Phase structure and thermal evolution in coatings and powders obtained by the sol-gel process: Part I. ZrO2−11.3 mol% Y2O3

1997 ◽  
Vol 12 (2) ◽  
pp. 493-500 ◽  
Author(s):  
P. C. Rivas ◽  
M. C. Caracoche ◽  
J. A. Martínez ◽  
A. M. Rodríguez ◽  
R. Caruso ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Thermal Evolution ◽  
Sol Gel ◽  
Correlation Spectroscopy ◽  
Cubic Phase ◽  
Perturbed Angular Correlation Spectroscopy ◽  
Heating And Cooling ◽  
Sol Gel Process ◽  
Fast Movement ◽  
Zirconia Powders

Yttria-stabilized cubic zirconia powders and coatings produced by the sol-gel method have been investigated by Perturbed Angular Correlation Spectroscopy (PAC). Results indicate that the metastable cubic phase is retained during heating and cooling cycles. The hyperfine interaction that describes this cubic phase, once crystallized, exhibits two components in a constant ratio of 4 : 1. The components represent different vacancy configurations. For the fast movement of oxygen vacancies starting at 750 °C, which is reflected by the damping of the hyperfine pattern, an activation energy of 0.96 eV was determined.

Nanostructural study of sol-gel-derived zirconium oxides

2003 ◽  
Vol 18 (1) ◽  
pp. 208-215 ◽  
Author(s):  
Mariía C. Caracoche ◽  
Patricia C. Rivas ◽  
Mario M. Cervera ◽  
Ricardo Caruso ◽  
Edgardo Benavídez ◽  
...  
Keyword(s):  
Perturbed Angular Correlation ◽  
Sol Gel ◽  
Correlation Spectroscopy ◽  
Perturbed Angular Correlation Spectroscopy ◽  
Zirconium Oxides ◽  
The Relationship ◽  
Highly Porous ◽  
Highly Porous Material ◽  
Thermal Stability Of ◽  
Zirconia Powders

Two sol-gel derived zirconia powders were prepared at pH = 0.5 and pH = 5.5. They were investigated as a function of temperature using mainly perturbed angular correlation spectroscopy. The aim was to elucidate the relationship between the nanoscopic configurations around Zr4+ ions and the morphology and structure of the powders. The highly porous material resulting from the solution at higher pH could be described mainly by defective and disordered, very hydrolyzed tetragonal arrays. As temperature increased, the amount of these arrays decreased while they became increasingly asymmetric, thus suggesting their superficial localization. The easy removal of hydroxyls led to the early appearance of the monoclinic phase. The gel obtained from the precursor at pH = 0.5 was entirely described by configurations still involving organic residues. After their calcination, the powder underwent a well-defined two-step hydroxyl removal thermal process leading to the crystallization of the tetragonal and the monoclinic phases. The thermal stability of the metastable tetragonal phase in the investigated powders seems to be controlled by their different capability to absorb oxygen.

Evaluations of Hydrogen Permeation on γ-Al2O3 Synthesized by Sol-Gel Process

2009 ◽  
Vol 620-622 ◽  
pp. 25-28
Author(s):  
Ji Hee Park ◽  
Mie Won Jung ◽  
Tae Whan Hong
Keyword(s):  
Room Temperature ◽  
Ceramic Membrane ◽  
Hydrogen Permeation ◽  
Thermal Evolution ◽  
Sol Gel ◽  
Alumina Ceramic ◽  
Distilled Water ◽  
Ceramic Support ◽  
Sol Gel Process ◽  
Metal Ceramic

The purpose of this work was hydrogen permeation of ceramic or metal/ceramic membrane using γ-Al2O3 by synthesizing. The γ-Al2O3 was synthesized by using the sol-gel process with aluminum isopropoxide and primary distilled water as the precursor and solvent. The γ-Al2O3-based membranes were prepared using HPS. The phase transformation, thermal evolution, surface are and morphology of γ-Al2O3 and γ-Al2O3-based membranes were characterized by XRD, TG-DTA, BET and FE-SEM. The hydrogen permeation of γ-Al2O3-based membranes was examined at room temperature comparing with other paper using nickel composited membrane on alumina ceramic support.

Zirconium oxide nanoparticles coated on sepiolite by sol–gel process — Their application as a solvent-free catalyst for condensation reactions

2011 ◽  
Vol 89 (3) ◽  
pp. 280-288 ◽  
Author(s):  
Sadok Letaief ◽  
Yun Liu ◽  
Christian Detellier
Keyword(s):  
Clay Mineral ◽  
Zirconium Oxide ◽  
Condensation Reaction ◽  
Sol Gel ◽  
Magic Angle Spinning ◽  
Solvent Free ◽  
Cubic Phase ◽  
Magic Angle ◽  
Solvent Free Conditions ◽  
Sol Gel Process

An inorganic nanocomposite made of zirconia nanoparticles coated on the external surfaces of the fibrous clay mineral sepiolite was prepared by using the sol–gel process under soft conditions using zirconium(IV) propoxide in 1-propanol as the precursor. The resulting materials were characterized by X-ray diffraction (XRD), thermal gravimetric analyses (TGA) and differential thermal analyses (DTA), microporosimetry, 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR), and high-resolution transmission electron microscopy (HR-TEM). The organic material from the precursor was fully removed after calcination at 450 °C, concurrently with the crystallization of the cubic phase of zirconium oxide. The coordinated water molecules of sepiolite were fully removed and its symmetrical layered structure was folded after calcination at 650 °C, as observed by XRD and 29Si cross-polarization (CP) / MAS NMR. The arrangement of the nanoparticles of zirconium oxide on the sepiolite external surfaces maintains a fibrous morphology for the nanocomposite. This material was applied as a catalyst for the Knoevenagel condensation reaction of benzaldehyde and malononitrile under solvent-free conditions. Strongly improved yields of reaction, attributed to larger catalytically active surfaces, were obtained compared with either the sepiolite clay mineral or the zirconium oxide tested individually.

Relaxor Behavior in Ba0.8Sr0.2TiO3/ZrO2 Heterostructured Thin Films

2012 ◽  
Vol 1454 ◽  
pp. 89-96 ◽  
Author(s):  
Santosh K. Sahoo ◽  
H. Bakhru ◽  
Sumit Kumar ◽  
D. Misra ◽  
Y. N. Mohapatra ◽  
...  
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Oxygen Vacancies ◽  
Sol Gel ◽  
Single Layer ◽  
Relaxor Behavior ◽  
Bst Thin Films ◽  
Si Substrates ◽  
Sol Gel Process ◽  
Loss Maximum

ABSTRACTBa0.8Sr0.2TiO3 (BST) thin films and Ba0.8Sr0.2TiO3/ZrO2 heterostructured thin films have been successfully fabricated on Pt/Ti/SiO2/Si substrates by a sol-gel process. The dielectric properties of these films were measured as a function of temperature in the frequency range of 1 kHz to 1 MHz. It is clearly observed that the dielectric peaks exist and shift to high temperature with the increase of frequency indicating the presence of relaxor-type behavior in the films. Also it is seen that one dielectric peak is observed in single layer BST thin films whereas two dielectric peaks are observed in BST/ZrO2 heterostructured thin films due to the presence of two dielectric layers having different band gap energies. The variation of peak temperature Tm, corresponding to dielectric loss maximum, with frequency and fitting to Arrhenius law gives activation energy of 1.24 eV which is very close to the activation energy of oxygen vacancies in BaTiO3. Hence, oxygen vacancies are the active defects which are contributing to the relaxation process in these films.

Hydrogen Permeability of NiO-Doped Alumina with Nickel Composites Membrane

2012 ◽  
Vol 724 ◽  
pp. 213-216 ◽  
Author(s):  
Bo Young Shon ◽  
Mie Won Jung
Keyword(s):  
Hydrogen Permeation ◽  
Thermal Evolution ◽  
Sol Gel ◽  
Hydrogen Permeability ◽  
Organic Additive ◽  
Hot Press ◽  
Sol Gel Process ◽  
Increase Surface Area ◽  
Nickel Composites ◽  
Hot Press Sintering

NiO-doped Al2O3was synthesized with 20 wt% of nickel nitrate using the sol-gel process. P123 as an organic additive added to increase surface area of powder. The phase transformation, thermal evolution and surface morphology of the powder were characterized by XRD, TG-DTA and FE-SEM. The 20 wt% NiO-doped Al2O3/10 wt% Ni composite membrane was prepared by hot press sintering (HPS) following with a mechanical alloying process. Hydrogen permeation flux for 20 wt% NiO-doped Al2O3/10 wt% Ni membrane was obtained as 0.1 mol/m2s at 673K.

Preparation of t-ZrO2 by a sol–gel process with carbon as a phase transformation promoter

RSC Advances ◽  
2015 ◽  
Vol 5 (43) ◽  
pp. 34451-34455 ◽  
Author(s):  
Yu Liu ◽  
Weidong Chi ◽  
Hui Liu ◽  
Yueyang Su ◽  
Liang Zhao
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Amorphous Carbon ◽  
Sol Gel ◽  
Cubic Phase ◽  
Sol Gel Process

Cubic phase ZrO2 can be synthesized with amorphous carbon as a phase transition promoter.

scholarly journals A Comparison of Different A-, A-B-, and B-Site Incorporated in (Ba0.5Sr0.5)TiO3 on Photocatalytic Application

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Tassanee Tubchareon ◽  
Rachan Klaysri ◽  
Piyasan Praserthdam
Keyword(s):  
Methylene Blue ◽  
Structural Modification ◽  
Oxygen Vacancies ◽  
Sol Gel ◽  
Lattice Oxygen ◽  
Photocatalytic Decolorization ◽  
Chemisorbed Oxygen ◽  
Photocatalytic Application ◽  
Sol Gel Process ◽  
A Site

The structural modification of Ba0.5Sr0.5TiO3 (BST) nanocatalyst was successfully synthesized via sol-gel process. The BST catalyst was modified by A-site (A-BST), A-B-site (A-B-BST), and B-site (B-BST) in order to investigate the effect of structurally modified BST catalyst for photocatalytic decolorization of methylene blue. The structurally modified BST catalysts can increase the nonradiation energy such as phonon energy compared to that of BST one. The partial incorporation of the A-BST catalyst was evidenced by the higher-ordered structure by increasing number of Ti4+ ions and the lattice oxygen. The A-B-BST and A-BST catalysts were given more electron-transfer in the TiO6 than that of BST and B-BST catalysts, respectively. The A-B-BST catalyst promoted the oxidation of the lattice oxygen by holes capturing to form the chemisorbed oxygen, presenting the highest photobleaching activity of methylene blue. On the other hand, more oxygen vacancies recombination of BST catalyst compared to that of structurally modified BST catalysts presented the reduction of photocatalytic activity.

scholarly journals Effect of Na Content on the Physical Properties ofBa0.5Sr0.5TiO3Powders

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Tassanee Tubchareon ◽  
Soipatta Soisuwan ◽  
Somchai Ratanathammaphan ◽  
Piyasan Praserthdam
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxygen Deficiency ◽  
Sol Gel ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Vacancy Defects ◽  
X Ray ◽  
Sol Gel Process ◽  
A Site

The different Na contents (0 ≤ Na ≤ 0.35, based on mole of NaOH) of doped Ba0.5Sr0.5TiO3(BST) powders synthesized via sol-gel process were studied. The substitution of Na+ions into a partial A-site of BST powders provided the reduction in vacancy defects as confirmed by electron paramagnetic resonance (EPR) and UV-visible spectroscopy. Photoluminescence (PL) spectra appeared in violet, blue, and green emissions. The phase structure, oxygen deficiency, and titanium deficiency of BST powders were further investigated as a function of Na content. X-ray diffraction (XRD) result was found that low Na content (0 ≤ Na ≤ 0.15) exhibited the tetragonal structure, while it was transformed to the cubic phase when high Na content. Moreover, X-ray photoelectron spectroscopy (XPS) result revealed that the partial oxidation of Ti3+ions to Ti4+ions was observed at Na content lower than 0.05 mole, while more addition of Na content resulted in the increasing of the oxygen and the titanium deficiency. Furthermore, the result indicated the oxygen deficiency significantly formed at the A-site of Sr atoms more than that of Ba atoms.

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