Impact of Thermal Oxidation on Morphological, Structural and Magnetic Properties of Fe-Ni Wire-Like Nanochains

Marcin Krajewski,Mateusz Tokarczyk,Anna Ślawska-Waniewska,Kamil Bochenek,Sabina Lewińska

doi:10.1007/s11661-021-06326-1

Abstract

This work presents the evolution of morphological, structural and magnetic properties of amorphous Fe-Ni wire-like nanochains caused by thermal oxidation. The initial Fe1−xNix samples (x = 0.75; 0.50; 0.25) were prepared through the magnetic-field-induced synthesis, and then they were heated in dry air at 400 °C and 500 °C. These treatments led to two competing simultaneous processes occurring in the investigated samples, i.e., (i) a conversion of amorphous material into crystalline material, and (ii) their oxidation. Both of them strictly affected the morphological and structural properties of the Fe-Ni nanochains which, in turn, were associated with the amount of iron in material. It was found that the Fe0.75Ni0.25 and Fe0.50Ni0.50 nanochains were covered during thermal treatment by the nanoparticle oxides. This coverage did not constitute a good barrier against oxidation, and these samples became more oxidized than the Fe0.25Ni0.75 sample which was covered by oxide nanosheets and contained additional Ni3B phase. The specific morphological evolutions of the Fe-Ni nanochains also influenced their saturation magnetizations, whereas their coercivities did not vary significantly. The obtained results constitute an important source of information for future application of the thermally treated Fe-Ni nanochains which could be applied in the energy storage devices or catalysis.

Highlights

THE conversion chemistry is a fast developing part of chemistry which describes the morphological changes of nanomaterials occurring during the chemical conversion reactions due to the formation of voids or hollows.[1]
According to the presented results, the as-prepared Fe-Ni nanostructures with all investigated chemical compositions look like long straight wires, whereas analyzing the scanning electron microscope (SEM) images of the thermally treated samples it is hardly difficult to observe whether they reveal the wire-like structures
The comprehensive studies describing the thermal oxidation at 400 °C and 500 °C in dry air of the amorphous Fe-Ni wire-like nanochains with various iron-to-nickel compositions, which are produced in the magnetic-field-induced synthesis, are presented in this work

Summary

INTRODUCTION

THE conversion chemistry is a fast developing part of chemistry which describes the morphological changes of nanomaterials occurring during the chemical conversion reactions due to the formation of voids or hollows.[1]. Nakamura et al [12] performed the advanced transmission electron microscopy (TEM) studies on the oxidized Ni nanoparticles (NPs) and they noticed that the condensation of vacancies into void during the oxidation process took place at an off-centered position. This observation was confirmed for small oxidized Ni NPs with diameter of about 26 nm by Railsback et al.[4] but, at the same time, they found that the oxidation of large Ni nanoparticles (diameter ~96 nm) resulted in the formation of porous NiO NPs possessing multiple voids. The results discussed in this paper can be considered as an important source of information for the future application of the thermally treated Fe-Ni nanochains in the sector of energy storage or catalysis

Fabrication of Iron-Nickel Wire-Like Nanostructures

Thermal Oxidation of Iron-Nickel Wire-Like Nanostructures

Characterization of Wire-Like Nanostructures

RESULTS AND DISCUSSION

CONCLUSIONS

Slawska-Waniewska