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1.
M. E. de Anda Reyes G. Torres Delgado R. Castanedo Pérez J. Márquez Marín O. Zelaya Ángel 《Journal of Sol-Gel Science and Technology》2012,61(2):310-315
TiO2 thin films were obtained on glass slide substrates by the sol–gel technique. The substrates were coated by the immersion-removal
method, at a constant withdrawal speed. The TiO2 precursor solution and the substrate were maintained in a closed box with a controlled relative humidity (RH) during the
removal of the substrate. The RH was varied in the 30–90% range in steps of 20%. The films were dried and after that sintered
in an open atmosphere. The effect of the RH was studied on the structural, optical and photocatalytic properties. The films
are polycrystalline with an anatase phase and show a high optical transmission in the UV–Vis range. The photocatalytic activity
was evaluated by the photobleaching of methylene blue in an aqueous solution. The best photocatalytic activity was obtained
for the films with 90% RH, this fact is mainly attributed to the highest porosity value obtained for these films. 相似文献
2.
M. Mosiadz R. I. Tomov S. C. Hopkins G. Martin D. Hardeman B. Holzapfel B. A. Glowacki 《Journal of Sol-Gel Science and Technology》2010,54(2):154-164
The successful inkjet printing of a cerium gadolinium oxide (Ce0.8Gd0.2O2) precursor solution on highly textured Ni-5%W is reported. A stable ink was synthesised from metal acetates and propionic
acid with rheological properties suitable for inkjet printing and also the development of solid–liquid interface comparable
with thin film formation by dip coating. Two different drop-on-demand print heads were used for deposition: a 16-nozzle piezoelectric
cartridge and a single electromagnetic nozzle. Two different rastering patterns with different droplet sizes and spacing were
compared. Thermogravimetry and X-ray diffractometry were used to study the thermal decomposition of the metal oxide precursors
and to determine the shortest possible heat treatment of the deposited layers, potentially suitable for continuous large scale
production. The results from X-ray diffraction show that the single phase Ce0.8Gd0.2O2 was obtained in all cases, but only piezoelectric inkjet printing with optimised drop overlapping produces a highly textured
buffer layer. Optical micrographs and atomic force microscopy also indicate the good quality of deposited films after heat
treatment. 相似文献
3.
Reverse micellar microemulsions were utilised to synthesise stable lead titanate colloids from typical sol–gel type molecular
precursors. The particles of a few nanometres in diameter that formed by hydrolysis in the micelle cores demonstrated a nanocrystalline
texture without the need for thermal treatment. In a chemical solution deposition routine based on the nanoparticle dispersions,
ferroelectric PbTiO3 thin films showing excellent remanent polarisation of more than 50 μC cm−2 were derived. The electrical characteristics of the layers were correlated to their microstructure which was controlled by
the precursor composition and the annealing conditions. A columnar morphology that was realised by spinning on coatings of
up to 100 nm in individual thickness proved most favourable with respect to the ferroelectric performance of the films. 相似文献
4.
E. P. Simonenko N. A. Ignatov N. P. Simonenko Yu. S. Ezhov V. G. Sevastyanov N. T. Kuznetsov 《Russian Journal of Inorganic Chemistry》2011,56(11):1681-1687
Nanocrystalline powders of super-refractory complex carbides Ta4HfC5 and Ta4ZrC5 were synthesized using a hybrid method comprising sol-gel technology for preparing highly dispersed metal oxidescarbon starting
mixtures and a relatively low-temperature (1300–1500°C) carbothermal synthesis under a dynamic vacuum (P = 1 × 10−3 to 1 × 10−5 MPa). The elemental and phase compositions of the products and average crystallite sizes were determined. TEM was used to
study particle morphology and dispersion. Microstructures were observed by SEM. BET specific surface areas were determined
for powders prepared at 1400°C. 相似文献
5.
V. H. Martínez-Landeros Bruce E. Gnade M. A. Quevedo-López R. Ramírez-Bon 《Journal of Sol-Gel Science and Technology》2011,59(2):345-351
In this work we report the performance of permeation barriers based on organic/inorganic multilayer stacks. We have used PMMA-SiO2 (poly methyl methacrylate-silica) hybrid films synthesized through a sol–gel route as organic–inorganic components, whereas
Al2O3 thin films were used as the inorganic component. The hybrid layers were deposited by dip coating and the Al2O3 by atomic layer deposition (ALD), films were prepared on polyethylene naphthalene (PEN) substrates. The permeability of the
films and stacks is evaluated using helium as the diffusion gas in a custom made ultra-high vacuum system. The results show
that permeability for PEN is reduced from 5 × 10−3 g/m2-day to about 9 × 10−5 g/m2-day for the best multiple barrier evaluated. Increased barrier properties are due to the increasing in the path and hence
the lag-time of the permeating gas. In particular, we report the surface roughness of the different layers and its impact
on the barrier performance. The hybrid layers reduced notably the roughness of the bare PEN substrate improving the quality
of the Al2O3 layer in the barrier. The optical transmittance of the barriers in the visible region is higher than 80% in all the studied
cases. 相似文献
6.
G. Nenartaviciene K. Tõnsuaadu D. Jasaitis A. Beganskiene A. Kareiva 《Journal of Thermal Analysis and Calorimetry》2007,90(1):173-178
In this study the formation of chromium substituted YBa2Cu4O8 (Y-124) superconductors has been investigated by TG/DTA measurements. The YBa2(Cu1−xCrx)4O8 ceramics with nominal compositions of x=0.01, 0.03, 0.05, 0.10 and 0.20 have been prepared by an aqueous sol-gel method using aqueous mixtures of the corresponding
metal acetates and nitrates. Homogeneous precursor gels were obtained by complexing metal ions with tartaric acid. To assist
the interpretation of the results obtained the synthesis products were additionally characterized by X-ray powder diffraction
(XRD) and resistivity measurements. It was determined that doping the YBa2Cu4O8 phase with chromium has a strong effect on the phase purity and superconducting properties of the synthesis products. 相似文献
7.
A novel electroless deposition method for depositing highly uniform adhesive thin films of copper selenide (Cu3Se2) on silicon substrates from aqueous solutions is described. The deposition is carried out by two coupled galvanic reactions in a single deposition bath containing copper cations, hydrogen fluoride, and selenous acid: the galvanic deposition of copper on silicon and the subsequent galvanic reaction between the deposited copper with selenous acid in the deposition bath. The powder X-ray diffraction and scanning electron microscopy are used to characterize and examine the deposited films. 相似文献
8.
Pb(Zr0.25Ti0.75)O3 (PZT25) thin films were prepared on LaNiO3-coated thermally oxidized silicon substrates by chemical solution deposition method, where LaNiO3 electrodes were also prepared by a chemical solution deposition technique. The dielectric constant and dielectric loss of
the PZT25 thin films were 570 and 0.057, respectively. The remanent polarization and coercive field were 20.11 μC/cm2 and 60.7 kV/cm, respectively. The PZT25 thin films on LaNiO3-coated thermally oxidized silicon substrates showed improved fatigue characteristics compared with their counterparts on
plantium-coated silicon substrates. 相似文献
9.
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
10.
Jinbao Xu Jiwei Zhai Xi Yao Jianqiang Xue Zhiming Huang 《Journal of Sol-Gel Science and Technology》2007,42(3):209-212
Barium titanate (BaTiO3) thin films have been prepared by low temperature processing on Pt/Ti/SiO2/Si substrates using sol-gel-hydrothermal (SGHT) technique, which combined the conventional sol-gel process and hydrothermal
method. X-ray diffraction analysis showed that the barium titanate thin films are polycrystalline. As-reacted barium titanate
films grown on Pt(111)/Ti/SiO2/Si(100) substrates had a dielectric constant (ε) and loss tangent (tanδ) of 80 and 0.05 at 1 MHz, respectively. The optical
constants including refractive index n, extinction coefficient k, and absorption coefficient α of the barium titanate thin films in the wavelength range of 2.5–12.6 μm were obtained by infrared
spectroscopic ellipsometry. 相似文献
11.
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
12.
Highly (111) oriented, phase-pure perovskite Pb(Zr0.3Ti0.7)O3 (or PZT 30/70) thin films were deposited on single-crystal, (0001) wurtzite GaN/sapphire substrates using the sol-gel process
and rapid thermal annealing. The phase, crystallinity, and stoichiometry of annealed PZT films were evaluated by X-ray diffraction
and Rutherford backscattering spectroscopy. The atomic force microscopy revealed a smooth PZT surface (rms roughness ∼1.5 nm)
with striations and undulations possibly influenced by the nature of the underlying GaN surface. The cross-sectional field-emission
scanning electron microscopic images indicated a sharper PZT/GaN interface compared to that of sol-gel derived PZT on (111)
Pt/TiO2/SiO2/(100) Si substrates. The capacitance-voltage (C-V) characteristics for PZT in the Pt/PZT/GaN (metal-ferroelectric-semiconductor
or MFS) configuration were evaluated as a function of annealing temperature and applied voltage. The observed C-V hysteresis
stemmed from trapped charge at defect sites within PZT. Also, the lower capacitance density (C/A = 0.35 μF/cm2, where A is the area of an electrode) and remnant polarization (P
r
∼ 4 μC/cm2) for PZT in the MFS configuration, compared to the values for PZT in the MFM configuration (Pt/PZT/Pt), were attributed to
the high depolarization field within PZT. 相似文献
13.
Emil D. Krumov Dimitar G. Popov Nikolay S. Starbov 《Central European Journal of Chemistry》2005,3(4):668-673
Thick aluminum oxide films are prepared on Al plates by anodizing. On the ceramic surface thus obtained a very thin Ag film
is deposited via vacuum thermal evaporation. The Ag/Al2O3/Al samples prepared are irradiated by Nd:YAG laser through a suitable metal mask in order to remove the top metal film in
the exposed areas. Thus, a negative silver image of the copied mask is obtained. Further, the samples are processed in Ni
electroless chemical bath activated by the rest of silver. All processing steps are studied by scanning electron microscopy
(SEM). EDS X-ray mapping is applied to study the final distribution of Al and Ni in the processed areas. In addition, the
DC conductivity of the fabricated Ni wires obtained is measured. The proposed new method for selective chemical deposition
of electroconductive Ni onto laser microstructured Ag/Al2O3/Al samples is simple, versatile and not restricted to the metal/ceramic system studied as well as to the electroless deposited
metal. 相似文献
14.
A. A. Solov’ev N. S. Sochugov A. V. Shipilova K. B. Efimova A. E. Tumashevskaya 《Russian Journal of Electrochemistry》2011,47(4):494-502
Data on the mid-temperature solid-oxide fuel cells (SOFC) with thin-film ZrO2-Y2O3 (YSZ) electrolyte are shown. Such a fuel cell comprises a carrying Ni-YSZ anode, a YSZ electrolyte 3–5 μm thick formed by
vacuum ion-plasma methods, and a LaSrMnO3 cathode. It is shown that the use of a combined method of YSZ electrolyte deposition, which involves the magnetron deposition
of a 0.5–1.5-μm thick sublayer and its pulse electron-beam processing allows a dense nanostructured electrolyte film to be
formed and the SOFC working temperature to be lowered down as the result of a decrease in both the solid electrolyte Ohmic
resistance and the Faradaic resistance to charge transfer. SOFC are studied by the methods of voltammentry and impedance spectroscopy.
The maximum power density of the SOFC under study is 250 and 600 mW/cm−2 at temperatures of 650 and 800°C, respectively. 相似文献
15.
Andrius Stanulis An Hardy Christopher De Dobbelaere Jan D’Haen Marlies Van Bael Aivaras Kareiva 《Journal of Sol-Gel Science and Technology》2012,62(1):57-64
In this work, tin(II) oxalate was studied as a novel chloride-free starting material for the preparation of a stable Sn-containing
precursor solution. This precursor was applied for the chemical solution deposition (CSD) of transparent conducting coatings
of SnO2 on Si/SiO2 substrates. An influence of synthesis parameters, such as pH, complexing agent to metal ion ratio on the stability of the
citrato peroxo Sn(IV) precursor has been investigated in this study. Insights into the precursor chemistry and its thermal
decomposition based on TG-DSC analysis are also presented. The obtained SnO2 films were characterized by high temperature X-ray diffraction (HT-XRD) and scanning electron microscopy (SEM) to evaluate
phase purity and film thickness, respectively. 相似文献
16.
Erdal Celik 《Journal of Sol-Gel Science and Technology》2010,53(3):561-569
High temperature 0, 5, 8 and 12 mol % Ho2O3–ZrO2 insulation coatings were successfully deposited on Ag and AgMg/Bi-2212 superconducting tapes using sol–gel technique for
magnet technologies. With this purpose, transparent solutions were prepared from Ho and Zr-based precursor materials and then
Ho2O3 effect on thermal, structural and microstructural properties were observed and discussed in the present study. It was found
that Ho2O3 additive has a propensity to generate tetragonal ZrO2 and help to stabilize it. It was observed that insulation coatings with a mosaic structure having cracks were fully compatible
with Ag/AgMg sheathed Bi-2212 tape substrates because of oxygen permeability, high and low actual temperatures and W&R process
in comparison with the conventional insulation process. In addition, surface roughness decreased with increasing Ho2O3 content, thereby decreasing the grain size. Although porosity values vary considerably from one porosity mesurement expression
to another, porosities of the insulation coatings can be estimated to be in the range of 3 and 30 vol %. 相似文献
17.
Ronaldo Santos da Silva Maria Inês Basso Bernardi Antonio Carlos Hernandes 《Journal of Sol-Gel Science and Technology》2007,42(2):173-179
In this work, we have studied the influence of the pH on the synthesis and structural properties of the Ba0.77Ca0.23TiO3 nanopowders synthesized by a modified polymeric precursor method, in order to achieve non-agglomerated powders. Synthesis,
morphology, thermal reactions, crystallite and average particle size of the synthesized powders were investigated through
thermal analysis (DTA/TG), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Infrared spectroscopy.
In summary, Ba0.77Ca0.23TiO3 nanopowders were synthesized for the first time at a relative low temperature (500 °C). It was also found that the alkalinity
and acidity of the solution presented a great influence on the powder properties. The best results were obtained from solutions
with pH = 8.5 and 11 whose nanopowders presented weakly agglomerate, with homogeneous particle size and a narrow size distribution
(30–40 nm). This behavior could be explained based on the FT-IR results in which it was possible to see the increased of the
chelation in higher pHs. 相似文献
18.
The thermal decomposition kinetics of nickel ferrite (NiFe2O4) precursor prepared using egg white solution route in dynamical air atmosphere was studied by means of TG with different
heating rates. The activation energy (E
α) values of one reaction process were estimated using the methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS),
which were found to be consistent. The dependent activation energies on extent of conversions of the decomposition reaction
indicate “multi-step” processes. XRD, SEM and FTIR showed that the synthesized NiFe2O4 precursor after calcination at 773 K has a pure spinel phase, having particle sizes of ~54 ± 29 nm. 相似文献
19.
Wataru Sakamoto Ken-ichi Mimura Takafumi Naka Tetsuo Shimura Toshinobu Yogo 《Journal of Sol-Gel Science and Technology》2007,42(3):213-220
Ba(Zr,Ti)O3/LaNiO3 layered thin films have been synthesized by chemical solution deposition (CSD) using metal-organic precursor solutions. Ba(Zr,Ti)O3 thin films with smooth surface morphology and excellent dielectric properties were prepared on Pt/TiO
x
/SiO2/Si substrates by controlling the Zr/Ti ratios in Ba(Zr,Ti)O3. Chemically derived LaNiO3 thin films crystallized into the perovskite single phase and their conductivity was sufficiently high as a thin-film electrode.
Ba(Zr,Ti)O3/LaNiO3 layered thin films of single phase perovskite were fabricated on SiO2/Si and fused silica substrates. The dielectric constant of a Ba(Zr0.2Ti0.8)O3 thin film prepared at 700°C on a LaNiO3/fused silica substrate was found to be approximately 830 with a dielectric loss of 5% at 1 kHz and room temperature. Although
the Ba(Zr0.2Ti0.8)O3 thin film on the LaNiO3/fused silica substrate showed a smaller dielectric constant than the Ba(Zr0.2Ti0.8)O3 thin film on Pt/TiO
x
/SiO2/Si, small temperature dependence of dielectric constant was achieved over a wide temperature range. Furthermore, the fabrication
of the Ba(Zr,Ti)O3/LaNiO3 films in alternate thin layers similar to a multilayer capacitor structure was performed by the same solution deposition
process. 相似文献
20.
Summary. Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents
the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics
information on the formation of calcium sulfate phases, including CaSO4-based double salts and solid solutions.
Uncertainties in the solubility diagram CaSO4–H2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization.
Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed
experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions
decrease the transition temperatures in dependence on water activity.
Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason
of which is still unclear. However, crystal morphology has a strong influence.
Gypsum forms solid solutions by incorporating the ions HPO4
2−, HAsO4
2−, SeO4
2−, CrO4
2−, as well as ion combinations Na+(H2PO4)− and Ln3+(PO4)3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases
and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of
gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite
hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline
earth sulfates (esp. Na2SO4, K2SO4, MgSO4, SrSO4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na2SO4–CaSO4 and K2SO4–CaSO4–H2O.
Corresponding author. E-mail: daniela.freyer@chemie.tu-freiberg.de
Received December 17, 2002; accepted January 10, 2003
Published online April 3, 2003 相似文献