Investigation of Failure Mechanisms in Ti Containing Brazing Alloys Used in SOFC/SOEC Environments

2010 ◽  
Author(s):  
Wolff-Ragnar Kiebach ◽  
Ruth Knibbe ◽  
Kristian B. Frederiksen ◽  
Ming Chen ◽  
Lars Mikkelsen ◽  
...  
Keyword(s):  
Ferritic Steel ◽  
Failure Mechanisms ◽  
Annealing Process ◽  
Yttria Stabilized Zirconia ◽  
Reaction Products ◽  
Stabilized Zirconia ◽  
Advantages And Disadvantages ◽  
Active Metal ◽  
Reported Data

The two braze alloys TiCuNi® and Silver-ABA® were tested as possible candidates for seals in SOFC or SOEC stacks. The different Ti amount in the samples allowed an evaluation of Ti as a matrix filler and as an active metal/wetting agent in brazing alloys. The sealing ability towards ferritic steel and yttria-stabilized-zirconia (YSZ) was investigated. After the sealing process steel/braze/YSZ joints were further annealed in oxidizing (Air) or reducing (9% H2 in Ar) atmospheres at 750 °C for 150 h. The boundaries of the braze and the joining partners for as-sealed and annealed samples were examined with SEM/EDS. XRD and EXAFS were used to characterize reaction products after the annealing process. Based on these results and taking before reported data into consideration, the advantages and disadvantages of Ti containing seals and the role of Ti in failure mechanism are discussed. Even if the use of Ti in active brazing alloys has its benefits, the disadvantages caused by Ti and its reaction products strongly suggest the use of Ti free brazes in SOFC/SOEC applications.

Grain-Size-Dependent Thermal Transport Properties in Nanocrystalline Yttria-Stabilized Zirconia

2001 ◽  
Vol 703 ◽  
Author(s):  
Ho-Soon Yang ◽  
J.A. Eastman ◽  
L.J. Thompson ◽  
G.-R. Bai
Keyword(s):  
Grain Boundaries ◽  
Thermal Transport ◽  
Chemical Vapor ◽  
Yttria Stabilized Zirconia ◽  
Organic Chemical ◽  
Stabilized Zirconia ◽  
Size Dependent ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

ABSTRACTUnderstanding the role of grain boundaries in controlling heat flow is critical to the success of many envisioned applications of nanocrystalline materials. This study focuses on the effect of grain boundaries on thermal transport behavior in nanocrystalline yttria-stabilized zirconia (YSZ) coatings prepared by metal-organic chemical vapor deposition.

Role of the First Atomic Layers in Epitaxial Relationship and Interface Characteristics of SrTiO3 Films on CeO2/YSZ/Si(001)

2002 ◽  
Vol 747 ◽  
Author(s):  
Tomoaki Yamada ◽  
Takanori Kiguchi ◽  
Naoki Wakiya ◽  
Kazuo Shinozaki ◽  
Nobuyasu Mizutani
Keyword(s):  
Atomic Layer ◽  
Yttria Stabilized Zirconia ◽  
The Other ◽  
Stabilized Zirconia ◽  
Epitaxial Relationship ◽  
Electron Traps ◽  
Ion Drift ◽  
Interface Characteristics ◽  
Injection Type

ABSTRACTThe role of the first atomic layers in epitaxial relationship and interface characteristics of SrTiO3 films on CeO2/yttria-stabilized zirconia (YSZ)/Si(001) substrates was investigated. Although SrTiO3 film deposited on CeO2/YSZ/Si directly was preferentially (110)-oriented, epitaxial SrTiO3(001) films could be grown on CeO2/YSZ/Si by controlling first atomic layer of the films. In the case of SrTiO3 film starting from TiO2 layer, the neither ion drift nor charge injection occurred in the SrTiO3/CeO2 interface. On the other hand, for the film starting from SrO layer, an injection-type hysteresis was observed. This is probably due to the electron traps in the interface.

Role of grain boundaries on the electrical properties of titania doped yttria stabilized zirconia

1995 ◽  
Vol 30 (4) ◽  
pp. 515-522 ◽  
Author(s):  
M.T. Colomer ◽  
L.S.M. Traqueia ◽  
J.R. Jurado ◽  
F.M.B. Marques
Keyword(s):  
Electrical Properties ◽  
Grain Boundaries ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia

Y1Ba2Cu3O7–x multilayer structures with a thick SiO2 interlayer for multichip modules

1997 ◽  
Vol 12 (11) ◽  
pp. 2947-2951 ◽  
Author(s):  
S. Afonso ◽  
K. Y. Chen ◽  
Q. Xiong ◽  
Y. Q. Tang ◽  
G. J. Salamo ◽  
...  
Keyword(s):  
Stress Relief ◽  
Annealing Process ◽  
Yttria Stabilized Zirconia ◽  
Multilayer Structures ◽  
Low Dielectric Constant ◽  
Multichip Modules ◽  
Stabilized Zirconia ◽  
Ybco Layer ◽  
Low Dielectric

For high temperature superconducting multichip modules and other related electronic applications, it is necessary to be able to fabricate several Y1Ba2Cu3O7–x (YBCO) layers separated by thick low dielectric constant dielectric layers. In this work, we report the successful fabrication of YBCO/YSZ/SiO2 (1–2 μm)/YSZ/YBCO multilayer structures on single crystal yttria stabilized zirconia (YSZ) substrates. In contrast to previously reported work, the top YBCO layer did not show any cracking. This is due to a technique that allows for stress relief in the SiO2 layer before the second YBCO layer is deposited. The top YBCO layer in our multilayer structure had Tc = 87 K and Jc = 105 A/cm2 (at 77 K), whereas the bottom YBCO layer had Tc = 90 K and Jc = 1.2 × 106 A/cm2 (at 77 K). We also showed that the quality of the bottom YBCO layer was preserved during the fabrication of the multilayer due to the annealing process during which O2 diffused into the YBCO, replacing the O2 lost during the deposition of the top YBCO layer.

X-ray absorption spectroscopy studies on the carbothermal reduction reaction products of 3 mol% yttria-stabilized zirconia

2014 ◽  
Vol 47 (5) ◽  
pp. 1512-1519
Author(s):  
A. Sondhi ◽  
O. Okobiah ◽  
S. Chattopadhyay ◽  
T. Shibata ◽  
T. W. Scharf ◽  
...  
Keyword(s):  
Bond Length ◽  
Absorption Spectroscopy ◽  
Carbothermal Reduction ◽  
Yttria Stabilized Zirconia ◽  
Sintered Pellet ◽  
Reaction Products ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Bond Lengths ◽  
X Ray Absorption

Extended X-ray absorption spectroscopy (EXAFS) at the ZrKedge has been used to determine changes in various bond lengths in 3 mol% yttria-stabilized zirconia (YSZ) during zirconium carbide (ZrC) formation. The principal objective of this study was to determine if ZrC formation at the YSZ/carbon interface alters the zirconia structure. A mixed-phase sample (YSZ and graphite) was carbothermally reduced to form ZrC. X-ray diffraction phase quantification by Rietveld analysis confirmed the formation of ∼50% ZrC in the analyzed sample volume. EXAFS data of ZrC and YSZ powders and a sintered YSZ pellet (∼96.7% density) were used as standards to compare with the carbothermally reduced sample.Ab initocalculations using these spectra quantified various Zr—O, Zr—C and Zr—Zr bond distances in the system. Best fit results revealed Zr—OI(tetragonal), Zr—O (monoclinic), Zr—Zr (tetragonal) and Zr—Zr (monoclinic) bond length values of 2.10, 2.25, 3.65 and 3.52 Å, respectively, in the YSZ powder, Zr—OI(tetragonal) and Zr—Zr (tetragonal) bond length values of 2.12 and 3.62 Å, respectively, in the sintered pellet, and Zr—C and Zr—Zr bond lengths of 2.32 and 3.33 Å, respectively, in the ZrC powder. Similar fitting procedures were carried out on the carbothermally reduced pellet, with measured Zr—O, Zr—Zr (of YSZ), Zr—C and Zr—Zr (of ZrC) bond lengths of 2.13, 3.62, 2.36 and 3.33 Å, respectively. These bond lengths indicate that the formation of ZrC in the YSZ matrix does not influence the local structure when compared to pure standards. Therefore, carbothermal reduction does not induce any apparent strain or thermally induced effects on the first and second coordination shells of Zr as measured by the X-ray absorption spectra of the carbothermally reduced sample. Interestingly, the results indicated that sintering of the YSZ powder into pellets did not result in any significant change in the Zr—O and Zr—Zr distances for tetragonal YSZ.

scholarly journals Role of dispersion conditions on grindability of yttria stabilized zirconia (YSZ) powders

2005 ◽  
Vol 28 (2) ◽  
pp. 109-114 ◽  
Author(s):  
S. Ramanathan ◽  
K. P. Krishna Kumar ◽  
P. K. De ◽  
S. Banerjee
Keyword(s):  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia

Burner Rig Evaluation of Ceramic Coatings With Vanadium-Contaminated Fuels

1990 ◽  
Vol 112 (4) ◽  
pp. 536-542 ◽  
Author(s):  
B. A. Nagaraj ◽  
D. J. Wortman
Keyword(s):  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Ceramic Coatings ◽  
Yttria Stabilized Zirconia ◽  
Reaction Products ◽  
Stabilized Zirconia ◽  
Test Environment ◽  
Turbine Engine ◽  
Partial Pressures ◽  
Ysz Coating

The performance of yttria-stabilized zirconia (YSZ), ceria-stabilized zirconia (CSZ), and magnesia-stabilized zirconia (MSZ) coatings was evaluated using an atmospheric burner rig; test environment contained compounds of vanadium, sodium, and sulfur. The coatings were deposited by plasma spraying and electron beam physical vapor deposition (EB-PVD); sputtered sealant layers of hafnia, alumina, and platinum were deposited on the YSZ coating. The tests were performed for up to 500 hours at 1650°F and 1300°F. The tests were designed to simulate the deposit chemistry and sulfur trioxide partial pressures expected in a marine gas turbine engine operating on contaminated fuel. YSZ, CSZ, and MSZ coatings all underwent reaction in the burner rig environment; the reaction products and their effects on spallation were varied. MSZ was by far the most reactive, readily forming MgSO4 in both 1650°F and 1300°F tests. The observed reaction products provided a measure of “protection” for the bond coat by preventing molten salt infiltration for the duration of the test. The mechanism of ceramic spallation is discussed. Sputtered overlayers of platinum, hafnia, and alumina did not prevent salt infiltration and reaction with the underlying ceramic, although no reaction product between the overlayer and the salt was observed.

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