共查询到20条相似文献,搜索用时 15 毫秒
1.
A. L. Stroyuk V. M. Dzhagan S. Ya. Kuchmii M. Ya. Valakh D. R. T. Zahn C. von Borczyskowski 《Theoretical and Experimental Chemistry》2007,43(5):297-305
The luminescent characteristics of CdxZn1−xS nanoparticles were studied. It was shown that the emission is due to the recombination of holes in the valence band with
electrons captured by two sorts of traps, of which the traps with lower energy were ascribed to the surface states of the
CdxZn1−xS nanoparticles. It was established that the CdxZn1−xS nanoparticles have more pronounced ability than CdS nanoparticles to accumulate excess negative charge under the conditions
of pulsed irradiation. It was shown that the consumption of the photogenerated electrons in nanosecond and microsecond time
scales involves the participation of one and the same electron traps. It was established that the rate of interaction of the
electrons captured by the surface traps with oxygen increases with decrease in the size of the nanoparticles.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 275–281, September–October, 2007. 相似文献
2.
A. E. Raevskaya A. L. Stroyuk A. I. Kryukov S. Ya. Kuchmii 《Theoretical and Experimental Chemistry》2006,42(3):181-185
The structural and optical characteristics of CdxZn1−xS nanoparticles, produced in aqueous solutions of sodium polyphosphate, polyvinyl alcohol, and gelatin, were studied. It was
shown that the stoichiometric ratio of Cd(II) and Zn(II) in the nanoparticles can differ from that in the initial mixture.
It was established that the main factors determining the final size of the CdxZn1−xS nanoparticles are the nature and concentration of the polymer, the ratio of the initial concentrations of the reagents,
and the temperature and duration of the post-synthesis treatment of the colloids.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 168–172, May–June, 2006. 相似文献
3.
A. E. Raevskaya A. L. Stroyuk S. Ya. Kuchmii Yu. M. Azhnyuk V. M. Dzhagan M. Ya. Valakh 《Theoretical and Experimental Chemistry》2006,42(3):162-168
The optical characteristics of CdSe nanoparticles, produced in aqueous solutions and polymer films in the reaction of cadmium
chloride and sodium selenosulfate, were studied. The main parameters that make it possible to vary the forbidden band width
were identified. The absorption, photoluminescence, Raman, and nonstationary decolorization spectra of CdSe nanoparticles
of various sizes were analyzed. It was demonstrated that under the conditions of pulsed irradiation the CdSe nanoparticles
are capable of accumulating excess electrons and inducing redox transformations in components of the solution (oxygen, methylviologen,
and sulfite ions).
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 150–155, May–June, 2006. 相似文献
4.
N. N. Gedam P. R. Padole S. K. Rithe G. N. Chaudhari 《Journal of Sol-Gel Science and Technology》2009,50(3):296-300
Thick film of nanocrystalline Co0.8Ni0.2Fe2O4 was obtained by sol–gel citrate method for gas sensing application. The synthesized powder was characterized by X-ray diffraction
(XRD) and transmission electron microscopy. The XRD pattern shows spinel type structure of Co0.8Ni0.2Fe2O4. XRD of Co0.8Ni0.2Fe2O4 revels formation of solid solution with average grain size of about 30 nm. From gas sensing properties it observed that nickel
doping improves the sensor response and selectivity towards ammonia gas and very low response to LPG, CO, and H2S at 280 °C. Furthermore, incorporation of Pd improves the sensor response and stability of ammonia gas and reduced the operating
temperature upto 210 °C. The sensor is a promising candidate for practical detector of ammonia. 相似文献
5.
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
6.
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
7.
P. Tabero 《Journal of Thermal Analysis and Calorimetry》2007,88(1):37-41
Solid solution phases of a formula Fe8V10W16–xMoxO85 where 0≤x≤4, have been obtained, possessing a structure
of the compound Fe8V10W16O85.
It was found on the base of XRD and DTA investigations that these solution
phases melted incongruently, with increasing the value of x, in the temperature
range from 1108 (x=0) to 1083 K (x=4) depositing Fe2WO6
and WO3. The increase of the Mo6+
ions content in the crystal lattice of Fe8V10W16O85
causes the lattice parameters a=b contraction with cbeing
almost constant. IR spectra of the Fe8V10W16–xMoxO85 solid solution phases have been recorded. 相似文献
8.
A. M. Garrido Pedrosa M. J. B. Souza D. M. A. Melo A. S. Araujo 《Journal of Thermal Analysis and Calorimetry》2007,87(2):351-355
The thermo-programmed reduction study of
Pt/WOx–ZrO2 materials
prepared with different tungsten loading were performed by thermogravimetry.
The samples were synthesized by impregnation method and calcined at 600, 700
and 800°C. The characterizations of both un-calcined and calcined materials
were carried out using different techniques: thermal analysis (TG and DTA),
X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA
analysis of un-calcined were used to determination of calcination temperatures
of the samples. XRD diffractograms were useful to help us in the determination
of phase presents. TPR profiles showed between three and four events at different
temperatures attributed to platinum reduction and the different stages of
tungsten specie reduction. 相似文献
9.
Fe3O4/Au composite particles with core/shell structure were prepared by reduction of Au3+ with hydroxylamine in the presence of an excess of Fe3
O4 as seeds. The resultant colloids, with an average diameter of less than 100 nm, were obtained; the remaining non-reacted
Fe3O4 seeds can be removed by treatment with diluted HCl solution. The Fe3O4/Au colloids exhibit a characteristic peak of UV-visible spectra, which largely depend on the size of the particle and the
suspension medium. The localized surface plasmon resonance peaks red shift and broaden with increased nanoparticle diameter
or increased solvent ionic strength. The optical property is very important in the establishment of means for the detection
of biomolecules. 相似文献
10.
The mono- and bisligands complexes formed by rare earth cation (Sc, Y) with pentazolato anion or cyclo-P5− anion, the all-nitrogen counterparts of metallocenes or the all-phosphorus counterparts of metallocenes, have been studied
at hybrid basis sets level with the DFT method. The geometric parameters, binding energy and the charge distributions of these
complexes were characterized. And their stable orders were obtained. Monoligand complexes incline to become bisligands complexes
due to their destabilization. The charge transferring between ligand and metallic cation has affinity with the stability of
complex. The possibility of forming stable [M(η
5-E5)2] (M = Sc, Y, E = N, P) complexes is predicted and they are viable synthetic targets theoretically, especially Sc(η
5-N5)2. 相似文献
11.
Large-scale Li1+x
V3O8 nanobelts were successfully fabricated using filter paper as deposition substrate through a simple surface sol–gel method.
The nanobelts were as long as tens of micrometers with widths of 0.4–1.0 μm and thickness of 50–100 nm. The nanobelts were
characterized by X-ray diffration (XRD), Fourier infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission
electron microscopy (TEM). The formation mechanism of the nanobelts was investigated, showing that the morphology of the nanobelts
is mainly determined by the calcination temperature. Electrochemical properties of the Li1+x
V3O8 nanobelts were characterized by charge–discharge experiments, and the results demonstrate that the Li1+x
V3O8 nanobelts exhibit a high discharge capacity (278 mAh g−1) and excellent cycling stability. 相似文献
12.
Junseo Choi Ji-Young Ban Suk-Jin Choung Jinsoo Kim Haznan Abimanyu Kye Sang Yoo 《Journal of Sol-Gel Science and Technology》2007,44(1):21-28
Mesoporous TiO2/γ-Al2O3 composite granules were prepared by combining sol–gel/oil-drop method, using various titania solution. The product granules
can be used as a photocatalyst or adsorbent in moving, fluidized bed reactors. The phase composition and pore structure of
the granules can be controlled by calcination temperature and using different titania solution. In the photocatalysis of NH3 decomposition, TiO2/γ-Al2O3 granules using Degussa P25 powder treated thermally at 450 °C showed the highest catalytic ability. However, TiO2/γ-Al2O3 granules using titania made by hydrothermal method had comparable performance in NH3 decomposition. 相似文献
13.
Ben Hui Wang Ji De Wang RuiQuan Liu Ya Hong Xie Zhi Jie Li 《Journal of Solid State Electrochemistry》2007,11(1):27-31
A new type of oxide–salt composite electrolyte, yttrium doped ceria YDC–Ca3(PO4)2–K3PO4, was developed and demonstrated for its promising use for ammonia synthesis. Using this composite electrolyte, ammonia was
synthesized from nitrogen and natural gas at atmospheric pressure in the solid-state proton conducting cell reactor, and the
optimal condition for ammonia production was determined . The evolved rate of ammonia is up to 6.95×10−9 mol s−1 cm−2. 相似文献
14.
Chun-guang Gao Yong-xiang Zhao Yin Zhang Dian-sheng Liu 《Journal of Sol-Gel Science and Technology》2007,44(2):145-151
The Ni/ZrO2/SiO2 aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO2–SiO2 composite aerogels with a aqueous solution of Ni(NO3)2, (ii) impregnation SiO2 aerogels with a mixed aqueous solution of Ni(NO3)2 and ZrO(NO3)2 · 2H2O, (iii) one-pot sol–gel procedure from precursors Ni(NO3)2/ZrO(NO3)2 · 2H2O/Si(OC2H5)4. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed
desorption (NH3-TPD), N2 adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride
(MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference
between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component,
texture, and catalytic selectivity. 相似文献
15.
The nanosized xerogel of titanium dioxide (TiO2) and manganese oxides (MnO2, Mn2O3, Mn3O4) was prepared by the sol-gel method using manganese chloride (MnCl2·4H2O) and titanium isopropoxide (Ti(O-iPr)4) as precursors in cetyltrimethylammonium bromide (CTAB)/ ethanol/H2O/HCl micelle solutions, following the calcinations of the produced powders at difference temperatures. The nanostructure
and phase composition of these nanoparticles were characterized with X-ray powder diffraction (XRD), transmission electron
microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The spectroscopic
characterizations of these nanoparticles were also done with UV-Vis spectroscopy and laser Raman spectroscopy (LRS). XRD patterns
show that the pyrophanite MnTiO3 phase was formed at the calcinations temperature of 900°C. The TEM images show that the nanoparticles are almost spherical
or slight ellipose and the sizes are 50 nm on average. The UV-Vis spectra show that the nanosized MnTiO3 have significant absorption bands in the visible region. There are new absorption peaks of MnTiO3 nanoparticles in LRS compared with the pure TiO2 powder. 相似文献
16.
Sagrario M. Montemayor L. A. García-Cerda J. R. Torres-Lubián O. S. Rodríguez-Fernández 《Journal of Sol-Gel Science and Technology》2007,42(2):181-186
In this work the synthesis of CoFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained
by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride
were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors,
without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric
precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray
diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe2O4 and NiFe2O4 in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of
the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic
behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe2O4-SiO2 and NiFe2O4-SiO2 compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C. 相似文献
17.
Žaneta Dohnalová Petra Šulcová M. Trojan 《Journal of Thermal Analysis and Calorimetry》2008,93(3):857-861
Inorganic pigments containing lanthanides based on orthorhombic perovskite structure of CaSnO3 have been prepared by solid state reaction of CaCO3, SnO2 and lanthanide oxides (Tb4O7, Pr6O11, CeO2). The TG-DTA analysis indicates the formation of Ca-stannates around of temperature 1200°C, but from the pigmentary — application
point of view, it is better to synthesize the product at higher temperature (1400 or 1500°C). The resultant materials were
characterised by XRD, particle size distribution and measurement of colour properties. The doping of Ca-stannates by ions
of rare earth elements (Tb, Pr, Ce) brings the production of two-and three-phase systems. The most interesting colour properties
provided the stannate doped by ions of terbium and cerium and synthesized by heating at temperature 1400°C. The pigment has
reddish brown colour hue. 相似文献
18.
Matthias Weil Franz Werner Frank Kubel 《Monatshefte für Chemie / Chemical Monthly》2002,133(3):267-275
Summary. Single crystals of MgAl2F8(H2O)2 have been obtained under hydrothermal conditions (250°C, 14 d) from a starting mixture of AlF3 and MgAlF5(H2O)2 in a 5% (w/w) HF solution. The crystal structure has been determined and refined from single crystal data (Fmmm (#69), Z = 4, a = 7.2691(7), b = 7.0954(16), c = 12.452(2) ?, 281 structure factors, 27 parameters, R(F
2 > 2σ (F
2)) = 0.0282, wR(F
2 all) = 0.0885). The obtained crystals were systematically twinned according to (010/100/001) as twinning matrix, reflecting
the pseudo-tetragonal metric. The crystal structure is composed of perowskite-type layers built of corner sharing AlF6 octahedra with an overall composition of AlF4
− which are connected via common fluorine atoms of [MgF4/2(H2O)2/1] octahedra. Group-subgroup relations of MgAl2F8(H2O)2 to WO3(H2O)0.33 and to other M(II)M(III)2 F8(H2O)2 structures are briefly discussed. Above 570°C, MgAl2F8(H2O)2 decomposes under elimination of water into α-AlF3, β-AlF3, and MgF2.
Received October 29, 2001. Accepted (revised) December 6, 2001 相似文献
19.
The photoluminescence properties of xZnO–(100−x)SiO2 (x = 0, 5, 10, 20) containing 1% Eu2O3 prepared by a sol–gel method were systematically investigated. The results indicated that the relative proportion of f–f transitions to charge transfer (CT) absorption decreased with the increase of ZnO concentration. The intensity of 5D0–7FJ transitions of Eu3+ ions was enhanced with the increase of ZnO content due to local structure changes and decreased quantities of Eu3+ ions clusters. The results of fluorescence line narrow (FLN) spectra indicated that Eu3+ ions occupied one site in SiO2 glass and two sites in ZnO–SiO2 glasses. The second-order crystal field parameters were calculated. B20 and B22 for site 1 increased with excitation energy, while ones hardly changed for site 2. 相似文献
20.
Carbon dioxide reforming (CDR) of methane to synthesis gas over supported nickel catalysts has been reviewed. The present
review mainly focuses on the advantage of ceria based nickel catalysts for the CDR of methane. Nickel catalysts supported
on ceria–zirconia showed the highest activity for CDR than nickel supported on other oxides such as zirconia, ceria and alumina.
The addition of zirconia to ceria enhances the catalytic activity as well as the catalyst stability. The catalytic performance
also depends on the crystal structure of Ni–Ce–ZrO2. For example, nickel catalysts co-precipitated with Ce0.8Zr0.2O2 having cubic phase gave synthesis gas with CH4 conversion more than 97% at 800 °C and the activity was maintained for 100 h during the reaction. On the contrary, Ni–Ce–ZrO2 having tetragonal phase (Ce0.8Zr0.2O2) or mixed oxide phase (Ce0.5Zr0.5O2) deactivated during the reaction due to carbon formation. The enhanced catalytic performance of co-precipitated catalyst
is attributed to a combination effect of nano-crystalline nature of cubic Ce0.8Zr0.2O2 support and the finely dispersed nano size NiO
x
crystallites, resulting in the intimate contact between Ni and Ce0.8Zr0.2O2 particles. The Ni/Ce–ZrO2/θ–Al2O3 also exhibited high catalytic activity during CDR with a synthesis gas conversion more than 97% at 800 °C without significant
deactivation for more than 40 h. The high stability of the catalyst is mainly ascribed to the beneficial pre-coating of Ce–ZrO2 resulting in the existence of stable NiO
x
species, a strong interaction between Ni and the support, and an abundance of mobile oxygen species in itself. TPR results
further confirmed that NiO
x
formation was more favorable than NiO or NiAl2O4 formation and further results suggested the existence of strong metal-support interaction (SMSI) between Ni and the support.
Some of the important factors to optimize the CDR of methane such as reaction temperature, space velocity, feed CO2/CH4 ratio and H2O and/or O2 addition were also examined. 相似文献