共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
A series of single phase solid-solution K4Ce2Ta10−xNbxO30 (x = 0-10) photocatalysts were synthesized by conventional high temperature solid state reaction. Their UV-vis diffuse reflectance spectra showed their absorbance edges shifted to long wavelength zone consistently with the increase of the amount of Nb for substituting Ta in these compounds, and the onsets of absorbance edges ranging from about 540 nm to 690 nm, corresponding to bandgap energy of 1.8-2.3 eV. These series of photocatalysts possess appropriate band gap (ca. 1.8-2.3 eV) and chemical level to use solar energy to decompose water into H2, and the photocatalytical activities under visible light (λ > 420 nm) demonstrated that the activities decreased correspondingly with the increase of the amount of Nb in these compounds, which is regarded as the result of the differences of their band structures. Furthermore, the photocatalytical activities and the photophysical properties of these visible light-driven photocatalysts K4Ce2Ta10−xNbxO30 (x = 0-10) were bridged by the first principle calculation based on Density Functional Theory with General Gradient Approximation and Plane-wave Pseudopotential methods. 相似文献
3.
Ar+ assisted carbidization of Mo nanoparticles supported on TiO2 (1 1 0) is studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In order to activate the diffusion of carbon into the bulk of Mo nanoparticles we applied Ar ions (1 keV) during the exposure of C2H4. XPS exhibited that the decomposition of C2H4 at 850 K accompanied by ion bombardment results in an almost complete carbidization of nanocrystalline Mo while this treatment performed without ion bombardment results only in the carbidization of the particle surface. The modification of the crystallinity of the Mo-carbide particles was deduced from STM measurements. 相似文献
4.
The formation of PdZnx alloy on Pd(1 0 0) and its characteristics were investigated by various methods, such as photoelectron, auger-electron, electron energy loss, thermal desorption spectroscopic methods and work-function measurement. The alloy was produced by the decomposition of diethyl zinc on Pd(1 0 0). The alloy surface reacts with O2 and ZnOx is formed. The reactivity of alloy to hydrogen is similar to that of K/Pd. The stability of adsorbed CO is lower than on clean Pd(1 0 0). 相似文献
5.
S. Veli?kovi? V. Djordjevi? J. Cveti?anin J. Djustebek M. Veljkovi? O. Neškovi? 《Vacuum》2008,83(2):378-380
Ionization energies of non-stoichiometric LinFn−1 (n = 3, 4, 6) clusters determined by a thermal ionization mass spectrometry (TIMS) were 4.2 ± 0.2 eV for Li3F2, 4.3 ± 0.2 eV for Li4F3 and 4.1 ± 0.2 eV for Li6F5. The ionization energy of Li6F5 cluster was obtained experimentally for the first time. The ionization energies of Li3F2 and Li4F3 are in correlation with the results obtained by photoionization time-of-flight mass spectrometry. The determined ionization energies are comparable with theoretical ionization energies calculated by ab initio method. The theoretical predictions supported that the most stable isomers of a non-stoichiometric cluster LinFn−1 (n = 3 and n = 4) in which the excess electron localizes on a specific site have a “segregated” electronic structure composed of the metallic part and ionic part. 相似文献
6.
An installation containing a DC negative corona discharge reactor, a pulse corona discharge reactor and a combined electron beam and microwave induced plasma reactor is presented. SO2 is removed up to 42% through spontaneous reaction with ammonia without electron beam or microwave irradiation at the temperature below 70 °C. For the same removal efficiency of 98% for SO2 and 80% for NOx at separate EB irradiation of 40 kGy, the required absorbed dose is about two times smaller for simultaneous electron beam and microwave irradiation. The SO2 removal efficiency of simultaneous DC or positive discharge and microwave discharge is higher than separate DC, pulse and MW discharge. Also, the applied voltage level at which the removal efficiency reaches the maximum value is less than for the separate application of DC or pulse discharge. The NOx removal efficiency of DC or pulse discharge suffers little change by additional use of the microwave energy. 相似文献
7.
Itzik Shturman 《Thin solid films》2009,517(8):2767-2774
The effects of LaNiO3 (LNO) and Pt electrodes on the properties of Pb(Zrx,Ti1 − x)O3 (PZT) films were compared. Both LNO and PZT were prepared by chemical solution deposition (CSD) methods. Specifically, the microstructure of LNO and its influence on the PZT properties were studied as a function of PbO excess. Conditions to minimize the Pyrochlore phase and porosity were found. Remnant polarization, coercive field and fatigue limit were improved in the PZT/LNO films relative to the PZT/Pt films. Additionally, the PZT crystallization temperature over LNO was 500 °C, about ~ 50 °C lower than over Pt. The crystallization temperature reported here is amongst the lowest values for CSD-based PZT films. 相似文献
8.
Hejuan Song Liqun Zhou Ling Li Ting WangFei Hong Xinru Luo 《Materials Science and Engineering: B》2013,178(16):1012-1018
In this paper, the YPO4:Eu3+ (5%) microflakes and YPO4·0.8H2O:Eu3+ (5%) microbundles have been synthesized by a simple EDTA-assisted hydrothermal method. The X-ray powder diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that the composition of the product could be changed from YPO4:Eu3+ (5%) to YPO4·0.8H2O:Eu3+ (5%) with a further increase in the amount of EDTA 0.5–1.0 g. The YPO4:Eu3+ (5%) presented the pure tetragonal phase and flake-like microstructure, while the YPO4·0.8H2O:Eu3+ (5%) exhibited the hexagonal phase and bundle-like morphology. The possible formation mechanisms of the two architectures were put forward on the basis of different EDTA amount-morphology experiments. A detailed investigation on the photoluminescence of YPO4·nH2O:Eu3+ (5%) different samples indicated that the luminescent properties of products were strongly dependent on the compositions, morphologies, coordination environment and crystal field symmetry. 相似文献
9.
Seung-Hyun Cho 《Materials Letters》2007,61(1):256-258
Powders of a Pb(Zn1 / 2W1 / 2)O3-introduced BaTiO3-PbTiO3 system were prepared. A two-step calcination route of a B-site precursor method was employed to promote perovskite formation. The overall effects of the Pb(Zn1 / 2W1 / 2)O3 incorporation on changes in crystalline aspects as well as dielectric properties were explored. 相似文献
10.
11.
R. Knizikevi?ius 《Vacuum》2009,83(6):953-189
Chemical etching of Si and SiO2 in SF6 + O2 plasma is considered. The concentrations of plasma components are calculated using values extrapolated from experimental data. Resulting calculations of plasma components are used for the calculation of Si and SiO2 etching rates. It is found that the reaction constants for reactions of F atoms with Si atoms and SiO2 molecules are equal to (3.5 ± 0.1) × 10−2 and (3.0 ± 0.1) × 10−4, respectively. The influence of O2 addition to SF6 plasma on the etching rate of Si is quantified. 相似文献
12.
Coatings of SiO2-TiO2 films are frequently used in a number of optical thin film applications. In this work we present results from depositing films with variable Si/Ti ratios prepared by reactive sputtering. The different Si/Ti ratios were obtained by varying the target composition of composite single targets. Compared to co-sputtering this facilitates process control and composition uniformity of the films. Varying the oxygen supply during sputter deposition can result in films ranging from metallic/substoichiometric to stoichiometric oxides. Transmittance spectra of the different films are presented and the optical constants are determined from these spectra. Furthermore, the deposition process, films structure and composition of the films are discussed. The study shows that by choosing the right composition and working in the proper oxygen flow range, it is possible to tune the refractive index. 相似文献
13.
The Gd2(TixZr1 − x)2O7 (x = 0, 0.25, 0.50, 0.75, 1.00) ceramics were synthesized by solid state reaction at 1650 °C for 10 h in air. The relative density and structure of Gd2(TixZr1 − x)2O7 were analyzed by the Archimedes method and X-ray diffraction. The thermal diffusivity of Gd2(TixZr1 − x)2O7 from room temperature to 1400 °C was measured by a laser-flash method. The Gd2Zr2O7 has a defect fluorite-type structure; however, Gd2(TixZr1 − x)2O7 (0.25 ≤ x ≤ 1.00) compositions exhibit an ordered pyrochlore-type structure. Gd2Zr2O7 and Gd2Ti2O7 are infinitely soluable. The thermal conductivity of Gd2(TixZr1 − x)2O7 increases with increasing Ti content under identical temperature conditions. The thermal conductivity of Gd2(TixZr1 − x)2O7 first decreases gradually with the increase of temperature below 1000 °C and then increases slightly above 1000 °C. The thermal conductivity of Gd2(TixZr1 − x)2O7 is within the range of 1.33 to 2.86 W m− 1 K− 1 from room temperature to 1400 °C. 相似文献
14.
TiO2/SiOx/TiOx multi-layers on quartz glass were prepared by electron-beam evaporation method and their structural and photocatalytic properties were investigated. The photocatalytic activity of the TiO2/SiOx/TiOx multi-layer was evaluated by the photodecomposition of methylene blue in aqueous solution. As the thickness of the SiOx inter-layer increased, the surface roughness of the TiO2/SiOx/TiOx multi-layer increased but the anatase crystallite size decreased. The TiO2/SiOx(80 nm)/TiOx multi-layer exhibited excellent photocatalytic activity resulting from higher surface roughness and more trap levels in the SiOx(80 nm) inter-layer. 相似文献
15.
Thermoelectric solid solutions of Bi2 (Te1−xSex)3 with x = 0, 0.2, 0.4, 0.6, 0.8 and 1 were grown using the Bridgman technique. Thin films of these materials of different compositions were prepared by conventional thermal evaporation of the prepared bulk materials. The temperature dependence of the electrical conductivity σ, free carriers concentration n, mobility μH, and seebeck coefficient S, of the as-deposited and films annealed at different temperatures, have been studied at temperature ranging from 300 to 500 K. The temperature dependence of σ revealed an intrinsic conduction mechanism above 400 K, while for temperatures less than 400 K an extrinsic conduction is dominant.The activation energy, ΔE, and the energy gap, Eg, were found to increase with increasing Se content. The variation of S with temperature revealed that the samples with different compositions x are degenerate semiconductors with n-type conduction. Both, the annealing and composition effects on Hall constant, RH, density of electron carriers, n, Hall mobility, μH, and the effective mass, m∗/m0 are studied in the above temperature range. 相似文献
16.
The influence of plasma heating of the Si and glass wafer substrates on silicon dioxide (SiO2) deposition rates by a tetraethylorthosilicate/O2 supermagnetron (high-density) plasma CVD were investigated. With a fixed RF power of 100 W supplied to both upper and lower electrodes, the SiO2 deposition rate on the Si wafer substrate decreased with increasing wafer-stage temperature, showing a negative activation energy for the deposition rate. When Si and glass wafers were attached to the electrode using adherent thermal conductors, the film thickness increased almost linearly with regard to the deposition time, and both deposition rates became almost the same (about 310 Å/min). When both wafers were simply laid on the electrode without an adhesive bond and hence with poor thermal contact, the film thickness increased nonlinearly with deposition time, showing a gradual decrease in deposition rate with time, being as low as 80 and 150 Å/min, respectively for Si and glass wafers, for a deposition time of 15 min. The difference between the two deposition rates on Si and glass wafers in the case of poor thermal contact to the lower electrode is thought to be caused by plasma heating and related mainly to differences in optical absorption characteristics of the two wafer substrates. Variations in measured thickness distributions across the substrate surface were attributed to an antisymmetric plasma density distribution in the direction perpendicular to the magnetic field lines caused by E×B electron drift. 相似文献
17.
B. RekikM. Derbal L. GuerbousD. Ouadjaout A. NehariE. Romeo A. BrenierA. Yoshikawa K. Lebbou 《Optical Materials》2011,33(11):1638-1642
We have determined the single phase domain of LiGd1−xYbx(WO4)2. The lattices parameters decrease as a function of Yb3+ substitution in Gd3+ sites. Transparent LiGd1−xYbx(WO4)2 fibers single crystals were successfully grown by the micro-pulling down technique (μ-PD). The Yb3+-doped LiGd(WO4)2 fibers single crystals have been pulled under stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to 120 μm. The fibers diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Fibers single crystals free of defects are observed for Ytterbium concentration in the melt up to 5 at%. Above this limit, inclusions and cracks appear and the optical quality of the fibers were deteriorated. The emission spectra of Yb3+-doped LiGd(WO4)2 were investigated. 相似文献
18.
High quality Tl2Ba2CaCu2O8 (Tl-2212) superconducting thin films are prepared on both sides of 2 in. LaAlO3(0 0 1) substrates by off-axis magnetron sputtering and post-annealing process. XRD measurements show that these films possess pure Tl-2212 phase with C-axis perpendicular to the substrate surface. The thickness unhomogeneity of the whole film on the 2 in. wafer is less than 5%. The superconducting transition temperatures Tcs of the films are around 105 K. At zero applied magnetic field, the critical current densities Jcs of the films on both sides of the wafer were measured to be above 2 × 106 A/cm2 at 77 K. The microwave surface resistance Rs of film was as low as 350 μΩ at 10 GHz and 77 K. In order to test the suitability of Tl-2212 thin films for passive microwave devices, 3-pole bandpass filters have been fabricated from double-sided Tl-2212 films on LaAlO3 substrates. 相似文献
19.
NiSix films were deposited using chemical vapor deposition (CVD) with a Ni(PF3)4 and Si3H8/H2 gas system. The step coverage quality of deposited NiSix was investigated using a horizontal type of hot-wall low pressure CVD reactor, which maintained a constant temperature throughout the deposition area. The step coverage quality improved as a function of the position of the gas flow direction, where PF3 gas from decomposition of Ni(PF3)4 increased. By injecting PF3 gas into the Ni(PF3)4 and Si3H8/H2 gas system, the step coverage quality markedly improved. This improvement in step coverage quality naturally occurred when PF3 gas was present, indicating a strong relationship. The Si/Ni deposit ratio at 250 °C is larger than at 180 °C. It caused a decreasing relative deposition rate of Ni to Si. PF3 molecules appear to be adsorbed on the surface of the deposited film and interfere with faster deposition of active Ni deposition species. 相似文献
20.
The Cu4SO4(OH)6 was synthesized by a simple hydrothermal reaction with a yield of ~ 90%. Using Cu4SO4(OH)6 as the starting material, novel fishbone-like Cu(OH)2 was produced by a direct reaction of Cu4SO4(OH)6 with NaOH solution. The Cu(OH)2 consists of many needle-like nanorods parallel to each other and perpendicular to the direction of backbone, forming fishbone-like structure. Using the fishbone-like Cu(OH)2 as the sacrificial precursor, CuO with similar size and morphology was obtained through a simple heat treatment. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-Vis absorption spectroscopy were employed to characterize the as-prepared samples. The conversion of the Cu4SO4(OH)6 to the fishbone-like Cu(OH)2 was visualized by time-dependent SEM images. A mechanism was also proposed based on the observed results. 相似文献