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1.
Most of the applications of electrochromic devices (ECDs) concern the visible whereas there is a significant need for ECDs active in the infrared (IR) region. After optimization, WO3 thin films show significant variation in emissivity, as high as 78% and 49% in the MW (3-5 μm) band and LW (8-12 μm) band, respectively. The incorporation of the EC WO3 layer in ECDs is discussed in terms (i) of device configuration (i.e. position of the active layer on top or bottom of the device), (ii) of the choice of materials including the transparent conductive layer, electrolyte, counter electrode, and (iii) of the thickness of each layer. Initial trends in optical modulation of the ECDs are deduced from simulation of the optical indexes (n and k). Experimental data based on half-cell assembly confirm the modulation in emissivity in the IR region for WO3/Ta2O5/NiO-based devices with however lower values than the predicted ones. 相似文献
2.
Z.X. Cheng S.J. ZhangF. Song H.C. GuoJ.R. Han H.C. Chen 《Journal of Physics and Chemistry of Solids》2002,63(11):2011-2017
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. 相似文献
3.
A novel magnetically separable composite photocatalyst (N-doped titania-coated γ-Fe2O3 magnetic activated carbon) was prepared. It consists of N-doped titania, activated carbon and γ-Fe2O3. The whole processes were carried out under low temperature. The prepared sample was characterized by XRD, DRS, SEM, BET and vibrating sample magnetometer (VSM). The photocatalytic activity was determined by degradation of Reactive Brilliant Red X-3B in an aqueous solution under solar irradiation. Results showed that this as-prepared composite photocatalyst exhibited much higher photocatalytic activity than Degussa P25. Furthermore, the photocatalyst can be separated easily by an external magnetic field. Thus, the photocatalyst can be recycled without mass losing, and the degradation percent of X-3B decreased less than 2% after six cycles. 相似文献
4.
Zhen-guo An Jing-jie Zhang Shun-long Pan 《Journal of Physics and Chemistry of Solids》2009,70(7):1083-10223
Low-density (about 0.9 g/cm3) composite core-shell hollow microspheres with tunable magnetic properties were fabricated by Ni-Fe-P deposition on hollow glass microspheres (HGM) with modified electroless plating process. The effects of mole ratio of Fe2+/Ni2+, concentration of the reducer and pH value of the solution on the magnetic properties of the products were investigated. In conclusion, the increase in the mole ratio of Fe2+/Ni2+ and pH value of the solution could improve the soft magnetic properties of composite microspheres remarkably, while the increase in the concentration of NaH2PO2 had the opposite effect. The as-obtained metallic shells were amorphous and the crystallization got better with increased annealing temperature after plating. In addition, the saturation intensity of the composite microspheres was enhanced monotonically by increasing the annealing temperature. This work provided a facile and effective strategy to fabricate core-shell composite hollow microspheres with tailored magnetic properties. 相似文献
5.
Photoluminescence spectra, photoluminescence decay curves and Raman scattering spectra have been investigated for stoichiometric rare-earth molybdate and tungstate compounds. NaNd(MoO4)2 and NaNd(WO4)2 show emissions due to the transition 4F3/2→4I9/2 in Nd3+. A possibility of laser oscillation in NaNd(MoO4)2 is pointed from comparisons of the emission intensity and the decay time constant with NaNd(WO4)2 where laser oscillations have been reported. In NaLa(MoO4)2 and NaLa(WO4)2, observed emissions which are not related to La3+ are probably due to the transitions in MoO42- and WO42- molecular ions, respectively, in scheelite crystal. Raman spectra of these compounds are similar, probably related to the same crystal structure. LiEr(MoO4)2 shows the emissions due to transitions 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 in Er3+, respectively, which are believed to be observed for the first time. 相似文献
6.
Chemical oxidation of multiwalled carbon nanotubes (MWCNTs) using H2SO4/HNO3 solution has been monitored by micro-Raman spectroscopy and X-ray absorption spectroscopy. The diameter distribution variation in MWCNTs due to chemical oxidation has been measured by scanning electron microscopy and transmission electron microscopy. The Raman dispersion behaviors of the intensity ratio and the band positions of the D, G, and G′ bands were found to be correlated with the MWCNT diameter distribution. It was also found that, during the nanotube unzipping process, defect formation complicates the observation of the diameter-dependent Raman dispersion effect. The curvature effect plays an important role in the intensity ratio trend. On the other hand, defect formation dominates the band position trend. 相似文献
7.
El Sayed Yousef Amin El-Adawy E.R. Shaaban 《Journal of Physics and Chemistry of Solids》2006,67(8):1649-1655
The optical and acoustic properties of tellurite glasses in the system TeO2/ZrO2/WO3 have been investigated. The refractive index at different wavelengths and the optical spectra of the glasses have been measured. From the refractive index and absorption edge studies for prepared glasses, the optical parameter viz; optical band gap (Eopt), Urbach energy, (ΔE), dispersion energy, Ed, and the average oscillator energy, E0, have been calculated. Sound velocities were measured by pulse echo technique. From these velocities and densities values, various elastic moduli were calculated. The variations in the refractive index, optical energy gap and elastic moduli with WO3 content have been discussed in terms of the glass structure. Quantitatively, we used the bond compression model for analyzing the room temperature elastic moduli data. By calculating the number of bonds per unit volume, the average stretching force constant, and the average ring size we can extract valuable information about the structure of the present glasses. 相似文献
8.
Sumesh George 《Journal of Physics and Chemistry of Solids》2009,70(1):107-111
Ba4Sm9.33Ti18O54-Ag (BST-Ag) composites were prepared by a solid-state ceramic route and its dielectric properties were investigated in the vicinity of percolation threshold. The structure and microstructure of the composites were analyzed by X-ray diffraction along with optical and scanning electron microscopy observations. The effects of silver content and frequency on the dielectric properties of BST-Ag composites were studied using a LCR meter. The relative permittivity (εr) of the composite increases with silver content below the percolation limit and is in agreement with power law. A 0.14 volume fraction of silver loading increases the relative permittivity of the composite from 50 to 450 at 10 kHz. Addition of 0.15 volume fraction of silver increases the relative permittivity of the composite in the order of 105. It is found that the giant relative permittivity is almost constant for frequencies from 1 kHz to 1 MHz. This high εr composite offers the perspectives for application in electromechanical devices. 相似文献
9.
Modification of multi-walled carbon nanotubes for electric double-layer capacitors: Tube opening and surface functionalization 总被引:1,自引:0,他引:1
Multi-walled carbon nanotubes (MWCNTs) obtained opening the closed ends and using surface functionalization by means of a combination of partial oxidation in air and chemical modifications are characterized systematically in 0.3 M H2SO4 between 0 and 1.0 V, and these nanotubes were planned to be used as electrode materials in electric double-layer capacitors (EDLCs). Opening of MWCNTs, clearly observed by means of transmission electron microscopy (TEM), can be easily achieved by the partial oxidation in air through a seven-step temperature program identified by thermogravimetric/differential thermal analyses (TG/DTA). An increase in 175% specific capacitance is obtained for the MWCNTs, partially oxidized in air and chemically modified in H2SO4+HNO3. The temperature-programmed desorption (TPD) data showed that evolutions of CO and CO2 are, respectively, promoted by the application of partial oxidation in air and chemical modification in H2SO4+HNO3. The above increase in specific capacitance for modified MWCNTs is attributed to an obvious increase in the BET surface area (double-layer capacitance) and the density of oxygen-containing surface functional groups (pseudocapacitance). 相似文献
10.
Aqueous electrochemical insertion of M+ (Na+ and H+) species into WO3(4,4′-bipyridyl)0.5 has been carried out. The chemical states and structure of the resulting product were analysed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS showed the presence of W6+ as well as the usual reduced W species (W5+) which is responsible for a change in colour. Moreover, the presence of these intercalates correlates with the evolution of the reduced W species. The bulk structure of the layered hybrid, as determined by powder X-ray diffraction, showed no alteration after electrochemistry, in contrast to the same measurements on tungsten trioxide (WO3). This however concurs with single-crystal X-ray studies, which show little change in lattice parameters with Na+ insertion. Four-probe resistance measurements of the layered hybrid coated film display a drop in resistance after electrochemistry, which can be attributed to the injection of charge-carriers into the conduction band. 相似文献
11.
Rare earth doped NaLa(WO4)2 nanoparticles have been prepared by a simply hydrothermal synthesis procedure. The X-ray diffraction (XRD) pattern shows that the Eu3+-doped NaLa(WO4)2 nanoparticles with an average size of 10-30 nm can be obtained via hydrothermal treatment for different time at 180 °C. The luminescence intensity of Eu3+-doped NaLa(WO4)2 nanoparticles depended on the size of the nanoparticles. The bright upconversion luminescence of the 2 mol% Er3+ and 20 mol% Yb3+ codoped NaLa(WO4)2 nanoparticles under 980 nm excitation could also be observed. The Yb3+-Er3+ codoped NaLa(WO4)2 nanoparticles prepared by the hydrothermal treatment at 180 °C and then heated at 600 °C shows a 20 times stronger upconversion luminescence than those prepared by hydrothermal treatment at 180 °C or by hydrothermal treatment at 180 °C and then heated at 400 °C. 相似文献
12.
G.P. Pandey R.C. Agrawal S.A. Hashmi 《Journal of Physics and Chemistry of Solids》2011,72(12):1408-1413
Effect of micron-sized MgO particles dispersion on poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF–HFP) based magnesium-ion (Mg2+) conducting gel polymer electrolyte has been studied using various electrical and electrochemical techniques. The composite gel films are free-standing and flexible with enough mechanical strength. The optimized composition with 10 wt% MgO particles offers a maximum electrical conductivity of ∼6×10−3 S cm−1 at room temperature (∼25°C). The Mg2+ ion conduction in gel film is confirmed from cyclic voltammetry, impedance spectroscopy and transport number measurements. The applicability of the composite gel electrolyte to a rechargeable battery system has been examined by fabricating a prototype cell consisting of Mg (or Mg–MWCNT composite) and V2O5 as negative and positive electrodes, respectively. The rechargeability of the cell has been improved, when Mg metal was substituted by Mg–MWCNT composite as negative electrode. 相似文献
13.
14.
Na2O–PbO–Al2O3–B2O3 (NPAB) glasses mixed with different concentrations of WO3 (ranging from 0 to 2.5 mol%) are synthesized by conventional melt quenching method. The samples are characterized by X-ray diffraction (XRD), optical absorption, Electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopic techniques. Glass formation is confirmed by X-ray diffraction spectra. The optical absorption spectra of these glasses exhibited a predominant broad band peak at about 850–870 nm is identified due to dxy–dx2−y2 transition of W5+ ions. From the optical absorption spectral data, optical band gap (Eopt) and Urbach energy (ΔE) are evaluated. From EPR spectra the strength of the signal is increased and hyperfine splitting is resolved with increasing concentration of WO3 in the glass matrix. The FT-IR spectral studies have pointed out the existence of conventional BO3, BO4, B–O–B, PbO4, WO4 and WO6 structural units of these glasses. Various physical properties and optical basicity are also evaluated with respect to the concentration of WO3 ions. 相似文献
15.
The enthalpies of solution of pure silver halides AgCl and AgI and a composite material with molar composition 0.5 AgCl-0.5 AgI were measured at 298 K in a mixture of Na2S2O3 (1 M) and NH4OH (1 M). X-ray diffraction patterns showed that the composite material contained the metastable γ-AgI phase; different mechanisms for its stabilization were discussed. The phase transition enthalpies of AgI modifications and the enthalpy of formation of the composite material were deduced from the measurements. The latter could be related to a change of interfacial enthalpies. 相似文献
16.
Beata Zielińska Ewa Borowiak-Palen Ryszard J. Kalenczuk 《Journal of Physics and Chemistry of Solids》2011,72(2):117-123
Fe-, Ni-, Co- and Ag- loaded NaNbO3 catalysts were prepared and their activities have been investigated in the reaction of photocatalytic hydrogen generation. Me/NaNbO3 were synthesized by impregnation of NaNbO3 in an aqueous solution of metal nitrates and then by calcination at the temperature of 400 °C. The crystallographic phases and optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-Ray spectrometer (EDX) as its mode. The detailed analysis has revealed that all the investigated catalysts exhibit high crystallinity and the presence of Fe2O3, NiO, Co3O4 and Ag2O oxides on Me/NaNbO3 was confirmed. Finally, the influence of different metal loadings (Fe, Ni, Co and Ag) on the photocatalytic activity of NaNbO3 for photocatalytic hydrogen generation has been investigated. Here we report that among all the Me/NaNbO3 photocatalysts Ag-loaded NaNbO3 exhibited higher photocatalytic efficiency for photocatalytic hydrogen generation than NaNbO3. 相似文献
17.
We aim to develop high-level applications of NR through the innovative use of multi-walled carbon nanotubes (MWCNTs) to improve reinforcing performance and thermal resistance. In this study, we examined the structures and characteristics of composite materials in which NR was the matrix and MWCNTs were the fillers. We studied the properties of composites containing surface-activated MWCNTs with three different diameters. The results show that the reinforcing performance improves as MWCNT diameter decreases, while thermal resistance improves as we decrease the heat-treatment temperature. The latter occurs because adherence between MWCNTs and NR becomes stronger at lower heat-treatment temperatures. We also found that for practical applications, we need to control active sites on MWCNTs to balance adhesion against thermal resistance. 相似文献
18.
《Journal of Physics and Chemistry of Solids》2014,75(4):491-494
Two kinds of plate-like NaNbO3 were separately prepared by the one- and two-step molten salt processes via topochemical micro-crystal conversion methods. Meanwhile, the composite photocatalysts were obtained via heating the mixture of corresponding NaNbO3 powders and urea. Their photocatalytic activities were evaluated from the photodegradation of Rhodamine B under full arc and visible light irradiation of Xe lamp. The sample containing NaNbO3 prepared by the one-step molten salt process and carbon nitride displays the highest activity. The enhancement of photocatalytic activity was attributed to the surface properties and the state of the carbon nitride. 相似文献
19.
W.A. Pisarski J. Pisarska M. M?czka 《Journal of Physics and Chemistry of Solids》2006,67(12):2452-2457
New multicomponent lead borate based glasses with various PbO/B2O3 weight ratio were prepared. The glass samples were analyzed in detail by using Raman and IR absorption spectroscopy. Optical properties of Eu3+ ions have been investigated in lead borate based systems, in which PbO/B2O3 weight ratios were changed from 1:2 to 8:1 in glass composition. The values of the phonon energy of the host and 5D0 lifetime of Eu3+ decrease, whereas absorption and emission intensities, as well as bonding parameter increase with increasing PbO concentration. Additionally, spectral lines are shifted in direction to the lower frequency region. Non-monotonic dependence of the fluorescence intensity ratio R (5D0-7F2/5D0-7F1) upon PbO/B2O3 content has been observed in contrast to bonding parameter that is also non-linear but monotonic. Some structural and spectroscopic aspects for Eu-doped lead borate based glasses are presented. 相似文献
20.
R.A. Secco H. LiuN. Imanaka G. AdachiM.D. Rutter 《Journal of Physics and Chemistry of Solids》2002,63(3):425-431
Impedance spectroscopy measurements and synchrotron X-ray diffraction studies of Sc2(WO4)3 at 400°C have been carried out as a function of pressure up to 4.4 GPa. Ionic conductivity shows normal decrease with increase in pressure up to 2.9 GPa, but then increases at higher pressures. The XRD results show that Sc2(WO4)3 undergoes pressure-induced amorphization at pressures coincident with the reversal in conductivity behavior. The loss of crystal structure at high pressure is consistent with growing evidence of pressure-induced amorphization in negative thermal expansion materials, such as Sc2(WO4)3. The increase in conductivity in the amorphized state is interpreted as the result of an increase in structural entropy and a concomitant reduction of energy barriers for ionic transport. 相似文献