The properties of nickel aluminate nanoparticles prepared by sol–gel and impregnation methods

Nickel aluminates were prepared by sol–gel and impregnation methods and calcined at 1100 °C. The sol–gel made samples were prepared with different amounts of nickel (Ni/Al molar ratio equal to 0, 0.25, 0.5, and 0.75) and aging times (24 and 48 h). The samples were characterized by X-ray diffraction, induced couple plasma, nitrogen physisorption, transmission and scanning electron microscopy, and ammonia temperature programmed desorption (NH₃-TPD). In the sol–gel made samples, only the NiAl₂O₄ structure of nickel aluminate was defined, while for impregnation, NiAl₁₀O₁₆ was formed as well. The sol–gel made samples had low specific surface areas (7.7–12.4 m²/g), but a sample prepared by impregnation method had higher specific surface area (67.2 m²/g). The surface acidity density decreased by increasing the amount of nickel and was the lowest for impregnation method.     

Optimization of reaction parameters for the sonophotocatalytic degradation of hydroquinone

Research on Chemical Intermediates - In the present work, the degradation of hydroquinone in synthetic wastewater under sonocatalytic, photocatalytic, and sonophotocatalytic conditions was...     

Effect of ceria and zirconia nanoparticles on mechanical behavior of nanocomposite hybrid coatings

Epoxy-silica based hybrid nanocomposite coatings have been developed with different organicinorganic contents by sol–gel process. Various ratios of ceria and zirconia colloidal dispersions as inorganic nanoparticles are uniformly distributed in the hybrid sol. The hybrid sols are prepared by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A (BPA) and 1-methyl-imidazol (MI). A thin layer of each sol is coated on a micro-glass slide and 1050 aluminum alloy as substrates. The effect of alkoxysilane precursors (i.e. TEOS and GPTMS) and inorganic to organic molar ratio are investigated. Nanoindentation and dynamic mechanical analysis (DMA) performed to characterize the mechanical properties of the coatings in nanorange scale. It is revealed that all hybrid nanocomposite coatings had appropriate flexibility and strong interfacial interaction with the aluminum alloy substrate. It is proposed that the ceria and zirconia nanoparticles can be bonded to the surrounding of siloxane ring which can be induced high restriction in polymeric chain mobility in dynamic mechanical analysis. Nanoindentation tests showed that by increasing the inorganic phase in the nanocomposite, both elastic modulus and hardness increase, especially they are very intense in the higher levels of inorganic content.     

Application of aeration‐assisted homogeneous liquid–liquid microextraction procedure using Box–Behnken design for determination of curcumin by HPLC

A simple, efficient, and rapid sample preparation method based on aeration‐assisted homogeneous liquid–liquid microextraction was developed for determination of curcumin in food samples by high‐performance liquid chromatography. The centrifuge step has been eliminated in this procedure. The effects of some variables, such as pH, volume of extraction solvent, extraction time, and salt effect, were studied through a Box–Behnken design method. Under the optimum conditions, calibration curves of curcumin were linear in the range of 0.08‐4000 μg/mL with R² = 0.997. Limit of detection and relative standard deviation were 0.019 μg/mL and 3.01%, respectively. The preconcentration factor achieved was 166. The proposed method was successfully applied to determination of curcumin in various food samples.     

Applications of Inorganic Polymeric Materials II: Polysilanes

Polysilanes which cover one of the most attractive and challenging fields, are high molecular weight polymers with inorganic elements in their backbone. These materials have silicon atoms in their main chain and exhibit unique properties resulting from the easy delocalization of sigma electrons in the Si─Si bonds. There are many technical uses as well as applications of these materials such as precursors of silicon carbide ceramics; a strengthening agent in porous ceramic; imaging materials in microlithography; photoiniting in radical reactions; and photoconducting, conducting, and semiconducting which are due to the unusual mobility of sigma electrons. In this work, the main structural features, properties, and some other important and recent applications of polysilanes are discussed.     

Relative Cohen–Macaulayness of bigraded modules

In this paper we study the local cohomology of finitely generated bigraded modules over a standard bigraded polynomial ring which have only one nonvanishing local cohomology with respect to one of the irrelevant bigraded ideals.     

Etched glass surfaces,atomic force microscopy and stochastic analysis

The effect of etching time scale of glass surface on its statistical properties has been studied using atomic force microscopy technique. We have characterized the complexity of the height fluctuation of an etched surface by the stochastic parameters such as intermittency exponents, roughness, roughness exponents, drift and diffusion coefficients and found their widths in terms of the etching time.     

Multipliers for p-Bessel Sequences in Banach Spaces

Multipliers have been recently introduced as operators for Bessel sequences and frames in Hilbert spaces. These operators are defined by a fixed multiplication pattern (the symbol) which is inserted between the analysis and synthesis operators. In this paper, we will generalize the concept of Bessel multipliers for p-Bessel and p-Riesz sequences in Banach spaces. It will be shown that bounded symbols lead to bounded operators. Symbols converging to zero induce compact operators. Furthermore, we will give sufficient conditions for multipliers to be nuclear operators. Finally, we will show the continuous dependency of the multipliers on their parameters.