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1.
I. C. Cosentino E. N. S. Muccillo R. Muccillo F. M. Vichi 《Journal of Sol-Gel Science and Technology》2006,37(1):31-37
Ceramic ZrTiO4 powders were prepared by a sol-gel method using zirconium oxychloride and titanium tetraisopropoxide. In situ high temperature X-ray diffraction results show that crystallization of the amorphous gel starts at 400 ∘C. Single-phase ZrTiO4 nanoparticles were obtained after heat treatment at 450 ∘C for one hour. An average particle size of 46 nm has been determined by nitrogen adsorption analysis. After pressing these
sinteractive powders, pellets with controlled pore size distribution were obtained by sintering at temperatures as low as
400 ∘C. The analysis of pores by mercury porosimetry gives an average porosity of 45%. The electrical resistivity, determined by
impedance spectroscopy measurements at 24 ∘C under different humidity environments, shows the ability of these pellets to adsorb water vapor in the porous surfaces.
Pellets fabricated with the nanosized powders prepared by the sol-gel technique are proposed as good candidates to be used
in humidity sensing devices. 相似文献
2.
Elisa Mercadelli Carmen Galassi Anna Luisa Costa Stefania Albonetti Alessandra Sanson 《Journal of Sol-Gel Science and Technology》2008,46(1):39-45
Ba-modified bismuth sodium titanate with composition 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3 (BNBT) was prepared by a citrate nitrate sol–gel combustion method. The sol was obtained using barium acetate, bismuth nitrate,
sodium nitrate and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate
(C/N) were considered for the sol production. The corresponding gels were fired at different temperatures (300, 400, 500 °C)
in order to evaluate the conditions necessary to obtain the decomposition of the precursors and the formation of the pure
BNBT perovskitic phase in a single step. The best conditions to obtain the desired phase are: (C/N) = 0.2, and combustion
temperature of 500 °C. Ball milled powders were densified at a temperature 100 °C lower than the one generally used for powder
produced with the conventional mixed oxide route. The electrical properties are comparable to those reported for conventionally
prepared materials. 相似文献
3.
SrAl2O4:Eu2+, Dy3+ powders were synthesized by sol–gel–combustion process using metal nitrates as the source of metal ions and citric acid as
a chelating agent of metal ions. The amounts of citric acid in mole were two times those of the metal ions. By tracing the
formation process of the sol–gel, it is found that decreasing the amount of NO3
− in the solution is necessary for the formation of transparent sol and gel, and the dropping of ethanol into the precursor
solution can decrease the amount of NO3
− in the solution. By combusting citrate sol at 600 °C, followed by heating the resultant combustion ash at 1,100–1,300 °C
in a weak reductive atmosphere containing active carbon, SrAl2O4:Eu2+, Dy3+ phosphors can prepared. X-ray diffraction, Thermogravimetry–differential thermal analysis, scanning electron microscopy and
fluorescence spectrophotometer were used to investigate the formation process and luminescent properties of the as-synthesized
SrAl2O4:Eu2+, Dy3+. The results reveal that the SrAl2O4 crystallizes completely when the combustion ash was sintered at 1,200–1,300 °C. The excitation and emission spectra indicate
that excitation broadband mainly lies in a visible range and the phosphors emit strong light at 510 nm under the excitation
of 348 nm. The afterglow of phosphors lasts for over 10 h when the excited source is cut off. 相似文献
4.
Haihong Fang Binyuan Hu Lingshen Wang Rongli Lu Cui Yang 《Frontiers of Chemistry in China》2008,3(2):193-197
Nanometer MgO was prepared via a sol-gel auto-combustion technique using magnesium nitrate as raw material and citric acid
as chelating agent. IR spectra of the dried gel were used to investigate the structure of the precursors. By studying the
different TG curves of magnesium citrate gel prepared by different methods, we found that a combustion process occurred and
the nitrate ions acted as an oxidant in the combustion process. TEM photographs of synthesized powders from the sol-gel auto-combustion
showed that the crystallites were uniform in size. In addition, the XRD pattern of this sample showed that the particle size
was 8.9 nm. The BET curves, in turn, showed that the specific surface of the sample was 26.34 m2/g. The mechanism of the frothing process in restraining agglomeration is discussed.
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Translated from Journal of East China Normal University (Natural Science), 2007, (2): 52–57 [译自: 华东师范大学学报(自然科学版)] 相似文献
5.
Hynek Bene? Jocelyne Galy Jean-Fran?ois Gérard Josef Ple?til Ludovic Valette 《Journal of Sol-Gel Science and Technology》2011,59(3):598-612
Prehydrolyzed-condensed precursors containing amino or glycido groups were prepared via sol gel process using various alkoxysilanes
in the bulk, without addition of solvent in any step of their preparation. The influence of the experimental set-up, the functionality
and ratio of alkoxysilanes, and type of catalyst, on the structure buildup was studied. In the case of amino precursors, the
sol–gel process was carried out at weak basic conditions while in the case of glycido precursors the sol–gel process was catalyzed
by acid or neutral pH. The sol–gel process was monitored by 29Si NMR in solution and the structure of the prehydrolysed-condensed precursors was characterized by small-angle X-Ray scattering.
The systems with high content of tetraethoxysilane led to the fast gel formation. In weak acid medium tetraethoxysilane formed
larger, more condensed species as well as small structures (based on Q
1, Q
2 and Q
3 species) with silanol groups. Strong acidic conditions led to the fast formation of insoluble silica particles in liquid
(sol) phase containing monomeric alkoxysilanes. The most suitable precursor formulations based on the alkoxysilanes with amino
groups, as well as the most efficient set-up, were selected and used to prepare hybrid organic/inorganic networks based on
an epoxy matrix. These networks were characterized using dynamic mechanical analysis. 相似文献
6.
S. Kurajica E. Tkalcec J. Sipusic G. Matijasic I. Brnardic I. Simcic 《Journal of Sol-Gel Science and Technology》2008,46(2):152-160
Nanosized zinc aluminate spinel (gahnite, ZnAl2O4) powders were prepared by sol−gel technique at low sintering temperatures. Aluminium-sec-butoxide [Al(OsBu)3] and zinc nitrate hexahydrate Zn(NO3)2 . 6H2O were used as starting materials. Gels with and without chelating agent were prepared. Ethyl-acetoacetate (C6H10O3) was used as a chelating agent in order to control the rate of hydrolysis of Al(OsBu)3. The dried gels and thermally treated samples were characterized by means of Differential Thermal Analysis and Thermo-Gravimetric
Analysis (DTA, TGA), X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Transmission Electron Microscopy
(TEM). The surface area was measured by Brunauer-Emmet-Teller (BET) adsorption–desorption isotherms. It has been established
that chelation enables to obtain a transparent gel. The thermal evolution of gels was characterized by two crystallization
processes in the range 200–400 °C and 600–700 °C. Both processes yielded pure ZnAl2O4 as evidenced by XRD, i.e. zinc aluminate spinel powders were produced by gel heat-treatment at temperatures as low as 300 °C.
The average gahnite crystallite size for the samples sintered in the temperature range of 400–1000 °C has been calculated
from the broadening of XRD lines revealing that nanocrystalline powders were prepared. The surface areas measured for the
samples fired at 700 °C for 2 h were 43.1 and 62.6 m2 g−1, for sample without and with the chelating agent, respectively. TEM micrographs confirmed the nano-scale size of particles. 相似文献
7.
Continuous mullite ceramic fibers were fabricated by a sol–gel dry spinning technique. The sol was prepared from an aqueous
solution of aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethylorthosilicate (TEOS). The sol–gel transition
was investigated by measuring the volume, the solid content, the viscosity and the rheological properties of the solution.
Shear viscosity η of the mullite sol varied dynamically with concentrating time and temperature. Combine size analysis of
sol particles and TEM analysis on this basis, the growth character of sol particles agglomeration and its structural evolution
were discussed. By adjusting the temperature, the gelling degree could stabilize at a certain value and the sol–gel transition
could be transferred to the spinning line. Continuous fibers were spun from such sols immediately before gelling in a laboratory
dry spinning apparatus. The spinneret contained thirty circular holes, each having a diameter of 0.2 mm. The temperature inside
the spinning channel was 100–120 °C, the winding speed was 100–300 m/min. Sintering of the precursor fibers at 1,100 °C yields
crack-free mullite ceramic fibers. 相似文献
8.
《Solid State Sciences》2012,14(5):655-660
The present research describes a modified sol-gel technique used to obtain nano-crystalline potassium niobate (KNbO3) powders by using ethylene diamine tetraacetic acid (EDTA)/citrate as a complexing agent. The metal ions chemically interact with EDTA in the precursor sol. The aging treatments lead to the formation of a precursor-polymeric gel network. The effects of the amounts of citric acid and EDTA on the stability of the precursor sol are investigated. The influence of excess K on the formation of pure-phase KNbO3 powders is also studied. The obtained gels and powders are characterized by thermogravimetric-differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that a stable precursor sol is formed when n(CA):n(Mn+) = 3:1 and n(EDTA) :n(NH4OH) = 1:3.5. The xerogel is calcined at 700–850 °C to prepare the KNbO3 nano-powder. The smallest grain size of the sample obtained at 850 °C is about 60 nm when the K/Nb molar ratio equals 1.2. 相似文献
9.
S. Acosta R. Corriu D. Leclercq P. H. Mutin A. Vioux 《Journal of Sol-Gel Science and Technology》1994,2(1-3):25-28
Monolithic alumina and aluminosilicate gels have been prepared using a novel sol-gel process based on the non-hydrolytic condensation reaction between a metal halide and a metal alkoxide. XRD indicated that the alumina gel remained amorphous at 750°C; solid state 27Al NMR indicated the presence in the dried gel and in the amorphous calcined sample of a large amount of pentacoordinated aluminum atoms. A study of the sol formation using liquid state 27Al NMR suggested that the gel structure was reminiscent of the oligomeric structure of the chloroisopropoxide precursors. Differential thermal analysis and XRD indicated that the aluminosilicate gels were converted to mullite below 1000°C, suggesting a high degree of homogeneity in these precursors. 相似文献
10.
Long Xia Guangwu Wen Liang Song Xinyu Wang 《Journal of Sol-Gel Science and Technology》2009,52(1):134-139
Lithium aluminum silicate powders in the form of β-spodumene were synthesized through sol–gel technique by mixing boehmite
sol, silica sol and lithium salt. The gel and oxide powders were characterized by thermogravimetry, differential thermal analysis
(DTA), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy. DTA, XRD
and FTIR results confirmed that crystallization of β-spodumene took place at about 800 °C. The tiny crystallites with average
size less than 1 μm appeared when the gel powders were sintered at 800 °C. A substantial increase of the crystal grain size
was observed with increasing sintering temperatures. 相似文献
11.
Effect of sol-gel preparation method on particle morphology in pure and nanocomposite PZT thin films
Double-scale composite lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) thin films of 360 nm thickness were prepared by a modified composite sol-gel method. PZT films were deposited from
both the pure sol and the composite suspension on Pt/Al2O3 substrates by the spin-coating method and were sintered at 650°C. The composite suspension formed after ultrasonic mixing
of the PZT nanopowder and PZT sol at the powder/sol mass concentration 0.5 g mL−1. PZT nanopowder (≈ 40–70 nm) was prepared using the conventional sol-gel method and calcination at 500°C. Pure PZT sol was
prepared by a modified sol-gel method using a propan-1-ol/propane-1,2-diol mixture as a stabilizing solution. X-ray diffraction
(XRD) analysis indicated that the thin films possess a single perovskite phase after their sintering at 650°C. The results
of scanning electron microscope (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and transmission electron
microscopy (TEM) analyses confirmed that the roughness of double-scale composite PZT films (≈ 17 nm) was significantly lower
than that of PZT films prepared from pure sol (≈ 40 nm). The composite film consisted of nanosized PZT powder uniformly dispersed
in the PZT matrix. In the surface micrograph of the film derived from sol, large round perovskite particles (≈ 100 nm) composed
of small spherical individual nanoparticles (≈ 60 nm) were observed. The composite PZT film had a higher crystallinity degree
and smoother surface morphology with necklace clusters of nanopowder particles in the sol-gel matrix compared to the pure
PZT film. Microstructure of the composite PZT film can be characterized by a bimodal particle size distribution containing
spherical perovskite particles from added PZT nanopowder and round perovskite particles from the sol-matrix, (≈ 30–50 nm and
≈ 100–120 nm), respectively. Effect of the PZT film preparation method on the morphology of pure and composite PZT thin films
deposited on Pt/Al2O3 substrates was evaluated. 相似文献
12.
De-Qing Zhang Zi-Cheng Qin Xiu-Ying Yang Hou-Bin Zhu Mao-Sheng Cao 《Journal of Sol-Gel Science and Technology》2011,57(1):31-35
Potassium sodium niobate (KNN) ceramic powders by a variation of sol–gel method is synthesized. The metal precursors used
for the KNN synthesis are potassium carbonate, sodium carbonate and niobium hydroxide, ethylene glycol are used as chelating
and esterification agent, respectively. The effects of amount of oxalic acid (OA) and ethylene glycol (EG), pH value on the
stability of the precursor sol were investigated. The evolution of (K0.5Na0.5)NbO3 crystal phase was also investigated by XRD, IR, SEM and TG-DTA. The results showed that stable precursor sol was formed when
n(OA):n(Mn+) = 3:1, n(OA):n(EG) = 1:2 and pH value was in the range of 2.5–3.5. Xerogel was sintered in the range of 500–650 °C to prepare K6Nb10.88O30 and Na2Nb4O11 powder. Then the compound was sintered at 750 °C to produce perovskite (K0.5Na0.5)NbO3 ceramic powders. The grain size is about 100–200 nm. 相似文献
13.
M. R. Barati 《Journal of Sol-Gel Science and Technology》2009,52(2):171-178
Nanocrystalline Mg–Cu–Zn ferrite powders were successfully synthesized through nitrate–citrate gel auto-combustion method.
Characterization of the nitrate–citrate gel, as-burnt powder and calcined powders at different calcination conditions were
investigated by using XRD, DTA/TG, IR spectra, EDX, VSM, SEM and TEM techniques. IR spectra and DTA/TGA studies revealed that
the combustion process is an oxidation–reduction reaction in which the NO3
− ion is oxidant and the carboxyl group is reductant. The results of XRD show that the decomposition of the gel indicated a
gradual transition from an amorphous material to a crystalline phase. In addition, increasing the calcination temperature
resulted in increasing the crystallite size of Mg–Cu–Zn ferrite powders. VSM measurement also indicated that the maximum saturation
magnetization (64.1 emu/g) appears for sample calcined at 800 °C while there is not much further increase in M
s at higher calcination temperature. The value of coercivity field (H
c) presents a maximum value of 182.7 Oe at calcination temperature 700 °C. TEM micrograph of the sample calcined at 800 °C
showed spherical nanocrystalline ferrite powders with mean size of 36 nm. The toroidal sample sintered at 900 °C for 4 h presents
the initial permeability (μ
i) of 405 at 1 MHz and electrical resistivity (ρ) of 1.02 × 108 Ω cm. 相似文献
14.
《Comptes Rendus Chimie》2017,20(1):47-54
ZnO particles with different morphological forms and various scale sizes were successfully synthesized as photocatalysts using two different methods (sol–gel and precipitation) and three precursors (zinc acetate dihydrate, zinc nitrate hexahydrate, and zinc sulfate heptahydrate). These materials were calcined at 500 °C for 3 h and characterized by various physicochemical techniques such as X-ray diffraction, Fourier transform infrared, transmission electron microscopy, SBET, and UV–vis diffuse reflectance. The results showed that the crystalline structure, size, and morphology of the ZnO particles are strongly influenced by the preparation method and by the nature of the precursor used as reactant. The photocatalytic efficiency of the synthesized photocatalysts was evaluated by the photodegradation of methyl orange in aqueous solution under UV-A light. The results showed that the ZnO nanoparticles prepared the by sol–gel method from zinc acetate are more efficient than those prepared by the precipitation method. 相似文献
15.
Excitation of hexanuclear molybdenum complexes such as Mo6Cl12 and its derivatives in the ultraviolet results in a strongly red-shifted luminescence centered at 750nm. Since oxygen efficiently
quenches the luminescence, these thermally stable inorganic complexes are candidate lumophores for real-time, high temperature
optical fiber based sensing of oxygen. Sol-gel films containing the acetonitrile complex of Mo6Cl12 were deposited on quartz substrates by dip coating. After drying, the films were heated at 200∘C for 1 h. The luminescence lineshapes of films before and after heating were unchanged, indicating that heating did not adversely
affect the cluster photophysics. Compared to solutions of the acetonitrile complex, quenching by oxygen was smaller in the
as-prepared films, but heating at 200∘C for 1 h increased the quenching, apparently due to increased oxygen permeability resulting from the loss of water or other
small molecules from the matrix. These results confirm the potential of hexanuclear molybdenum complexes such as Mo6Cl12⋅2CH3CN as the lumophores in fiber optic oxygen sensors that can operate up to 200∘C. 相似文献
16.
Glasses along the composition line 0.5Al2O3–xSiO2 (1 ≤ x ≤ 6) were prepared via a novel sol–gel route using tetraethylorthosilicate and aluminum lactate as precursors. The structural evolution from solution to gel to glass is monitored by standard 27Al and 29Si nuclear magnetic resonance (NMR) spectroscopies, revealing important insights about molecular level mechanisms occurring at the various stages of glass formation. Under the experimental conditions reported, silica and alumina precursors undergo homoatomic condensation processes when the gel is heat treated at about 100 and 300 °C, respectively, and only little heteroatomic co-condensation occurs in this temperature range. The latter is promoted only upon elimination of the residual lactate and water ligands upon annealing the gels above 300 °C. Following calcination at 650 °C, mesoporous glasses are obtained, having average pore diameter of about 3 nm and a surface areas near 500 m2/g. Si–O–Al connectivities are detected by 29Si magic angle spinning (MAS)-NMR. 27Al MAS-NMR spectra reveal aluminum in four-, five- and six-coordination. The spectra differ significantly from those of other sol–gel derived Al2O3–SiO2 materials prepared from different precursor routes, suggesting that the lactate route results in a higher degree of compositional homogeneity. 相似文献
17.
Al2O3–TiO2 nanocrystalline powders were synthesized by sol–gel process. Aluminum sec-butoxide and titanium isopropoxide chemicals were
used as precursors and ethyl acetoacetate was used as chelating agent. Thermal and crystallization behaviors of the precursor
powders were investigated by thermal gravimetric-differential thermal analysis, Fourier-transform infrared spectrum and X-ray
diffraction. The average crystalline size of heat treated Al2O3–TiO2 powders at 1,100 °C is ~100 nm. 相似文献
18.
M. R. Mohammadi M. C. Cordero-Cabrera M. Ghorbani D. J. Fray 《Journal of Sol-Gel Science and Technology》2006,40(1):15-23
Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism,
with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO2 concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest
zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO2 concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher
zeta potential (46.3 mV) were achieved with increasing TiO2 concentration up to 0.4 M. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) results of produced powders annealed
at different temperatures showed that the 300°C annealed powder made from 0.1 M sol prepared at 50°C was a mixture of anatase
and brookite, corresponding to a major phase of anatase (∼95% estimated), with the smallest average crystallite size of 1.3 nm
and the highest specific surface area (SSA) of 193 m2/g. Furthermore, increasing TiO2 concentration up to 0.4 molar for the sols prepared at 70°C resulted in decreasing the average crystallite size (1.9 nm at
300°C) and increasing SSA (116 m2/g at 300°C) of the powders annealed at different temperatures. Anatase-to-rutile phase transformation temperature was increased
with decreasing peptisation temperature down to 50°C, whereas TiO2 concentration had no effect on this transition. Anatase percentage increased with decreasing both peptisation temperature
and TiO2 concentration. Such prepared powders can be used in many applications in areas from photo catalysts to gas sensors. 相似文献
19.
Xiangqian Shen Mingquan Liu Fuzhan Song Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2010,53(2):448-453
The SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fiber precursors were prepared by the sol-gel assisted electrospinning with ferric
nitrate, strontium nitrate and PVP as starting reagents. Subsequently, the M-type strontium ferrite (SrFe12O19) nanofibers were derived from calcination of these precursors at 750–1,000 °C.The composite precursors and strontium ferrite
nanofibers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy
and vibrating sample magnetometer. The structural evolution process of strontium ferrite consists of the thermal decomposition
and M-type strontium ferrite formation. After calcined at 750 °C for 2 h the single M-type strontium ferrite phase is formed
by reactions of iron oxide and strontium oxide produced during the precursor decomposition process. The nanofiber morphology,
diameter, crystallite size and grain morphology are mainly influenced by the calcination temperature and holding time. The
SrFe12O19 nanofibers characterized with diameters of around 100 nm and a necklace-like structure obtained at 900 °C for 2 h, which
is fabricated by nanosized particles about 60 nm with the plate-like morphology elongated in the preferred direction perpendicular
to the c-axis, show the optimized magnetic property with saturation magnetization 59 A m2 kg−1 and coercivity 521 kA m−1. It is found that the single domain critical size for these M-type strontium ferrite nanofibers is around 60 nm. 相似文献
20.
Functional coatings incorporating different types of particles developed by the sol–gel method have been proposed in the last few years for diverse applications. This work focuses on the preparation of homogeneous coatings prepared from stable suspensions with 10 wt% of glass and glass ceramic particles in a hybrid organic–inorganic solution as dispersing media. For this purpose, the pH was shifted up to 6–7 by adding tetrapropylammonium hydroxide (TPAH) which behaves as a cationic surfactant being probably adsorbed on the particles surface, while the sol maintains stable. Rheological measurements were performed to study the stability of the suspensions prepared at different conditions such as the kind and concentration of dispersant and the pH conditions. After sintering at 450∘C/30 min, coatings around 2 μ m in thickness were obtained. 相似文献