共查询到20条相似文献,搜索用时 11 毫秒
1.
P. Pasierb Ewa Drożdż-Cieśla R. Gajerski S. Łabuś S. Komornicki M. Rękas 《Journal of Thermal Analysis and Calorimetry》2009,96(2):475-480
The purpose of this work was to investigate the influence of titanium and yttrium dopants on chemical stability of selected
Ba(Ce1−xTix)1−yYyO3 compounds. The presented results are the part of wider research concerning the crystallographic structure, microstructure,
electrical and transport properties of these groups of materials.
Samples of Ba(Ce1−xTix)1−yYyO3 with x=0.05, 0.07, 0.10, 0.15, 0.20, 0.30 and y=0.05, 0.10, 0.20 (for x=0.05) were prepared by solid-state reaction method. Initially, differential thermal analysis (DTA) and thermogravimetry (TG)
were used for optimization of preparation conditions. Subsequently, DTA-TG-MS (mass spectrometry) techniques were applied
for evaluation of the stability of prepared materials in the presence of CO2. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results were used to determine the phase composition,
structure and microstructure of materials and to assist the interpretation of DTA-TG-MS results.
The strong influence of Ti and Y dopants contents (x and y) on the properties was found. The introduction of Ti dopant led to the improvement of chemical stability against CO2. The lower Ti concentration the better resistance against CO2 corrosion was observed. Doping by Y had the opposite effect; the decrease of chemical stability was determined. In this case
the higher Y dopant concentration the better resistance was observed. The attempt to correlate the influence of dopant on
structure and chemical stability was also presented. 相似文献
2.
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
3.
4.
Glauciane N. Barbosa Tatiana C. O. Mac Leod Débora F. C. Guedes Marilda D. Assis Herenilton P. Oliveira 《Journal of Sol-Gel Science and Technology》2008,46(1):99-105
In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide–silicon oxide composite
xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously
synthesized via protonation of metavanadate species to an “in situ” progressive polycondensation into silica gel. The material
has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy.
Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene,
hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent. 相似文献
5.
Yu. E. Lebedeva N. V. Popovich L. A. Orlova A. S. Chainikova O. Yu. Sorokin M. L. Vaganova D. V. Grashchenkov 《Russian Journal of Inorganic Chemistry》2017,62(8):1032-1037
The effects caused by modifying additives, namely nonionic surfactants (Tween 80 and Neonol AF 9-6) and oxides (B2O3 and HfO2), on the rheology, film formation, and phase formation in the yttrium aluminum silicate system prepared by sol–gel technology were studied. The effect of 1 wt % HfO2 additions on the activation energy of crystallization was studied. 相似文献
6.
E. D. Sushchenko T. S. Kharlamova T. I. Izaak O. V. Vodyankina 《Kinetics and Catalysis》2017,58(5):630-641
The physicochemical properties of V2O5/Al2O3 and MgO–V2O5/Al2O3 supported catalysts (Mg : V = 1 : 1, 2 : 1, and 3 : 2) obtained by consecutive impregnation of the support with solutions of vanadium and magnesium precursors are studied using a complex of mutually complementary methods (XRD, Raman spectroscopy, UV–Vis spectrometry, and TPR-H2). The effect of the formation of surface magnesium vanadates of various composition and structure on the catalytic properties of the supported vanadium oxide catalysts in the oxidative dehydrogenation of propane is studied. The introduction of magnesium in the samples and an increase in its content, accompanied by a change in the structure of the surface vanadium oxide phases from polymeric VO6/VO5 species to surface metavanadate species, magnesium metavanadate, and further to magnesium divanadate, significantly affects their catalytic properties in the reaction of the oxidative dehydrogenation of propane to propylene. 相似文献
7.
Mohamed Triki Zouhaier Ksibi Abdelhamid Ghorbel Francisco Medina 《Journal of Sol-Gel Science and Technology》2011,59(1):1-6
Catalytic wet air oxidation of an aqueous solution of p-hydroxybenzoic acid was conducted over ruthenium catalysts (1 wt%)
supported on CeO2–Al2O3 aerogels mixed oxides at 140 °C and 50 bars of air. We study the effect of the amount of CeO2 in the catalyst. We found that the optimal cerium content in the Al2O3 support was 20 wt%. The activity of the Ru/Al2O3 and Ru/CeO2 was also tested for comparison. It was found that the addition of CeO2 on the alumina support improves the activity of Ru catalysts. The activity of the samples decreases in the following order:
Ru/Ce–Al (20) > Ru/Ce–Al (10) > Ru/Ce–Al (5) ≈ Ru/Al2O3 > Ru/CeO2. Samples characterization was performed by means of N2 adsorption–desorption, XRD, UV–Vis, TPR, SEM and TEM. 相似文献
8.
Weizhong Lv Zhongkuan Luo Wenjian Weng Hui Yang 《Journal of Sol-Gel Science and Technology》2009,51(1):58-62
A series of organic–inorganic hybrid coatings consisting of organic waterborne polyurethane (WPU) and inorganic nanosized
bismuth-doped tin dioxide were successfully synthesized by the in situ polymerization approach. Bi0.1Sn0.9O2 nano-powders were prepared via a new route of sol–gel combustion hybrid method using acetylene black as the fuel. The formed
nano-powders were characterized by transmission electron microscopy and X-ray diffraction (XRD). Bi0.1Sn0.9O2–WPU was then fabricated with isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and nano-Bi0.1Sn0.9O2-poly(ε-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable
contents of Bi0.1Sn0.9O2. The hybrid coatings with Bi0.1Sn0.9O2 loading on the glass substrate exhibited good heat insulation efficiency. The tensile strength and breaking extensibility
of nanocomposite film containing 1.0% of the nano-Bi0.1Sn0.9O2 were measured as 9.35 MPa and 248%, respectively. The transmittance of visible light was above 80%. The heat insulation of
glass coated with nano-Bi0.1Sn0.9O2–WPU hybrid was over 60 °C in contrast to the commercial blank glass. 相似文献
9.
M. Wiśniewska V. Bogatyrov I. Ostolska K. Szewczuk-Karpisz K. Terpiłowski A. Nosal-Wiercińska 《Adsorption》2016,22(4-6):417-423
The poly(vinyl alcohol) (PVA) influence on the adsorption and electrokinetic properties of the mixed oxide Mn x O y –SiO2/polymer solution system was examined. Three oxides differing with the Mn x O y contents were applied (0.2; 1 and 3 mmol/g SiO2, respectively). The PVA with the molecular weight 100 kDa was characterized with the acetate groups content equal to 14 %. Adsorption, solid surface charge and zeta potential measurements were made as a function of solution pH (3–10). The obtained results showed that the PVA adsorption amount strongly depends on not only the solution pH, but also manganese oxide content on the mixed oxide surface. The higher solution pH value (or Mn x O y content) is, the higher polymer adsorption is obtained. The PVA addition to the solid suspension causes minimal changes of the mixed oxide surface charge density, whereas the zeta potential of solid particles increases significantly in the polymer presence. 相似文献
10.
The synthesis of new compounds based on Bi2O3 is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the (Bi2O3)1−x(Y2O3)x type were synthesized. The host lattice of these pigments is Bi2O3 that is doped by Y3+ ions. The incorporation of doped ions provides the interesting colours and contributes to a growth of the thermal stability
of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment
formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray
powder diffraction and their colour properties. 相似文献
11.
V. Yu. Pereyma P. P. Dik O. V. Klimov S. V. Budukva K. A. Leonova A. S. Noskov 《Russian Journal of Applied Chemistry》2015,88(12):1969-1975
Supported nickel–molybdenum and nickel–tungsten hydrocracking catalysts prepared using a support that consists of 70% Al2O3 and 30% amorphous aluminosilicate were characterized by nitrogen and mercury porosimetry, IR spectroscopy of adsorbed CO, and high-resolution electron microscopy. The catalytic tests in hydrocracking of vacuum gas oil containing 3.39% sulfur showed that the nature of the hydrogenating component (NiMo or NiW) only slightly influences the vacuum gas oil conversion and the diesel fraction yield, but noticeable influences the properties of the diesel fraction obtained. The catalyst NiMo/Al2O3–amorphous aluminosilicates, compared to NiW/Al2O3–amorphous aluminosilicates, ensures lower sulfur content in the diesel fraction obtained, whereas the catalyst NiW/Al2O3–amorphous aluminosilicates allows obtaining a diesel fraction with lower content of polyaromatic compounds. 相似文献
12.
T. N. Afonasenko N. N. Leont’eva V. P. Talzi N. S. Smirnova G. G. Savel’eva A. V. Shilova P. G. Tsyrul’nikov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(10):1939-1945
The textural and structural properties of mixed oxides Ga2O3–Al2O3, obtained via impregnating γ-Al2O3 with a solution of Ga(NO3)3 and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga2O3–Al2O3 up to a Ga2O3 content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga2O3 content exceeds 50 wt %, the β-Ga2O3 phase is observed along with γ-Ga2O3–Al2O3 solid solution. 71Ga and 27Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga2O3–Al2O3. 相似文献
13.
M. A. Kerzhentsev E. V. Matus I. A. Rundau V. V. Kuznetsov I. Z. Ismagilov V. A. Ushakov S. A. Yashnik Z. R. Ismagilov 《Kinetics and Catalysis》2017,58(5):601-609
The effects of the Pd content (0–1 wt %) and the synthesis method (joint impregnation with Ni + Pd and Pd/Ni or Ni/Pd sequential impregnation) on the physicochemical and catalytic properties of Ni–Pd/CeZrO2/Al2O3 were studied in order to develop an efficient catalyst for the conversion of methane into hydrogen-containing gas. It was shown that variation in the palladium content and a change in the method used for the introduction of an active constituent into the support matrix make it possible to regulate the redox properties of nickel cations but do not affect the size of NiO particles (14.0 ± 0.5 nm) and the phase composition of the catalyst ((γ + δ)-Al2O3, CeZrO2 solid solution, and NiO). It was established that the activity of Ni–Pd catalysts in the reaction of autothermal methane reforming depends on the method of synthesis and increases in the following order: Ni + Pd < Ni/Pd < Pd/Ni. It was found that, as the Pd content of the Ni–Pd/CeZrO2/Al2O3 catalyst was decreased from 1 to 0.05 wt %, the ability for self-activation, high activity, and operational stability of the catalyst under the conditions of autothermal methane reforming remained unaffected: at 850°C, the yield of hydrogen was ~70% at a methane conversion of ~100% during a 24-h reaction. 相似文献
14.
S. G. Semenov M. E. Bedrina V. A. Klemeshev A. V. Titov 《Russian Journal of General Chemistry》2018,88(4):622-625
Structural parameters and vibrational frequencies of the clusters (Td)–Nb4O10, (C3v)-TaNb3O10, (D2d)-Nb4O 10 – , and (Cs)-TaNb3O 10 – were calculated. According to the (U)DFT/SDD calculations with BLYP, B3LYP, and PBE0 functionals magnetization of the anion (D2d)-Nb4O 10 – is distributed equally among four niobium atoms. In the anion (Cs)-TaNb3O 10 – unpaired electron presumably occupies niobium atoms. The distinction in contributions from Nb atoms in the magnetization of the tantalum-containing cluster grows with the exchange component of the DFT functional in the series of functionals BLYP < B3LYP < PBE0 < UHF. 相似文献
15.
T. N. Afonasenko N. S. Smirnova V. L. Temerev N. N. Leont’eva T. I. Gulyaeva P. G. Tsyrul’nikov 《Kinetics and Catalysis》2016,57(4):490-496
The structure of Ga2O3–Al2O3 supports and Pd/Ga2O3–Al2O3 catalysts and the performance of these catalysts in liquid-phase acetylene hydrogenation have been investigated. The deposition of Ga(NO3)3 onto Al2O3 by impregnation followed by calcination of the impregnated support at 600°C yields γ-Ga2O3–Al2O3 solid solutions containing up to 50 wt % Ga2O3. X-ray diffraction characterization of model palladium catalysts and their temperature-programmed reduction with hydrogen have demonstrated that, while palladium in Pd/Ga2O3 is in the form of a Pd2Ga alloy, in the Pd/γ-Ga2O3–Al2O3 catalyst there is no direct interaction between PdО and Ga2O3 particles and palladium is in the monometallic state. The introduction of 10–20 wt % gallium oxide into Al2O3 lowers the activity of the supported palladium catalyst relative to that of the initial Pd/Al2O3 but increases the ethylene yield by enhancing the ethylene formation selectivity. 相似文献
16.
E. V. Petrova A. F. Dresvyannikov M. Ahmadi Daryakenari A. I. Khairullina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(5):1021-1026
Scanning electron microscopy, X-ray, and thermal analysis are used to examine the structure and properties of dispersive systems based on aluminum and zirconium oxides prepared electrochemically. The effect the conditions of synthesis have on the structure and morphology of Al2O3–ZrO2 particles is studied. It is shown that the effect of an electric field on the reaction medium allows us to adjust the physicоchemical properties and morphology. 相似文献
17.
Via sol–gel processing metal–organic fibers were produced and dried up to 140 °C. For these gel fibers the influence of a
treatment in different atmospheres was investigated for the temperature range of 200–850 °C. The atmospheres were nitrogen,
water vapor, evaporated nitric and hydrochloric acid and evaporated hydrogen peroxide. In the presence of moisture and especially
with acidic moisture fibers were transformed almost completely to their oxide composition (82 mol% Al2O3·18 mol% Y2O3). In these inorganic amorphous structures considerable differences were observed on several structural levels. On the atomic
scale, the coordination of Al ions was investigated by 27Al MAS NMR and skeletal density by He-pycnometry. Porosity in the nm scale was characterized by N2-sorption. As a macroscopic effect of different treatment atmospheres, the longitudinal shrinkage was observed. For fibers
treated at 500 °C the relative shrinkage varied by 100% (comparing water vapor and nitrogen atmosphere). No simple correlation
between the release of organic constituents, the formation of porosity and the shrinkage could be found. These aspects were
controlled by the rigidity of the inorganic network against atomic reconstitution. The kind of atmosphere was found to be
an effective parameter to control various aspects of the xerogel structure. 相似文献
18.
Aiju Zhang Zhihong Li Zicheng Li Yumei Zhu 《Journal of Sol-Gel Science and Technology》2009,49(1):6-11
SiO2–Al2O3–Na2O glass coated cubic boron nitride (cBN) abrasive particles were prepared by sol–gel technique. The results indicated that
SiO2–Al2O3–Na2O glass was excellent material for oxidation protection of cBN abrasive grains because coefficient of thermal expansion of
this glass closely matched that of cBN materials. The single particle compressive strength and impact toughness of this glass
coated cBN abrasive particles were significantly increased. For the application of glass coated cBN abrasives to vitrified
grinding wheels, it was evident that the glass coating provided high bonding strength between cBN abrasive grains and vitrified
bond system. 相似文献
19.
The concentration space of homogeneous garnet in the system Ga2O3–(Y, Bi)3(Fe, Ga)5O12–Fe2O3 was determined by X-ray powder diffraction analysis. The obtained results expand the knowledge of the possible variations of cation ratios Y : Bi : Fe : Ga in garnet, which can be used for searching for and creating new stable magneto-optical materials. 相似文献
20.
Ce
x
Sn1−x
O2 metal oxides were prepared by a citrate method and used as supports for CuO/Ce
x
Sn1−x
O2 catalysts. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, high-resolution
TEM, and temperature-programmed reduction techniques. XRD analysis indicated that the Ce
x
Sn1−x
O2 samples maintain the fluorite structure and form a solid solution when x = 0.9 or 0.8. TPR analysis revealed that two kinds of copper species are present on the surface of the Ce
x
Sn1−x
O2 support. The catalytic properties of the CuO/Ce
x
Sn1−x
O2 catalysts were evaluated for low-temperature CO oxidation using a microreactor-GC system. The effects of Ce/Sn ratio and
CuO loading on the catalytic performance were investigated. The results showed that these CuO/Ce
x
Sn1−x
O2 catalysts are very active for low-temperature CO oxidation. The 650 °C calcined 7 wt%-CuO/Ce
x
Sn1−x
O2 catalyst exhibited the highest catalytic activity. 相似文献