scholarly journals Heat treatment induced phase transformations in zirconia and yttria-stabilized zirconia monolithic aerogels

2019 ◽  
Vol 149 ◽  
pp. 54-63 ◽  
Author(s):  
Jorge Torres-Rodríguez ◽  
József Kalmár ◽  
Melita Menelaou ◽  
Ladislav Čelko ◽  
Karel Dvořak ◽  
...  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Francisco J. Cano ◽  
Orlando Castilleja-Escobedo ◽  
L. J. Espinoza-Pérez ◽  
Cecilia Reynosa-Martínez ◽  
Eddie Lopez-Honorato

The effect of yttria concentration (0-33.4 mol%), extraction rates (0.17, 0.33, 0.50, and 0.67 mm s-1), and the number of layers (up to four) on the phase content, surface defects, thickness, hardness, adhesion strength, and wear rate of yttria-stabilized zirconia coatings produced by sol-gel/dip-coating were studied for its use on thermolabile substrates. At 700°C, a metastable tetragonal phase ( t ″ ) was obtained even with 33.4 mol% yttria when heat treated for 24 hours; however, a fully cubic structure was attained by extending the heat treatment up to 48 hours as confirmed by Raman spectroscopy. Furthermore, it was necessary to use withdrawal speeds of at least 0.67 mm s-1 to produce defect-free coatings. Although the coatings were produced at low temperature, they showed 41% lower wear rate than steel and an adhesion strength of 30 MPa. Our work stresses the importance of the heat treatment history on the stabilization of the cubic phase in sol-gel YSZ coatings.


2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
S. Rezaee ◽  
Gh. R. Rashed ◽  
M. A. Golozar

Sol-gel 8 wt.% Yttria Stabilized Zirconia (YSZ) thin films were prepared on zirconium (zircaloy-4 alloy) by dip-coating technique followed by heat treating at various temperatures (200°C, 400°C, and 700°C) in order to improve both electrochemical corrosion and high temperature oxidation properties of the substrate. Differential thermal analysis and thermogravimetric analysis (DTA-TG) revealed the coating formation process. X-ray diffraction (XRD) was used to determine the crystalline phase structure transformation. The morphological characterization of the coatings was carried out using scanning electron microscopy (SEM). The electrochemical behavior of the coated and uncoated samples was investigated by means of open circuit potential, Tafel, and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. The homogeneity and surface appearance of coatings produced was affected by the heat treatment temperature. According to the corrosion parameters, the YSZ coatings showed a considerable increase in the corrosion resistance, especially at higher heat treatment temperatures. The coating with the best quality, from the surface and corrosion point of view, was subjected to oxidation test in air at 800°C. The coated sample presented a 25% reduction in oxidation rate in comparison with bare substrate.


Author(s):  
Camila Pauleski Zucuni ◽  
Luís Felipe Guilardi ◽  
Marilia Pivetta Rippe ◽  
Gabriel Kalil Rocha Pereira ◽  
Luiz Felipe Valandro

2005 ◽  
Vol 885 ◽  
Author(s):  
Jeremy Cheng ◽  
Kevin Crabb ◽  
Rojana Pornprasertsuk ◽  
Hong Huang ◽  
Yuji Saito ◽  
...  

ABSTRACTThe performance of solid oxide fuel cells is limited largely by ion transport in the electrolyte. Thin film electrolytes of yttria-stabilized zirconia were deposited by pulsed laser deposition. The electrolyte material was subjected to heavy ion irradiation and heat treatment and the effects on conductivity were measured using electrical impedance spectroscopy. Following irradiation there is a drop in conductivity by a factor of 3-4. After heat treatment at 800°C, the conductivity recovers to the as-deposited value.


1996 ◽  
Vol 451 ◽  
Author(s):  
T. Sasaki ◽  
Y. Matsumoto

ABSTRACTA LaMnO3precursor was electrolessly deposited on a YSZ substrate in a solution containing Mn2+, La3+, an oxidizing agent and some additives. Peroxydisulfate was used as the oxidizing agent. The LaMnO3precursor was an amorphous and hydrous MnO2which contained La3+ions. The incorporation of La3+ions into the precursor oxide film was based on the ion-exchange reaction, where La3+ions in the solution were exchanged for H+ions on the deposited amorphous and hydrous MnO2. A La1-xSrxMnO3precursor was also prepared from the LaMnO3precursor by the ion-exchange reaction of some of the La3+ions in the LaMnO3precursor for Sr2+ions in the solution. (La0.5Sr0.5)0.75MnO3perovskite film was obtained from the precursor films on Pt substrate by heat-treatment at 800 °C.


2018 ◽  
Vol 107 (1) ◽  
pp. 104-111 ◽  
Author(s):  
Amanda M. O. Dal Piva ◽  
Ronaldo L. A. Carvalho ◽  
Aline L. Lima ◽  
Marco A. Bottino ◽  
Renata M. Melo ◽  
...  

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