scholarly journals Properties of Alumina/Chromia Scales in N2-Containing Low Oxygen Activity Environment Investigated by Experiment and Theory

2017 ◽  
Vol 87 (3-4) ◽  
pp. 321-332 ◽  
Author(s):  
Christine Geers ◽  
Vedad Babic ◽  
Nooshin Mortazavi ◽  
Mats Halvarsson ◽  
Bo Jönsson ◽  
...  
Keyword(s):  
Oxygen Activity ◽  
Low Oxygen ◽  
Chromia Scales

Non-Stoichiometry and Cation Tracer Diffusion Studies in the Magnetite-UlvÖSpinel Solution, (Fe,Ti)3-δO4

1994 ◽  
Vol 369 ◽  
Author(s):  
Sanjeev Aggarwal ◽  
Rudiger Dieckmann
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Deviation From Stoichiometry ◽  
Diffusion Studies ◽  
Tracer Diffusion Coefficients ◽  
Point Defect Structure

AbstractCation diffusion in the spinel solid solution (Fe1-xTix)3-δO4 (0≤ x ≤ 0.3) was investigated at 1200 ºC as a function of oxygen activity, aO2 and cationic composition, x. At different cationic compositions, cation tracer diffusion coefficients, D*Me of Me = Fe and Ti were measured as a function of oxygen activity. Plots of log DMe vs. loga0 show V-shaped curves, indicating that different types of point defects prevail at high anc low oxygen activities. Thermogravimetric experiments were conducted, using a high resolution microbalance, to determine the deviation from stoichiometry in (Fe1-xTix)3-δO4 at 1200 °C. δversus log aO2 curves are S-shaped. An analysis of the oxygen activity dependences of thecation diffusion coefficients and the deviation from stoichiometry with regardto the point defect structure suggests that at high oxygen activities cation vacancies are the predominant defects governing the deviation from stoichiometry and the diffusion ofcations. At low oxygen activities, and at small values of x, cation interstitials determine the deviation from stoichiometry, while they dominate for 0 ≤ x ≤ 0.3 inthe cation diffusion.

Accelerated ceria–zirconia solubilization by cationic diffusion inversion at low oxygen activity

2016 ◽  
Vol 4 (43) ◽  
pp. 16871-16878 ◽  
Author(s):  
Vincenzo Esposito ◽  
De Wei Ni ◽  
Debora Marani ◽  
Francesca Teocoli ◽  
Karl Tor Sune Thydén ◽  
...  
Keyword(s):  
High Temperatures ◽  
Oxygen Activity ◽  
Doped Ceria ◽  
Low Oxygen ◽  
Stabilized Zirconia ◽  
Reducing Conditions ◽  
Elemental Diffusion

Fast elemental diffusion at the Gd-doped ceria/Y-stabilized zirconia interface occurs under reducing conditions at low oxygen activity and high temperatures.

Mullite as an electrochemical probe for the determination of low oxygen activity in liquid iron

1992 ◽  
Vol 63 (10) ◽  
pp. 419-425 ◽  
Author(s):  
Hideaki Suito ◽  
Ryo Inoue ◽  
Akihiro Nagatani
Keyword(s):  
Liquid Iron ◽  
Oxygen Activity ◽  
Low Oxygen ◽  
Electrochemical Probe

Study on Refining Technology for Reducing the Content of T[O] in Steel

2011 ◽  
Vol 418-420 ◽  
pp. 419-423
Author(s):  
Xing Di Yang
Keyword(s):  
Continuous Casting ◽  
Converter Slag ◽  
Casting Process ◽  
Refining Process ◽  
Oxygen Activity ◽  
Low Oxygen ◽  
Continuous Casting Process ◽  
High Quality

In order to produce low oxygen steel with high quality, converter slag-tapping, slag oxidability and oxygen activity have been analyzed. In addition, modifying and adding process of slag, control of slag oxidability and bottom argon-blowing in ladle were studied as well. On this basis, refining process which is beneficial to low oxygen steel producing with converter-continuous casting process has been developed. The results show that content of T[O] in steel is not more than 15×10-6.

scholarly journals The Effects of Low Oxygen Activity Conditions on the Phase Equilibria and Cation Occupancy of Strontium Barium Niobate

2016 ◽  
Vol 99 (10) ◽  
pp. 3435-3442 ◽  
Author(s):  
Jonathan A. Bock ◽  
Jason H. Chan ◽  
Yoed Tsur ◽  
Susan Trolier-McKinstry ◽  
Clive A. Randall
Keyword(s):  
Phase Equilibria ◽  
Oxygen Activity ◽  
Low Oxygen ◽  
Strontium Barium Niobate ◽  
Strontium Barium

Point Defects and Cation Tracer Diffusion in (CrxFe1-x)3-δO4 Spinels

1994 ◽  
Vol 369 ◽  
Author(s):  
J. TÖpfer ◽  
R. Dieckmann
Keyword(s):  
Point Defect ◽  
Tracer Diffusion ◽  
Oxygen Activity ◽  
Spinel Solid Solution ◽  
Low Oxygen ◽  
Cation Diffusion ◽  
Cationic Composition ◽  
Deviation From Stoichiometry ◽  
Tracer Diffusion Coefficients ◽  
Defect Species

AbstractThe cation diffusion in the spinel solid solution (CrxFe1-x)3-δO4 (0 ≤ x ≤ 0.5) was experimentally investigated at 1200 °C as a function of oxygen activity, aO2 (= PO2/P°with P° = 1 bar) and cationic composition, x. Cation tracer diffusion coefficients, DMe' of Me = Co, Cr, Fe and Mn, were determined using the radioactiveisotopes Co-60, Cr-51, Fe-59 and Mn-54. For each cationic composition V-shaped log DMe vs. log aO2 plots were obtained. The observed oxygen activity dependences indicate that the cation diffusion is determined by different point defect species prevailing at high and low oxygen activities, respectively. The observed oxygen activity dependences, in comparison with considerations based on point defect thermodynamics, suggest that cations diffuse via cation vacancies at high aO2' while at low aO2 cation interstitials prevail in the cation diffusion. In addition, new experimental data for tihe deviation from stoichiometry ≤in (CrxFe1-x)3-≤O4 are presented and discussed.

Chromite alteration in the Panton Sill, East Kimberley Region, Western Australia

1975 ◽  
Vol 40 (310) ◽  
pp. 181-192 ◽  
Author(s):  
Paul R. Hamlyn
Keyword(s):  
Western Australia ◽  
Oxygen Activity ◽  
Normal Type ◽  
Low Oxygen ◽  
End Members ◽  
Ground Mass

SummaryIn addition to the normal type of chromite alteration, an antipathetic form of alteration has been observed in the ultramafic zone of the Panton Sill, Western Australia. The chromites display margins of lower reflectivity related to a marked enrichment in MgO and Al2O3 and depletion in Cr2O3, Fe2O3, and FeO, such that a spinellid of composition lying between the end members MgAl2O4 and FeAlaO4 is formed. The alteration is related to the formation of secondary spinel in the ground-mass during the hornblendization of primary silicates under metasomatic conditions accompanied by low oxygen activity.

High spatial resolution AEM observations of yttrium segregation in chromia scales grown on Co-45%Cr

1986 ◽  
Vol 44 ◽  
pp. 518-519
Author(s):  
K. Przybylski ◽  
A. J. Garratt-Reed ◽  
G. J. Yurek
Keyword(s):  
Spatial Resolution ◽  
Outer Surface ◽  
Maximum Concentration ◽  
High Spatial Resolution ◽  
Reactive Elements ◽  
Chromia Scales

The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.

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