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1.
Mixed Fe–Mo oxides are used in industrial catalytic processes of selective oxidation of methanol to formaldehyde. For better understanding of the structure-reactivity relationships of these catalysts we aim to prepare well-ordered iron–molybdate thin films as model catalysts. Here we have studied Mo deposition onto Fe 3O 4 (111) thin films produced on Pt(111) as a function of Mo coverage and annealing temperature using LEED, AES, STM and IRAS. At low temperatures, the iron oxide film is covered by Mo = O terminated molybdena nanoparticles. Upon oxidation at elevated temperatures (T > 900 K), Mo species migrate into the film and form new bonds with oxygen in the film. The resulting films maintain the crystal structure of Fe 3O 4, and the surface undergoes a (√3 × √3)R30° reconstruction. The structure is rationalized in terms of Fe substitution by Mo in the surface layers. 相似文献
2.
We report on optical and structural properties of α-Fe 2O 3 and Co 3O 4 thin films, grown by direct oxidation of pure metal films deposited on soda-lime glass. Structural characteristics and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning electron microscopy. Linear optical absorption, and linear refraction as well as nonlinear optical properties were investigated. The third-order optical susceptibilities were measured applying the Thermally managed Z- scan technique using a Ti: sapphire laser (150 fs; 800 nm). The results obtained for the Co 3O 4 film were \( \text{Re} \chi^{\left( 3 \right)} \) = ?(5.7 ± 2.4) ×10 ?9 esu and \( \text{Im} \chi^{(3)} \) = ?(1.8 ± 0.2) ×10 ?8 esu while for the α-Fe 2O 3 film we determined \( \text{Re} \chi^{(3)} \) = +(6.6 ± 2.4) ×10 ?10 esu and \( \text{Im} \chi^{(3)} \) = +(2.2 ± 0.4) ×10 ?10 esu. 相似文献
3.
The electroplating of Zn–Ni–P thin film alloys from a sulfate bath containing phosphoric and phosphorous acid was investigated. The bath composition and the deposition parameters were optimized through Hull cell experiments, and the optimum experimental conditions were determined(p H = 2, temperature = 298–313 K, zinc sulfate concentration =30 g·L-1, EDTA concentration = 15 g·L-1, and current density = 1.0–2.0 A·dm-2). The SEM analysis of the coating deposited from the optimum bath revealed fine-grained deposits of the alloy in the presence of EDTA. Optical microscopy analysis indicated an electrodeposited thin film with uniform thickness and good adhesion to the steel substrate. The good adherence of the coatings was also demonstrated by the scratch tests that were performed, with a maximum determined value of 25 N for the critical load. Corrosion resistance tests revealed good protection of the steel substrate by the obtained Zn–Ni–P coatings, with values up to 85.89% for samples with Ni contents higher than 76%. The surface analysis of the thin film samples before and after corrosion was performed by X-ray photoelectron spectroscopy(XPS). 相似文献
4.
Nanostructured single phase strontium hexaferrite, SrFe 12O 19, thin films have been synthesized on the (100) silicon substrate using a spin coating sol–gel process. The thin films with various Fe/Sr molar ratios of 8–12 were calcined at different temperatures from 500 to 900 °C. The composition, microstructure and magnetic properties of the SrFe 12O 19 thin films were characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetry, X-ray diffraction, electron microscopy and vibrating sample magnetometer. The results showed that the optimum molar ratio for Fe/Sr was 10 at which the lowest calcination temperature to obtain the single phase strontium hexaferrite thin film was 800 °C. The magnetic measurements revealed that the sample with Fe/Sr molar ratio of 10, exhibited higher saturation magnetization (267.5 emu/cm 3) and coercivity (4290 Oe) in comparison with those synthesized under other Fe/Sr molar ratios. 相似文献
5.
Nano-sized and well dispersed manganese oxide and nickel–manganese oxide (Ni–Mn–O) powders are synthesized via the hydrothermal route. The addition of nickel ions significantly affects the morphology, particle size and the electrochemical properties of the obtained powders. Adding nickel ions results in a significant change in the shape of the powders from rod-like to plate-like. The electrochemical analysis of the electrode reveals that the specific capacitance of the synthesized powders is greatly increased with the addition of nickel ions. When the hydrothermal temperature is increased to 125 °C, the specific capacitance also increases to 284 F/g and decreases by about 4% after 1500 cycles of charge and recharge. Ni–Mn–O is considered to be a promising material for the electrodes used in electrochemical capacitors. 相似文献
6.
Pt–Bi films were synthesized on glass and thermally oxidized silicon substrates by e-beam evaporation and annealing. The structures were characterized using X-ray diffraction (XRD) and transmission electron microscopy/selected area electron diffraction (TEM/SAED) techniques. Single-phase PtBi was obtained at an annealing temperature of 300°C, whereas a higher annealing temperature of 400°C was required to obtain the highly textured γ-PtBi 2 phase. TEM/SAED analysis showed that the films annealed at 400°C contain a dominant γ-PtBi 2 phase with a small amount of β-PtBi 2 and α-PtBi 2 phases. Both the PtBi and γ-PtBi 2 phases are highly textured in these two kinds of film: the c-axis of the hexagonal PtBi phase is mostly in the film plane, whereas the c-axis of the trigonal γ-PtBi 2 phase is perpendicular to the film plane. The electrical resistivity of the film with the γ-PtBi 2 phase was smaller by one order of magnitude than that of the film with the PtBi phase. 相似文献
7.
Distinct thermal transitions have been observed in nanocomposites based on iron oxide–polypyrrole prepared by simultaneous gelation and polymerization process. The transition behaviour for various iron oxide–polypyrrole compositions was investigated with the help of differential scanning calorimetery. It has been observed that the samples show a magnetic to nonmagnetic transition at 410 °C. The presence of exothermic peak at 410 °C is a strong indication of magnetic transition corresponding to γ-Fe 2O 3 phase of iron oxide to a nonmagnetic α-Fe 2O 3 phase in these nanocomposites. However such a transition was not observed in nanocomposites containing lesser concentration of conducting polymer. 相似文献
8.
We have investigated the effect of zinc concentration ([Zn]/[Cu]=0–100 at%) on nanostructural, optical and electrical properties of CuS–ZnS binary thin films grown on glass substrate by the spray pyrolysis technique. X-ray diffraction analysis showed that the films were crystallized with mixed structures of CuS hexagonal and ZnS cubic structure. UV–vis optical measurements analysis showed that these binary films have a relatively high absorption coefficient (~10 5 cm ?1) in the visible spectrum with a direct band gap in the range of 2.57–2.45 eV in agreement with the corresponding room temperature PL spectra. The electrical studies showed that all these samples have a p-type conductivity and the free hole density decreases with increasing [Zn]/[Cu] molar ratio, in agreement with the reflectance spectra of the layers, originating from plasma oscillations. 相似文献
9.
Zinc oxide (ZnO) thin films and micro- and nanostructures are very promising candidates for novel applications in emerging
thin-film transistors, solar cells, sensors and optoelectronic devices. In this paper, a low-cost sol–gel spin coating technique
was used to fabricate ZnO films on glass substrates. The sol–gel fabrication process of the ZnO films is described. The influence
of precursor concentration on the material properties of the ZnO films was investigated. Atomic force microscopy and X-ray
diffractometry were employed to examine the structural properties of the ZnO films. The optical properties of the ZnO films
were characterized with ultraviolet–visible spectroscopy. The experimental results reveal that the precursor concentration
in the sol–gel spin coating process exerts a strong influence on the properties of the ZnO films. The effects of the precursor
concentration are discussed. 相似文献
10.
Iron phosphate (FePO 4) is a promising candidate for the cathode material in lithium-ion cells due to its easy synthesis and low cost. However, the intrinsic drawbacks of FePO 4 material (i.e., the low electronic conductivity and the low lithium-ion diffusion coefficient) result in poor capacity. To overcome the shortcomings, multi-wall carbon nanotubes (MWNTs) supported hydrated iron phosphate nanocomposites (FePO 4·2H 2O/MWNTs) are prepared using a novel homogeneous precipitation method. Meanwhile, the formation mechanism of highly dispersed and ultrafine FePO 4·2H 2O nanoparticles is discussed in detail. Electrochemical measurements show that FePO 4·2H 2O/MWNTs nanocomposites have a superior discharge capacity and stability. For example, FePO 4·2H 2O/MWNTs nanocomposites exhibit a high initial discharge capacity (129.9?mAhg ?1) and a stable capacity retention (114.3?mAhg ?1 after 20 cycles). The excellent electrochemical performance is attributed to the small particle size of FePO 4·2H 2O nanoparticles, the good electronic conductivity of MWNTs, and the three-dimensional conductive network structure of FePO 4·2H 2O/MWNTs nanocomposites. 相似文献
11.
The nonlinear thermo–magneto–mechanical magnetostrictive constitutive and the linear thermo–mechanical-electric piezoelectric constitutive are adopted in this paper. The bias magnetic field and ambient temperature are equivalent to a magnetic source and a thermo source, respectively. An equivalent circuit, which contains a magnetic source and a thermo source at the input, for the thermo–magneto–electric coupling effect in magnetoelectric(ME) laminates, is established. The theoretical models of the output voltage and static ME coefficient for ME laminates can be derived from this equivalent circuit model. The predicted static ME coefficient versus temperature curves are in excellent agreement with the experimental data available both qualitatively and quantitatively. It confirms the validity of the proposed model. Then the models are adopted to predict variations in the output voltages and ME coefficients in the laminates under different ambient temperatures, bias magnetic fields, and the volume ratios of magnetostrictive phases. This shows that the output voltage increases with both increasing temperature and increasing volume ratio of magnetostrictive phases; the ME coefficient decreases with increasing temperature; the ME coefficient shows an initial sharp increase and then decreases slowly with the increase in the bias magnetic field, and there is an optimum volume ratio of magnetostrictive phases that maximize the ME coefficient.This paper can not only provide a new idea for the study of the thermo–magneto–electric coupling characteristics of ME laminates, but also provide a theoretical basis for the design and application of ME laminates, operating under different sensors. 相似文献
12.
Monodisperse iron oxide nanocrystals have been produced following non-hydrolytic, thermal decomposition routes. Spherically shaped particles with diameter of 4 and 12 nm and cubic shaped particles with an edge length of 9 nm have been studied. The particles have been shown to consist of mainly maghemite. A reduction of the saturation magnetic hyperfine field is observed for the 4 nm particles as compared to the corresponding bulk value. The anisotropy energy determined from the temperature variation of the magnetic hyperfine field was strongly enhanced for the 4 nm particles. 相似文献
13.
The indium–tin oxide(ITO) film as the antireflection layer and front electrodes is of key importance to obtaining high efficiency Si heterojunction(HJ) solar cells. To obtain high transmittance and low resistivity ITO films by direct-current(DC) magnetron sputtering, we studied the impacts of the ITO film deposition conditions, such as the oxygen flow rate,pressure, and sputter power, on the electrical and optical properties of the ITO films. ITO films of resistivity of 4×10-4?·m and average transmittance of 89% in the wavelength range of 380–780 nm were obtained under the optimized conditions:oxygen flow rate of 0.1 sccm, pressure of 0.8 Pa, and sputtering power of 110 W. These ITO films were used to fabricate the single-side HJ solar cell without an intrinsic a-Si:H layer. However, the best HJ solar cell was fabricated with a lower sputtering power of 95 W, which had an efficiency of 11.47%, an open circuit voltage(V oc) of 0.626 V, a filling factor(FF) of 0.50, and a short circuit current density(J sc) of 36.4 m A/cm2. The decrease in the performance of the solar cell fabricated with high sputtering power of 110 W is attributed to the ion bombardment to the emitter. The V oc was improved to 0.673 V when a 5 nm thick intrinsic a-Si:H layer was inserted between the(p) a-Si:H and(n) c-Si layer. The higher V oc of 0.673 V for the single-side HJ solar cell implies the excellent c-Si surface passivation by a-Si:H. 相似文献
15.
The resistive switching effects in composite films containing polyfunctional polymers, such as derivatives of carbazole (PVK), fluorene (PFD), and polyvinyl chloride (PVC), and also graphene particles (Gr) and graphene oxide (GO), the concentration of which in the polymer matrices varied in the range from 1 to 3 wt % corresponding to the percolation threshold in such systems, have been studied. The analysis of the elemental composition of the investigated composites by means of X-ray photoelectron spectroscopy have shown that the oxidation degree of Gr in GO is about 9 to 10%. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK (PFD; PVC): Gr (GO)/ITO/PET structures, where ITO is indium tin oxide, and PET is poly(ethylene terephthalate), with the switching time, t, in the range from 1 to 30 μs. The observed effects are attributed to the influence of redox reactions taking place on the Gr and GO particles enclosed in the polymer matrix, and the additional influence of thermomechanical properties of the polymer constituent of the matrix. 相似文献
16.
Technical Physics - Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt %), and cuprite (2 wt %) have been obtained by laser evaporation of a solid target, which... 相似文献
17.
Stable composition of Iron Neodymium Boron nanoparticles are formed by a chemical method. Conventional borohydride reduction
method was used. The particles are in the size range of 30–100 nm. Silica coating was applied to stabilize and prepare the
particles for in vitro applications such as cell separation and diagnostics. Morphology of particles has been studied along with the structure and
magnetic properties. 相似文献
18.
Design of polymer anti-reflective (AR) optical coatings for plastic substrates is challenging because polymers exhibit a relatively narrow range of refractive indices. Here, we report synthesis of a four-layer AR stack using hybrid polymer:nanoparticle materials deposited by resonant infrared matrix-assisted pulsed laser evaporation. An Er:YAG laser ablated frozen solutions of a high-index composite containing TiO 2 nanoparticles and poly(methyl-methacrylate) ( PMMA), alternating with a layer of PMMA. The optimized AR coatings, with thicknesses calculated using commercial software, yielded a coating for polycarbonate with transmission over 97 %, scattering <3 %, and a reflection coefficient below 0.5 % across the visible range, with a much smaller number of layers than would be predicted by a standard thin film calculation. The TiO 2 nanoparticles contribute more to the enhanced refractive index of the high-index layers than can be accounted for by an effective medium model of the nanocomposite. 相似文献
19.
This paper deals with the formation of Cu 2ZnSnSe 4 (CZTS) in the process of selenization of metal precursor layers in elemental selenium vapour. Metallic precursors were sequentially evaported from Sn, Zn and Cu sources. Precursor Sn–Zn–Cu films have a “mesa-like” structure and consist mainly of Cu 5Zn 8 and Cu 6Sn 5 phases. It was confirmed that the formation of different binary copper selenides is the dominating process of selenization in elemental Se vapour at temperatures up to 300 °C. The formation of kesterite CZTS films begins at 300 °C and dominates at higher temperatures, always resulting in multiphase films that consist of high-quality Cu 2ZnSnSe 4 crystals and of a separate phase of ZnSe. 相似文献
20.
In this study, ultrasonic assisted synthesis of Pd-Ni/Fe 3O 4 core–shell nanoalloys is reported. Unique reaction condition was prepared by ultrasonic irradiation, releasing the stored energy in the collapsed bubbles and heats the bubble contents that leads to Pd(II) and Ni(II) reduction. Co-precipitation method was applied for the synthesis of Fe 3O 4 nanoparticles (NPs). Immobilized solution was produced by sonicating the aqueous mixture of Fe 3O 4 and mercaptosuccinic acid to obtain Pd-Ni alloys on Fe 3O 4 magnetic NP cores. The catalytic activity of the synthesized Pd-Ni/Fe 3O 4 core–shells was investigated in the Suzuki-Miyaura CC coupling reaction and 4-nitrophenol reduction, which exhibited a high catalytic activity in both reactions. These magnetic NPs can be separated from the reaction mixture by external magnetic field. This strategy is simple, economical and promising for industrial applications. 相似文献
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