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1.
A crystalline titanium dioxide coating was deposited onto silica insulated magnetite particles to prepare a stable magnetic
photocatalyst. The direct deposition of crystalline titanium dioxide was conducted by aging dispersions of insulated magnetite
particles in a titanium sol–gel precursor mixture at 60–90°C. The coating process was found to be influenced by pH, alkoxide
precursor concentration, aging time and reaction temperature. A mechanism for the formation of the titanium dioxide coating
has been proposed. The photocatalytic performance of the prepared particles was found to be related to the preparation conditions. 相似文献
2.
不同干燥法制备纳米TiO2光催化剂的光谱研究 总被引:5,自引:0,他引:5
本文分别用常态、超临界乙醇和超临界CO2干燥法干燥钛酸正丁酯的醇凝胶,制备纳米TiO2光催化剂。应用XRD,FTIR,FT-Raman和Fluorescent spectrum(FS)等光谱技术对催化剂进行了表征。以光催化降解罗丹明B为模型反应,比较所得样品光催化活性。实验结果表明,不同干燥方法对催化剂的晶相结构、半导体能带结构、光吸收性能、表面性质及光催化活性均产生显著的影响,用超临界CO2干燥法制备的TiO2光催化剂具有较好的光催化活性。 相似文献
3.
Aneta Slodczyk Philippe Colomban Daniel Lamago Marie-Helene Limage François Romain Stephanie Willemin Beatrice Sala 《Ionics》2008,14(3):215-222
H+-containing lanthanide-doped perovskites A(Ba, Sr etc.)B(Zr, Ce, Ti etc.)O3 are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). The comparison studies
of the hydrated and non-hydrated Yb-doped BaZrO3 and SrZrO3 were performed by thermal expansion, medium–high temperature neutron and room-temperature high-pressure Raman scattering.
Neutron diffraction and elastic/quasi-elastic studies carried out for BaZrO3 ceramic show the presence of the protons, their successive diffusion above ∼600 °C, and then their departure above 750 °C
(under vacuum). Phase transitions and their modification by proton insertion are discussed. A high-pressure Raman study of
SrZrO3 performed at room temperature in the diamond anvil cell reveals the presence of two pressure-induced phase transitions at
about 5 and 22 GPa and confirms that proton insertion modifies the phase transition sequences.
Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007. 相似文献
4.
S. Mahalingam M.J. Edirisinghe 《Applied Physics A: Materials Science & Processing》2007,89(4):987-993
A titanium dioxide precursor sol flowing through a needle at a flow rate of 10-10 m3 s-1 was subjected to an electric field of 4.5 kV to generate droplets in the size range 0.3–6 μm. The droplets were collected
on a silicon substrate to form uniformly thick, dense films. Raman spectroscopy, X-ray diffraction, field emission scanning
electron microscopy and UV/Vis spectroscopy were used to characterize as-deposited and annealed films. Raman spectra show
the annealed films were anatase phase with annealing converting it to the rutile phase. The energy bandgap of the titanium
dioxide film annealed to 500 °C shows an indirect bandgap energy of 3.50 eV and a direct bandgap energy of 3.95 eV.
PACS 81.15.Rs; 81.07.-b; 78.20.-e; 78.30.-j; 78.67.-n; 78.70.ck 相似文献
5.
V. V. Turov V. M. Gun’ko V. E. Gaishun Ya. A. Kosenok A. P. Golovan 《Journal of Applied Spectroscopy》2010,77(4):588-594
We have used low-temperature 1H NMR spectroscopy to determine the thermodynamic characteristics of water bound to OX-50 nanosilica
(SBET ≈ 50 m2/g) in different media: aqueous, air, chloroform medium, and gaseous methane. We demonstrate the difference between
the hydration parameters of silica OX-50 on going from an aqueous suspension to a hydrated powder. We present the water cluster
size distributions in the studied systems, calculated from the Gibbs–Thomson equation. We found that the average water cluster
size in suspension is considerably larger than the cluster sizes in hydrated powders. 相似文献
6.
V. V. Uglov V. I. Shimanski D. P. Rusalsky M. P. Samtsov 《Journal of Applied Spectroscopy》2008,75(4):546-549
The structure of ultradispersed diamonds (UDD) is studied by spectral methods. The presence of diamond crystal phase in the
UDD is found based on x-ray analysis and Raman spectra. The Raman spectra also show sp2-and sp3-hybridized carbon. Analysis of IR absorption spectra suggests that the composition of functional groups present in the particles
changes during the treatment.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 524–528, July–August, 2008. 相似文献
7.
C. P. Pang J. T. Lue 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):593-600
The linear refractive indices and nonlinear second-order susceptibility of
hydrated and dehydrated silica micro-spheres are studied using attenuated
total reflectance (ATR) and the second harmonic generation (SHG) method in
direct transmission, respectively. A dramatic change of the effective
dielectric constant of silica suspension under an electric bias was
observed, which is attributed to particle redistribution in the fluid.
Dielectric constants of dehydrated silica spheres change slightly under an
electric field due to Pockels effect, for which we measure a linear
electro-optical coefficient of r33 ∼3.4±0.7 pm/V. The
transmission second harmonic generation comes from the third-order
susceptibility χ(3), which is a coupling of two photons and the
electrostatic field induced by the surface –OH charges as characterized by
the Gouy-Chapman model. The SH signal from the dehydrated silica vanishes
because of the loss of –OH groups on the particle surfaces. Dehydration of
silica beads is irreversible. The optical properties of dried silica spheres
do not recover their original hydrated state when distilled water is added. 相似文献
8.
Thin TiO2 films obtained by cathodic electrosynthesis from an acidic aqueous bath containing TiOSO4, H2O2 and KNO3 on conductive glass indium tin oxide have been physically and electrochemically characterised. Secondary ion mass spectroscopy
profile of the crystallised gel after heat treatment at 400 °C shows the presence of TiO2 with traces of TiO and oxygen. X-ray patterns confirm the presence of anatase nanocrystallites for the annealed film and
an amorphous structure for the non-annealed gel. Scattering electron microscopy surface micrographies reveal an opened porous
nanostructure of the deposits. Cyclic voltammetry and impedance spectroscopic measurements reveal the different behaviour
of the films obtained before and after the annealing, showing an important electrical activity of the non-annealed films.
The dependence of capacitance values with potential in the anodic domain of depletion is obviously remarked from impedance
plots for both gel and crystal forms of the film, which confirmed the fact that films obtained in this way have n-type properties.
The potential of flat band equals −0.6 V/Ag/AgCl in pH range of 6.5 has been estimated according to Mott–Shottky curves for
the crystallised oxide; meanwhile, the Mott–Shottky curve for the hydrated gel was nonlinear. 相似文献
9.
I.A. Veselovskii H.K. Cha D.H. Kim S.C. Choi J.M. Lee 《Applied physics. B, Lasers and optics》2001,73(7):739-744
A combined elastic–Raman lidar system based on a tripled Nd:YAG laser is used for the separate detection of elastic backscatter
and Raman signals from atmospheric nitrogen, water vapor and liquid water and for their depolarization measurement. Vertical
profiles of water-vapor and liquid-water content measured under clear-sky conditions behave differently: inside the boundary
layer the ratio of liquid-water to water-vapor Raman backscatters rises with altitude. The depolarization measurements bring
additional information about atmospheric scattering. The observed depolarization ratio of the water-vapor Raman signal is
about 14%, while for liquid water this ratio varies in the 30–75% range, which exceeds the depolarization of bulk water and
is attributed to the water-aerosol effects. Raman contours of water vapor and liquid water are partially overlapped, and bleed-through
of liquid-water Raman backscatter leads to enhancement of depolarization of the water-vapor Raman signal. This parameter may
be used as a convenient indicator of liquid-water interference in water-vapor measurements.
Received: 12 December 2000 / Revised version: 27 September 2001 / Published online: 7 November 2001 相似文献
10.
Zinc oxide nanothin films were prepared on glass substrate by sol–gel dip-coating method using zinc acetate dihydrate, methanol,
and monoethanolamine as precursor, solvent, and stabilizer, respectively. The relationship between drying conditions and the
characteristics of ZnO nanocrystalline films (c-axis orientation, grain size, roughness and optical properties) was studied. The films were dried in an oven at different
temperatures and by IR radiation. Then, the films were annealed at 500°C in a furnace. The chemical composition, transmission
spectra, structure, and morphology of the samples were studied using infrared (IR) and UV–visible spectroscopy, X-ray diffraction
(XRD), and atomic force microscopy (AFM), respectively. The XRD results show that the drying conditions affect the orientation
of crystallization along the (0 0 2) plane. AFM images show that the thicknesses of the films decrease from 128 to 93 nm by
changing the drying conditions. The photoluminescence (PL) of ZnO nanothin films shows the UV emission at near band edge and
broad green radiation at about 465 nm wavelength. 相似文献
11.
A. V. Radaev N. R. Batrakov A. A. Muhamadiev A. N. Sabirzyanov 《Russian Journal of Physical Chemistry B, Focus on Physics》2009,3(8):1134-1139
An experimental setup was constructed that makes it possible to study oil displacement over wide pressure (up to 20 MPa) and
temperature (up to 373 K) ranges under conditions reproducing the thermobaric, geological, and physicochemical conditions
in real oil beds, as well as the parameters of displacing agents. Experiments on the displacement of kerosene from a model
oil bed with supercritical carbon dioxide at temperatures of 313–353 K and pressures within 7–12 MPa were performed. The results
are indicative of a high efficiency of recovery of low-viscosity oils with supercritical carbon dioxide. 相似文献
12.
A. A. Zhokhov V. M. Masalov D. V. Matveev M. Yu. Maksimuk I. I. Zver’kova S. S. Khasanov S. Z. Shmurak A. P. Kiselev A. V. Bazhenov G. A. Emel’chenko 《Physics of the Solid State》2009,51(8):1723-1729
The method for carbothermal reduction of spherical particles of amorphous silicon dioxide is developed, and hexagonal α-SiC polytype nanocrystals are synthesized. The prepared samples are characterized by X-ray diffraction, Raman spectroscopy, photoluminescence spectroscopy, and electron microscopy. The silicon carbide nanocrystals prepared have sizes in the range 5–50 nm depending on the diameter of initial silicon dioxide particles. A detailed analysis of the positions of the lines in the Raman spectra, their broadening, and shift makes it possible to reliably establish that the samples under investigation predominantly contain the 6H and 4H silicon carbide polytypes and insignificant amounts of the 2H and 3C phases. The 15R and 21R polytypes in the samples are absent. It is noted that the samples are characterized by a substantial size effect: the luminescence intensity of small silicon carbide nanocrystals is more than three times higher than that of large SiC nanocrystals. 相似文献
13.
Z.Y. Chen J.P. Zhao T. Yano T. Ooie 《Applied Physics A: Materials Science & Processing》2002,75(2):213-216
Raman characteristics of carbon nitride films synthesized by nitrogen-ion-beam-assisted pulsed laser deposition were investigated.
In addition to the D (disorder) band and G (graphitic) band commonly observed in carbon nitride films, two Raman bands located
at 1080–1100 and 1465–1480 cm-1 were found from our carbon nitride films. These two bands were well matched with the predicted Raman frequencies for βC3N4 and the observed Raman bands reported for carbon nitride films, indicating their relation to carbon-nitrogen stretching vibrations.
Furthermore, the relative intensity ratio of the two Raman bands to the D and G bands increased linearly with increasing nitrogen
content of the carbon nitride films.
Received: 30 October 2000 / Accepted: 5 February 2001 / Published online: 2 October 2001 相似文献
14.
Ceramics powder of BaCe0.95Yb0.05O2.975 was successfully prepared by sol–gel method. Thermogravimetric analysis showed that the decomposition of the dried powder
was completed at 1,000 °C. Three strongly exothermic peaks observed in differential thermogravimetric signal indicated three
major stages of weight loss in the sample. The high crystallinity of sample with orthorhombic structure was confirmed by X-ray
diffraction. The loose particles size obtained from scanning electron microscope was in the range of 65–100 nm, which is almost
in the same range as that observed in particle size distribution. The sample showed a dc conductivity of ~1.3 × 10−4 S cm−1 at 650 °C and the activation energy, E
a, was found to be 1.4 eV. Result of chemical stability test showed that the compound was unstable in atmosphere containing
pure carbon dioxide. 相似文献
15.
Marco Castriota Nathalie Epervrier Tiziana Barone Giuseppe De Santo Enzo Cazzanelli 《Ionics》2007,13(4):205-211
In this work, the mechanism of the “gelation” process and the thermal-induced structural modifications of thin film of vanadium
pentoxide xerogels deposited on indium tin oxide (ITO)-coated glasses have been studied. Vanadium pentoxide xerogel has been
prepared by using the sol–gel proton exchange resin route without any resin pretreatment. To monitor the effect of the “resin
efficiency” on the gelation process, the solution coming out from the resin has been collected in a sequence of different
containers (vials), separately investigated by Raman spectroscopy. After the spin coating deposition, the thin films of vanadium
pentoxide gel have been subjected to different annealing treatments. The highest thermal treatment (600 °C) induces a complete
transformation of the gel phase into an anhydrous polycrystalline phase of a sodium-containing vanadate, different from the
usual V2O5 crystal. It is due to the diffusion of foreign ions (mainly sodium) coming from the substrate into the vanadium oxide layer. 相似文献
16.
The broadening and shift of the Q bands of the 1388/1285-cm−1 Fermi doublet of carbon dioxide have been measured by means of the spectroscopy of coherent anti-Stokes Raman scattering
in a wide density range realized at compression in dense gaseous and liquid states. The spectrum of the low-frequency Q band exhibits an essential narrowing upon the compression of the liquid in the density range of 320–400 amagat from a maximum
width of about 2.2 cm−1 to about 1.7 cm−1 determined by elastic dephasing. The observed dependence is connected with the progressive narrowing of the spectral contribution
attributed to the collapsed rotational structure. 相似文献
17.
M.J. Šćepanović M. Grujić-Brojčin Z.D. Dohčević-Mitrović Z.V. Popović 《Applied Physics A: Materials Science & Processing》2007,86(3):365-371
Nanosized titanium dioxide (TiO2) powder was prepared by a laser-induced pyrolysis. Specific surface area of the as-grown powder measured by BET method was
109 m2/g. The grain size (14.5 nm) estimated from these data coincides well with the crystallite size (12.3 nm) determined by XRD
measurements. The average grain size (∼35 nm) obtained from the subsequent SEM measurements refers to considerable agglomeration
of nanoparticles. Raman spectroscopy has been used to investigate the structural properties of TiO2 nanopowder and its anatase structure is confirmed. The blueshift and broadening of the lowest frequency Eg Raman mode at temperature range ∼25–550 K have been analyzed using a phonon-confinement model. Dominant influence of the
strong anharmonic effect at higher temperatures was demonstrated.
PACS 81.07.Wx; 78.30.-j; 63.22.+m 相似文献
18.
The Raman interaction of optical fields with a Bose condensate is studied in the adiabatic regime. A superposition of operators
is found — one annihilating an atom in a metastable state and the other annihilating a photon in resonance with a transition
from the ground state to an excited state — which is an adiabatic invariant of the problem (Raman polariton). Possible applications
for Bose-condensate diagnostics and development of atomic lasers are proposed.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 473–477 (10 October 1996) 相似文献
19.
N. N. Brandt N. L. Rebrikova A. Yu. Chikishev 《Moscow University Physics Bulletin》2009,64(6):600-604
The method of Raman spectroscopy is employed in the analysis of lead-containing pigments in ancient Russian painting, transformed
pigments, chalk, and drying oil. The Raman spectra of white lead and the mixture of yellow lead oxide, red lead, and lead
dioxide are measured, and the test Raman measurements of various fragments of the paint layer of the 18th-century Russian
icon Evangelist Mark from the Kirillo-Belozerski State Historical Architectural Art Museum-Reserve are performed. The destructive
action of laser radiation on various pigments is evaluated when measuring their Raman spectra. 相似文献
20.
Solid–liquid–solid (SLS) combined with Vapor-liquid–solid (VLS) growth mechanism has been used for synthesizing Core-clad
silicon nanowires (SiNWs) by thermal annealing onto two different catalyst substrates (Au/Si and Ni/Ti/Si). It provides a
novel method to synthesize SiNWs which is cost-effective, large-area-compatible and may give a higher degree of control of
the end product, facilitated by the simple experimental process for further device applications. The first-order Raman peaks
of the SiNWs were found to shift and to broaden asymmetrically in comparison to the c-Si Raman peak. Using a phonon confinement
model, the average diameter of the wires can be estimated from the Raman spectra but are consistently lower than the diameters
measured using high-resolution transmission electron microscopy. We interpret this as due to the confining contribution of
the oxide clad. Due to the simplicity of the method, it could be adapted in industry for large scale synthesis of SiNWs with
oxide clad for device fabrication, e.g., surround-gate field effect transistors. 相似文献