Characterisation of the Oxide/Metal Interface of Fluorine Treated Titanium Aluminides

2009 ◽  
Vol 289-292 ◽  
pp. 397-404 ◽  
Author(s):  
Patrick J. Masset ◽  
Mathieu Laurent ◽  
Michael Schütze
Keyword(s):  
Oxide Layer ◽  
Titanium Aluminides ◽  
Kinetic Constant ◽  
Subsurface Layer ◽  
Alumina Layer ◽  
Pure Alumina ◽  
Environmental Embrittlement ◽  
True Value ◽  
Parabolic Law ◽  
Sem Analyses

Surface modifications with well defined amounts of fluorine have proven to improve significantly the oxidation resistance of titanium aluminides and to offer the potential to decrease the sensibility of TiAl-based alloys against environmental embrittlement. By means of combined EPMA and SEM analyses the formation of an oxide layer on fluorine treated specimens was characterised. The thicknesses of the external oxide layer as well as the oxygen and nitrogen-rich subsurface layer were measured. Their growth kinetics was found to follow a cubic and a parabolic law, respectively. By subtracting the mass variation due to the ingress of oxygen and nitrogen into 2-Ti3Al, underneath the alumina layer, this allowed calculating the true value of the kinetic constant for the growth of a pure alumina layer on titanium aluminides.

Sintering of Textured YBa2Cu307-x Under Intensive 60Co Gamma Irradiation

1994 ◽  
Vol 354 ◽  
Author(s):  
Elvira M. Ibragimova ◽  
Eldar M. Gasanov ◽  
Makhmud Kalanov ◽  
Marquis A. Kirk ◽  
Ken C. Goretta
Keyword(s):  
Gamma Irradiation ◽  
Dose Rate ◽  
Subsurface Layer ◽  
Gamma Dose ◽  
Ordered Structure ◽  
Sintering Process ◽  
Superconducting Properties ◽  
Oxygen Sublattice ◽  
60Co Gamma ◽  
Sem Analyses

AbstractA study of structural and superconducting characteristics of YBa2Cu307-x ceramics sintered after and in the course of gamma-irradiation is reported. Using X-difraction and SEM analyses and transport measurements, it has been shown that mainly the subsurface layer of crystallites and intergrain contacts are affected by the irradiation by means of sorption/desorption of oxygen and ordering/disordering in oxygen sublattice, which depends on gamma dose rate and dose. The irradiation provides the sintering process with an additional superthermal energy to form the orthorhombic well-ordered structure and to obtain dense ceramics possessing strong intergrain contacts and improved and stable superconducting properties

Interaction between SiC and Ti powder

1993 ◽  
Vol 8 (10) ◽  
pp. 2725-2733 ◽  
Author(s):  
I. Gotman ◽  
E.Y. Gutmanas ◽  
P. Mogilevsky
Keyword(s):  
Electron Microscopy ◽  
Reaction Zone ◽  
Kinetic Constant ◽  
Auger Spectroscopy ◽  
Ceramic Surface ◽  
X Ray Diffraction ◽  
Parabolic Law ◽  
Transmission Electron ◽  
Ti Powder ◽  
Mixed Reaction

The interaction between SiC and Ti powder at 1073–1523 K was investigated employing a combination of x-ray diffraction, scanning electron microscopy with EDS, Auger spectroscopy, and transmission electron microscopy. As a result of the interaction, a triple-layer reaction zone was formed. The most important part of the reaction zone was a mixed TiC–Ti5Si3(C) layer. Thin TiC sublayers were formed on both the inner and the outer sides of the mixed reaction layer. The reaction zone was found to grow by a parabolic law with the kinetic constant, k = 1.3 × 10−3 exp (-21800/t) cm2/s. The growth process of the SiC/Ti reaction zone was assumed to be controlled by diffusion of all three components of the system: Ti, Si, and C. Thin reaction layers (<5 μm) obtained after short exposures at relatively low temperatures formed coatings on the SiC surface; thicker reaction layers spalled off the ceramic surface. Experiments with the samples partially immersed into the metal powder showed that interaction between SiC and Ti was very sensitive to the environment.

Role of Fe and Ni Nanoparticles on Mechanical Properties of Alumina Thin Films deposited by Laser Ablation

2005 ◽  
Vol 890 ◽  
Author(s):  
Sergey Yarmolenko ◽  
Sudheer Neralla ◽  
Dhananjay Kumar ◽  
Jag Sankar ◽  
Fude Liu ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Laser Ablation ◽  
Metal Deposition ◽  
Metal Nanoparticle ◽  
Ni Nanoparticles ◽  
Alumina Layer ◽  
Pure Alumina ◽  
Composite Thin Films ◽  
Alumina Films

AbstractThis paper reports our recent work on the improved mechanical properties of alumina thin films with embedded Fe and Ni nanoparticle layers. The Fe/Ni nanoparticles-alumina composite thin films have been deposited using a multi-target pulsed laser ablation technique. Every film consists of 10 layers of alumina and 9 intermediate layers of Fe or Ni nanoparticles. Alumina layer thickness kept constant (∼22 nm) and total thickness of multilayered films was in range 220-280 nm depending on metal deposition time. Composite thin films were deposited at six different substrate temperatures in the range 200-800°C. The mechanical properties measurements, performed by nanoindentation in continuous stiffness mode and applying Nix-Bhattacharya (hardness H) and King's model (Young's modulus E) for film-only properties, have shown that pure alumina films deposited at temperatures 200-500°C are relatively soft (H = 15 GPa, E = 190 GPa), while films deposited at ≥600°C are significantly harder (H = 32 GPa, E = 320 GPa). Grazing incidence XRD (GIXRD) data indicated that γ-alumina peaks exist in high temperature samples while alumina films deposited at ≥500°C were amorphous. Embedding Ni and Fe nanoparticle layers at 500°C led to significant increase of H and E (31 GPa and 365 GPa with Fe and 33 GPa and 380 GPa with Ni) and appearance of γ-alumina peaks in GIXRD. Embedding on metal nanoparticle layers does not change mechanical properties of alumina films deposited at 200°C, and significant hardening of metal containing films starts at 400°C. These results suggest that metal nanoparticles have a catalytic effect on the growth of alumina thin films with enhanced crystallinty. The effect of Ni and Fe nanoparticle size on mechanical properties of thin films has been studied times at substrate temperature 500°C using eight different metal deposition. HRTEM data have shown that metal nanopartiles have uniform particle size distribution and inter-particle separation in the layer. Size of Ni and Fe nanoparticles with highest effect on mechanical properties was 4 -6 nm.

The Use of Fluorine to Protect β-Solidifying γ-TiAl-Based Alloys against High-Temperature Oxidation

MRS Advances ◽  
2017 ◽  
Vol 2 (25) ◽  
pp. 1361-1367
Author(s):  
Alexander Donchev ◽  
Mathias Galetz ◽  
Svea Mayer ◽  
Helmut Clemens ◽  
Michael Schütze
Keyword(s):  
High Temperature ◽  
Titanium Aluminides ◽  
Elevated Temperatures ◽  
Turbine Blades ◽  
Nominal Composition ◽  
Hot Workability ◽  
Two Phase ◽  
Alumina Layer ◽  
Temperature Oxidation ◽  
Al Content

ABSTRACTLight-weight alloys based on intermetallic titanium aluminides (TiAl) are structural materials considered for high-temperature applications, e.g. in aero engines or automotive engines. TiAl alloys of engineering interest consist of two phases, the γ-TiAl and the α2-Ti3Al-phase. Recent developments have led to the so-called TNM alloys (T = TiAl; N = Nb; M = Mo) with an Al-content of 43.5 at.%. These alloys also possess the disordered body centered cubic β-Ti(Al)-phase at elevated temperatures, which ensures a better hot-workability compared to conventional two-phase alloys. However, the relatively low Al content (< 45 at.%) limits the high-temperature capability due to reduced oxidation resistance. This impedes their application in a temperature range above 800°C. The present work shows how the fluorine effect counteracts this disadvantage due to the formation of a protective alumina layer. The performance of the TNM alloy with the nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (at.%) is compared with another TNM alloy variant containing additional elements, such as Si and C, and the so-called GE alloy (Ti-48Al-2Cr-2Nb; at.%), which is already in use for turbine blades. The results of isothermal and thermocyclic high-temperature exposure tests of untreated and fluorine treated specimens will be compared. The effect of composition and microstructure of the alloys on the oxidation behavior with and without fluorine treatment are discussed.

scholarly journals Effect of the Removal of an Initial Oxide Layer and the Anodization Time on the Growth of the Porous Alumina Layer

2010 ◽  
Vol 20 (5) ◽  
pp. 191-195
Author(s):  
Dae-Hwan Kim ◽  
Sang-Hee Lue ◽  
Hyo-Jin Lee ◽  
Young-Ok Park ◽  
Eun-Joong Lee ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Porous Alumina ◽  
Alumina Layer ◽  
Anodization Time

Improvement of the Resistance of Titanium Aluminides to Environmental Embrittlement

2013 ◽  
Vol 50 (44) ◽  
pp. 127-141
Author(s):  
P. J. Masset ◽  
F. Bleicher ◽  
L. Bortolotto ◽  
G. Geiger ◽  
A. Kolitsch ◽  
...  
Keyword(s):  
Titanium Aluminides ◽  
Environmental Embrittlement

Photocatalytic Degradation of 4-Nitrophenol in a Continuous Reactor Containing Titanium Dioxide Supported on Glass Beads

2008 ◽  
Vol 11 (3) ◽  
Author(s):  
S. Yurdakala ◽  
V. Loddo ◽  
G. Palmisanob ◽  
V. Augugliarob ◽  
H. Berbera ◽  
...  
Keyword(s):  
Thin Film ◽  
Titanium Dioxide ◽  
Photocatalytic Degradation ◽  
Kinetic Constant ◽  
Fixed Bed ◽  
Volumetric Flow Rate ◽  
Total Surface Area ◽  
Glass Beads ◽  
Continuous Reactor ◽  
True Value

AbstractThe photocatalytic degradation of 4-nitrophenol in aqueous solution was performed by using a continuous fixed bed annular photoreactor. Titanium dioxide was used as the photocatalyst, supported as thin film on Pyrex glass beads. The influence of different operative parameters as substrate and oxygen concentrations, volumetric flow rate and incident photonic flow on the kinetics was studied. The Langmuir-Hinshelwood model has been satisfactorily fitted to the experimental results and its parameters have been determined. The true value of the kinetic constant can not be determined as the model contains a parameter very difficult to be measured, i.e. the total surface area active for the occurrence of photoreaction.

Effective Fluorine Treatment for Improved High Temperature Oxidation Behavior of Novel Cu, Mo and Si Containing TiAl-Alloys

2014 ◽  
Vol 783-786 ◽  
pp. 1117-1122
Author(s):  
Alexander Donchev ◽  
M. Galetz ◽  
M. Schütze
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Titanium Aluminides ◽  
Turbine Blades ◽  
Surface Region ◽  
Alumina Layer ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
High Temperature Oxidation Behavior

Intermetallic light weight TiAl-alloys are expected to replace the heavy Ni-based super alloys in several high temperature applications. However until now they cannot be used at temperatures above 700°C for longer times due to their insufficient oxidation resistance. The high temperature oxidation behavior can be improved drastically for the use at temperatures up to at least 1050°C by small amounts of fluorine in the surface region of TiAl-components. A thin protective alumina layer is formed after an optimized fluorine treatment during exposure in oxidizing high temperature environments. Results of isothermal and thermocyclic high temperature oxidation tests of untreated and halogen treated TiAl-samples of new types of TiAl-alloys containing Mo, Cu and Si will be presented in this paper. These results will be compared and discussed considering the beneficial effect of fluorine for a later use as e.g. turbine blades in jet engines. Key words: Titanium aluminides, high temperature oxidation, halogen effect,

scholarly journals Perturbation approach to metal surface oxidation considering volume variation

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401667678 ◽  
Author(s):  
Yaohong Suo ◽  
Zhonghua Zhang ◽  
Xiaoxiang Yang
Keyword(s):  
Oxide Layer ◽  
Metal Surface ◽  
Moving Boundary ◽  
Classical Model ◽  
Surface Oxidation ◽  
Higher Order ◽  
Perturbation Approach ◽  
Perturbation Scheme ◽  
First Order ◽  
Parabolic Law

In this article, kinetics equation of the metal surface oxidation is presented using the perturbation approach. A moving boundary is converted into a fixed one by Landau transformation. The perturbation results show that (1) the solution of the zeroth-order stands for the quasi-steady state and that of the first-order is instantaneous and (2) the reaction rate, diffusion coefficient, and the thickness of the initial oxide layer have important effects on the oxidation kinetics. If the chemical reaction is supposed to be instantaneous, our results are reduced to the classical parabolic law, no matter whether there exists the initial oxide layer or not. Moreover, the kinetic coefficient of the parabolic law is analytically presented. The proposed perturbation scheme can be easily extended to the higher order, and the higher order solution will provide a method to correct the error offered by the classical model.

Corrosion Behavior of Pre-Treated Fe-Al Alloys in Aqueous Acid Solutions

2007 ◽  
Vol 127 ◽  
pp. 233-238 ◽  
Author(s):  
Naoya Masahashi ◽  
G. Kimura ◽  
M. Oku ◽  
Shuji Hanada
Keyword(s):  
Corrosion Resistance ◽  
Oxide Layer ◽  
Corrosion Behavior ◽  
Dip Coating ◽  
Al Alloy ◽  
Aqueous Corrosion ◽  
Alumina Layer ◽  
Al2o3 Layer ◽  
Aqueous Acid

The corrosion behavior of pre-treated Fe–Al alloy in a sulfuric acid solution and chloride-containing solution was studied. Alumina layer formed at 1073–1173 K on the surface of Fe–Al alloy improves the corrosion resistance of the alloy, whereas that at 1273 K does not improve it. This was explained by the defects of Al2O3 layer, the fraction of Al2O3 in the oxides, crystallity of Al2O3, and residual stress in the oxide layer. On the other hand, TiO2 layer produced by dip coating and subsequent annealing at 523–773 K slightly improved the corrosion resistance of the alloy. The effect of the oxide layer on the aqueous corrosion was discussed focusing on the quality of the oxide.

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