Nitrogen uptake and rate-limiting step in low-temperature nitriding of iron

Inia, D. K.; Vredenberg, A. M.; Habraken, F.H.P.M.; Boerma, D.O.

doi:10.1063/1.370808

Cited by 11 publications

(5 citation statements)

References 17 publications

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“…87 Acicular-structured γ′-Fe 4 N + α-ferrite sheets were synthesized from a 0.75 mm thick Fe sheet in the presence of the 1.3:98.7 NH 3 :H 2 mixture at 840 °C for 2 h. 88 A Ni catalyst coating of nanometer thickness on the Fe layer can control the decomposition of NH 3 on the surface. 89 The Fe−N phases formed by gas nitriding also depend on the temperature of the reaction, the composition of the gas mixture, and time of exposure of the metal precursor to the flowing gas. A gas mixture of NH 3 + H 2 at 275−325 °C resulted in γ′-Fe 4 N within 3 min and ε-Fe 3−x N at longer durations.…”

Section: Synthesis Of Iron Nitridesmentioning

confidence: 99%

Iron Nitride Family at Reduced Dimensions: A Review of Their Synthesis Protocols and Structural and Magnetic Properties

Bhattacharyya

2015

J. Phys. Chem. C

121

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Magnetic nanoparticles (NPs) are prominent in various fields of scientific research and applications such as magnetic energy storage, magnetic fluids, biomedical fields, and catalysis. Metallic Fe NPs are difficult to protect from air oxidation, and iron oxide NPs suffer from reduced magnetization. Iron nitrides have the advantage of retaining high saturation magnetization (M S ); for example, α″-Fe 16 N 2 and γ′-Fe 4 N have average magnetic moments of 2.9 and 2 μ B /Fe, respectively, which are comparable to 2.2 μ B /Fe for α-Fe. The iron nitrides are ferromagnetic (FM) up to a maximum lattice dilution of 25% nitrogen for ε-Fe 3 N. Even though Fe−N NPs are extremely attractive as magnetic materials, the focus has been majorly on the bulk powders and thin films. This review provides a comprehensive overview of the crystal structures, nitriding kinetics, and synthesis methodologies of binary, doped, and ternary nanostructures, thin films, and bulk materials and their magnetism. Substitution of Fe by any other metal atom in the doped and ternary nanostructures breaks the long-range FM ordering but equally provides interesting low-temperature magnetic ordering such as spin glass and exchange bias. The dopant concentration dependence of the magnetic properties of the hybrid systems is discussed.

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Section: Synthesis Of Iron Nitridesmentioning

confidence: 99%

Iron Nitride Family at Reduced Dimensions: A Review of Their Synthesis Protocols and Structural and Magnetic Properties

Bhattacharyya

2015

J. Phys. Chem. C

121

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“…It is generally accepted that the diffusion of nitrogen atoms in iron and iron nitrides is the limiting step of the monolithic materials nitriding 30 -32 . According to literature 33 diffusion of nitrogen in iron and iron nitrides will slow down in a sequence: α-Fe > γ'-Fe 4 N > ε-Fe x N. In the case of thin films and presumably nanocrystalline materials the dissociative adsorption of ammonia on iron surface is considered as the limiting step of the process 10,34,35 . The adsorption is dependent on the structure of the surface on which it takes place.…”

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confidence: 99%

Kinetics of nanocrystalline iron nitriding

Arabczyk

Zamłynny

Moszyński

2010

Polish Journal of Chemical Technology

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Nitriding of nanocrystalline iron was studied under the atmosphere of pure ammonia and in the mixtures of ammonia -hydrogen -nitrogen at temperatures between 350 o C and 500 o C using thermogravimetry and x-ray diffraction. Three stages of nitriding were observed and have been ascribed to the following schematic reactions: (1) α-Fe → γ'-Fe 4 N, (2) γ'-Fe 4 N → ε -Fe 3 N and (3) ε -Fe 3 N → ε -Fe 2 N. The products of these reactions appeared in the nitrided nanocrystalline iron not sequentially but co-existed at certain reaction ranges. The dependence of a reaction rate for each nitriding stage on partial pressure of ammonia is linear. Moreover, a minimal ammonia partial pressure is required to initiate the nitriding at each stage.

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“…The thermodynamic activity of nitrogen is determined mainly on the ratio of un-dissociated ammonia partial pressure to hydrogen partial pressure, called the nitriding potential (K N ). Therefore, in order to correct realization of the nitriding process, it is meant to increase the ammonia dissociation rate to the nitrogen sorption, which finally should be faster than diffusion in the substrate [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Archives of Metallurgy and Materials

Jasiński¹,

Sitarz²,

Frączek³

et al. 2018

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The paper presents a comparison of the nitrided layer structure and morphology formed with a conventional controlled gas method, widely use in industrial applications and a layer formed with cathode plasma nitriding (CPN) and active screen plasma nitriding (ASPN). Nitriding processes were realized at 793K for different times and altering parameters, depending on the nitriding process technique. Research have been realized on the Fe Armco material using light microscopy (LM), scanning electron microscopy (SEM, SEM/EBSD), X-ray diffraction (XRD-GID) and atomic force microscopy (AFM). Analysis of the results has confirmed that the structure of the nitrided layer depends mainly on process methodology. In addition Authors has also analyzed kinetics of the process which varies and depends mainly from the surface layer saturation mechanism and nitriding parameters. Acquired knowledge on the structural components of the nitrided layer made it possible to optimize the nitriding parameters in order to reduce or even eliminate the usually unfavorable, brittle compounds and porous zones and of the nitrided layer in the aspect of exploitation properties improvement of the metallic materials.

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Nitrogen uptake and rate-limiting step in low-temperature nitriding of iron

Cited by 11 publications

References 17 publications

Iron Nitride Family at Reduced Dimensions: A Review of Their Synthesis Protocols and Structural and Magnetic Properties

Iron Nitride Family at Reduced Dimensions: A Review of Their Synthesis Protocols and Structural and Magnetic Properties

Kinetics of nanocrystalline iron nitriding

Archives of Metallurgy and Materials

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