Papers by Keyword: Mixed Oxide

Abstract: Mixed oxide of titanium dioxide was synthesized by adding SnO₂ and CeO₂ through a precipitation method for the degradation of methylene blue (MB) under visible light. The as-prepared was dried and calcined at various temperatures, i.e. 450-750 °C. The calcined products were characterized by XRD, DRUV, and FTIR. The effect of calcination temperature was studied on the photodegradation of MB under visible light. The photocatalytic activity showed that calcined photocatalytic at 650 °C shows the lowest bandgap energy and the highest photocatalytic activity in the decomposition of methylene blue under visible light.

Abstract: The composite formation of steel and ceramics is especially for medical applications of great interest. By use of the multicomponent tape casting metal-ceramic composite components like bipolar scissors and other surgical instruments can be produced. A coating technology that comes from the paper industry, allows to apply a very thin insulating layer of a few microns between the electrodes consisting of stainless steel. Until now bipolar surgical instruments are produced by mechanical joining of steel and ceramic parts or by spraying a ceramic layer on the steel instruments. This joining steps can lead to stresses in the sensitive ceramic material and leave fine interstices or pores that are not only avoidable with a force and / or tight fit. Both factors are reasons for premature failure of the instrument, even if the materials are not yet at the limits of their resistance. Through the joint shaping by the tape casting and subsequent co-sintering of both materials, a material bond is achieved in addition to the previously existing mechanisms of force and form fit. This optimizes the composite properties and increases the usage time of metal-ceramic layered composites. Special focus is given to the formation of the interface and the associated changes in properties of the individual components of the laminate. These investigantions illustrate the influence of co-manufacturing on the texture of the laminate materials and the formed interface between them. By x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), x-ray fluorescence analysis (RFA) and thermodynamic calculations (FactSage) of the material bond at the metal-ceramic interface is investigated. In various application areas where steel and zirconia should occur as integral partners, this material combination may be established.

Abstract: In this work, we report on the synthesis of MgMoO₄ crystals by oxide mixed method. The powder was calcined at 1100 °C for 4h and analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Field emission gun scanning electron microscopy (FEG-SEM), Ultraviolet-visible (UV-vis) absorption spectroscopy and Photoluminescence (PL) measurement. XRD analyses revealed that the MgMoO₄ powders crystallize in a monoclinic structure and are free secondary phases. UVvis technique was employed to determine the optical band gap of this material. MgMoO₄ crystals exhibit an intense PL emission at room temperature with maximum peak at 579 nm (yellow region) when excited by 350 nm wavelength at room temperature.

Abstract: Au-Pd alloy nanoparticles supported on Ni-Al mixed oxide were prepared by impregnation-reduction method. Characterizations of the catalysts were applied by X-ray diffraction and UV-Vis spectrum. The bimetallic catalysts exhibited excellent catalytic activity in Heck reaction under mild conditions. Due to the easy separation of solid catalyst, it is thought as environmental friendly and these catalysts will be potential material in the synthesis of fine chemistry.

Abstract: Nano-structured hydrotalcite based mixed oxides have been synthesized using coprecipitation method under variable pH and low supersaturation condition. XRD technique has been used to confirm the hydrotalcite structure and its derived different phase of mixed oxides. The metal dispersion of mixed oxides was analyzed using ICP-MS. The nanostructures of the mixed oxides have been investigated using FESEM and HRTEM. The textural properties of mixed oxides were analyzed using N₂ adsorption-desorption (BET) technique. The Characterizations have revealed that the developed mixed oxides were consisted with hexagonal/rhombohedral well dispersed nano-particles. Polycrystalline mixed oxides formed mesopore surface and narrower pore size distribution.

Abstract: The comparative experiments for removing humic acid as environmental pollutant were conducted by adsorption on iron oxide, photooxidation in the presence of titanium dioxide catalyst and combined adsorption-photooxidation by iron-titanium mixed metal oxides, where all these active components were immobilized on polypropylene granules. The main purpose of the work was the combination of adsorption and photocatalytic oxidation processes to remove humic acid. The granules with iron-titanium mixed oxide for treating humic acid gave much better results with 1.2~3 times higher removal rates comparing to the other two single coated oxides at certain pH values. And the order of removal efficiency according to pH was the same as for single iron oxide-coated granules. The ratio 1:2 of iron oxide/titanium dioxide was found optimal for maximal decolorization of humic acid solution. The total organic carbon decrease of humic acid in each experiments, when it was pre-equilibrated with mixed oxides-coated granules in the dark for 30 min and without pre-equilibration, was very similar. The results suggested that the mechanism of humic acid removal may be not only a respectively combined adsorption and photooxidation by iron oxide and titanium oxides, but an enhanced photooxidation reaction as a result of concentrating humic acid on titanium oxide surface by iron oxide.

Abstract: nanocrystalline mixed oxides containing magnesium, nickel and chromium (MNCM) have been synthesized as an adsorbent using coprecipitation method and showed its reversible hydrogen storage capacity at ambient conditions using fixed bed. XRD and ICP-MS analyses ensured the adsorbents phase and homogeneity. The microstructure of mixed oxide has been investigated using FESEM and BET and TEM technique respectively. The adsorbent consisted of mesoporous surface with a surface area of 254-370 m²gm^-1 and SAED pattern showed that the adsorbents are poly-crystalline. The mixed oxides exhibited a 3.2 wt% H₂ storage capacity and release 57% of adsorbed H₂. Adsorption enthalpy (H) and entropy (S) change of-27.58 kJ/mol and-70.21 J/mol.K are indicating favorable thermodynamics for reversible hydrogen storage material.

Abstract: In the recent years most of the studies are confined to the mixing of ZrO₂, SiO₂, WO₄ or ceria with titania in different composition so as to stabilize anatase phase, maintain high surface area and increase visible light absorption for better photocatalytic activity. Method of synthesis also helps in effective doping and enhancing surface area of the resultant materials. Nonmetal doping of oxide semiconductor materials facilitates the visible light application of photocatalysis. Based on the recent literature this review elaborately discuss on the development of titania based mixed oxide catalyst with or without different doping for visible light application. In addition this review deals with critical analysis of these materials towards photocatalytic oxidation of organics and reduction of pollutants like toxic metal ions and nitrates.

Abstract: This paper describes an original method to measure the plutonium self-diffusion coefficient in the mixed oxide U_0.55Pu_0.45O_2±x. This method is based on using ²⁴²Pu as a tracer atom. A thin film of the tracer was deposited on the well-polished surface of the samples and then diffusion annealings were performed from 1500°C to 1700°C, in an Ar-H₂ 5% atmosphere. The oxygen potential was fixed at-395 kJ.mol^-1. After annealing, the ²⁴²Pu self-diffusion profiles were established by means of secondary ion mass spectrometry (SIMS). The ²⁴²Pu concentration profiles were determined by assessing the relative U, Am and Pu ionisation yields according to the experimental parameters. The choice of favourable experimental conditions and the relevance of the resulting concentration profiles are discussed at length.

Abstract: ZnO-Fe₂O₃ catalysts were prepared by thermal decomposition of layered double hydroxides containing zinc and iron within the brucite-like layers and carbonate as the interlayer anion, then the hydrotalcite precursor and mixed oxides were characterized by ICP, XRD and N₂ adsorption/desorption techniques. XRD patterns showed that both ZnO and ZnFe₂O₄ phases appeared for the mixed oxides and their proportion and crystalline degrees depended on the heat treatment temperature. Furthermore, these mixed oxides were tested for the diethyl carbonate (DEC) synthesis from ethyl carbamate and ethanol. More important, the DEC yield could reach to about 32.3% in the bacth reactor under the optimal reactions.