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1.
Andrei Jitianu John Doyle Glenn Amatucci Lisa C. Klein 《Journal of Sol-Gel Science and Technology》2010,53(2):272-279
Hybrid melting gels were prepared by a sol–gel process, starting with a mono-substituted siloxane and a di-substituted siloxane.
Methyl-modified melting gels were prepared using (a) methyltriethoxysilane (MTES) with dimethyldiethoxysilane (DMDES) and
(b) methyltrimethoxysilane (MTMS) together with dimethyldimethoxysilane (DMDMS). The gels with MTES–DMDES were prepared with
concentrations between 50–50 and 75–25 mol%. The gels with MTMS–DMDMS were prepared with concentrations between 50–50 and
70–30 mol%. For both systems, the consolidation temperature, after which the melting gel no longer softens, increased with
an increase in the amount of the mono-substituted siloxane, increasing from 135 to 160 °C for MTES–DMDES and increasing from
145 to 170 °C for MTMS–DMDMS. Coatings formed on mica substrates were about 1 mm thick, and showed no visible cracks. The
surfaces of the coatings were profiled using micro-Raman spectroscopy, which revealed that methyl groups were concentrated
at the surfaces of the films. All contact angles measured with water were greater than 90°. 相似文献
2.
Raquel Peña-Alonso Gian Domenico Sorarù 《Journal of Sol-Gel Science and Technology》2007,43(3):313-319
The sol–gel method has been used for the synthesis of borosilicate gels from mixtures of methyltriethoxysilane (MTES) and
dimethyldiethoxysilane (DMDES) and boric acid. The use of boric acid, B(OH)3 allows the hydrolysis and condensation of hybrid silicon alkoxides without further addition of water or catalyst. The use
of difunctional silicon units, –(CH3)2SiO– promote the formation, during the sol–gel process, of linear oligomers which facilitate fiber drawing before gelation.
Gel characterization performed by FT-IR, XRD, TG-DTA and DCS analysis indicates the formation of a mixed network with incorporation
of the boron units via =B-O-Si≡ bridges. The formation of borosiloxane bonds seems favored by the presence of DMDES. SiBOC
glasses were obtained after pyrolysis of the borosilicate gels in argon atmosphere at 1000 °C. TG-DTA study indicates that
the ceramic yield decreases by increasing the amount of DMDES. Gel fibers were successfully prepared from convenient partially-aged
solutions by hand drawing. Pyrolysis of the obtained gel fibers under argon atmosphere at 1000 °C open the possibility to
produce SiBOC homogeneous glass fibers with diameter as low as 10 μm. 相似文献
3.
M. Saeed Butt Zareen Akhter M. Zafar-uz-Zaman Humaira Masood Siddiqi 《Colloid and polymer science》2008,286(12):1455-1461
The diamine, 4-aminophenyloxy-N-4-[(4-amiophenyloxy)benzylidene]aniline, was prepared via the nucleophilic substitution reaction and was polymerized with
different dianhydrides either by one-step solution polymerization reaction or two-step procedure. The latter includes ring-opening
polyaddition to give poly(amic acid), followed by cyclodehydration to polyimides. The inherent viscosity ranges from 0.61–0.79 dl/g.
Some of the polymers were soluble in most of the organic solvents such as DMSO, DMF, DMAc, NMP, and m-cresol even at room temperature. The degradation temperature of the resultant polymers falls in the ranges from 240–500 °C
in nitrogen with only 10% weight loss. Specific heat capacity at 200 °C ranges from 1.0929–2.6275 J g−1 k−1. The temperature at which the maximum degradation of the polymer occurs ranges from 600–630 °C. The glass transition temperature
(Tg) values of the polyimides ranged from 185 to 272 °C. The activation energy and enthalpy of the polyimides ranged from
47.5–55.0 kJ/mole and 45.7–53.0 kJ/mole and the moisture absorption in the range of 0.23–0.72%. 相似文献
4.
T. M. W. J. Bandara B.-E. Mellander I. Albinsson M. A. K. L. Dissanayake H. M. J. C. Pitawala 《Journal of Solid State Electrochemistry》2009,13(8):1227-1232
The anion-conducting polymer electrolyte polyethylene oxide (PEO)/ethylene carbonate (EC)/Pr4N+I−/I2 is a candidate material for fabricating photo-electrochemical (PEC) solar cells. Relatively high ionic conductivity values
are obtained for the plasticized electrolytes; at room temperature, the conductivity increases from 7.6 × 10−9 to 9.5 × 10−5 S cm−1 when the amount of EC plasticizer increases from 0% to 50% by weight. An abrupt conductivity enhancement occurs at the melting
of the polymer; above the melting temperature, the conductivity can reach values of the order of 10−3 S cm−1. The melting temperature decreases from 66.1 to 45.1 °C when the EC mass fraction is increased from 0% to 50%, and there
is a corresponding reduction in the glass transition temperature from −57.6 to −70.9 °C with the incorporation of the plasticizer.
The static dielectric constant values, , increase with the mass fraction of plasticizer, from 3.3 for the unplasticized sample to 17.5 for the 50% EC sample. The
dielectric results show only small traces of ion-pair relaxations, indicating that the amount of ion association is low. Thus,
the iodide ion is well dissociated, and despite its large size and relatively low concentration in these samples, the iodide
ion to ether oxygen ratio is 1:68, a relatively efficient charge carrier. A further enhancement of the ionic conductivity,
especially at lower temperatures, is however desired for these applications. 相似文献
5.
A. Syku?a-Zaj?c E. ?odyga-Chru?cińska B. Pa?ecz R. E. Dinnebier U. J. Griesser V. Niederwanger 《Journal of Thermal Analysis and Calorimetry》2011,105(3):1031-1036
An amide-type local anesthetic drug, bupivacaine hydrochloride (BupiHCl), in the form of racemate is listed in the European
and American pharmacopoeias and continues to be used in medicine. Thermal and X-ray analysis of commercial BupiHCl monohydrate
was performed by differential scanning calorimetry with thermogravimetry, hot stage microscopy, and X-ray diffraction. Endothermic
dehydration occurs at the temperature range of 73–130 °C for DSC–TG 111 (Setaram) and at 83–150 °C for DSC 404 (Netzsch).
Both curves at 2 and 10 °C min−1 clearly reflect phase transformation of anhydrous Form I into II before reaching the melting point. A well-defined exothermic
phase transition of BupiHCl was detected at a lower heating rate. Temperature-resolved X-ray diffraction in conjunction with
DSC led to determining a similarity between the obtained thermal events. Microscopic investigation also confirmed the above-mentioned
transformations. 相似文献
6.
Fanelli Esther Turco Maria Russo Annamaria Bagnasco Giovanni Marchese Stefania Pernice Pasquale Aronne Antonio 《Journal of Sol-Gel Science and Technology》2011,60(3):426-436
Manganese-yttrium-zirconium mixed oxide nanocomposites with three different Mn loadings (5, 15 and 30 wt%) were prepared by
sol–gel synthesis. Amorphous xerogels were obtained for each composition. Their structural evolution with the temperature
and textural properties were examined by thermogravimetry/differential thermal analysis, X-ray diffraction, diffuse reflectance
UV–vis spectroscopy and N2 adsorption isotherms. Mesoporous materials with high surface area values (70–100 m2 g−1) were obtained by annealing in air at 550 °C. They are amorphous or contain nanocrystals of the tetragonal ZrO2 phase (T-ZrO2) depending on the Mn amount and exhibit Mn species with oxidation state higher than 2 as confirmed by temperature programmed
reduction experiments. T-ZrO2 is the only crystallizing phase at 700 °C while the monoclinic polymorph and Mn3O4 start to appear only after a prolonged annealing at 1,000 °C. The samples annealed at 550 °C were studied as catalysts for
H2O2 decomposition in liquid phase. Their catalytic activity was higher than that of previously studied Mn/Zr oxide systems prepared
by impregnation. Catalytic data were described by a rate equation of Langmuir type. The decrease of catalytic activity with
time was related to dissolution of a limited fraction (up to 15%) of Mn into the H2O2/H2O solution. 相似文献
7.
8.
Liang Zhao Xiaoru Zhao Jinming Liu An Zhang Danhong Wang Bingbo Wei 《Journal of Sol-Gel Science and Technology》2010,53(2):475-479
Anatase Ti0.94Nb0.06O2 (TNO) films were fabricated on glass substrates by sol–gel method using a dip-coating technique. The annealing treatment
was separated into two steps, first in air at 350–550 °C for 1 h and then in vacuum of 4.0 × 10−4 Pa at 550 °C for 1 h. The influence of vacuum annealing treatment to the electrical and optical properties was discussed.
Especially, the role of air annealing treatment from 350 to 550 °C on the crystallization and the structure of the films was
analyzed. It is proved that the films annealed at 550 °C in air and then 550 °C in vacuum exhibited the minimum resistivity
of 19.3 Ω·cm and the average optical transmittance of about 75% in the visible range, indicating that the sol–gel method is a feasible
and promising method to fabricate TNO films. 相似文献
9.
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
10.
Masoud Salavati-Niasari Masoud Farhadi-Khouzani Fatemeh Davar 《Journal of Sol-Gel Science and Technology》2009,50(3):321-327
Nanocrystalline films of magnetite have been prepared by a novel sol–gel route in which, a solution of iron (III) nitrate
dissolved in ethylene glycol was applied on glass substrates by spin coating. Coating solution showed Newtonian behaviour
and viscosity was found as 0.0215 Pa.s. Annealing temperature was selected between 291 and 350 °C by DTA analysis in order
to obtain magnetite films. In-plane grazing angle XRD and TEM studies showed that magnetite phase was present upon annealing
the films at 300 °C. The films had crack free surfaces and their thicknesses varied between ~10 and 200 nm. UV–Vis spectrum
results showed that transmittance of the films increases with decreasing annealing temperature and increasing spinning rate.
Up to 96% transmittance was observed between the wavelengths of 900–1,100 nm. Vibrating sample magnetometer measurements indicated
that magnetite thin films showed ferromagnetic behavior and the saturation magnetization value was found as ~35 emu/cm3. 相似文献
11.
The physical–chemical properties and fatty acid composition of sheep subcutaneous, tallow, intestinal, and tail fats were
determined. Sheep fat types contained C16:0, C18:0, and C18:1 as the major components of fatty acid composition (19.56–23.40, 20.77–29.50, 32.07–38.30%, respectively). Differential scanning
calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major
peaks (T
peak) of tallow and intestinal fats were similar and determined as 31.25–24.69 and 7.44–3.90 °C, respectively, for crystallization
peaks and 15.36–13.44 and 45.98–44.60 °C, respectively, for melting peaks in DSC curves; but those of tail fat (18.29 and
−2.13 °C for crystallization peaks and 6.56 and 33.46 °C for melting peaks) differed remarkably from those of other fat types. 相似文献
12.
Anushree Purushottam Khandale Shyam Shashibhushan Bhoga 《Journal of Solid State Electrochemistry》2012,16(1):341-352
The solid solubility limit of Ce in Nd2–x
Ce
x
CuO4 ± δ
, prepared by sol–gel process, is established up to x = 0.2. The transition from negative temperature coefficient to positive temperature coefficient, within the solid solubility
region, is observed at 620 °C. The area-specific-resistance (ASR) is optimized for electrochemical cell sintered at 800 °C.
ASR enhances with increase in sintering temperature of cell. ASR value of 0.93 ohm cm2 at 700 °C, determined by electrochemical impedance spectroscopy is comparable against that by voltage versus current (V–I)
characteristics at 0.98 ohm cm2 at the same temperature. Electrochemical performance and ASR of Nd1.8Ce0.2CuO4 ± δ
is improved when prepared by sol–gel route over solid-state reaction, which is attributed to uniform size and shape of nanocrystalline
grains. 相似文献
13.
Qiwu Shi Wanxia Huang Jiazhen Yan Yubo Zhang Mao Mao Yang Zhang Yuanjie Xu Yaxin Zhang 《Journal of Sol-Gel Science and Technology》2011,59(3):591-597
Vanadium dioxide (VO2) thin films were fabricated on single crystal Si (100) substrates by sol–gel method, including a process of annealing a vanadium
pentoxide (V2O5) gel precursor at different temperatures. The crystalline structure and morphology of the films were investigated by XRD,
FE-SEM and AFM, indicating that the films underwent the grain growth, agglomeration and grain refinement process with increased
annealing temperatures. The film annealed at 500 °C exhibits the formation of VO2 phase with a strong (011) preferred orientation and high crystallinity, the surface of the film is uniform and compact with
a grain size of about 120 nm. Meanwhile, the film exhibits excellent phase transition properties, with a decrease of transmittance
from 35.5 to 2.5% at λ = 25 μm and more than 3 orders of resistivity magnitude variation bellow and above the phase transition
temperature. The phase transition temperature is evaluated at 60.4 °C in the heating transition and 55.8 °C in the cooling
transition. Furthermore, the phase transition property of the VO2 film appears to be able to remain stable over repetitive cycles 100 times. 相似文献
14.
T. Kakavand M. Sadeghi L. Mokhtari A. Majdabadi 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):197-201
The electroplating of zinc is carried out in an alkaline cyanide bath. Operating parameters such as pH, temperature, and current
density and amount of the electrolyte components are optimized. The optimum conditions of the electrodeposition of zinc were
as follows: 2.7 g L−1 ZnO, 7.1 g L−1 KCN, 11.1 g L−1 KOH, pH = 13–14, DC current density of ca 8.55 mA cm−2 at 40–50 °C temperature with 89% current efficiency. SEM photomicrographs revealed fine-grained structure of the deposit
from the bath. 相似文献
15.
ITO films on glass substrate by sol–gel technique: synthesis,characterization and optical properties
E. Celik U. Aybarc M. F. Ebeoglugil I. Birlik O. Culha 《Journal of Sol-Gel Science and Technology》2009,50(3):337-347
The present paper extensively demonstrates synthesis, characterization and optical properties of semiconductor indium tin
oxide (ITO) thin films on glass substrate using sol–gel technique for gas sensor applications. Turbidity, pH values, wettability
and rheological properties of the prepared solutions were measured to determine solution characteristics by turbidimeter,
pH meter, contact angle goniometer and rheometer machines prior to coating process. Thermal, structural, microstructural,
mechanical and optical properties of the coatings were characterized by differential thermal analysis–thermogravimetry (DTA/TG),
fourier transform infrarared, X-ray diffraction (XRD), scanning electron microscopy, scratch tester, refractometer and spectrophotometer.
Four different solutions were prepared by changing solvent concentration. Turbidity, pH, contact angle and viscosity values
of the solutions were convenient for coating process. Glass substrates were coated using the solutions of InCl3, SnCl2, methanol and glacial acetic acid. The obtained gel films were dried at 300 °C for 10 min and subsequently heat-treated at
500 °C for 10 min in air. The oxide thin films were annealed at 600 °C for 60 min in air. DTA/TG results revealed that endothermic
and exothermic reactions are observed at temperature between 70 and 560 °C due to solvent removal, combustion of carbon based
materials and oxidation of Sn and In. The spectrum of ITO precursor film annealed at 500–600 °C shows an absence of absorption
bands corresponding to organics and hydroxyls. In2Sn2O7−x
phase was dominantly found as well as SnO2 with low intensity from XRD patterns. It was found that surface morphologies of the film change from coating island with
homogeneous structures to regular surface and thinner film structures with increasing solvent concentration. The films prepared
from the solutions with 8 mL methanol have better adhesion strength to the glass substrate among other coatings. Refractive
index, thickness and band gap of ITO thin films were determined to be 1.3171, 0.625 μm and 3.67, respectively. 相似文献
16.
Tomoe Sanada Hisakazu Seto Yusuke Morimoto Kazuhiro Yamamoto Noriyuki Wada Kazuo Kojima 《Journal of Sol-Gel Science and Technology》2010,56(1):82-86
To develop new fluorescent and afterglow materials, Mn2+ and Eu3+ co-doped ZnO–GeO2 glasses and glass ceramics were prepared by a sol–gel method and their optical properties were investigated by measuring
luminescence, excitation and afterglow spectra, and luminescence quantum yield (QY). Under UV irradiation at 254 nm, some
glasses and all of the glass ceramics showed green luminescence peaking at 534 nm due to the 4T1 → 6A1 transition of tetrahedrally coordinated Mn2+ ions. The strongest luminescence was observed in a glass ceramic of 0.1MnO–0.3Eu2O3–25ZnO–75GeO2 heat treated at 900 °C, with QY of 49.8%. All of the green-luminescent glasses and glass ceramics showed green afterglow,
and the afterglow lasting for more than 60 min was obtained in a glass ceramic heat treated at 900 °C. It is considered that
the Eu3+ ions may behave as electron trapping centers to be associated with the occurrence of the green afterglow due to the Mn2+ ions in the co-doped system. 相似文献
17.
Cellulose films were successfully prepared from NaOH/urea/zincate aqueous solution pre-cooled to −13 °C by coagulating with
5% H2SO4. The cellulose solution and regenerated cellulose films were characterized with dynamic rheology, ultraviolet–visible spectroscope,
scanning electron microscopy, wide angle X-ray diffraction, Fourier transform infrared (FT-IR) spectrometer, thermogravimetry
and tensile testing. The results indicated that at higher temperature (above 65 °C) or lower temperature (below −10 °C) or
for longer storage time, gels could form in the cellulose dope. However, the cellulose solution remained a liquid state for
a long time at 0–10 °C. Moreover, there was an irreversible gelation in the cellulose solution system. The films with cellulose
II exhibited better optical transmittance, high thermal stability and tensile strength than that prepared by NaOH/urea aqueous
solution without zincate. Therefore, the addition of zincate in the NaOH/urea aqueous system could enhance the cellulose solubility
and improve the structure and properties of the regenerated cellulose films. 相似文献
18.
Carina Gargori García Roberto Galindo Llorach Mario Llusar Vicent Maria Angeles Tena Gómez Guillermo Monrós Tomás Jose A. Badenes March 《Journal of Sol-Gel Science and Technology》2009,50(3):314-320
Glasses on SiO2–CaO–ZnO–B2O3–K2O–Al2O3 oxide system modified by addition of titania (0, 3, 5, 12, and 20% w) have been prepared by sol–gel method. The obtained
gels were aged, dried and fired at 600 °C/1 h in order to stabilise the glass. The resulting fired powders were characterised
by UV–Vis–NIR spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD).
Their photocatalytic capacity on the degradation of Orange II dye has been studied. The XRD and TEM studies indicate that
system becomes amorphous with a nanostructured microstructure. From UV–Vis–NIR results the band gap calculated is around 3.5 eV
for all modified glasses. Photoactivity of powders depends on amount of titania in glass composition and the specific surface
area of prepared samples. The sample with highest surface area and lowest addition of titania (3% w sample) shows similar
activity than commercial anatase used as reference. 相似文献
19.
We investigate effects of Co dopant concentration on the structure and low temperature Raman scattering properties in SrTi1−x
Co
x
O3 (x = 0.00, 0.10, 0.20, 0.30) nanoparticles prepared by sol–gel method. The dopant induced changes are studied by XRD, and Raman
scattering measurements. The results show an average particle size of about 20 nm depending on the Co content and the lattice
parameters decrease as increasing the Co content. In the Raman spectra, a broad structure in the region 100–500 cm−1 is almost absent and the peaks in the region 600–800 cm−1 show different weights with respect to SrTiO3, relating to structural changes. The anomalous change in the area ratio of Raman peaks as function of temperature suggests
a phase transition in our samples in the range of 110–130 K. These results indicate that the Co ion has replaced the site
of Ti in unit cell. This novel route also demonstrates the advantage of synthesizing the compound with low annealing temperature. 相似文献
20.
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