共查询到20条相似文献,搜索用时 24 毫秒
1.
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
2.
Monolithic titania materials with macro-mesoporosity bimodal texture have been prepared through a template-free sol–gel approach,
based on the reaction of hydrolysis and polycondensation of titanium isopropoxide promoted by the slow released water from
esterification between acetic acid and methanol under a strong acidic condition. With the coarsening of the titania oligomers,
phase separation and sol–gel transition processes take place so as to form a homogeneous gel system that will change into
a monolith after aging, drying and heat treatment. The synthesized titania monolith possesses a specific surface area of 77 m2 g−1 (calcined at 350 °C), an anatase with partly rutile crystallite structure and great mechanical strength. The synthesis method
applied here is simple and easy to implement as no extra chemical modifier such as poly(ethylene oxide) (PEO) and formamide
is needed to control the process. The properties of biomodal porous structure, satisfactory surface area and high mechanical
strength will enable the monolith to be served as a chromatography column to separate phosphorus organo-compounds. 相似文献
3.
Chunming Huang Lihua Chen Gang Xu Lei Miao 《Journal of Sol-Gel Science and Technology》2012,63(1):103-107
In this paper, we report on the obtention of highly ordered VO2 nanotube arrays synthesized by the simple sol?Cgel template method. Techniques of transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy were used to characterize the morphology and structure of the as-synthesized nanotube arrays. It is found that the size of the as-obtained nanotubes has the dimension of 180?C220?nm in outer diameter, 110?C140?nm in inner diameter and up to 10???m in length. The results show that as-synthesized sample is assigned to VO2 (B) phase in expected V/O ratio with V existing in the +4 oxidation state. 相似文献
4.
Trisita Chatterjee Kaustav Bhattacharjee Mahua Ghosh Chaudhuri M. K. Mitra G. C. Das 《Journal of Sol-Gel Science and Technology》2014,72(1):189-196
Nanocrystalline tantalum carbide (TaC) particles of average size ~15 nm dispersed in silica matrix, have been synthesized by the carbothermal reduction of Ta2O5 over a range of temperature 1,100–1,360 °C in Ar atmosphere. Investigation of the stability diagram of carbon saturated Ta–O–N system suggests that the TaC phase can be successfully synthesized within the SiO2 matrix when the partial pressure of O2 and N2 are restricted to approximately lower than 1.25 and 0.0001 atm. respectively. Two different synthesis routes are investigated in the present study which differ fundamentally in the order of addition of the precursors, tetraethyl orthosilicate (TEOS) and tantalum isopropoxide (Ta-iso). Rietveld refinement analyses of the powder X-ray diffraction data are carried out for the quantitative estimation of the two phases in the samples. The yield of TaC increases from 18 to 52 % when both TEOS and Ta-iso are added simultaneously to the water compared to the process where TEOS is added first to the water followed by the delayed addition of Ta-iso. Samples are further characterized by field emission scanning electron microscopy and high resolution transmission electron microscopy. 相似文献
5.
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
6.
B. Samuneva L. Kabaivanova G. Chernev P. Djambaski E. Kashchieva E. Emanuilova Isabel M. Miranda Salvado M. H. V. Fernandes A. Wu 《Journal of Sol-Gel Science and Technology》2008,48(1-2):73-79
In this work the research results on the sol–gel synthesis and structure of silica nanocomposites, containing carrageenan and their application as carriers for cell immobilization were described. The samples were prepared at room temperature by replacing different quantity of the inorganic precursor with κ-carrageenan. For studying the structure of the synthesized hybrids the following methods were used: FT-IR, XRD, BET-Analysis, SEM, AFM and Roughness Analysis. The influence of the type of silicon precursors, nature and quantity of organic component on the structure, surface area, design and size of nanostructures was established. The possibility of application of the synthesized biocatalysts in an enzyme degradation process of the toxic, carcinogenic and mutagenic substances benzonitrile, fumaronitrile, o-, m-, and p-tolunitriles was investigated at batch experiments. A two-step biodegradation process in a column bioreactor of fumaronitrile was followed. After operation of the system for 8 h at a flow rate 45 mL h?1 and at 60 °C, the overall conversion was 89%, showing a good stability of the developed process. 相似文献
7.
Sandra Hildebrandt Andreas Eva Philipp Komissinskiy Claudia Fasel Ingo Fritsch Lambert Alff 《Journal of Sol-Gel Science and Technology》2012,63(3):307-314
Sodium and lithium cobaltates are important materials for thermoelectric and battery applications due to their large thermoelectric power and ability to (de-) intercalate the alkali metal. For these applications, phase pure materials with controlled microstructure are required. We report on the sol?Cgel synthesis of sodium- and lithium-based materials by using acetate precursors. The produced Na2/3CoO2, Li(Ni1/3Mn1/3Co1/3)O2, and Li(Ni1/2Co1/2)O2 powders are phase pure with grain sizes below 1???m. X-ray diffraction and energy-dispersive spectral analyses show that the cation stoichiometry is preserved in the lithium-based compounds. Despite the low temperatures, the sodium content is reduced by 1/3 as compared to the initial value. Chemical phases of the investigated powders are formed in the sol?Cgel route at temperatures typically 100?C200?K lower than those used in the conventional solid-state synthesis of these materials. The suggested sol?Cgel synthesis is a low temperature process suited for production of phase pure and homogeneous materials with volatile cations. 相似文献
8.
A novel processing technique based on sol–gel drop generation method has been developed to prepare fine zirconia minispheres
for use as grinding media. Zirconium oxalate gel formation from the prepared sol was obtained in proper synthesis condition
using Zirconium oxy-chloride octahydrate(ZrOCl2·8H2O) as starting material. The transparent oxalate gel was then added dropwise into the setting solution for the formation minispheres.
To obtain the required fluidity and viscosity a suitable binder was mixed to the sol and stabilizing agent of required mol%
was added to stabilize the phase formation. The addition of stabilizing agent transformation toughened the minispheres, with
a complete retention of the tetragonal phase in the final product sintered at 1500 °C. Thermogravimetric analysis indicated
the removal of most of the volatiles by 600 °C. Density and Crystallite size were found to be increasing linearly with sintering
temperature. The phase identification, density variation, chemical decomposition, functional group specification and microstructural
features for the dried and sintered final product were studied. 相似文献
9.
Vladimir V. Vinogradov Alexander V. Vinogradov Anton S. Kraev Alexander V. Agafonov Vadim G. Kessler 《Journal of Sol-Gel Science and Technology》2013,68(2):155-161
In this study, boehmite sols were used for preparation of mesoporous γ-alumina with bimodal mesopore distribution. Superfine nanospheres of poly(methyl methacrylate) (PMMA) prepared by water based emulsion polymerization method were used as a template. Nitrogen sorption revealed that aluminas prepared using this approach demonstrated bimodal mesopore size distribution with maxima at 3.8 and 25.7 nm, respectively. Catalytic tests showed that bimodal mesopore distribution within γ-Al2O3 prepared with PMMA nanospheres as a template provides improved catalytic activity in the methanol dehydration reaction. 相似文献
10.
Ashok Kumar Subhash Thota Sri Sivakumar Shashank Priya Jitendra Kumar 《Journal of Sol-Gel Science and Technology》2013,68(1):46-53
The Mg–Ce–O powder are shown to contain periclase-type MgO and/or fluoride-type cerium oxide (CeO2) depending upon the composition (x) defined by Ce/(Ce + Mg) atomic ratio. Lattice contraction of pariclase phase of MgO (average crystallite size ~8.8 nm) at Ce content of ‘x’ = 0.20 in comparison to pure MgO (crystallite size ~9.5 nm) has been realized due to oxygen vacancy formation. The optical band gap values of CeO2 varies (3.0–3.2 eV) due to oxygen vacancy formation in CeO2 phase, crystallite size and/or Ce3+/Ce4+ ratio. Further, the addition of Ce has shown to reduce the physisorption and chemisorption of water significantly as reflected by (1) suppression of related absorption peaks and (2) absence of magnesium hydroxide, Mg(OH)2, bands in Fourier transform infrared spectra. 相似文献
11.
Joanna Lewandowska Magdalena Staszewska Mariusz Kepczynski Micha? Szuwarzyński Anna ?atkiewicz Zbigniew Olejniczak Maria Nowakowska 《Journal of Sol-Gel Science and Technology》2012,64(1):67-77
Spherical silica particles doped with iron oxide have been synthesized via base-catalyzed one-pot sol?Cgel process using tetraethoxysilane (TEOS) and iron(III) ethoxide (ITE) as co-precursors. In the modified St?ber process adopted, depending on the concentration of ITE in the starting composition, materials of various morphologies were observed under a scanning electron microscope and an atomic force microscope. The presence of ITE significantly affected the formation process of particulate silica; the spherical particles were formed accompanied by the co-presence of irregular-shaped finer aggregates. The fraction of the aggregates with rough surfaces increased with an increase of the ITE content in the reaction mixture. Both the spherical particles and irregular-shaped aggregates contained iron hydroxide and they exhibited paramagnetic behavior. The chemical composition and physicochemical properties of the materials were determined using various complementary spectroscopic methods. 相似文献
12.
Georg Lieser Melanie Schroeder Holger Geßwein Volker Winkler Sven Glatthaar Murat Yavuz Joachim R. Binder 《Journal of Sol-Gel Science and Technology》2014,71(1):50-59
To find new cathode materials for future applications in lithium-ion batteries, lithium transition metal fluorides represent an interesting class of materials. In principle the Li intercalation voltage can be increased by replacing oxygen in the cathode host structure with the more electronegative fluorine. A facile pyrolytic sol–gel process with trifluoroacetic acid as fluorine source was established to synthesize monoclinic Li3FeF6 using nontoxic chemicals. The acicular Li3FeF6 powder was characterized with X-ray diffraction and a detailed structure model was calculated by Rietveld analysis. For the preparation of cathode films to cycle versus lithium monoclinic Li3FeF6 was ball milled with carbon and binder down to nanoscale. After 100 cycles galvanostatic cycling (C/20) 47 % fully reversible capacity of the initial capacity (129 mAh/g) could be retained. To the best of our knowledge the results presented in this work include the first rate performance test for monoclinic Li3FeF6 up to 1 C maintaining a capacity of 71 mAh/g. The redox reaction involving Fe3+/Fe2+ during Li insertion/extraction was confirmed by post-mortem XPS and cyclic voltammetry. 相似文献
13.
Yanan Hao Xiaohui Wang Hui Zhang Limin Guo Longtu Li 《Journal of Sol-Gel Science and Technology》2013,67(1):182-187
Ultrafine tetragonal BaTiO3 nanocrystals have been prepared by a sol–gel based method. By adjusting the volume ratio of H2O/DEG (diethylene glycol) in the solutions, hydrolysis rate of tetra-n-butyl titanate was strongly inhibited and the particle size could be controlled as small as 4–8 nm. The powder X-ray diffraction and transmission electron microscopy characterizations exhibit that the nanocrystals are spherical and well crystallized. The Raman spectrum shows the products are composed of the orthorhombic phase and tetragonal phase. The Fourier transform infrared spectrum revealed that a surface modification layer was formed around the BaTiO3 nanocrystals, which can prevent them from aggregation and help to form a stable, high solid content sol. 相似文献
14.
Catauro Michelina Naviglio Daniele Risoluti Roberta Vecchio Ciprioti Stefano 《Journal of Thermal Analysis and Calorimetry》2018,133(2):1085-1092
Journal of Thermal Analysis and Calorimetry - Imbalance of the iron level in the body causes several diseases. In particular, the low level of iron, during pregnancy, is responsible for the iron... 相似文献
15.
V. Bondarenka V. Jasulaitienė R. Sereika A. Stirkė 《Journal of Sol-Gel Science and Technology》2014,71(3):385-390
Vanadium–glucose xerogels (C6H12O6)xV2O5·nH2O with different amounts of glucose (x = 0; 0.3 and 0.5) have been synthesized by sol–gel method. The scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods were used to investigate the morphology and composition of obtained xerogels. SEM results show that after intercalation of the glucose molecules the surface structure became more spongy and porously. XPS analysis show that the increasing of glucose concentration in the compounds the reduction ratio of vanadium ions increases. The oxygen ions in the synthesized vanadium–glucose xerogels are bounded to the vanadium ions, carbon ions are involved in a chemical bounding in the hydroxyl group. The determined carbon ions chemical bonds are characteristic for glucose (C–C, CH–OH and C–O bonds). Some of the oxygen ions in the pure vanadium pentoxide xerogels are bonded in water molecules. This fact and the absence of the oxygen component which corresponds to the water in glucose-vanadium xerogels indicate that glucose molecules displaced structural water in vanadium hydrate and are intercalated between the vanadium–oxygen layers. 相似文献
16.
A. Najafi F. Golestani-Fard H. R. Rezaie N. Ehsani 《Journal of Sol-Gel Science and Technology》2011,59(2):205-214
Nano sized β-SiC particles were synthesized from sol–gel process. Mono dispersed β-SiC nano particles with semi spherical
morphology were obtained by employing APC as a dispersant agent and adjusting pH in the range of 2.5–4. Phenolic resin and
TEOS were employed as precursors and heat treatment was conducted up to 1500 °C. Different techniques such as XRD, DTA, FTIR,
PSA, SEM and TEM were used to characterize the formation of β-SiC. The (Si–O-C) bonds were formed by hydrolysis and condensation
reactions in the gel while the nucleation of crystalline β-SiC was found to be initiated at 1400 °C. The primary particles
in the sol were found to be (< 10 nm) while the size distribution in the final product was recorded in the range of 30–50 nm. 相似文献
17.
V. V. Vinogradov A. V. Agafonov A. V. Vinogradov T. I. Gulyaeva V. A. Drozdov V. A. Likholobov 《Journal of Sol-Gel Science and Technology》2010,56(3):333-339
In this study, boehmite sols were used as alumina precursors for preparing mesoporous γ-aluminas by two different methods.
In one case polyethylenimine was used as a structure-directing agent, and in another case ultrasound treatment was applied.
Nitrogen physisorption showed that aluminas that had been prepared by these methods demonstrated different porous structures.
The sample obtained without additional treatment had closely packed spherical particles and pores had ink-bottle neck morphology.
Ultrasound treatment led to the transformation of ink-bottle pores into cylindrical form and to the increase in surface area
and pore volume. Aluminas prepared using polyethylenimine as a template showed larger cylindrical wormhole-like mesopores
with a broader pore size distribution, high surface area and pore volume. Catalytic tests showed that textural properties
as well as crystallite size were very important parameters of synthesized samples which affected the catalytic activity in
the methanol dehydration reaction. It was found that γ-Al2O3 prepared by ultrasound treatment had large crystallite size and demonstrated high catalytic activity. 相似文献
18.
Qaiser Mahmood Adeel Afzal Humaira M. Siddiqi Amir Habib 《Journal of Sol-Gel Science and Technology》2013,67(3):670-674
In this letter, we present a facile route to produce metastable tetragonal zirconia (ZrO2) nanoparticles via pH-controlled precipitation of dilute zirconyl nitrate dihydrate [ZrO(NO3)2·2H2O] solution in liquid NH3 under ambient conditions and calcination at 500 °C for 2 h. The phase pure tetragonal ZrO2 nanoparticles are obtained at pH 9. The effect of pH on metastable phase stabilization in precipitated ZrO2 nanoparticles is demonstrated with the help of XRD, SEM/EDX, and X-ray photoelectron spectroscopy techniques. The stability of tetragonal ZrO2 phase is attributed to the smaller crystallite size and greater oxygen deficiency in phase-pure tetragonal ZrO2. 相似文献
19.
In the present work, three neutral 99mTc(CO)3 complexes of nitroimidazole were synthesized and their potential to detect tumor hypoxia is evaluated in vivo. Triazole derivatives of 2-, 4- and 5-nitroimidazole were synthesized via ‘click chemistry’ route. The ligands synthesized were characterized and subsequently radiolabeled using [99mTc(CO)3(H2O)3]+ precursor complex to obtain corresponding neutral 99mTc(CO)3 complexes in >90 % radio chemical purity. The complexes were subsequently evaluated in Swiss mice bearing fibrosarcoma tumor and in vivo distribution observed was thoroughly analyzed. All complexes showed uptake in tumor, however, contrary to general expectations, the 5-nitroimidazole complex showed significantly higher tumor uptake (p < 0.05) at 30 min and 60 min p.i., compared to the 2-nitroimidazole counterpart. Though a conclusive explanation for this observation could not be obtained, present study underlined the significance of evaluating nitroimidazole radiotracers other than 2-nitroimidazole for detecting tissue hypoxia. 相似文献
20.
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