Papers by Keyword: Ultrasonic Spray Pyrolysis

Abstract: Zinc oxide (ZnO) has attracted considerable attention because of its potential applications in optoelectronic devices. Many scientists have reported on the preparation of ZnO based photodetectors in metal-semiconductor-metal (MSM) structures where expensive noble metals are used as electrodes. Here, we propose the preparation of full metal-oxide photoconductors by using indium tin oxide (ITO) as the electrodes and ZnO thin films as sensing materials. ZnO thin films were prepared by employing a simple ultrasonic spray pyrolysis (USP) technique with a commercial ultrasonic nebulizer (1.7 MHz). In this work, we developed a high performance ZnO based photodetector on interdigitated ITO with a simple and low-cost USP method. The I-V characteristic shows that ZnO thin film works in a photoconductive mode and has better performance as a UV (325 nm) detector than other wavelengths (505, 625 and 810 nm). As a UV detector, the devices exhibit high sensitivity (1255.51%), high responsivity (22.6 x 10³ A/W), high detectivity (1.49 x 10¹⁴ Jones), good stability, a fast response time of 0.87 s and a relatively slow recovery time of 34.8 s. This high performance may be related to the large crystallite size that facilitates higher electron mobility.

Abstract: Zinc oxide Nanorods (ZnO-NRs) were deposited onto glass substrates using zinc chloride by Ultrasonic Spray Pyrolysis (USP) method. The films were prepared in different deposition time at optimum deposition parameters. The effect of deposition time on the structural, morphological and optical properties of ZnO-NRs was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectrometry (UV-Vis). XRD and SEM measurements indicated that all films show a hexagonal wurtzite Nano rods (NRs) structure growing preferentially along c-axis perpendicular to the surface of the substrate. Optical transmission spectra showed high transmittance of 80-85% in the visible range for all thin films, and increase of optical band gap from 3.24 to 3.265 eV with deposition time. The high quality c-axis orientated ZnO thin films with minimum strain and tuneable optical properties could be used as a transparent conducting oxide (TCO) for optoelectronic applications.

Abstract: This work is focused on the preparation of Mg doped ZnO films by ultrasonic spray pyrolysis and investigated the physical, optical and electrical properties of the films. These films were prepared from 0.02 M of Zn (CH₃OO)₂.2H₂O and MgCl₂ was used for doping. The atomic percentage ratio of Mg/Zn was varied from 0 to 9 at.%. The crystalline phase of all films was identified as ZnO polycrystalline structure with preferred orientation along the (002) plane. While, the grain shape of ZnO film was irregular shape, this shape changed to spherical shape with doped Mg concentration and changed again to rod shape with doped Mg concentration to 9 at.%. Although, the Mg dopant affects the shape of ZnO films but don’t affect resistivity of the films. Moreover, the Mg dopant shifts the absorption edge in transmittance spectra of films to lower wavelength and increases band gap of the films.

Abstract: Synthesis of nanoCu/ZnO catalyst for LPG production was prepared by ultrasonic spray pyrolysis (USP). Hollow spherical particles were obtained by USP technique using an aqueous solution of Cu (NO₃)₃.6H₂O and Zn (NO₃)₃.3H₂O with different concentration of 0.05, 0.1 and 0.5 molar under the pyrolysis temperatures of 600, 700 and 800°C. Mists of the solution were generated from the precursor solution by ultra sonic vibrators at frequency of ~1.7 MHz. The physicochemical properties of catalysts were characterized by X-ray diffraction, temperature-programmed reduction, scanning electron microscope, nitrogen adsorption-desorption, and energy dispersive X-ray spectrometer. The results showed that increasing in precursor concentration resulted in a large particle and particles size distributed in a range of 0.63-1.21 μm. Particles prepared at pyrolysis temperature 700°C exhibited homogeneous in size and shape compared to other temperature. The catalytic activity of nanoCu/ZnO-Pd-β catalysts was performed in a fixed-bed reactor for synthesizing LPG. The reaction took place at 260°C, 3.0 MPa, and the ratio of H₂/CO = 2/1. All the products from the reactor were in gaseous state, and analyzed by on-line gas chromatography. The results showed that %CO conversion was high but decreased rapidly with increasing reaction time. Cu/ZnO catalyst prepared by co-precipitation gave higher %CO conversion than that prepared by ultrasonic spray pyrolysis. Moreover, hydrocarbon product distribution for Cu/ZnO catalyst produced at concentration 0.1 M 700°C by ultrasonic spray pyrolysis gave the highest LPG selectivity.

Abstract: Boron doped ZnO (BZO) thin films were deposited on glass substrate by ultrasonic spray pyrolysis method using zinc acetylacetonate and boric acid. The structural, morphological, optical and electrical properties of BZO thin films under various doping level of boron and substrate temperature were investigated. The results show that zinc acetylacetonate is helpful to deposit BZO thin films at low temperature. The morphology of grains at low and high substrate temperature is circular and flake-like. The preferred orientation along (101) plane is obvious at 360 °C. The doping level and substrate temperature have remarkable influence on sheet resistance, but little impact on visible transmittance. The optimal sheet resistance of 173 Ω/sq and average visible transmittance of above 80% can be achieved at doping level of 5 at% and growth temperature of 340 °C.

Abstract: Hollow (Ni_0.8Co_0.1Mn_0.1)O_y spheres were fabricated with ultrasonic spray pyrolysis method. Particle morphology of (Ni_0.8Co_0.1Mn_0.1)O_y was carefully controlled by regulating the concentration of the solution containing mixed sulfates and reaction temperature. Lower solution concentration contributes to cracked hollow structure and higher temperature leads to lager particle size. Crystal phase of precursors was characterized by XRD. Morphology and microstructures of (Ni_0.8Co_0.1Mn_0.1)O_y were observed by SEM and TEM. The results of ultrasonic atomization process show promise properties requirement for commercial applications.

Abstract: LiFePO₄/C powders were synthesized by ultrasonic spray pyrolysis using carbon powder instead of organic substances as the carbon source. LiFePO₄ (LFP) powders containing different types of carbon powders were prepared and used as cathode active materials in lithium ion batteries. The charge-discharge properties of lithium ion batteries with LFP, LFP/AB, and LFP/CNT powders as the cathode material were worse than those of the battery with LFP/sucrose powder as the cathode active material.

Abstract: The microstructure and photoluminescence properties of Gd0_.94-xAl_xEu_0.06VO₄ (0≤x≤0.04) phosphors with various Al³⁺ contents were investigated. The phosphors showed a nanocrystalline nature and a high-quality powder characteristic. The crystallite sizes of the phosphors were calculated to be 46-48 nm. The annealed Gd_0.94-xAl_xEu_0.06VO₄ phosphors crystallized in the tetragonal structure. In the emission spectra, several emission peaks were observed over the measured wavelength range (500-750 nm), which were caused by the difference in the transitions of Eu3+ ions, depending on the local symmetry (⁵D0 → ⁷Fj, j = 1, 2, 3, and 4). The strongest emission peak was located at 619 nm, providing a high-purity red emission. The doped Al3+ yielded significantly enhanced the emission intensity. The most intense high-purity red emission was obtained for Gd_0.93Al_0.01Eu_0.06VO₄.

Abstract: Fluorine doped tin oxide (FTO) film is one of the most promising transparent conducting materials. It can be used for Low-E glasses, thin film solar cells, displays, etc. FTO film can be fabricated by various techniques. The technique of sol-gel combined with ultrasonic spray pyrolysis gives the possibility to produce high-quality large-scale FTO films. In this paper, the FTO sol is successfully prepared using pentahydrate stannic chloride (SnCl₄•5H₂O), hydrogen fluoride (HF) and methanol. Using the FTO sol, FTO films are prepared by ultrasonic spray pyrolysis technique. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used to characterize the FTO films coated on glass substrates. Results indicate that the as-deposited films are polycrystalline SnO₂ phase with tetragonal crystal structure, and that the average grain size for the samples is 160nm. The optical and electrical properties of the FTO film are also analyzed.

Abstract: In₂S₃ thin films have been prepared on heated glass substrates by ultrasonic spray pyrolysis method. Structure, surface morphology and properties of films with different S/In ratios have been investigated. XRD analysis demonstrated that as-prepared In₂S₃ thin films have a preferential orientation along the (220) direction and no other phases are observed. Uniformity, density, crystallinity of films were significantly affected by S/In ratios, which influence photoelectric properties of the films. In₂S₃ thin film is close to standard stoichiometric composition when S/In ratio is 2. Optical transmittance of films is over 90% in the visible region and its energy band gap come up to 2.46eV.