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1.
Cadmium selenide films have been synthesized by dip method. Cadmium selenide acts as photoanode in photoelectrochemical (PEC) cells. The photoanode was annealed upto 473 K. The cell configuration is n-CdSe∣NaOH (1 M) +S (1 M) +Na2S (1 M) ∣C(graphite). Various performance parameters were examined with respect to annealed temperature. It is found that the fill factor and efficiency are maximum for photoelectrode annealed at 473 K. This is due to low resistance, high flat-band potential, maximum open-circuit voltage as well as maximum short-circuit current. The barrier height was examined from the temperature dependence of the reverse saturation current. The lighted ideality factor was found to be minimum for photoelectrode annealed at 473 K. A cell utilizing annealed photoelectrode showed a wider spectral response. The utility of this work is in improving the efficiency of PEC cells.  相似文献   

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The bulk properties and relative stabilities of B–C structures are studied using both first-principles and molecular dynamics simulations that employ Tersoff potentials. The elastic properties of the B–C structures are deduced and some properties of random structures compared with possible crystalline counterparts.  相似文献   

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In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.  相似文献   

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《Composite Interfaces》2013,20(1):61-75
Macroscopically homogeneous and uniform coatings of polyaniline, polypyrrole and their blend were successfully deposited on carbon fibers by aqueous electropolymerization technique. Electrochemical polymerization of aniline and pyrrole blend with p-toluene sulfonic acid as the electrolyte was carried out by cyclic voltammetry in the potential range of -0.2 V to 1.0 V vs. SCE. The electrochemical polymerization parameters such as the molar feed ratio of monomers and number of cycles were systematically varied. Gravimetric analysis showed that the amount of blend coatings on carbon fibers was dependant on the electrochemical deposition parameters. As the pyrrole concentration in the feed increases, the deposition rate increases. Analysis of the blend coating on the carbon fibers by infrared spectrophotometry (IR) showed that both polyaniline and polypyrrole are present in the coating. The morphology of composite coating varied from smooth to rough and globular structure during deposition.  相似文献   

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High spin states in 107Ag are studied via the 100Mo(11B, 4n)107Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to 107Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg9/2 νh11/2(g7/2/d5/2).  相似文献   

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A survey is presented on recent investigations of the metal-to-insulator transition in two-dimensional systems with special emphasis on n-Si–MOS structures. Experimental facts are presented and the currently open questions on the nature of this transition are addressed.  相似文献   

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Intrinsic stresses of carbon films deposited by direct current (DC) magnetron sputtering were investigated. The bombardments of energetic particles during the growth of films were considered to be the main reason for compressive intrinsic stresses.The values of intrinsic stresses were determined by measuring the radius of curvature of substrates before and after film deposition.By varying argon pressure and target-substrate distance,energies of neutral carbon atoms impinging on the growing films were optimized to control the intrinsic stresses level.The stress evolution in carbon films as a function of film thickness was investigated and a void-related stress relief mechanism was proposed to interpret this evolution.  相似文献   

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《Physics letters. A》2002,296(6):259-264
A realization of various algebraic structures in terms of the Cλ-extended oscillator algebras is introduced. In particular, the Cλ-extended oscillator algebras realization of the Fairlie–Fletcher–Zachos (FFZ) algebra is given. This latter lead easily to the realization of the quantum Ut(sl(2)) algebra. The new deformed Virasoro algebra is also presented.  相似文献   

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The Andreev subgap conductance at 0.08–0.2 K in thin-film superconductor (aluminum)–insulator–normal metal (copper, hafnium, or aluminum with iron-sublayer-suppressed superconductivity) structures is studied. The measurements are performed in a magnetic field oriented either along the normal or in the plane of the structure. The dc current–voltage (I–U) characteristics of samples are described using a sum of the Andreev subgap current dominating in the absence of the field at bias voltages U < (0.2–0.4)Δc/e (where Δc is the energy gap of the superconductor) and the single-carrier tunneling current that predominates at large voltages. To within the measurement accuracy of 1–2%, the Andreev current corresponds to the formula \({I_n} + {I_s} = {K_n}\tanh \left( {{{eU} \mathord{\left/ {\vphantom {{eU} {2k{T_{eff}}}}} \right. \kern-\nulldelimiterspace} {2k{T_{eff}}}}} \right) + {K_s}{{\left( {{{eU} \mathord{\left/ {\vphantom {{eU} {{\Delta _c}}}} \right. \kern-\nulldelimiterspace} {{\Delta _c}}}} \right)} \mathord{\left/ {\vphantom {{\left( {{{eU} \mathord{\left/ {\vphantom {{eU} {{\Delta _c}}}} \right. \kern-\nulldelimiterspace} {{\Delta _c}}}} \right)} {\sqrt {1 - {{eU} \mathord{\left/ {\vphantom {{eU} {{\Delta _c}}}} \right. \kern-\nulldelimiterspace} {{\Delta _c}}}} }}} \right. \kern-\nulldelimiterspace} {\sqrt {1 - {{eU} \mathord{\left/ {\vphantom {{eU} {{\Delta _c}}}} \right. \kern-\nulldelimiterspace} {{\Delta _c}}}} }}\) following from a theory that takes into account mesoscopic phenomena with properly selected effective temperature T eff and the temperature- and fieldindependent parameters K n and K s (characterizing the diffusion of electrons in the normal metal and superconductor, respectively). The experimental value of K n agrees in order of magnitude with the theoretical prediction, while K s is several dozen times larger than the theoretical value. The values of T eff in the absence of the field for the structures with copper and hafnium are close to the sample temperature, while the value for aluminum with an iron sublayer is several times greater than this temperature. For the structure with copper at T = 0.08–0.1 K in the magnetic field B|| = 200–300 G oriented in the plane of the sample, the effective temperature T eff increases to 0.4 K, while that in the perpendicular (normal) field B ≈ 30 G increases to 0.17 K. In large fields, the Andreev conductance cannot be reliably recognized against the background of single- carrier tunneling current. In the structures with hafnium and in those with aluminum on an iron sublayer, the influence of the magnetic field is not observed.  相似文献   

13.
Boron-doped amorphous graphite-like carbon (GLC) films have been prepared with different boron concentrations. Electrical transport measurements in the temperature range 1.3–300?K on the films shows a doping-induced metal–insulator (MI) transition. On the metallic side of the transition, the experimental data are interpreted in terms of weak localization and the effect of electron–electron interactions. Data on the insulator side of transition are analyzed in terms of hopping conduction. Critical behaviour is observed near the transition, with the resistivity obeying a power-law temperature dependence.  相似文献   

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The bonding features and electronic structures of a series of transition metal carbon dioxide complexes have been studied by density functional theory (DFT) calculations combined with natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). NBO analysis shows that the interaction between the metal center and the carbon atom of the carbon dioxide ligand (M–C) is stronger than the other interaction between the metal center and the carbon dioxide ligand. Natural hybrid orbital (NHO) analysis gives the detailed bonding features of the M–C bond for each complex. The NBO charge distribution on the carbon dioxide unit in all studied complexes is negative, which indicates charge transfer from the metal center to the carbon dioxide ligand for all studied complexes. The hyperconjugation effect of the metal center and the two C–O bonds of the carbon dioxide ligand has been estimated using the NBO second-order perturbation stabilization energy. It was found that the NBO second-order stabilization energy of C–O?→?nM* is sensitive to the coordinated sphere and the metal center. Frontier molecular orbital (FMO) analysis shows that complexes 1 and 4 may be good nucleophilic reagents for activation of the carbon dioxide molecule. However, the EDAs show that the M–CO2 bond interaction energy of complex 4 is about two times as large as that of complex 1. The high M–CO2 bond interaction energy of complex 4 may limit its practical application.  相似文献   

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Anisotropic etching of hexagonal boron nitride (h-BN) and boron–carbon–nitrogen (BCN) basal plane can be an exciting platform to develop well-defined structures with interesting properties. Here, we developed an etching process of atomically thin h-BN and BCN layers to fabricate nanoribbons (NRs) and other distinct structures by annealing in H2 and Ar gas mixture. BCN and h-BN films are grown on Cu foil by chemical vapor deposition (CVD) using solid camphor and ammonia borane as carbon, nitrogen and boron source, respectively. Formation of micron size well-defined etched holes and NRs are obtained in both h-BN and BCN layers by the post growth annealing process. The etching process of h-BN and BCN basal plane to fabricate NRs and other structures with pronounced edges can open up new possibilities in 2D hybrid materials.  相似文献   

17.
The present paper investigates the tensile properties of post-irradiation annealed Cu–Ni alloy. The specimens were irradiated with a 15 MeV electron beam at room temperature and the post-irradiation annealing (PIA) of the specimens was carried out under vacuum at 450 °C for 15–120 min. The yield stress (YS), ultimate tensile stress (UTS), percentage elongation, stress relaxation rate and activation volume of both as-irradiated and post-irradiation annealed specimens were examined at room temperature using a universal testing machine. The results show that PIA of the specimen at 450 °C for 15 min decreases its YS and UTS, whereas the percentage elongation is increased. The changes in the tensile parameters become more pronounced with increases in annealing time. Effects of PIA on the stress relaxation rate and activation volume indicate that the relaxation rate of post-irradiation annealed specimens increases, and the activation volume decreases, with an increase in annealing time.  相似文献   

18.
Experiments on hybrid superconducting normal-metal structures have revealed that even in the absence of tunnel junctions the onset of superconductivity can lead to a decrease in the electrical conductance by an amount many orders of magnitude greater than e2 / h. In this paper, we provide a theory of this phenomenon which shows that it originates from an instability in the four-probe conductance which is absent from two-probe measurements. We compare the zero-bias, zero-temperature four-probe conductances GNand GSof a normal diffusive metal in contact with a superconductor in both the normal (N) and superconducting (S) states, respectively. In the absence of tunnel barriers, the ensemble average of the difference δG = GS  GNvanishes, in agreement with quasiclassical theory. However, we also predict that there exist macroscopic sample specific fluctuations in δG, which lie beyond quasiclassical theory and allow large negative values of δG to occur.  相似文献   

19.
Experimental data for reaction-diffusion-induced explosive crystallization in a nanodimensional metal (Cu, Ag)/selenium structure are presented. It is found that after the metal layer has completely diffused into the amorphous Se film, the electrical potential rises from 0.14 to 1.21 V in the Cu(30 nm)/Se(140 nm) heterolayer and from 0.01 to 1.17 V in the Ag(30 nm)/Se(140 nm) heterolayer. The metals diffusing into the amorphous Se layer interact with Se, forming nuclei of a new phase (CuSe or Ag2Se). The intense growth of the CuSe and Ag2Se crystallization centers results in a considerable liberation of latent energy in the form of phase transformation heat and in explosive growth of CuSe and Ag2Se nanocrystalline particles. The mean size of CuSe and Ag2Se crystallites equals 25 and 50 nm, respectively.  相似文献   

20.
Changes in the intensity of light transmitted through polyaniline films caused by an external voltage are used to control the photoluminescence spectrum of nanoporous silicon. A study of the optical-luminescence properties of hybrid porous silicon-polyaniline structures under the influence of an applied external potential shows that polyaniline films deposited on a porous silicon surface can serve as an optical filter for the photoluminescence of porous silicon with an electrically controlled transmission band.  相似文献   

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