Cationic and Anionic Vacancies in the Crystalline Phases of Sol−Gel Magnesia−Alumina Catalysts

1999 ◽  
Vol 11 (2) ◽  
pp. 308-313 ◽  
Author(s):  
J. A. Wang ◽  
A. Morales ◽  
X. Bokhimi ◽  
O. Novaro ◽  
T. López ◽  
...  
Keyword(s):  
Sol Gel ◽  
Crystalline Phases ◽  
Alumina Catalysts

scholarly journals Eco-Friendly Colloidal Aqueous Sol-Gel Process for TiO2 Synthesis: The Peptization Method to Obtain Crystalline and Photoactive Materials at Low Temperature

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 768
Author(s):  
Julien G. Mahy ◽  
Louise Lejeune ◽  
Tommy Haynes ◽  
Stéphanie D. Lambert ◽  
Raphael Henrique Marques Marcilli ◽  
...  
Keyword(s):  
Organic Pollutant ◽  
Sol Gel ◽  
Synthesis Method ◽  
Specific Treatment ◽  
High Specific Surface Area ◽  
Crystalline Phases ◽  
Tio2 Photocatalysts ◽  
Tio2 Anatase ◽  
Synthesis Parameters ◽  
Calcination Step

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is the peptizing agent. Indeed, depending on its acidic or basic character and also on its amount, it can modulate the crystallinity and morphology of TiO2. Colloidal aqueous TiO2 photocatalysts are mainly being used in various photocatalytic reactions for organic pollutant degradation. The as-synthesized materials seem to have equivalent photocatalytic efficiency to the photocatalysts post-treated with thermal treatments and the commercial Evonik Aeroxide P25, which is produced by a high-temperature process. Indeed, as-prepared, the TiO2 photocatalysts present a high specific surface area and crystalline phases. Emerging applications are also referenced, such as elaborating catalysts for fuel cells, nanocomposite drug delivery systems, or the inkjet printing of microstructures. Only a few works have explored these new properties, giving a lot of potential avenues for studying this eco-friendly TiO2 synthesis method for innovative implementations.

Preparation of novel uniform mesoporous alumina catalysts by the sol–gel method

2001 ◽  
Vol 68 (1-3) ◽  
pp. 97-109 ◽  
Author(s):  
Nan Yao ◽  
Guoxing Xiong ◽  
Yuhong Zhang ◽  
Mingyuan He ◽  
Weishen Yang
Keyword(s):  
Sol Gel ◽  
Mesoporous Alumina ◽  
Gel Method ◽  
Sol Gel Method ◽  
Alumina Catalysts

Effect of Annealing Temperature on Phase Transition of Nanoalumina Synthesized by Auto-Combustion Route

2016 ◽  
Vol 41 ◽  
pp. 74-86 ◽  
Author(s):  
Muhammad Adil ◽  
Hasnah Mohd Zaid ◽  
Kean Chuan Lee ◽  
Noor Rasyada Ahmad Latiff
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Sol Gel ◽  
Thermo Gravimetric Analysis ◽  
Amorphous State ◽  
Specific Area ◽  
Combustion Method ◽  
Gravimetric Analysis ◽  
Crystalline Phases ◽  
Auto Combustion

Nanocrystalline Al2O3 powder has been successfully synthesized by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders was investigated through X-ray diffraction in terms of their crystallinity and crystallite size. Subsequently, a detailed transmission electron microscopy (TEM) investigation, including specific area electron diffraction (SAED) analysis revealed the crystallographic alterations and morphological information even at lattice scale which co-include the XRD analysis. The results obtained allow to explain the evolution of an amorphous state into different crystalline phases with increased calcining temperature; and their relation to particle size. The particle size is found to be closely related to phase transition of Al2O3 from γ → δ → θ → κ →α. The existence of distinctive bonds and band energy were studied by employing Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy, respectively. On the other hand, thermo gravimetric analysis (TGA) had also been performed to confirm the phase purity of nano powder.

Influence of Annealing Temperature on the Properties of Sol-Gel Deposited Nb-Doped TiO2 Thin Films

2020 ◽  
Vol 845 ◽  
pp. 59-64
Author(s):  
Wen Cheng Tzou ◽  
Hon Kuan ◽  
You Cheng Chang
Keyword(s):  
Thin Films ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Optical Transmittance ◽  
Crystalline Phases ◽  
Air Atmosphere ◽  
Coating Method ◽  
Nb Content ◽  
Xrd Patterns ◽  
Surface Morphologies

Nb-doped TiO2 (TNO) thin films were prepared by a sol-gel spin coating method with Nb content of 5 at.%, and then annealed in the temperature range of 500-900 °C. The surface morphologies and the crystalline phases of the TNO thin films were investigated by using SEM and XRD patterns. The grain sizes increased with rising annealing temperature, and the crystalline phases were completely transformed from anatase into rutile when the annealing temperature was above 900 °C in air atmosphere. In addition, the optical band gap decreased and the average optical transmittance was between 75 and 70 % in the range of visible light. Furthermore, the better electrical properties were obtained at the annealing temperature of 600 °C.

Thin Film Phosphate Based Bioactive Substrates

1995 ◽  
Vol 414 ◽  
Author(s):  
S Langstaff ◽  
M Sayer ◽  
L Weaver ◽  
S Pugh ◽  
T Smith
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Calcium Phosphate ◽  
Tricalcium Phosphate ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Crystalline Phases ◽  
Sintering Conditions ◽  
Quartz Substrates ◽  
Osteoclast Resorption

AbstractCalcium phosphate based thin films prepared by colloidal sol-gel slow draw dipping of quartz substrates are bioactive to both osteoclast resorption and osteoblast deposition. The bioactivity is related to the presence of mixed crystalline phases in the films generated under different sintering conditions. As the sintering temperature was increased from 800°C to 1000°C, a transition in film composition from calcium hydroxylapatite to alpha-tricalcium phosphate is achieved.

A comparison of sol–gel and impregnated Pt or/and Ni based γ-alumina catalysts for bioglycerol aqueous phase reforming

2012 ◽  
Vol 125 ◽  
pp. 516-529 ◽  
Author(s):  
M. El Doukkali ◽  
A. Iriondo ◽  
P.L. Arias ◽  
J. Requies ◽  
I. Gandarías ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Sol Gel ◽  
Aqueous Phase Reforming ◽  
Alumina Catalysts

Mechanical Characterization of Zirconia Synthesized by the Sol-Gel Process

2012 ◽  
Vol 727-728 ◽  
pp. 945-950
Author(s):  
Ana Márcia Barbosa da Silva Antunes ◽  
Carlos Antonio Reis Pereira Baptista ◽  
Simone Pereira Taguchi
Keyword(s):  
Mechanical Characterization ◽  
Sol Gel ◽  
Zirconia Ceramic ◽  
Complexing Agent ◽  
Zirconia Ceramics ◽  
Crystalline Phases ◽  
Structural Applications ◽  
Sol Gel Process ◽  
Small Grains

Zirconia ceramics (ZrO2) are bioinert materials with excellent biocompatibility, high resistance to corrosion and to wear, high toughness in comparison with other advanced ceramics, and suitable for various structural applications. These properties are related to their microstructure and effects caused by crystalline phases transformation, intrinsic of zirconia. In this work, stabilized zirconia ceramic (ZrO2 with 3 mol % yttria) was produced using the synthesized powder obtained by the sol-gel process, in which citric acid was chosen as complexing agent and maize starch as gelling. The zirconia ceramic was characterized with respect to relative density (99.75±0.10 %), crystalline phases (predominantly tetragonal), microstructure (homogeneous and small grains), flexural strength (510±60 MPa), Vickers hardness (11.6±0.3 GPa) and fracture toughness (Niihara = 11.8±2.9 MPa.m1/2 and Evans = 10.9±1.2 MPa.m1/2). It can be concluded that the sol-gel process is an attractive route to obtain zirconia ceramics with good mechanical properties.

Sol-gel Prepared Cu-Ce-Ni Nanoparticle Alumina Catalysts for WGS Hydrogen Production

2008 ◽  
Vol 14 (S2) ◽  
pp. 308-309
Author(s):  
NV Seetala ◽  
J Bass ◽  
AMR Jayasingha ◽  
RK Garudadri ◽  
U Siriwardane
Keyword(s):  
New Mexico ◽  
Hydrogen Production ◽  
Sol Gel ◽  
Alumina Catalysts

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

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