共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
A. Mesquita M. I. B. Bernardi L. J. Q. Maia V. R. Mastelaro 《Journal of Thermal Analysis and Calorimetry》2007,87(3):747-751
Pb1–xLaxTiO3
(PLT) nanocrystalline powders were obtained by polymeric precursor method.
The samples were analyzed by differential scanning calorimetry (DSC) and thermogravimetry
(TG) techniques to characterize properly the distinct thermal events occurring
during synthesis. The X-ray diffraction patterns show a tetragonal structure
for the samples with x=0.10 and 0.15. An
increase of the lanthanum concentration to x=0.20
led to a highly symmetric structure, cubic on average. The powders obtained
at the end of the synthesis had an average particle size of 30 to 70 nm. 相似文献
3.
N. A. Kochetova I. E. Animitsa A. Ya. Neiman 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(2):203-208
(Ba1 ? x Ca x )6Nb2O11 solid solutions were synthesized. The compositions were shown to be single-phase at 0.23 ≤ x ≤ 0.47 and have a double perovskite cubic structure with an incomplete oxygen sublattice. The interaction of solid solutions with water vapor and their electrical properties were studied. In dry atmosphere, these complex oxides were mixed oxygen-hole conductors. In humid atmosphere, they intercalated water and exhibited protonic conductivity. The influence of Ba/Ca isovalent substitution, the dynamics of the oxygen sublattice, and the concentration of intercalated water on the value and contribution of protonic and hole conductivity was analyzed. 相似文献
4.
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
5.
Yiping Guo Daisuke Akai Kazuaki Sawada Makoto Ishida Mingyuan Gu 《Journal of Sol-Gel Science and Technology》2009,49(1):66-70
Highly (110)-oriented Ba0.65Sr0.35TiO3 films were deposited on Pt/LaNiO3/SiO2/Si substrates by a sol–gel method. It was found that the (110)-preferred Pt film was very effective for growing (110)-oriented
ferroelectric films with perovskite structure. The as-grown Ba0.65Sr0.35TiO3 films showed good dielectric properties with dielectric constant and loss tangent tan δ = 0.026. Excellent dielectric tunability was also achieved in the (110)-oriented films. With applying
an electric field of 230 kV/cm at 100 kHz, the dielectric tunability and the figure of merit can reach up to 63.4% and 16,
respectively. These results indicate that the highly (110)-oriented Ba0.65Sr0.35TiO3 film is a promising candidate for the applications in microwave tunable devices. 相似文献
6.
Piyabutr Sunsap Dong-Joo Kim Tawatchai Charinpanitkul Kyo-Seon Kim 《Research on Chemical Intermediates》2008,34(4):319-329
TiO2 nanoparticles were produced in the diffusion flame reactor, and the size and anatase/rutile content of TiO2 were examined by a Particle Size Analyzer and X-ray diffraction, respectively. Increase in fuel/O2 ratio, initial concentration of TiCl4 or total gas flow rate causes the larger particle size and the higher rutile composition. The photocatalytic activities of
TiO2 powders were tested on the decompositions of phenol and toluene in the aqueous solution under UV irradiation. The degradation
rate increases as the TiO2 particle size decreases and as the initial concentration of phenol or toluene increases. The photodegradation rate of phenol
by TiO2 particles is higher than that of toluene at the same process conditions. The computational method was used to simulate the
gas temperature, velocity and species mass fractions inside the diffusion flame reactor during synthesis of TiO2 nanoparticles. The measured and simulated temperature results were compared on several positions above the burner and both
of them show good agreements. The typical contours of TiCl4, TiO2 mass fractions and gas velocities in flame reactor were presented. 相似文献
7.
A. Karami 《Journal of the Iranian Chemical Society》2010,7(2):S154-S160
In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO2-A), 7 (TiO2-N) and 9 (TiO2-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented. Based on these results the nanoparticle TiO2, which was prepared in acidic pH 3 with the pure anatase phase and the lowest particle size has the highest reactivity for the photocatalytic reduction of nitric oxide. 相似文献
8.
9.
Ali Hassanzadeh Behrang Moazzez Hossein Haghgooie Mohsen Nasseri Mir Maqsood Golzan Hassan Sedghi 《Central European Journal of Chemistry》2008,6(4):651-656
A simple sol-gel process is proposed for synthesizing SnO2 nanopowders utilizing normal propanol and isopropanol mixture instead of just using normal alcohols such as ethanol, propanol
or butanol for Sol preparation. No surfactant was used in this Sol preparation process. The structure of sol is studied by
FT-IR-ATR technique. On altering propanol to isopropanol ratio, three different nanopowders were obtained. X-ray powder diffraction,
high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction pattern (SAED) and BET techniques
were used to characterize prepared powders. Results show that smaller grain size was obtained via altering alcohols ratio.
In addition, Merck commercial SnO2 powder was also used as a reference material for comparing purposes; because it has nanometer scale (ca. 60 nm). HRTEM images
show that obtained nanopowders were polycrystalline and their average diameters fall into the range of 6–80 nm. Finally, the
effect of alkoxide ligand size through sol-gel synthesis on product particle size is discussed.
相似文献
10.
In the present study, nanoparticles of perovskite-type Gd0.5Sr0.5FeO3 (GSFO) were fabricated by a sol–gel method. A series of analytical techniques were used to characterize the crystallinity, morphology, specific surface area and grain size of GSFO powders. The thermal decomposition process of the complex precursor was examined by means of differential thermal analysis–thermal gravimetric analysis. X-ray diffraction results showed that a single perovskite phase was completely formed after calcination at 700 °C. In addition, transmission electron microscopy images revealed that the average size of the particles is approximately 35.23 nm in diameter. The surface morphology and composition of these nanopowders were also investigated using a scanning electron microscope and an energy dispersive X-ray spectrometer. GSFO nanoparticles showed excellent adsorption efficiency towards methylene blue dye in aqueous solution. The adsorption studies were carried out at different pH values, initial dye concentrations, various adsorbent doses and contact time in batch experiments. The dye removal efficiency was found to be increased with increasing the initial pH of the dye solution, and GSFO exhibited good dye removal efficiency at a basic pH, especially at a pH of 12. Experimental results indicated that the adsorption kinetic data follow a pseudo-second-order rate for the tested dye. The isotherm evaluations revealed that the Redlich–Peterson model attained better fits to the experiment's equilibrium data than the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. 相似文献
11.
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
12.
R. G. Pavelko A. A. Vasil’ev V. G. Sevast’yanov F. Gispert-Guirado X. Vilanova N. T. Kuznetsov 《Russian Journal of Electrochemistry》2009,45(4):470-475
The thermal stability of synthesized and commercial SnO2, ZrO2, and SiC nanopowders is compared. The crystallite growth rate during the isothermal annealing of the materials at 700°C for 30 h is evaluated. The crystallites’ average size was determined by X-ray phase analysis (using the Scherrer method). The effect of impurity content on the kinetics of crystallite growth is studied for the synthesized SnO2 and ZrO2. Semiconductor and thermocatalytic sensors, based on the synthesized and commercial materials, are manufactured. The long-term stability of the sensors’ signal is compared with the thermal stability of the nanopowders. 相似文献
13.
Uraiwan Sirimahachai Nicholas Ndiege Ramesh Chandrasekharan Sumpun Wongnawa Mark A. Shannon 《Journal of Sol-Gel Science and Technology》2010,56(1):53-60
Nanosized TiO2 and nano-anatase TiO2 decorated on SiO2 spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO2 nano particle and TiO2 grafted on SiO2 sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray
photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy
(TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated
using methylene blue as a model pollutant. The synthesized TiO2/SiO2 particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO2 particles. 相似文献
14.
Preparation of nanocrystalline Fe-doped TiO<Subscript>2</Subscript> powders as a visible-light-responsive photocatalyst 总被引:1,自引:0,他引:1
Nanocrystalline Fe-doped TiO2 powders were prepared using TiOSO4, urea, and Fe(NO3)3 · 9H2O as precursors through a hydrothermal method. The as-synthesized yellowish-colored powders are composed of anatase TiO2, identified by X-ray diffraction (XRD). The grain size ranged from 9.7 to 12.1 nm, calculated by Scherrer’s method. The specific
surface area ranged from 141 to 170 m2/g, obtained by the Brunauer–Emmett–Teller (BET) method. The transmission electron microscopy (TEM) micrograph of the sample
shows that the diameter of the grains is uniformly distributed at about 10 nm, which is consistent with that calculated by
Scherrer’s method. Fe3+ and Fe2+ have been detected on the surface of TiO2 powders by X-ray photoelectron spectroscopy (XPS). The UV–Vis diffuse reflection spectra indicate that the light absorption
thresholds of the Fe-doped TiO2 powders have been red-shifted into the visible light region. The photocatalytic activity of the Fe-doped TiO2 was evaluated through the degradation of methylene blue (MB) under visible light irradiation. The Fe-doped TiO2 powders have shown good visible-light photocatalytic activities and the maximum degradation ratio is achieved within 4.5 h. 相似文献
15.
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
16.
S. X. Wang L. X. Sun Z. C. Tan F. Xu Y. S. Li 《Journal of Thermal Analysis and Calorimetry》2007,89(2):609-612
Conducting polyaniline/Cobaltosic oxide (PANI/Co3O4) composites were synthesized for the first time, by in situ deposition technique in the presence of hydrochloric acid (HCl)
as a dopant by adding the fine grade powder (an average particle size of approximately 80 nm) of Co3O4 into the polymerization reaction mixture of aniline. The composites obtained were characterized by infrared spectra (IR)
and X-ray diffraction (XRD). The composition and the thermal stability of the composites were investigated by TG-DTG. The
results suggest that the thermal stability of the composites is higher than that of the pure PANI. The improvement in the
thermal stability for the composites is attributed to the interaction between PANI and nano-Co3O4. 相似文献
17.
A. I. Gavrilov A. V. Garshev K. A. Kovnir B. R. Churagulov Yu. V. Kolen’ko Yu. D. Tretyakov 《Russian Chemical Bulletin》2005,54(1):71-74
Nanorods of sodium titanium dioxide bronze NaxTiO2 were synthesized by the hydrothermal treatment of the amorphous TiO2·nH2O gel with 10 M NaOH followed by ultrasonication in 0.1 M HCl and thermal treatment (500°C, 10 h). The thermal treatment of the nanorods does not change the morphology of the particles. According to the electron diffraction data, the NaxTiO2 nanorods grow along the c axis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 71–73, January, 2005. 相似文献
18.
A new titanium complex [Ti(Me–Q)2(Cl)2] (1) is prepared by reacting titanium tetrachloride with 2-methyl-8-hydroxyquinoline in a fast and facile process. The complex is fully characterized based on its 1H and 13C NMR, IR, and UV spectra and elemental analysis. The prepared nanostructured compound is synthesized by the sonochemical method. This new nanostructure is characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), IR spectroscopy, and elemental analysis. Thermal stability of single crystalline and nanosize samples of the prepared compound is studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The prepared complexes both bulk and nanosized are utilized as a precursor for the preparation of TiO2 nanoparticles by direct thermal decomposition at 600°C in air. The morphology and size of TiO2 nanoparticles are determined by SEM, powder XRD, and IR spectroscopy and the results show that the TiO2 nanoparticle size depends on the initial particle size of 1. Photoluminescence (PL) properties of the nanostructured and crystalline bulk prepared complex and their TiO2 nanoparticle cores are investigated. 相似文献
19.
Pinyang Fang Huiqing Fan Shaojun Qiu Liajun Liu Jin Chen 《Journal of Sol-Gel Science and Technology》2009,50(3):290-295
Lanthanum-modified bismuth titanate (Bi3.25La0.75Ti3O12, BLTO) powders were prepared by the complex polymerization method. The structure and morphology of BLTO powders were investigated
by X-ray diffraction and scanning electron microscopy. The complexation of citric acid with the metallic cations was detected
by Fourier transformed infrared (FT-IR). The thermal analyses of obtained gels were investigated by differential thermal gravimetric
(DTG). The pure and normally stoichiometric phase of BLTO powders could be obtained at relatively low temperature of 550–700 °C
even if the bismuth content is not excess in the starting precursors, while the secondary phase could be detected at lower
and higher calcination temperatures. The shape of the BLTO grains is similarly to platelet in Bi-layer structure and stoichiometry
BLTO was detected by the analysis of energy dispersive spectrometry. 相似文献
20.
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