NPs from the reaction system soon after the formation of NPs and enables feeding the fresh NaBH4 solution throughout the synthesis. Fourier Transform Infrared (FTIR) spectrometry measurements of adsorbed [Formula: see text]CO molecules on Pt NPs showed that the NPs surface were negatively charged with a high population of edge and vertices atoms.

Synthesis of variously shaped magnetic FeCo nanoparticles and the growth mechanism of FeCo nanocubes

TEM characterization of FeCo nanosheets and FeCo cubes.

A facile method to improving the electromagnetic interference shielding of a free-standing and foldable carbon nanotube mat

Free-standing and foldable CNT mats with high saturation magnetization and low electrical resistance were prepared, and a high EMI SE of 40.4–60.3 dB can be achieved at frequency ranges of 1 GHz to 18 GHz with a low mat thickness of 1.0 μm.

Atomically mixed Fe-group nanoalloys: catalyst design for the selective electrooxidation of ethylene glycol to oxalic acid

Catalytic performances of Fe-group-nanoalloys, which serve as anode catalysts in direct ethylene glycol alkaline fuel cells, were fine tuned.

Preparation of solid–solution type Fe–Co nanoalloys by synchronous deposition of Fe and Co using dual arc plasma guns

We succeeded in the efficient preparation of well-dispersed Fe–Co nanoalloys (NAs) using the arc plasma deposition method.

CO2-free power generation on an iron group nanoalloy catalyst via selective oxidation of ethylene glycol to oxalic acid in alkaline media

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system.