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1.
Judy N. Hart Laure Bourgeois Raoul Cervini Yi-Bing Cheng George P. Simon Leone Spiccia 《Journal of Sol-Gel Science and Technology》2007,42(2):107-117
TiO2 nanoparticles are widely used for many applications and an understanding of the crystallization behavior of TiO2 is essential, so that heat treatment conditions can be optimized for particular applications. The effect of sol–gel synthesis
conditions on the crystallization behavior of TiO2 has, therefore, been investigated. Complete crystallization to the anatase phase (determined by XRD and TEM analysis) was
achieved during drying of the synthesis product at 95 °C. The nanoparticles grew during heat treatment, reaching ∼10–15 nm
in diameter with a heat treatment at 450 °C. Explanations are offered for the observed differences in the crystallization
and particle growth behavior of TiO2 synthesized under various conditions. 相似文献
2.
Li Chen Haixia Shen Zhen Lu Cang Feng Su Chen Yanru Wang 《Colloid and polymer science》2007,285(13):1515-1520
TiO2–SiO2 composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO2–SiO2 composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO2–SiO2) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO2–SiO2 composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO2–SiO2 composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO2–SiO2 core surface via surface functionalized reaction. The particle size of TiO2–SiO2 composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and
Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid
films. The average particle size of the TiO2–SiO2 composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO2–SiO2 composite nanoparticles are well dispersed in the PU matrix. 相似文献
3.
Julian R. Osman Joe A. Crayston Allin Pratt David T. Richens 《Journal of Sol-Gel Science and Technology》2007,44(3):219-225
Mixed IrO2–TiO2 oxides were prepared by the sol–gel method upon acid-catalysed hydrolysis of an iridium solution in ethanol mixed with titanium
tetraethoxide in ethanol. The iridium solution was obtained by reaction of the sodium hexachloroiridate(IV) precursor in the
presence of sodium ethoxide in ethanol. Gels were formed in all but the high-Ir samples. Analysis of the dried gels showed
minority-phase enrichment at the surface and the presence of Ir(III), while microscopy showed evidence for dispersed iridium-containing
nanoparticles (1–20 nm in diameter). XRD powder patterns of the calcined material showed peaks due to a small amount of crystalline
NaCl impurity which could be removed by washing. This left amorphous phases, except in the Ir:Ti 3:2 case, which showed evidence
for the presence of separate crystalline oxide phases: anatase, IrO2 and Ti
x
Ir1−x
O2. 相似文献
4.
M. Crişan Ana Brăileanu M. Răileanu D. Crişan V. S. Teodorescu R. Bîrjega V. E. Marinescu J. Madarász G. Pokol 《Journal of Thermal Analysis and Calorimetry》2007,88(1):171-176
Pure TiO2
and S-doped TiO2 sol–gel nanopowders were prepared
by controlled hydrolysis-condensation of titanium alkoxides. The influence
of different Ti-alkoxides (tetraethyl-, tetraisopropyl- and tetrabutyl-orthotitanate)
used in obtaining TiO2 porous materials in similar
conditions (water/alkoxide ratio, solvent/alkoxide ratio, pH and temperature
of reaction) has been investigated. The relationship between the synthesis
conditions and the properties of titania nanosized powders, such as thermal
stability, phase composition, crystallinity, morphology and size of particles,
BET surface area and the influence of dopant was investigated. The nature
of the alkyl group strongly influences the main characteristics of the obtained
oxide powders, fact which is pointed out by thermal analysis, X-ray diffraction,
TEM and BET surface area measurements. 相似文献
5.
Ming Feng Wen Wang Yu Zhou Dechang Jia 《Journal of Sol-Gel Science and Technology》2009,52(1):120-123
Ferroelectric SrBi2Ta2O9 nanotubes were fabricated by sol–gel dipping template technique and characterized by X-ray diffraction, field emission scanning
electron microscopy, and transmission electron microscopy. They had a single orthorhombic perovskite structure, and most of
SBT nanotubes showed highly preferential crystal growth along the [115] orientation. FE-SEM and TEM investigations showed
that nanotubes have smooth wall morphologies and well-defined diameters corresponding to the diameter of the applied template.
From HRTEM results, the clear lattice fringes indicated that the nanotubes are structurally uniform and well crystallized.
The growth mechanisms of SBT nanotubes into the AAO templates were explored. 相似文献
6.
Lili Chen Mingrong Shen Liang Fang Yu Xu 《Journal of Sol-Gel Science and Technology》2007,42(3):299-303
A TiO2 thin buffer layer was introduced between the (Pb0.4Sr0.6)TiO3 (PST) film and the Pt/Ti/SiO2/Si substrate in an attempt to improve their electrical properties. Both TiO2 and PST layers were prepared by a chemical solution deposition method. It was found that the TiO2 buffer layer increased the (100)/(001) preferred orientation of PST and decreased the surface roughness of the films, leading
to an enhancement in electrical properties including an increase in dielectric constant and in its tunability by DC voltage,
as well as a decrease in dielectric loss and leakage current density. At an optimized thickness of the TiO2 buffer layer deposited using 0.02 mol/l TiO2 sol, the 330-nm-thick PST films had a dielectric constant, loss and tunability of 1126, 0.044 and 60.7% at 10 kHz, respectively,
while the leakage current density was 1.95 × 10−6 A/cm2 at 100 kV/cm. 相似文献
7.
Chun-guang Gao Yong-xiang Zhao Yin Zhang Dian-sheng Liu 《Journal of Sol-Gel Science and Technology》2007,44(2):145-151
The Ni/ZrO2/SiO2 aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO2–SiO2 composite aerogels with a aqueous solution of Ni(NO3)2, (ii) impregnation SiO2 aerogels with a mixed aqueous solution of Ni(NO3)2 and ZrO(NO3)2 · 2H2O, (iii) one-pot sol–gel procedure from precursors Ni(NO3)2/ZrO(NO3)2 · 2H2O/Si(OC2H5)4. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed
desorption (NH3-TPD), N2 adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride
(MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference
between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component,
texture, and catalytic selectivity. 相似文献
8.
Xiangzhong Ren Yingkai Jiang Peixin Zhang Jianhong Liu Qianling Zhang 《Journal of Sol-Gel Science and Technology》2009,51(2):133-138
One-dimensional (1D) submicron-belts of V2O5 have been prepared by a sol–gel route using V2O5, H2O2 and aniline as starting materials. Thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform
infrared spectroscopy and scanning electron microscopy were employed to characterize the samples. Electrochemical behaviors
as cathode material in rechargeable lithium-ion batteries were investigated by galvanostatic charge–discharge measurement
and cyclic voltammeter. The results showed that the synthesized V2O5 appeared to be submicron-belts and orthorhombic structure. The V2O5 submicron-belts exhibited a high initial discharge capacity of 346 mAh/g and stayed 240 mAh/g after 20 cycles at 0.1 C discharge
rate in the potential region 1.8–4.0 V. 相似文献
9.
At present, carbon dioxide is considered the largest contributor among greenhouse gases. This review covers the current state
of problem of carbon dioxide emissions from industrial and combustion processes, the principle of photocatalysis, existing
literature related to photocatalytic CO2 reduction over TiO2 based catalysts and the effects of important parameters on the process performance including light wavelength and intensity,
type of reductant, metal-modified surface, temperature and pressure.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
10.
Jianxia Jiao Qun Xu Limin Li Takano Tsubasa Takaomi Kobayashi 《Colloid and polymer science》2008,286(13):1485-1491
Titania–silica composite have been prepared using polyethylene glycol (PEG) with different molecular weights (M
w), PEG20000, PEG10000, and PEG2000, as template in supercritical carbon dioxide (SC CO2). The composite precursors were dissolved in SC CO2 and impregnated into PEG templates using SC CO2 as swelling agent and carrier. After removing the template by calcination at suitable temperature, the titania–silica composite
were obtained. The composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen
sorption–desorption experiment. Photocatalytic activity of the samples has been investigated by photodegradation of methyl
orange. Results indicate that there are many Si–O–Ti linkages in the TiO2/SiO2 composite; the PEG template has a significant influence on the structure of TiO2/SiO2. In addition, the TiO2/SiO2 prepared with PEG10000 exhibited high photocatalytic efficiency. So this work supplies a clue to control and obtain the TiO2/SiO2 composite with different photocatalytic reactivity with the aid of suitable PEG template in supercritical CO2. 相似文献
11.
Jun Wang Tianjin Zhang Hongying Xia Junhuai Xiang Wenkui Li Shuwang Duo 《Journal of Sol-Gel Science and Technology》2008,47(1):102-106
Compositionally graded Ba1−x
Sr
x
TiO3 (BST) (0 ≤ x ≤ 0.4) thin films were fabricated on Pt/Ti/SiO2/Si and YSZ/Pt/Ti/SiO2/Si substrates by a modified sol–gel technique. The YSZ buffer layer was prepared by RF magnetron sputtering. The microstructure
of the graded BST films was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force
microscopy (AFM). The results showed that all the films have uniform and crack-free surface with a perovskite structure. The
graded BST film with an YSZ buffer layer has larger dielectric constant and lower dielectric loss. The leakage current density
of the graded BST film with an YSZ buffer layer lowers two orders than the film without buffer layer. The improved electric
properties of the graded films with an YSZ buffer layer was attributed to the YSZ buffer layer act as an excellent seeding
layer to enhance the graded BST film growth. 相似文献
12.
Chengbin Jing Xiujian Zhao Yongheng Zhang 《Journal of Sol-Gel Science and Technology》2007,42(2):151-156
Multilayered alumina film was deposited onto metallic substrate using cycles of dip-coating method. The film thickness was
found not always growing linearly with the increase of the number of dipping cycles, and even a zero-growth in thickness was
observed after 20 cycles of dip coatings. This phenomenon was found to be attributed to the dissolving behavior of alumina
gel material in original sol. A heat treatment at a temperature higher than 230 °C was found to be able to effectively lower
the dissolvability of Al2O3 gel material, but an extra high temperature, i.e., 600 °C led to the formation of cracks in the multilayered film due to
the increase of interfacial tension force. It was examined by IR and XRD analyses that a heat treatment at 250 °C for 10 min
before each coating process could yield an amorphous multilayered film with no crack formed after calcinations at 600 °C.
A crack-free Al2O3 film with a thickness up to 2 μm after 22 cycles of dip coating process could be produced and it showed an excellent antioxidation
performance for steel substrate. 相似文献
13.
Sagrario M. Montemayor L. A. García-Cerda J. R. Torres-Lubián O. S. Rodríguez-Fernández 《Journal of Sol-Gel Science and Technology》2007,42(2):181-186
In this work the synthesis of CoFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained
by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride
were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors,
without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric
precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray
diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe2O4 and NiFe2O4 in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of
the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic
behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe2O4-SiO2 and NiFe2O4-SiO2 compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C. 相似文献
14.
Klaartje De Buysser Philippe F. Smet Bart Schoofs Els Bruneel Dirk Poelman Serge Hoste Isabel Van Driessche 《Journal of Sol-Gel Science and Technology》2007,43(3):347-353
This paper describes the synthesis of ZrW2O8 by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic
processing. The thermal expansion coefficient thus obtained for α-ZrW2O8 is −10.6 × 10−6 °C−1 (50–125 °C) whereas for the β-ZrW2O8 a value of −3.2 × 10−6 °C−1 (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products.
The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW2O8 material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed.
These effects support our views that the precursors show homogeneity up to nanometer level. 相似文献
15.
Blue-light-emitting Sr2CeO4 phosphors were synthesized via a sol–gel process and the conventional solid-state method in this study. The developed sol–gel
process lowered the synthesis temperature of monophasic Sr2CeO4 to as low as 900 °C. In comparison with the solid-state derived powders, the sol–gel derived powders had more uniform morphology
and smaller particle sizes. In addition, sol–gel derived Sr2CeO4 displayed higher luminescent intensity than that prepared via the solid-state route under the same heating conditions. This
is attributed to the improved compositional homogeneity and crystallinity in the sol–gel process. During the heating processes,
Sr2CeO4 tended to thermally decompose at elevated temperatures. This decomposition reaction resulted in the formation of an impurity
phase- SrCeO3 and thereby a decrease in the luminescent intensity. For obtaining Sr2CeO4 phosphors with high luminescent intensity, the heating conditions in both processes need to be well modulated. 相似文献
16.
Stefano Livraghi Maria Cristina Paganini Mario Chiesa Elio Giamello 《Research on Chemical Intermediates》2007,33(8):739-747
Nitrogen-doped TiO2, a novel photocatalyst active in the decomposition of organic pollutants using visible light, contains several different
types of paramagnetic centers. These are molecular species, such as NO and NO2 radicals and other species, deeply interacting with the TiO2 structure. All or part of these species is related to specific properties of the solid. Electron paramagnetic resonance has
been employed to characterize the N-containing paramagnetic species present in N-doped anatase TiO2 powders obtained via sol-gel synthesis. In the present work attention is focused on molecular species generated during the synthesis process and
segregated in cavities of the TiO2 structure. 相似文献
17.
TiO2 nano-crystalline film and fixed bed photocatalytic reactor were prepared by the sol-gel process using tetrabutylorthotitanate
as a precursor and glass tube as the substrate. XRD, AFM, SEM and thickness analysis results indicate that the preparation
of nano-crystalline film can be controlled by optimizing experiment process. Under the optimized process, the phase of TiO2 in film is anatase, and the grain size is 3–4 nm. The size of particles, which is about 20-80 nm, can be controlled. The
thickness of monolayer film is in nanometer grade. The thickness and particles size in films growing on nanometer film can
also be controlled in nanometer grade. As a result, the crack of film can be effectively avoided. Rhodamine degradation results
using UV-Vis spectrophotometer show that the activity of nano-crystalline film in the photocatalytic reactor has a good relation
with the diameter of TiO2 particles, that is, the film shows high activity when the size is 20 –30 nm and greatly reduced when the size is above 60
nm. The activity of film does not decrease with the increase of film thickness, and this result indicates that nano-crystalline
film has no ill influence on the transmissivity of ultraviolet light. 相似文献
18.
Amorphous precursor powders have proven to be highly advantageous for the sol–gel processing of TiO2 thin films. Oxide yield, density, solubility, and thermal degradation of powders prepared under various conditions were determined; the thermoanalytical data could be assigned to the oxidative decomposition of different organic constituents. Certain powders are suitable for the preparation of alcohol-based sols, whereas also aqueous coating solutions can be prepared from others. Thin films prepared from both systems show excellent adhesion and optical properties when deposited on borosilicate glass substrates. 相似文献
19.
Junseo Choi Ji-Young Ban Suk-Jin Choung Jinsoo Kim Haznan Abimanyu Kye Sang Yoo 《Journal of Sol-Gel Science and Technology》2007,44(1):21-28
Mesoporous TiO2/γ-Al2O3 composite granules were prepared by combining sol–gel/oil-drop method, using various titania solution. The product granules
can be used as a photocatalyst or adsorbent in moving, fluidized bed reactors. The phase composition and pore structure of
the granules can be controlled by calcination temperature and using different titania solution. In the photocatalysis of NH3 decomposition, TiO2/γ-Al2O3 granules using Degussa P25 powder treated thermally at 450 °C showed the highest catalytic ability. However, TiO2/γ-Al2O3 granules using titania made by hydrothermal method had comparable performance in NH3 decomposition. 相似文献
20.
Yuanxiang Gu Dairong Chen Xiuling Jiao 《Journal of Sol-Gel Science and Technology》2007,43(2):245-249
Hollow LiNiO2 fibers have been prepared with a capillary spinneret electrospinning technique combined with the sol–gel method, and the
possible mechanism for the fabrication of the hollow fibers was discussed. The xerogel fibers and those calcined at different
temperatures were characterized by thermogravimetric (TG) analysis, X-ray diffractometry (XRD), Fourier transform infrared
(FT-IR) spectrum, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and etc. The Polyvinyl Pyrrolidone
(PVP) has an important role in the formation of hollow LiNiO2 fibers. 相似文献