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1.
Jianxia Jiao Qun Xu Limin Li Takano Tsubasa Takaomi Kobayashi 《Colloid and polymer science》2008,286(13):1485-1491
Titania–silica composite have been prepared using polyethylene glycol (PEG) with different molecular weights (M
w), PEG20000, PEG10000, and PEG2000, as template in supercritical carbon dioxide (SC CO2). The composite precursors were dissolved in SC CO2 and impregnated into PEG templates using SC CO2 as swelling agent and carrier. After removing the template by calcination at suitable temperature, the titania–silica composite
were obtained. The composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen
sorption–desorption experiment. Photocatalytic activity of the samples has been investigated by photodegradation of methyl
orange. Results indicate that there are many Si–O–Ti linkages in the TiO2/SiO2 composite; the PEG template has a significant influence on the structure of TiO2/SiO2. In addition, the TiO2/SiO2 prepared with PEG10000 exhibited high photocatalytic efficiency. So this work supplies a clue to control and obtain the TiO2/SiO2 composite with different photocatalytic reactivity with the aid of suitable PEG template in supercritical CO2. 相似文献
2.
Within the framework of the density functional theory (DFT), the electronic structure of monooxodioxovanadium functional groups in tetrahedral coordination, which model the active centers (ACs) of fine supported catalysts V2O5/SiO2 and V2O5/TiO2, has been analyzed. The optimal structures of three ACs as possible models of monomeric and polymeric oxovanadium forms on the carriers with low vanadium content were determined. The modified DFT method involving the time dependence of Kohn-Sham equation (TDDFT) was used for the adopted AC models to calculate the energies of the excited states, and optical spectra of the absorption in 25000–60000 cm?1 region were reconstructed on their base. The spectrum in this region is due to O → V charge transfer. The features of electronic spectra with the charge transfer for V2O5/SiO2 and V2O5/TiO2 catalysts and the vibrational spectra of three AC models corresponding to the monomeric and dimeric oxovanadium forms of the supported catalysts V2O5/SiO2 and V2O5/TiO2 were defined. The detailed interpretation of normal vibration frequencies is given. The frequencies typical of the monomeric and dimeric oxovanadium forms on the carrier surface were identified. 相似文献
3.
Dry potassium-based sorbents were prepared by impregnation with potassium carbonate on supports such as activated carbon (AC),
TiO2, Al2O3, MgO, CaO, SiO2 and various zeolites. The CO2 capture capacity and regeneration property of various sorbents were measured in the presence of H2O in a fixed bed reactor, during multiple cycles at various temperature conditions (CO2 absorption at 50–100 °C and regeneration at 130–400 °C). The KAlI30, KCaI30, and KMgI30 sorbents formed new structures such
as KAl(CO3)2(OH)2, K2Ca(CO3)2, K2Mg(CO3)2, and K2Mg(CO3)2·4(H2O), which did not completely convert to the original K2CO3 phase at temperatures below 200 °C, during the CO2 absorption process in the presence of 9 vol.% H2O. In the case of KACI30, KTiI30, and KZrI30, only a KHCO3 crystal structure was formed during CO2 absorption. The formation of active species, K2CO3·1.5H2O, by the pretreatment with water vapor and the formation of the KHCO3 crystal structure after CO2 absorption are important factors for absorption and regeneration, respectively, even at low temperatures (130–150 °C). In
particular, the KTiI30 sorbent showed excellent characteristics with respect to CO2 absorption and regeneration in that it satisfies the requirements of a large amount of CO2 absorption (87 mg CO2/g sorbent) without the pretreatment with water vapor, unlike KACI30, and a fast and complete regeneration at a low temperature
condition (1 atm, 150 °C). In addition, the higher total CO2 capture capacity of KMgI30 (178.6 mg CO2/g sorbent) than that of the theoretical value (95 mg CO2/g sorbent) was explained through the contribution of the absorption ability of MgO support. In this review, we introduce
the CO2 capture capacities and regeneration properties of several potassium-based sorbents, the changes in the physical properties
of the sorbents before/after CO2 absorption, and the role of water vapor and its effects on CO2 absorption. 相似文献
4.
Atomic models are proposed for nanotubes of the titanium silicocarbides Ti2SiC, Ti3SiC2, and Ti4SiC3, and their electronic structure and interatomic interactions are investigated by the density functional tight-binding method
(DFTB) in comparison with the corresponding crystalline phases.
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 88-92, March-April, 2009. 相似文献
5.
A. V. Shlyakhtina A. E. Ukshe L. G. Shcherbakova 《Russian Journal of Electrochemistry》2005,41(3):265-269
A nanoceramic product of the composition Lu2Ti2O7 is synthesized by a coprecipitation method with a subsequent sublimation drying and an annealing at 650–1650°C. The conduction of Lu2Ti2O7 synthesized at 1650°C is ionic (10–3 S cm–1 at 800°C). Thus, a new material with a high ionic conduction has been discovered. The ordering in Lu2Ti2O7 is studied by methods of RFA, RSA, IK spectroscopy, electron microscopy, and impedance spectroscopy. The existence of a low-temperature phase transition fluorite-pyrochlore at 800°C and a high-temperature conversion order-disorder at 1650°C are established.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 298–303.Original Russian Text Copyright © 2005 by Shlyakhtina, Ukshe, Shcherbakova. 相似文献
6.
Johan Jacquemin Pascale Husson Vladimir Majer Margarida F. Costa Gomes 《Journal of solution chemistry》2007,36(8):967-979
Experimental values for the solubility of carbon dioxide and hydrogen in three room temperature ionic liquids based on the
same anion—(bistrifluoromethylsulfonyl)imide [Ntf2]—and three different cations—1-butyl-3-methylimidazolium, [C4mim], 1-ethyl-3-methylimidazolium, [C2mim] and trimethyl-butylammonium, [N4111]—are reported between 283 and 343 K and close to atmospheric pressure. Carbon dioxide, with a mole-fraction solubility of
the order of 10−2, is two orders of magnitude more soluble than hydrogen. The solubility of CO2 is very similar in the three ionic liquids although slightly lower in the presence of the [C2mim] cation. In the case of H2, noticeable differences were observed with larger mole fraction solubilities in the presence of [N4111] followed by [C4mim]. All of the mole-fraction solubilities decrease with increasing temperature. From the variation of Henry’s law constants
with temperature, the thermodynamic functions of solvation were calculated. The precision of the experimental data, considered
as the average absolute deviation of the Henry’s law constants from appropriate smoothing equations, is always better than
±1%. 相似文献
7.
Inorganic-organic hybrid membranes containing silica as the structure matrix, poly(N-vinylpyrrolidone) (PVP) as the organic mediating agent and silver ions as olefinic carriers were prepared using sol–gel method and dip-coating process. The structure and permeances of the membranes for N2, He, C2H4, C2H6 at different temperatures indicated that defect-free membranes were obtained and the transportation of the C2H4 through the membranes followed the dissolution and diffusion mechanism. Ideal separation factors of C2H4/C2H6 through the membranes were evaluated at the temperature of 298, 373 and 423 K respectively using mixture gas of 50% C2H4-50% C2H6. The results showed that the ideal separation factors of C2H4/C2H6 through the membranes were obviously greater than the ratio of PC2H4/PC2H6 obtained from the single gas measurement due to the hindering effect by the adsorbed C2H4. The ideal separation factors of C2H4/C2H6 increased with temperature and reached 10 at 423 K, which suggested that C2H4 and C2H6 could be separated at lower humidity compared to the reported organic polymer/silver salt membranes in which humidified gases and higher silver loading were usually used. The transport of C2H4 in the inorganic-organic hybrid membrane was proposed to follow the hopping mechanism, that is, olefins moved across the fixed silver sites. 相似文献
8.
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
9.
Lei Ge 《Journal of Sol-Gel Science and Technology》2007,44(3):263-268
Novel visible-light-activated In2O3–CaIn2O4 photocatalysts were developed in this paper through a sol–gel method. The photocatalytic activities of In2O3–CaIn2O4 composite photocatalysts were investigated based on the decomposition of methyl orange under visible light irradiation (λ > 400 nm).
The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive
spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and UV–vis diffused reflectance spectroscopy (DRS). The results revealed
that the In2O3–CaIn2O4 composite samples with different In2O3 and CaIn2O4 content can be obtained by controlling the synthesis temperature, and the composite photocatalysts extended the light absorption
spectrum toward the visible region. The photocatalytic tests indicated that the composite samples demonstrated high visible-light
activity for decomposition of methyl orange. The significant enhancement in the In2O3–CaIn2O4 photo-activity under visible light irradiation can be ascribed to the efficient separation of photo-generated carriers in
the In2O3 and CaIn2O4 coupling semiconductors. 相似文献
10.
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
11.
G. V. Girichev N. I. Giricheva N. P. Kuzmina Yu. S. Levina A. Yu. Rogachev 《Journal of Structural Chemistry》2005,46(5):813-823
Gas-phase electron diffractometry was used to study the molecular structure of N,N′-ethylenebis(salicylaldiminato)nickel(II), NiO2N2C16H14, [hereinafter Ni(salen)] at 583(5) K. The molecule has C 2 symmetry with a practically planar structure of the NiN2O2 coordination unit and with internuclear distances r α (Ni-O) = 1.882(21) Å and r α (Ni-N) = 1.889(22) Å. The results of B3LYP/CEP-31G molecular structure calculations are in good agreement with experimental data, whereas the RHF/CEP-31G method significantly overestimates the Ni-N internuclear distance and gives worse results for other structural parameters. According to 3LYP/CEP-31G calculations, the 1 A low-spin state is 28 kJ/mole lower in energy than the 3 B high-spin state. 相似文献
12.
2CaO·3B2O3·H2O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and
TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B2O3·H2O in HCl·54.572H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.501H2O and of CaO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol−1 of 2CaO·3B2O3·H2O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method. 相似文献
13.
14.
V. M. Zainullina V. L. Volkov N. V. Podvalnaya A. L. Ivanovskii 《Journal of Structural Chemistry》2005,46(2):340-342
The calculations of the electronic structure of layered polyvanadate K2V3O8 were made employing the spin-polarized tight-binding LMTO method. Calculated magnetic moment for K4V6O16 compound phase equals 1.97 μB. V-O interactions were established to be dominating in the chemical bonding generation in this polyvanadate according to the estimated crystal orbital overlap population. The covalent bonds V(2)-V(2) in V(2)2O7 groups and electron density localization on vanadium atoms in isolated pyramids V(1)O5 were found. 相似文献
15.
Fe3O4 nanorods and Fe2O3 nanowires have been synthesized through a simple thermal oxide reaction of Fe with C2H2O4 solution at 200–600°C for 1 h in the air. The morphology and structure of Fe3O4 nanorods and Fe2O3 nanowires were detected with powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy.
The influence of temperature on the morphology development was experimentally investigated. The results show that the polycrystals
Fe3O4 nanorods with cubic structure and the average diameter of 0.5–0.8 μm grow after reaction at 200–500°C for 1 h in the air.
When the temperature was 600°C, the samples completely became Fe2O3 nanowires with hexagonal structure. It was found that C2H2O4 molecules had a significant effect on the formation of Fe3O4 nanorods. A possible mechanism was also proposed to account for the growth of these Fe3O4 nanorods.
Supported by the Fund of Weinan Teacher’s University (Grant No. 08YKZ008), the National Natural Science Foundation of China
(Grant No. 20573072) and the Doctoral Fund of Ministry of Education of China (Grant No. 20060718010) 相似文献
16.
New composite cathode materials xLiMn2O4/(1 ? x) LiCoO2(x = 0.7, 0.6, 0.5 и 0.4) were obtained by mechanical activation. According to scanning electron microscopy data, the process was accompanied by pronounced dispersion and fine mixing of the initial components. In the course of the preparation and electrochemical cycling of the composites, LiMn2O4 and LiCoO2 partially reacted, leading to the replacement of manganese with cobalt in the structure of spinel, which was detected by powder X-ray diffraction (XRD), IR and X-ray photoelectron spectroscopy (XPS), and cyclic chronopotentiometry. The specific discharge capacity of composites was ~100 mAh/g. 相似文献
17.
Fluorine-doped tin dioxide
(FTO) films were deposited on silicon wafers by inverted pyrosol technique
using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75
and 2.50). The physical and electrical properties of the deposited films were
analyzed by SEM, XRF, resistivity measurement by four-point-probe method and
Hall coefficient measurement by van der Pauw method. The electrical properties
showed that the FTO film deposited using the solution with F/Sn=0.75 gave
a lowest resistivity of 3.2·10–4 ohm
cm. The FTO films were analyzed by temperature programmed desorption (TPD).
Evolved gases from the heated specimens were detected using a quadruple mass
analyzer for mass fragments m/z, 1(H+),
2(H2
+), 12(C+),
14(N+), 15(CH3
+),
16(O+), 17(OH+ or NH3
+),
18(H2O+ or NH4
+),
19(F+), 20(HF+), 28(CO+
or N2
+), 32(O2
+),
37(NH4F+), 44(CO2
+),
120(Sn+), 136(SnO+)
and 152(SnO2
+). The majority
of evolved gases from all FTO films were water vapor, carbon monoxide and
carbon dioxide. Fluorine (m/z 19) was detected
only in doped films and its intensity was very strong for highly-doped films
at temperature above 400°C. 相似文献
18.
Anna Blonska-Tabero 《Journal of Thermal Analysis and Calorimetry》2007,88(1):201-205
Thermal properties of Co2FeV3O11
have been reinvestigated. It has been proved that this compound does not exhibit
polymorphism. It melts incongruently at the temperature of 770±5°C
and the phase with lyonsite type structure is the solid product of this melting.
Phase relations in the whole subsolidus area of the CoO–V2O5–Fe2O3 system have been determined. The solidus area projection onto
the component concentration triangle plane of this system has been constructed
using the DTA and XRD methods. 15 subsidiary subsystems can be distinguished
in this system. 相似文献
19.
Areas of fusion and crystallization peaks of K3TaO2F4 and KTaF6 were measured using the DSC mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering
the temperature dependence of the calorimeter sensitivity, values of the fusion enthalpy of K3TaO2F4 at the fusion temperature of 1181 K of (43 ± 4) kJ mol−1 and of KTaF6 at the fusion temperature of 760 K of (8 ± 1) kJ mol−1 were determined. 相似文献
20.
Nanocrystalline La2Mo2O9 oxide-ion conductor has been successfully synthesized by microwave-assisted combustion method within a very short time duration
using aspartic acid as the newer fuel in a domestic microwave oven. The synthesized nanocrystalline powder showed good sinterability
and reached more than 97% of theoretical density even at low temperature of 800 °C for 5 h. The sintered La2Mo2O9 sample exhibited a conductivity of 0.159 S/cm in air at 750 °C. 相似文献