Kinetics of nanocrystalline iron nitriding

Arabczyk, W.; Zamłynny, J.; Moszyński, Dariusz

doi:10.2478/v10026-010-0008-z

Cited by 19 publications

(22 citation statements)

References 27 publications

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“…The nitriding reaction dominated up to a temperature of 723 K, above which the iron nitride gradually decomposed. This nitriding behavior agrees with the results obtained by Arabczyk et al 25) Fig. 4.…”

Section: Mechanisms Of Hematite Reduction and Nitridingsupporting

confidence: 93%

Reduction and Nitriding Behavior of Hematite with Ammonia

et al. 2015

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This paper describes the reduction and nitriding behavior of hematite with ammonia in the context of ironmaking. The effects of temperature and ammonia concentration on the products were investigated. In the temperature range from 793 to 863 K, hematite was directly reduced to magnetite by ammonia (1/2Fe2O3 + 1/9NH3 → 1/3Fe3O4 + 1/6H2O + 1/18N2). The ammonia started to decompose at 873 K, triggered by the generation of α-Fe. Magnetite was reduced mainly to iron by hydrogen generated from the decomposition of ammonia (1/3Fe3O4 + 4/3H2 → Fe + 4/3H2O). According to in-situ X-ray diffraction (XRD) measurements, α-Fe was immediately nitrided to an ε-Fe 3-x N (0 ≤ x ≤ 1) phase, and the N/Fe atomic ratio decreased gradually with increasing temperatures. The rate of hematite reduction increased with the ammonia concentration for 5% to 20% NH3, but plateaus for NH3 concentrations greater than 20%. This was attributed to the mechanism of ammonia decomposition; the amount of hydrogen generated also plateaus at ammonia concentrations above 20%. The reduction rate was therefore limited by the rate at which hydrogen was generated during ammonia decomposition. The N content of the product was affected not only by the temperature but also by the nitriding potential (KN = P NH 3 /P H 2 3/2 ). The nitriding potential increased with increasing ammonia concentrations and decreasing temperatures. The addition of nitrogen gas to the reactive gas inhibited ammonia decomposition and increased the nitrogen potential and N content of the product.

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Section: Mechanisms Of Hematite Reduction and Nitridingsupporting

confidence: 93%

Reduction and Nitriding Behavior of Hematite with Ammonia

et al. 2015

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“…The influence of sulphur [13,14] or water vapour [15] present in the gas phase on the rate of ammonia decomposition process over iron was investigated. Catalytic ammonia decomposition reaction at a stable temperature occurs with various rates depending on the solid state phase (Fe or Fe x N) present in the reaction system [16].…”

Section: Introductionmentioning

confidence: 99%

Catalytic Ammonia Decomposition Over Fe/Fe4N

2008

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The catalytic ammonia decomposition over iron and iron nitride, Fe 4 N, under the atmosphere of ammonia-hydrogen mixtures of different amounts of ammonia in the temperature range of 400-550°C by means of thermogravimetry has been studied. A differential tubular reactor with mixing has been used. The ammonia concentration in the gas phase during all the process was analysed. The balance between the inlet and outlet ammonia quantity has been used to determine a degree of ammonia conversion and the values of decomposition reaction rate. The activation energy of ammonia decomposition reaction over Fe and Fe 4 N was found to be 68 and 143 kJ/mol, respectively.

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“…The absence of metallic iron indicates that its conversion into iron nitride was complete during the activation at 700 °C. It is also noted that the value of y in Fe 3 N y nanoparticles increases from 0.94 to 1.39 (as evidenced by a decrease in the peak positions in XRD 29 ) upon increasing the activation temperature from 600 to 700 °C accompanied by an increase in activation time from 1 to 10 h. This increase in y in Fe 3 N y also indicates a higher degree of nitriding in RM-700R@700 than in the case of RM-700R@600 29 .…”

Section: Resultsmentioning

confidence: 92%

Red Mud as an Efficient, Stable and Cost-Free Catalyst for COx-Free Hydrogen Production from Ammonia

Kurtoğlu

Uzun

2016

Sci Rep

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Red mud, one of the mostly produced industrial wastes, was converted into a catalyst with exceptionally high and stable performance for hydrogen production from ammonia. Results showed that iron species produced after reduction of the HCl digested red mud were converted into ε-Fe2N during the induction period of ammonia decomposition reaction at 700 °C. The catalytic performance measurements indicated that the modified red mud catalyst provides a record high hydrogen production rate for a non-noble metal catalyst at this temperature. For instance, stable hydrogen production rates were measured as 72 and 196 mmol H2 min−1 gcat−1 for the corresponding space velocities of 72 000 and 240 000 cm3 NH3 h−1 gcat−1, respectively, at 700 °C. These results offer opportunities to utilize one of the key hazardous industrial wastes as an eco-friendly, efficient, stable, and almost cost-free catalyst for COx-free hydrogen production from ammonia decomposition.

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Kinetics of nanocrystalline iron nitriding

Cited by 19 publications

References 27 publications

Reduction and Nitriding Behavior of Hematite with Ammonia

Reduction and Nitriding Behavior of Hematite with Ammonia

Catalytic Ammonia Decomposition Over Fe/Fe4N

Red Mud as an Efficient, Stable and Cost-Free Catalyst for COx-Free Hydrogen Production from Ammonia

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