Search

In the present paper, (ZnO)–(Co3O4) nanocomposite thin films have been prepared by using spray pyrolysis deposition on a glass substrate at 350∘C. After that, the as-obtained films have been characterized and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the double beam UV-visible (UV-vis) spectrophotometer. Furthermore, the Bruggeman model is used to predict the evolution of the optical dielectric constant (real and imaginary parts: [Formula: see text] and [Formula: see text] to compare them with those obtained from the experimental results. The XRD pattern reveals that the nanocomposite film has diffraction peaks 2[Formula: see text], 36.95∘ corresponding respectively to the (220), (311) planes of cubic Co3O4 and another about of 2[Formula: see text] corresponding to the (101) plane of Wurtzite ZnO. Using the Debye Scherrer formula, the crystallite size of (ZnO)[Formula: see text]–(Co3O[Formula: see text] nanocomposite is found about 32[Formula: see text]nm, while the obtained thickness of this nanocomposite is about 780[Formula: see text]nm using the DekTak Stylus profilometer. Besides, the morphology analysis shows that the nanocomposite sample is well covered without holes and/or cracks and it has uniform dense grains. The evaluation of the transmittance, reflectance, refraction index, extinction coefficient, real and imaginary parts of dielectric constant as function of wavelength illustrates that the optical response of nanocomposite thin film (ZnO)[Formula: see text]–(Co3O[Formula: see text] depends on the influence of two mediums of pure materials ZnO and Co3O4 and their interaction. In addition, the direct band gap vs incident photon energy obtained from the Tauc plot equation shows that this nanocomposite has three values of band gap energy which are [Formula: see text][Formula: see text]eV, [Formula: see text][Formula: see text]eV (correspond to pure Co3O4 film) and [Formula: see text][Formula: see text]eV (correspond to pure ZnO film). Besides, the application of the Bruggeman equation indicates that the influence of the values of volume concentration and optical dielectric constant of the ingredient nanomaterials (ZnO and Co3O[Formula: see text] is significant on the value of the effective dielectric constant of nanocomposite thin film. The specific result of this study is the similarity between the spectra obtained from the Bruggeman model and the measured one, which proves that the application of this model is useful for the prediction of the optical properties of the composite.

SnO2 including different concentrations of ZnO has synthesized using spray pyrolysis technique for preparing on glass substrate at 350 °C. Effect of ZnO ratio has been researched to study optical and structural properties of SnO2. X-ray diffraction scheme indicates the presence of different peaks that attribute to a mixture of rutile SnO2 and hexagonal ZnO. The crystallite size of SnO2 decreases as ZnO ratio increases. The synthesized nanocomposites are characterized via field emission-scanning electron microscopy. The reflectance and transmittance in the wavelength range, 200–2500 nm have been measured. The direct band gaps vary from 3.04 to 3.78 eV to show contrary concept to Ubach's energy. The refractive index and extinction coefficient display vibrations due to ZnO ratio effect. Dielectric constants of SnO2 are deduced effectively in terms of ZnO ratio using Maxwell-Garnett ‘s effective medium theory, they are compared with experimental spectra. The optical properties can be interpreted correctly with Maxwell-Garnett theory of small underestimation, indicating that adaptation of optical properties can take place by varying the volume fraction. Our results present good agreement with experimental data.

SnO2 thin films were deposited on glass substrates at 350 °C by spray pyrolysis technique for different deposition times (i.e. 4, 7, 10 and 13 min) from tin chloride (SnCl2, 2H2O). The X-ray diffraction analysis showed that all the synthesized films correspond to the tetragonal structure of SnO2. Depending on the deposition time, the estimated average crystallite size varied from 29 to 55 nm using Williamson-Hall analysis (36 to 65 nm using the Scherrer method). Atomic force microscopy analysis revealed homogenous surfaces with low values of roughness (9.9 to 27.7 nm). As measured by spectroscopic ellipsometry, the thickness of the films was ranging from 150 to 350 nm. The obtained SnO2 films displayed an average transmittance of 80% and a direct optical band gap ranging from 3.98 to 4.09 eV. The Hall-effect measurements revealed that all the films are conductive with values of conductivity varying from 32.3 up to 127 Ω−1. cm−1. From the obtained morphological, optical and electrical results, we conclude that spray pyrolysed tin oxide thin films are good candidates to be used in different fields, mainly in solar cell applications.

In the present paper, experimental investigations on structural, morphological, optical and electrical properties of Co3O4 thin film deposited by spray pyrolysis method are reported. Using the interplanar spacing of the XRD reflection and Scherrer formula, respectively, we observed that the obtained films identified crystallize in the cubic spinel structure with [Formula: see text] nm and [Formula: see text] nm. From the SEM picture, a dense grain in the morphology of Co3O4 is detected which has a uniform spherical shape. In addition, transmittance, absorbance, optical bandgap and extinction coefficient of the film versus incident photon energy were calculated. We found that Co3O4 film has a direct bandgap and direct forbidden transition varying from 1.69 eV to 2.85 eV and 1.62 eV to 1.88 eV, respectively. Further, the variation of (DC) electrical resistivity with temperature (from the room temperature of 27∘C to 350∘C) shows that the electrical resistivity was decreased with increasing temperature indicating a semiconducting transport behavior.

Recent developments concerning the meth- odology used to prepare composites of iPP and nanoclays are reported. Conventional (reactive melt mixing) and in situ preparations were performed, and the structural prop- erties exhibited by the composites are discussed. Results suggest that the nanoclay could exhibit partial and, maybe, total exfoliation within the composites. Adhe- sion between the polymeric matrix and the nanoclay layers is similar to that obtained after grafting. The ex- perimental procedure used and the analysis performed by means of the wide-angle X-ray scattering and differ- ential scanning calorimetry techniques permit to describe, at nanoscale level, the contribution of the nanoclay to the polymer composite system. The micro- hardness values of the iPP-clay composites depend on the clay content and on the preparation method, and linearly correlate, according to the additivity law, with the degree of crystallinity. V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2654-2662, 2010

Thin films of Bi2S3 were prepared by spray pyrolysis method. Optical constants, electrical and photoelectrical studies have been carried out on these films. The optical constants confirm that the Bi2S3 thin film has a direct band gap of 1.69 eV. The Hall Effect measurements indicate that the Bi2S3 thin films prepared by spray pyrolysis method are n-type in nature with a carrier concentration of 3.51 × 1017 cm− 3. An activated process with activation energy of 65 meV governs the conduction in these films. The photoconductivity measurement indicates the presence of continuously distributed localized gap states in this material.

Zn x Cd 1− x O thin films were prepared on glass substrates by spray pyrolysis technique. The precursor solutions were obtained by varying the concentration of Zn(NO 3 ) 2 ·6H 2 O and Cd(NO 3 ) 2 ·4H 2 O in bi-distilled water. The structural properties have been studied using X-ray diffraction spectra. All the structures include the basic compounds, i.e. ZnO and CdO. The orientation and the crystalline phases of the deposited films were specified. With the addition of Zn to the precursor solution, we can observe the preferential orientation of the CdO in the [2 0 0] direction. The electrical measurements were performed using method of four contacts. Thin films transmittances, in the 1.5–4.3 eV range, for different compositions have been measured and the optical gaps have been determined. The variations are explained considering the gaps of the two pure films. The influence of increased Cd concentration in the films on the structural, electrical and optical properties is investigated in this study.

Polycrystalline films of Bi2S3 compound have been prepared, at substrate temperature of 570 K, from Bismuth chloride (BiCl3) and Thiourea (CS (NH2)2) solutions. The structural characterisation has been carried out by the X-ray diffraction analysis (XRD). Study of optical properties shows that Bi2S3 compound has an allowed indirect transition at 1.43 eV energy. The photoelectrical parameters (diffusion length and lifetime) have been determined from the study of the photoconductivity.

Thin layers of bismuth trisulfide (Bi2S3) have been prepared for the first time by the spray pyrolysis method on glass substrates from bismuth chloride (BiCl3) and thiourea (CS(NH2)2) solutions with a concentration of 0.2 M. Films deposited on substrate at 570 K have a polycrystalline structure with crystallites size in the order of 120 A. X-Ray characterization by grazing angles diffraction (GAD) at 0.4 and 2° shows crystalline structures in surface and volume. Diffraction spectra of these films are indexed in the orthorhombic system. Studies of optical absorption in the energy range 1.5–4 eV indicate an optical gap of 1.66 eV. The Hall effect measurements indicate a carrier concentration of n=3.45×1017 cm−3.

The crosslinking of isotactic polypropylene (iPP) using crosslinking agents (CAs) based on a peroxide/sulfur/accelerator system is a very attractive new method that has been reported recently. The present work deals with the study of the dynamic rheological behavior of iPP during and after the crosslinking process. The influence of the CA concentration and the processing temperature T on the rheological behavior of the iPP was analyzed. The kinetics of the crosslinking reaction was established using the technique described by G. A. Harpell and D. H. Walrod. This reaction is found to be of order one. At T = 180 ºC, the crosslinking reaction was faster. By varying the crosslinking agent content, different crosslinking degrees of iPP, expressed by the corresponding gel content, are achieved. On the other hand, the modified polypropylene exhibits an unexpected viscosity shear rate pattern, which describes the reverse crosslinking reaction mainly occurring by the opening of the bridges of the new interpenetrating network (IPN) formed.

Thin films of Molybdenum oxide were prepared by spray pyrolysis technique on glass substrates, by using 0.1 M of molybdenum chloride (MoCl 5 ) dissolved in deionized water. Influence of substrate temperature on structural and optical properties is studied in the range from 200 to 300 °C. The prepared samples correspond to MoO 3 phase with orientation and crystallites size which are modified by deposition temperature, the films prepared at 200 °C are monoclinic and the films prepared in the range from 250 to 300 °C are polycrystalline with orthorhombic symmetry. The samples present transmission coefficient and optical gap which vary as function of substrate temperature. Gap energy is located between 3.14 and 3.34 eV depending on the substrate temperature.