scholarly journals Fe Nitride Formation in Fe–Si Alloys: Crystallographic and Thermodynamic Aspects

2021 ◽  
Author(s):  
Stefan Kante ◽  
Andreas Leineweber
Keyword(s):  
Single Phase ◽  
Compound Layer ◽  
Nitride Layer ◽  
Layer Formation ◽  
Orientation Relationships ◽  
Transformation Mechanism ◽  
Displacive Transformation ◽  
Nitride Formation ◽  
Nitriding Potential ◽  
Stability Ranges

AbstractA Fe–3wt pctSi alloy was gas nitrided to study the effect of Si on the Fe nitride formation. Both ε-Fe3N1+x and γ′-Fe4N were observed at nitriding conditions only allowing to form single-phase γ′ layers in pure α-Fe. During short nitriding times, ε and γ′ simultaneously grow in contact with Si-supersaturated α-Fe(Si). Both nitrides almost invariably exhibit crystallographic orientation relationships with α-Fe, which are indicative of a partially displacive transformation of α-Fe being involved in the initial formation of ε and γ′. Due to Si constraining the Fe nitride growth, such transformation mechanism becomes highly important to the nitride layer formation, causing α-Fe-grain-dependent variations in the nitride layer morphology and thickness, as well as microstructure refinement within the nitride layer. After prolonged nitriding, α-Fe is depleted in Si due the pronounced precipitation of Si-rich nitride in α-Fe. The growth mode of the compound layer changes, now advancing by conventional planar-type growth. During nitriding times of 1 to 48 hours, ε exists in contact with the NH3/H2-containing nitriding atmosphere at a nitriding potential of 1 atm−1/2 and 540 °C, only allowing for the formation of γ′ in pure Fe, indicating that Si affects the thermodynamic stability ranges of ε and γ′.

Diffusional-displacive transformation mechanism for the β1 precipitate in a model Mg-rare-earth alloy

2021 ◽  
Vol 174 ◽  
pp. 111018
Author(s):  
Hongbo Xie ◽  
Xiaobo Zhao ◽  
Jingchun Jiang ◽  
Junyuan Bai ◽  
Shanshan Li ◽  
...  
Keyword(s):  
Rare Earth ◽  
Transformation Mechanism ◽  
Rare Earth Alloy ◽  
Displacive Transformation

Epitaxial Growth OF (001)- and (111)-Oriented PTMNSB Films and Multilayers

1995 ◽  
Vol 384 ◽  
Author(s):  
M.C. Kautzky ◽  
B.M. Clemens
Keyword(s):  
Kerr Effect ◽  
Single Phase ◽  
Single Layer ◽  
Film Structure ◽  
Interference Effects ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
Rocking Curve ◽  
Large Rotations

ABSTRACTIn this paper we report the successful growth of single-phase epitaxial PtMnSb films and multilayers by dc magnetron cosputtering, both in the (001) orientation on MgO(001) and W(001), and in the (111) orientation on Al2O3 (0001). Single-layer films in the thickness range 50Å≤t≤1000Å were grown and characterized using x-ray diffraction (XRD), magneto-optic Kerr effect (MOKE), and vibrating sample magnetometry (VSM). The in-plane orientation relationships, as determined by asymmetric XRD, were PtMnSb[100]∥MgO[110], PtMnSb[100]∥W[100], and PtMnSb[101∥Al2O3[2110]. The crystalline quality of the films was found to depend strongly upon the substrate, growth temperature, film thickness, and presence of a capping layer, but rocking curve widths of 1° or less were achieved on each substrate. Measurement of the in-plane strain showed that the films were almost entirely relaxed, with strains <1%. In-plane magnetization was observed in all cases, with moments and coercivities in the 400-500 emu/cm3 and 100-200 Oe ranges respectively. Polar Kerr spectra showed large rotations (0.75° - 1.03°), whose peak wavelengths appear to depend on both film structure and optical interference effects.

scholarly journals Single Step Process for Crystalline Ni-B Compounds

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1259 ◽  
Author(s):  
Mahboobeh Shahbazi ◽  
Henrietta Cathey ◽  
Natalia Danilova ◽  
Ian Mackinnon
Keyword(s):  
Single Phase ◽  
Single Step ◽  
Transformation Mechanism ◽  
Solid Reaction ◽  
Step Method ◽  
Step Process ◽  
Pressure Time ◽  
Autogenous Pressure ◽  
Higher Temperature ◽  
High Yields

Crystalline Ni2B, Ni3B, and Ni4B3 are synthesized by a single-step method using autogenous pressure from the reaction of NaBH4 and Ni precursors. The effect of reaction temperature, pressure, time, and starting materials on the composition of synthesized products, particle morphologies, and magnetic properties is demonstrated. High yields of Ni2B (>98%) are achieved at 2.3–3.4 MPa and ~670 °C over five hours. Crystalline Ni3B or Ni4B3 form in conjunction with Ni2B at higher temperature or higher autogenous pressure in proportions influenced by the ratios of initial reactants. For the same starting ratios of reactants, a longer reaction time or higher pressure shifts equilibria to lower yields of Ni2B. Using this approach, yields of ~88% Ni4B3 (single phase orthorhombic) and ~72% Ni3B are obtained for conditions 1.9 MPa < Pmax < 4.9 MPa and 670 °C < Tmax < 725 °C. Gas-solid reaction is the dominant transformation mechanism that results in formation of Ni2B at lower temperatures than conventional solid-state methods.

Phase Transformation Crystallography of Lath Martensite

2006 ◽  
Vol 979 ◽  
Author(s):  
Xiao Ma ◽  
R.C. Pond
Keyword(s):  
Phase Transformation ◽  
Habit Plane ◽  
Lath Martensite ◽  
Martensitic Transformations ◽  
Phenomenological Theory ◽  
Orientation Relationships ◽  
Transformation Mechanism ◽  
Ferrous Alloys ◽  
Model Phase ◽  
Good Agreement

AbstractOur current understanding of martensitic transformations has been based on the Phenomenological Theory of Martensite Crystallography developed in the 1950s. Recently, a Topological Model of martensitic transformations has been presented wherein the habit plane is a semi-coherent structure, and the transformation mechanism is shown explicitly to be diffusionless. This approach is used here to model phase transformation crystallography of lath martensite in ferrous alloys. A range of network geometries is predicted corresponding to orientation relationships varying from Nishiyama-Wasserman to Kurdjumov-Sachs. Experimental observations from the literature of the dislocation and disconnection arrays, habit plane and orientation relationship are in good agreement with the model.

Hydroxyapatite Nucleation on Modified Silicon Surface for Use in Biosensors

2008 ◽  
Vol 396-398 ◽  
pp. 337-340
Author(s):  
Luci Cristina de Oliveira Vercik ◽  
E.C.S. Rigo ◽  
A. Vercik
Keyword(s):  
Calcium Phosphate ◽  
Sodium Silicate ◽  
Silicon Surface ◽  
Single Phase ◽  
Crystalline Silicon ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Layer Formation ◽  
Calcium Phosphate Layer ◽  
Coating Formation

In this work, we explore the deposition of single-phase and uniform HA coatings on a crystalline silicon surface of microelectronic quality. The used methodology includes an NaOH treatment to produce the silanization of Si surface and a modified biomimetic technique, using sodium silicate solution (SS) as nucleant agent, for apatite-based coating formation. The sodium silicate solution (SS) demonstrated to be effective for the calcium phosphate layer formation, but the treatment can reduce the induction to obtain a uniform surface coating of HA. This suggests that, among the factors that determine nucleation of calcium phosphate on silicon, surface electrical charge could play a key role.

Surface Characterization of a Nitrided Low Alloy Steel

2011 ◽  
Vol 312-315 ◽  
pp. 70-75
Author(s):  
Mourad Keddam ◽  
R. Kouba ◽  
Redoune Chegroune ◽  
B. Bouarour
Keyword(s):  
Alloy Steel ◽  
Surface Characterization ◽  
Surface Hardness ◽  
Xrd Analysis ◽  
Compound Layer ◽  
Iron Nitrides ◽  
Low Alloy Steel ◽  
Nitrogen Concentrations ◽  
Nitriding Potential ◽  
Nitride Layers

The 32CrMoV13 low alloy steel was gas nitrided at 550°C, for three time durations (6.5, 13 and 20 h) and under a variable nitriding potential (1, 2.2 and 6 atm-0.5). The generated nitride layers were characterized by SEM observations, XRD and GDOS analyses as well as microhardness testing. The XRD analysis indicates that the compound layer was composed of and iron nitrides and CrN phase. The surface hardness (inside the compound layer) was found to be dependent on the nitriding potential value, its value increases as rises. It was shown by GDOS analysis that the upper and lower nitrogen concentrations at the (compound layer / diffusion zone) interface are approximatively: 4 and 0.88 wt. % N, respectively.

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