Nanocrystalline Zn-Ni (crystallite sizes 13-68 nm) alloy coatings were produced from an alkaline glycinate bath containing saccharin as additive. X-ray diffraction (XRD) was used to determine the phase composition and average crystallite size of nanocrystalline Zn-Ni alloy coatings. The average grain size of a deposit was also studied by transmission electron microscopy (TEM). The effects of saccharin concentration and current density on the crystallite size and surface roughness of the coatings were studied. Crystallite size and average surface roughness were diminished as a result of increasing saccharin concentration. Scanning electron microscopy (SEM) examination showed that coatings had a colony-like morphology and the colony size was increased with increasing current density. Microhardness testing was carried out in order to determine the degree of dependence of this mechanical property on the crystallite size. It was found that microhardness did not depend on crystallite size (Hall-Petch). 相似文献
Heat transfer enhancement of a mixed convection laminar Al2O3–water nanofluid flow in an annulus with constant heat flux boundary condition has been studied employing two phase mixture model and effective expressions of nanofluid properties. The fluid flow properties are assumed constant except for the density in the body force, which varies linearly with the temperature (Boussinesq’s hypothesis), thus the fluid flow characteristics are affected by the buoyancy force. The Brownian motions of nanoparticles have been considered to determine the effective thermal conductivity and the effective dynamic viscosity of Al2O3–water nanofluid, which depend on temperature. Three-dimensional Navier–Stokes, energy and volume fraction equations have been discretized using the finite volume method while the SIMPELC algorithm has been introduced to couple the velocity–pressure. Numerical simulations have been presented for the nanoparticles volume fraction (?) between 0 and 0.05 and different values of the Grashof and Reynolds numbers. The calculated results show that at a given Re and Gr, increasing nanoparticles volume fraction increases the Nusselt number at the inner and outer walls while it does not have any significant effect on the friction factor. Both the Nusselt number and the friction coefficient at the inner wall are more than their corresponding values at the outer wall. 相似文献
The emergence and prevalence of
multi-drug-resistant bacterial strains increase the potential for outbreaks of incurable infections. The discovery of novel antibiotics and pharmacological preparations requires the identification of novel bioactive small molecules. A specific, sensitive, and reliable quantification method using high-performance liquid chromatography (HPLC) with UV detection was developed for the determination of total persipeptides (A and B), which are cyclic pentapeptides found in the fermentation broth of Streptomyces zagrosensis UTMC 1154 that exhibit bioactivity against methicillin-resistant Staphylococcus aureus (MRSA). A simple liquid–liquid extraction (LLE) method using butanol was employed to extract persipeptides from the fermentation broth prior to HPLC analysis. The chromatographic separation of persipeptides and the internal standard, virginiamycin, was achieved with a gradient of acetonitrile and water on a C18 reversed-phase analytical column in a 25-min analytical run utilizing a flow rate of 0.8 mL min−1 and detection at 210 nm. The whole assay was validated, and the method presented a linear response range with a regression coefficient of determination R2 of 0.9996 for the quantification of persipeptides in the concentration range of 3.9–250.0 µg mL−1, as well as extraction recoveries ranging from 54.78 ± 9.83 % to 56.45 ± 16.33 %. The bias and the precision of the proposed method were <10 %. The detection and quantification limits for the persipeptides were 27 and 83 µg L−1, respectively.
Journal of Sol-Gel Science and Technology - Although dental ceramic restorations are biocompatible, they are not necessarily bioactive. They can be modified by bioactive glasses to exhibit... 相似文献
In this work, we introduce a new method using non-equilibrium atmospheric pressure plasma jet (N-APPJ) for the synthesis of semiconductor quantum dots in liquid media with low power consumption at room temperature. In this method, the solution containing CdSO4, Na2S2O3 and thioglycolic acid (TGA) was treated by N-APPJ. Firstly, the key role of plasma applied voltage on the power consumption and the produced plasma reactive species was considered. We then continue to demonstrate that the optical properties such as absorption and photoluminescence of cadmium sulfide quantum dots (QDs) can carefully be controlled with the plasma parameters. Here, the effects of two major plasma parameters such as the plasma applied voltage and treatment time on the size of CdS QDs were investigated. The size of nanoparticles increases with the increase of the voltage and treatment time. It was also displayed that the change of the concentration of Na2S2O3 and TGA in the solution had no significant effect on the size of QDs in plasma method. Finally, X-ray diffraction, X-ray fluorescence spectrometry and transmission electron microscopy were employed to determine the composition, size and crystallinity of prepared CdS QDs. 相似文献
A new method has been designed to prepare the known benzoxazinone derivative 2-(N-phthaloylmethyl)-4H-3,1-benzoxazin-4-one (4). The acyl chloride derivative N-phthaloylglycine reacts with anthranilic acid in chloroform, in the presence of triethylamine, to give an intermediate that is then reacted with cyanuric chloride, used as a cyclization agent, to produce the benzoxazinone derivative. 相似文献
In the present investigation, we have developed a novel technique to prepare azines using nano-WCl6 loaded on Montmorillonite K10 clay as a highly active catalyst. A variety of aldehydes and ketones were efficiently converted to the corresponding azines using catalytic amounts of nanosized WCl6/Mont. K10 under mild conditions. The nanostructures of WCl6 loaded on Mont. K10 as solid acid catalyst have been prepared by solid dispersion method. The advantages of this catalyst are rapid completion of the reactions, simplicity of performance, lack of pollution and mild and green reaction conditions. The morphologies, structure, and chemical components of parent and modified clay were successfully characterized using SEM, FT-IR, CV, XRD and EDX measurements. 相似文献
Yttria doped zirconia solid electrolytes with non-equilibrium composite structure were prepared by impregnation of a porous 3Y-TZP matrix with a solution of yttrium nitrate. Microstructures were characterized by XRD and SEM. The electrical properties were studied by impedance spectroscopy as a function of temperature. Biaxial flexural strength and fracture toughness of composite samples were measured by ring on ring and Vickers microhardness indentation methods respectively. The yttria content of the electrolytes was increased by a multi impregnation process. It was concluded that electrical and mechanical properties of the electrolytes can be adjusted by controlling the amount of doped yttria especially if severe sintering treatments are avoided. Electrolytes with conductivity of 0.08 S/cm at 900 °C and fracture strength and fracture toughness of respectively 390 MPa and 2.9 MPa m1/2 were obtained. 相似文献
A powder mixture of Al/TiO2/H3BO3 = 10/3/6 in molar ratio was used in this study to form the Al2O3–TiB2 ceramic composite via thermite reactions (combustion synthesis). As no combustion synthesis occurred for an unmilled sample
in a furnace, the mixture was milled in a planetary ball-mill for various milling times, and the as-milled samples were in
situ synthesized in the furnace at a heating rate of 10 °C/min. The differential scanning calorimetry (DSC) measurements were
performed with the same heating rate on the unmilled and the as-milled samples to evaluate the influences of the milling on
the mechanisms and efficiencies of reactions. Although no combustion synthesis occurred for the unmilled sample in the furnace,
two exothermic peaks were detected in its DSC curve after the melting of the Al. For the as-milled samples, significant changes
revealed in the DSC curves, suggest that the milling process before the combustion synthesis changed the mechanisms and efficiencies
of reactions. In addition, the intensity and the temperature of the exothermic peaks in the DSC curves changed by increasing
the milling time. According to the XRD analyses, by enhancing the milling time, the purity of the final products would increase,
confirming that the efficiency of the reactions increased. Finally, the microstructures of the as-milled and as-synthesized
samples were examined by a SEM, and it was shown that the morphology of the reactant powders was altered by increasing the
milling time. 相似文献