Studies of the Kinetics of Ammonia Decomposition on Promoted Nanocrystalline Iron Using Gas Phases of Different Nitriding Degree

2010 ◽  
Vol 114 (13) ◽  
pp. 4531-4534 ◽  
Author(s):  
Karolina Kiełbasa ◽  
Rafał Pelka ◽  
Walerian Arabczyk
Keyword(s):  
Ammonia Decomposition ◽  
Gas Phases ◽  
Nanocrystalline Iron ◽  
Kinetics Of

Grain-Growth Kinetics of Nanocrystalline Iron Studied In Situ by Synchrotron Real-Time X-ray Diffraction

2000 ◽  
Vol 104 (11) ◽  
pp. 2467-2476 ◽  
Author(s):  
H. Natter ◽  
M. Schmelzer ◽  
M.-S Löffler ◽  
C. E. Krill ◽  
A. Fitch ◽  
...  
Keyword(s):  
Real Time ◽  
Grain Growth ◽  
Growth Kinetics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystalline Iron ◽  
Grain Growth Kinetics ◽  
Kinetics Of

Mechanism of Ammonia Decomposition on Tungsten; NH3 and ND3 Isotope Effect

1979 ◽  
Vol 34 (1) ◽  
pp. 96-98 ◽  
Author(s):  
H. Shindo ◽  
C. Egawa ◽  
T. Onishi ◽  
K. Tamara
Keyword(s):  
Isotope Effect ◽  
Nitrogen Uptake ◽  
Dynamic Balance ◽  
Nitride Layer ◽  
Ammonia Decomposition ◽  
Tungsten Foil ◽  
Nitride Layers ◽  
Kinetics Of ◽  
Rate Determining Steps

Abstract Light and heavy ammonia were decomposed on a clean tungsten foil at 973-1123 K and at pNH₃, ND₃ ≈ 0.2 Torr. The nitrogen uptake and the kinetics of the formation of nitride layers were examined during the course of the reaction. The amount of nitrogen chemisorbed (or the thickness of the nitride layers formed) at higher pressures was found to be appreciably larger from NH3 than from ND3. Addition of hydrogen had no effect on the thickness of the nitride layer nor on the rate of ammonia decomposition. These facts support the concept of a dynamic balance between two consecutive rate determining steps: supply of chemisorbed nitrogen from ammonia into the surface and consumption of the chemisorbed nitrogen through its desorption from the surface to form nitrogen molecules.

scholarly journals Kinetics of nanocrystalline iron nitriding

2010 ◽  
Vol 12 (1) ◽  
pp. 38-43 ◽  
Author(s):  
Walerian Arabczyk ◽  
Jacek Zamłynny ◽  
Dariusz Moszyński
Keyword(s):  
Partial Pressure ◽  
Reaction Rate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystalline Iron ◽  
Partial Pressure Of Ammonia ◽  
Three Stages ◽  
Kinetics Of

Kinetics of nanocrystalline iron nitriding Nitriding of nanocrystalline iron was studied under the atmosphere of pure ammonia and in the mixtures of ammonia - hydrogen - nitrogen at temperatures between 350°C and 500°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'-Fe4N, (2) γ'- Fe4N → ε - Fe3N and (3) ε - Fe3N → ε - Fe2N. 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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