High-pressure sintering behavior of α″-Fe16N2 nanopowder

Abstract

α″-Fe16N2 nanopowder was sintered at high-pressure and low temperature in order to explore its feasibility as a bulk magnet. TEM observation confirmed that the nanopowder was densely consolidated by sintering at a pressure of 1.2 GPa and temperatures around 200 °C. Increasing the sintering temperature enhanced the densification, leading to a suppression of oxidization. However, XRD analysis revealed that sintering at 222 °C caused the decomposition α″ → α-Fe + ε-Fe3N, which reduced the saturated magnetization (Ms) and coercivity (Hc). Consequently, sintering at 190 °C produced a dense magnet that retained the Ms of the raw powder due to the avoidances of oxidization and decomposition. On the other hand, it was found that Hc degrades after sintering, which is believed to be due to magnetic interaction between the particles.

High pressure densification and dielectric properties of perovskite-type oxynitride SrTaO2N

“…Similar diffraction line broadening has been reported for oxides, nitrides and carbides, where the grain size was reduced to the nanometer scale under microstructural strain [13,23,24]. The electron diffraction shown in Fig.…”

“…The synthesis and sintering of metal nitrides have been examined on optical, magnetic, electronic and refractory materials, such as GaN, FeN x , BN, and AlN [10][11][12][13][14][15].…”

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

“…For example, higher-than-Fe magnetic moment for α ′′ − Fe 16 N 2 2 and Fe 4 N 3,4 ), has been the driving force for the intense research work in carried out in the Fe-N system. 5,6 Though former is a heavily debated compound, 7 the origin of high magnetic moment in tetra metal nitrides (M 4 N) is relatively well-understood. In M 4 N enhanced magnetic moment is caused by a volume expansion (compared to a hypothetical fcc metal).…”

Preparation of an α″‐Fe16N2 Magnet via a Ball Milling and Shock Compaction Approach

“…It is shown that the a 00 -Fe 16 N 2 phase decomposed into g 0 -Fe 4 N þ Fe. Some groups have found that the a 00 -Fe 16 N 2 decomposes into an e-Fe 3 N phase, [15] which may be because their sample was prepared by an ammonia reaction approach. [15] The results suggest that the ball-milling sample is different from the chemical-reaction sample in terms of the decomposition process and products formed.…”

“…[5,[7][8][9][10][11] a 00 -Fe 16 N 2 thin film with high Ms has potential applications in the magnetic recording field. Besides the thin film investigation, many groups are working on a 00 -Fe 16 N 2 powder preparation, [12][13][14][15][16] which could be used for permanent magnet preparation. This is the so-called "bottom-up" approach, [17,18] in which the a 00 -Fe 16 N 2 powder is first synthesized and then compressed into the required shape.…”