Modelling nitriding of iron: From thermodynamics to residual stress

2004 ◽  
Vol 120 ◽  
pp. 21-23
Author(s):  
M. A.J. Somers
Keyword(s):  
Gas Phase ◽  
Nucleation And Growth ◽  
Stress Generation ◽  
Model Description ◽  
Iron Nitride ◽  
Gaseous Nitriding ◽  
State Diffusion ◽  
Long Range Ordering ◽  
Nitride Layers ◽  
Kinetics Of

The present article presents a few selected aspects of the modelling of gaseous nitriding of pure iron. After descriptions of the thermodynamics of the gas phase and the reactions at the gas/solid interface, a model description of the thermodynamics of $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ is given, which takes the long-range ordering of nitrogen atoms into account. Subsequently, the kinetics of nucleation and growth of iron nitride layers is described in terms of the rates of the surface reactions and solid state diffusion. Thereafter, the mechanisms of stress generation in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers during nitriding are summarized. Finally, the model for stress development in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers is compared with published experimental work.

Ion beam synthesis of nitride layers in iron

1992 ◽  
Vol 7 (10) ◽  
pp. 2689-2712 ◽  
Author(s):  
A.M. Vredenberg ◽  
C.M. Pérez-Martin ◽  
J.S. Custer ◽  
D.O. Boerma ◽  
L. de Wit ◽  
...  
Keyword(s):  
Ion Beam ◽  
High Energy ◽  
Nitride Layer ◽  
Layer Growth ◽  
Stable Phase ◽  
Iron Nitride ◽  
High Dose ◽  
Nitride Layers ◽  
Induced Defects ◽  
Kinetics Of

Stoichiometric iron nitride layers have been synthesized by high dose, high energy nitrogen implantation into Fe using a two-step implantation process. First, a nitrogen preimplantation at ~100 °C is used to form nitride precipitates. A low temperature is necessary to restrict the nitrogen mobility. Second, 1 MeV implantation at ~300 °C leads to the formation of a stoichiometric γ′–Fe4N layer at the position of the preimplanted N atoms. Growth of this nitride layer proceeds by diffusion of the implanted N through either the α–Fe matrix (for 200 or 500 keV preimplantations) or the nitride layer itself (for 1 MeV preimplantation). During annealing above 350 °C the γ′ layers dissolve in a planar fashion, characterized by an activation energy of 2.3 eV. Phase formation during preimplantation and phase transformations during subsequent annealing or hot implantation can be understood from the thermodynamics for the Fe–N system, while the kinetics of layer growth is influenced by the beam-induced defects. The experiment and model suggest that γ′ is not a thermodynamically stable phase below 310 ± 10 °C and should decompose into α (ferrite) and ∊ nitride.

Microstructural investigation of iron nitride layers formed by low-temperature gaseous nitriding

1999 ◽  
Vol 14 (6) ◽  
pp. 2674-2679 ◽  
Author(s):  
D. K. Inia ◽  
A. M. Vredenberg ◽  
D. O. Boerma ◽  
F. D. Tichelaar ◽  
H. Schut ◽  
...  
Keyword(s):  
Low Temperature ◽  
Iron Nitride ◽  
Depth Range ◽  
Elastic Recoil ◽  
Cross Sectional ◽  
Microstructural Investigation ◽  
Elastic Recoil Detection ◽  
Growth Modes ◽  
Gaseous Nitriding ◽  
Nitride Layers

Iron nitride layers were formed by a novel low-temperature gaseous nitriding process. Nitriding occurs at a temperature of 325 °C through NH3 decomposition at the surface of Ni (25 nm) coated Fe, followed by N transport through the Ni film into the underlying Fe, where nitride precipitation takes place. The role of Ni is to protect Fe from oxidation by gas impurities and to serve as a catalyst for NH3 decomposition. The precipitation behavior and the development of microstructure were studied by means of elastic recoil detection, cross-sectional transmission electron diffraction (XTEM), and positron annihilation (PA). From PA and XTEM no evidence was found for the occurrence of porosity during nitriding (an effect found at higher temperatures due to the decomposition of the nitrides into Fe and N2). XTEM showed that the original columnar α–Fe grains transform into smaller ′–Fe4N grains which subsequently transform into larger ε–Fe3−xN grains. This microstructural evolution of smaller ′ grains forming in the original columnar α–Fe structure occurs in one of two growth modes of the nitride in the Fe layer, i.e., throughout the entire depth range of the Fe layer, or preferentially at the Ni/Fe interface when an iron oxide layer is present at this interface.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

Gas-Phase Anionic Metal Clusters are Model Systems for Surface Oxidation: Kinetics of the Reactions of Mn– with O2 (M = V, Cr, Co, Ni; n = 1–15)

2021 ◽  
Vol 125 (10) ◽  
pp. 2069-2076
Author(s):  
Brendan C. Sweeny ◽  
David C. McDonald ◽  
Nicholas S. Shuman ◽  
Albert A. Viggiano ◽  
Juergen Troe ◽  
...  
Keyword(s):  
Gas Phase ◽  
Oxidation Kinetics ◽  
Metal Clusters ◽  
Surface Oxidation ◽  
Model Systems ◽  
Kinetics Of

Kinetics of silicon nitride crystallization in N+-implanted silicon

1989 ◽  
Vol 4 (2) ◽  
pp. 394-398 ◽  
Author(s):  
V. S. Kaushik ◽  
A. K. Datye ◽  
D. L. Kendall ◽  
B. Martinez-Tovar ◽  
D. S. Simons ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Wafer Surface ◽  
Amorphous Silicon Nitride ◽  
Silicon Lattice ◽  
Nitrogen Ions ◽  
The Mean ◽  
Nitride Layers ◽  
Kinetics Of

Implantation of nitrogen at 150 KeV and a dose of 1 ⊠ 1018/cm2 into (110) silicon results in the formation of an amorphized layer at the mean ion range, and a deeper tail of nitrogen ions. Annealing studies show that the amorphized layer recrystallizes into a continuous polycrystalline Si3N4 layer after annealing for 1 h at 1200 °C. In contrast, the deeper nitrogen fraction forms discrete precipitates (located 1μm below the wafer surface) in less than 1 min at this temperature. The arcal density of these precipitates is 5 ⊠ 107/cm2 compared with a nuclei density of 1.6 ⊠ 105/cm2 in the amorphized layer at comparable annealing times. These data suggest that the nucleation step limits the recrystallization rate of amorphous silicon nitride to form continuous buried nitride layers. The nitrogen located within the damaged crystalline silicon lattice precipitates very rapidly, yielding semicoherent crystallites of β–Si3N4.

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