Papers by Keyword: Iron Nitride

Abstract: Iron nitride is a promising material for soft magnetic composite. In the current research, iron nitride compound was produced from natural iron sand, involving coprecipitation and gas nitriding. Prior to coprecipitation, natural iron sands were separated magnetically to obtain pure Fe₃O₄. Afterward, the coprecipitation was carried out to obtain nanosized Fe₃O₄. Gas nitriding of Fe₃O₄ powders was performed at different temperatures i.e. 500 °C, 600 °C and 700 °C, under flowing NH₃ gas. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) are used to investigate the phases obtained after the nitriding process. XRD patterns of the resulted powder indicate that nitriding temperature at 600 °C and 700 °C can produce iron nitride material, i.e. ε-Fe₃N. While nitriding temperature of 500 °C is not able to yield iron nitrides. SEM examination reveals that the ε-Fe₃N has irregular lamellar morphology. Some impurities are still detected, in the form of Fe₃O₄, Fe₂O₃, Ti₂O₃ and TiO₂. Further works regarding the examination of the magnetic properties of the powders will be carried out.

Abstract: Employing NH3/H2 gas mixtures, Fe-4.65at% Al alloy specimens were nitrided to assess how the presence of Al, originally dissolved in the ferrite matrix, influences the development of γ-Fe4N1-x phase in the surface adjacent region. The nitrided specimens were characterized by light microscopy, X-ray diffraction, Electron Backscatter Diffraction and Electron Probe Micro Analysis. Surprisingly, formation of ε-Fe2N1-x was observed, although, for the applied nitriding parameters (nitriding potential and temperature), only the formation of γ-Fe4N1-x would be expected in case of nitriding pure ferrite. An unusual plate-type morphology of γ-Fe4N1-x was observed, contrasting with the usual continuous layer-type growth observed upon nitriding iron, Fe-Cr and Fe-V alloys. These unexpected phenomena may be explained as consequences of the need to realize a very high nitrogen supersaturation in the ferrite matrix in order to initiate the precipitation of AlN.

Abstract: This work deals with a study of the nitriding potential effect on development of the compound layer during the gas nitriding of Armco Fe samples. The gas nitriding experiments were performed in an atmosphere of partially dissociated gas ammonia (NH3) at 520 °C under a nitriding potential varying from 0.25 to 3.5 atm-0.5 during 2 h. Through this experimental work including XRD analysis, optical and SEM observations of the cross-sections of the treated samples, it is shown that the microstructural nature of the compound layer depends upon the nitriding potential value. By use of the inverse problem based on a diffusion model previously published, it was possible to estimate the diffusion coefficient of N in ' iron nitride as a function of the applied nitriding potential. XRD analysis has shown that the compound layer was composed of iron nitride. A linear semi-logarithmic relationship relating the nitriding potential to the diffusion coefficient of nitrogen in iron nitride was also derived.

Abstract: As a series of fundamental study on the gas evaporation method, a levitation-melted iron was evaporated in the gas mixtures of argon + ammonia, argon + nitrogen to synthesize ultrafine particles of iron nitride that got attention as one of the magnetic materials. The particles that were obtained in the gas mixture of argon and nitrogen were α-Fe. But nitrogen was chemisorbed on the surface of the particle, because nitrogen content in the particles was larger than the solubility of nitrogen in iron. The particles that formed in the mixed gas of argon and ammonia were Fe4N. The mean size of the particles of iron nitride was approximately 60 nm. The formation ratio of iron nitride was about 86 %.

Abstract: Iron nitrides thermally decompose to α-Fe releasing their nitrogen above 300°C. MR effect was found out in the thin films obtained by post-annealing of the following two kinds of sputter deposited iron nitride related films. (1) α-Fe particles dispersed in AlN granular film was obtained by an annealing of Al0.31Fe0.69N sputter deposited film in hydrogen. The MR=0.82% was found out in this nitride system. (2) Fe3O4 thin films were prepared by thermal decomposition of sputter deposited iron nitride films in low oxygen partial pressure. The iron nitrides were defect rock salt type γ΄˝-FeNx (0.5≤x≤0.7) and zinc blende type γ˝-FeNy (0.8≤y≤0.9) at the sputter nitrogen gas pressure of 1Pa and 6Pa. MR ratios of the oxide films were about 2%.

Abstract: Iron and its nitride (e-Fe3N) nanoparticles were fabricated by the CVC using Fe(CO)5 precursor without the aid of LN2 chiller. The iron particles synthesized at 400 oC were a mixture of amorphous and crystalline a-Fe. Fully crystallized iron particles were then obtained above 600 oC. Iron-nitride particles that were easily formed at 500 oC at 1 atm., however, were not fully developed in vacuum unless the reaction temperature reached 850 oC. Nevertheless, the work chamber needed to be maintained in vacuum to obtain finer iron-nitride particles. The synthesized particles possessing the core-shell type structure were all nearly spherical and enclosed with Fe3O4 or Fe3O4-related amorphous layer. The iron nanoparticles (~20 nm) synthesized at 600 oC at 760 torr exhibited iHc ~ 1.0 kOe and Ms ~ 170 emu/g, whereas the iron-nitride particles (~20 nm) synthesized at 850 oC at 0.01 torr exhibited iHc ~ 0.45 kOe and Ms ~ 115 emu/g.

Abstract: Ion-implantation on high purity iron substrates with nitrogen ions were carried out by using a Cockcroft Walton type accelerator under an accelerating voltage of 150 kV. Hardness measurements on the implanted surfaces showed that hardness effectively increased in the cold rolled specimens by ion-implantation in comparison with in an annealed specimen. Iron nitride, Fe16N2, was formed in the ion-implanted specimens. In the annealed specimen, relatively large particles of Fe₁₆N₂ were formed with low number density, while in the deformed specimens, dislocation substructures due to cold rolling were disappeared by ion-implantation and fine particles were densely formed. Strain field around dislocations induced by deformation provides nucleation sites for Fe₁₆N₂ particles.