Nanoscale Iron Nitride, ε-Fe₃N: Preparation from Liquid Ammonia and Magnetic Properties

Abstract

e-Fe 3 N shows interesting magnetism but is difficult to obtain as a pure and single-phase sample. We report a new preparation method using the reduction of iron(II) bromide with elemental sodium in liquid ammonia at -78 °C, followed by annealing at 573 K. Nanostructured and monophasic oxygen-free iron nitride, e-Fe 3 N, is produced according to X-ray diffraction and transmission electron microscopy experiments. The magnetic properties between 2 K and 625 K were characterized using a vibrating sample magnetometer, revealing soft ferromagnetic behavior with a low-temperature average moment of 1.5 µ B /Fe and a Curie temperature of 500 K. T C is lower than that of bulk e-Fe 3 N (575 K), 1 which corresponds well with the small particle size within the agglomerates (15.4 (± 4.1) nm according to TEM, 15.8(1) according to XRD). Samples were analyzed before and after partial oxidation (Fe 3 N-Fe x O y core-shell nanoparticles with a 2-3 nm thick shell) by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy and magnetic measurements. Both the pristine Fe 3 N nanoparticles and the oxidized core-shell particles showed shifting and broadening of the magnetic hysteresis loops upon cooling in a magnetic field.

Metallic Porous Iron Nitride and Tantalum Nitride Single Crystals with Enhanced Electrocatalysis Performance

“…The Fe 3 N and Ta 5 N 6 crystals grown on other facets of substrates show polycrystalline features as further confirmed by X-ray diffraction (XRD) patterns (Figures S1 and S2, Supporting Information). [14] The single-crystalline structure is further confirmed by selected area electron diffraction pattern with a diameter of ≈1 µm in the inset of Figure 2a. Figure The crystalline structure of Fe 3 N single crystal is investigated using Cs-corrected scanning transmission electron microscopy (STEM) coupled with focused ion beam.…”

Magnetic γ′‐Fe4N/Fe3C, χ‐Fe5C2, and θ‐Fe3C by a Simple Route for Application as Electrochemical Catalysts

“…[20,21] It demonstrates the N-doping in carbond uring the nitridation process. [10] The peak at 707.3 eV is considered as metallic iron nitride (g'-Fe 4 N). [22,23] It is confirmed that the F-1 :2.5 600 contains ac ertain amount of carbon and furtherp rovest hat heteroatoms (O and N) are dopedi nto the Chem.E ur.J.2017, 23,17592 -17597 www.chemeurj.org carbon.I na ddition, the high-resolution Fe 2p spectrum is shown in Figure 5d.I tc an be clearly observed that the Fe 2p spectrum consists of five peaks:t he peaks at 710.0 and 713.0 eV are ascribed to Fe 2p 3/2 of Fe 2 + and Fe 3 + ,a nd the peaks at 724.5 and 726.4 eV are ascribed to Fe 2p 1/2 of Fe 2 + and Fe 3 + .…”

“…Thus, this iron oxide is an amorphous iron oxide.B ased on previousr eports, this amorphous iron oxide is iron monoxide (Fe 1-x O). [10] The peak at 707.3 eV is considered as metallic iron nitride (g'-Fe 4 N). [25] Additionally,t he XPS spectra of F-1 :2.5 580 and F-1 :2.5 620 are shown in Figure S5.…”

“…[6][7][8][9][10][11][12][13] Generally,i ron nitridee xhibits ferromagnetism at room temperature, with high saturation magnetization and high magnetic moment. [6][7][8][9][10][11][12][13] Generally,i ron nitridee xhibits ferromagnetism at room temperature, with high saturation magnetization and high magnetic moment.…”

“…Recently,t he research of iron nitride was mainly concentrated on the electrochemical catalysis and magnetism. [6][7][8][9][10][11][12][13] Generally,i ron nitridee xhibits ferromagnetism at room temperature, with high saturation magnetization and high magnetic moment. Owing to the difference of nitrogen content and crystal structure,t he magnetic moment of the ferromagnetic iron nitride shows certain differences.…”