Papers by Keyword: MoO₃

Abstract: In this work, Molybdenum trioxide and conventional copper particles were used as precursors, reduced in hydrogen atmosphere. Then Cu@Mo Powders were successfully synthesized. Effects of reduction temperature on the microstructure of the composite powders and the performance of the intermediate product (molybdenum dioxide) were investigated. Results show that 700°C is the optimal reduction temperature, because Mo is reduced from its oxide and forms a coating layer on the surface of copper particles tightly without serious crack. Mo-20wt.% Cu composite powders where Cu is coated uniformly with continuous molybdenum layer are successfully obtained by co-reduction method.

Abstract: MoO₃ film is successfully prepared by water bath heating method. The existence of Mo element in the MoO₃ solution is determined by infrared test. The characteristic peak of Mo element roughly appears within the range from 500 cm^–1 to 700 cm^–1.Then the MoO₃ peak is found appearing at the location of the 30°–40° using XRD, which proves the existence of MoO₃ in the solution. SEM observations indicate that the MoO₃ film is smooth as the reaction continues for 4 h. Finally, the results of light absorption test show that MoO₃ film has a good absorbency.

Abstract: Two-dimensional microstructures of molybdenum trioxide (MoO₃) were synthesized by heptamolybdate tetrahydrate ammonium acidification, followed by calcination. A solution of the precursor compound heptamolybdate tetrahydrate ammonium acidified to pH 3,5 using glacial acetic acid followed by hydrothermal treatment for 150, 180 and 200 °C for 1, 6 and 12 hours. Then, the intermediate was calcined at 300 °C for varying time 6 and 12h to obtain MoO₃. X-ray diffraction revealed that the crystals grew with crystalline structure corresponding to the orthorhombic phase of MoO₃ (a-MoO₃) as major phase, with a preferential growth direction along the planes (0K0). Raman spectroscopy and IR confirmed the formation of the characteristic modes of molybdenum trioxide for stage found. With Scanning Electron Microscopy (SEM) was possible to observe the formation of nanoplates.

Abstract: A simple and efficient method has been developed to eliminate the internal stress in molybdenum oxides by an ultraviolet ozone treatment. The results of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Raman spectroscopy indicate that oxygen vacancy was a determining factor of the compressive stress in MoO₃, which can be released by ultraviolet ozone treatment. Based on this hole-transporting layer, the photovoltaic power conversion efficiency up to 3.91% was achieved, which is 22% higher than that without ultraviolet ozone treatment. And ultraviolet ozone treatment on MoO₃ is a useful method to embellish the interface to enhance the ability of collecting hole of hole-transporting layer to improve the performance of OSC with MoO₃ film as hole-transporting layer.

Abstract: Mo behavior in Fe-rich Mn-Zn ferrites during sintering process was studied by adding MoO₃ or MnMoO₄ as additive. The influences of the additive amounts and treatment temperatures on microstructure, density, porosity as well as magnetic properties were investigated. It is found that formation of MnMoO₄ in the grain boundary plays an important role. Saturation flux density (Bs) at 373 K as high as about 513mT could be obtained when the equivalent Mo content is 133ppm. Based on the experimental results, a new hypothesis is proposed to explain why proper Mo addition is essential to obtain ferrites of good qualities.

Abstract: Possible chemical states of molybdenum in Mn-Zn ferrite at high temperatures were investigated by experiments and thermodynamic calculations. It is found that solid or liquid MnMoO₄(s,l) is the main Mo-containing phase during the sintering process of Mn-Zn ferrite up to about 1623 K, even if MoO₃ is employed as the additive. When temperature is higher than the melting point of MnMoO₄, Mo in Mn-Zn ferrite tends to evaporate in form of Mo₃O₉ (g) from thermodynamic point of view.

Abstract: The modified sol-gel technique for the preparation of Со, Ni, Mo and W oxides nanoand submicron powders as well as binary composites based on them was developed. The optimal parameters of synthesis of metal oxide nanopowders with a particle size less than 100 nm were determined. The developed approach allows to obtain the nanoscale metal oxide particles with the given sizes, varying their within range 10-1000 nm. Mesoporous composites containing Mo-, Co-, Ni-oxides, Al₂O₃ and Ti-silicate were synthesized, characterized and tested in the catalytic alcohol synthesis from CO and H₂. It was found that selectivity to C₁-C₄-alcohols formed over model catalytic systems reaches 50-85% in temperature range 280-360°С.

Abstract: MoO₃ was synthesized by thermal decomposition of ammonium molybdate. The structure and surface morphology of the as-prepared MoO₃ was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The supercapacitive behaviour of MoO₃ in 1 mol L^-1 KCl electrolyte was studied by cyclic voltammetry (CV), galvanostatic charge-discharge cycling (CD). The affect of thermal decomposition temperature on the capacitive behaviour of MoO₃ was also discussed here. The results indicate that MoO₃ show good capacitive behaviour with a specific capacitance of 148.9 F g^-1 at 0.7 A g^-1. Thermal decomposition temperature has an important influence on the capacitive behaviour and crystallization of MoO₃.

Abstract: This paper explains the influence of oxygen partial pressure on crystallographic structure, surface morphology and sensing properties of sputtered MoO₃ thin films. The MoO₃ thin films were deposited by DC reactive magnetron sputtering technique on glass substrate at different oxygen partial pressures in the range of 5×10^-5-4×10^-4 mbar. X-ray diffraction (XRD) results showed that all prepared films were polycrystalline of α-MoO₃ stable orthorhombic phase. Atomic force microscopy (AFM) images depicted a needle-like structure for deposited film at lowest oxygen partial pressure (5×10^-5 mbar) and a granular structure for formed samples at higher oxygen partial pressures (1×10^-4 and 2×10^-4 mbar). These results also showed that increasing of oxygen partial pressure up to 2×10^-4 mbar caused increasing of grains size and surface roughness, while an increase in oxygen partial pressure to the highest pressure (4×10^-4 mbar) had an inverse effect. The electrical response of samples was measured in vacuum and NO environments in the temperature range of 150-350 K. This study showed that the NO gas detection sensitivity of MoO₃ thin films improved with increasing of oxygen partial pressure up to 2×10^-4 mbar, and then decreased.

Abstract: Sol-gel tequnique was used to prepare disordered tungsten oxide and molybdenum oxide sols. A series ratio of W:Mo compound sols were obtained via mettalic powder co-peroxided by H₂O₂ as precursors in ethonal. Compound films were achieved by dip-coating method. Fourier Transform Infrared Spectroscopy, Raman Spectroscopy were taken to characterize the structure of these compound films. Uv-visible Spectroscopy was used to test the gasochromic property. The results showed that the gasochromics property was much different from that of pure tungsten oxide and molybdenum oxide sol-gel thin films. The effect was origined from the structrue alteration, which was not due to the spectrum superposition but the co-reaction of W and Mo.