Thermochromic VO2 thin films were deposited on soda-lime glass via sol-gel method. Doping was done through adding tungstic acid solution to the vanadium solution precursor. Grazing incidence x-ray diffractometer (GIXRD) results showed that VO2 and V6O13 phases were formed together in the heat-treated sample. According to the GIXRD result of the W-doped sample, only VO2 remained. Field-emission scanning electron microscopy (FESEM) micrographs showed that the VO2 grain size decreased from about 70 to about 25 nm for undoped film and 2 wt% W-doped films, respectively. Atomic force microscopy (AFM) results showed that the root mean square roughness for the film with 180 nm thickness was about 18 nm, and 2 wt% W-doped film had a smoother surface. Diffuse reflectance spectroscopy (DRS) results showed that the band gap energy for undoped, 1 wt% W- doped, and 2 wt% W-doped VO2 thin films was 1.7, 1.3, and 0 eV, respectively. Four-point probe resistivity measurements showed a significant decrement, from approximately 1 MΩ at 15°C to <100 Ω at 80°C. Regarding Vis-NIR spectroscopy results, maximum optical transmission for undoped and W-doped films was approximately 75% and 35%, respectively. 相似文献
Taguchi method (TM) and response surface methodology (RSM) have been employed to optimize three parameters, including the amounts of P123, the amounts of nitric acid and calcination temperature, in order to define an optimal setting for sol-gel synthesis of high surface area mesoporous alumina powder (MA). Herein, the comparison of the both statistical approaches has been examined and discussed considering the nitrogen adsorption as the response variable because this important character for mesoporous materials is exceedingly sensitive to the synthesis parameters. The BET surface area (SBET) and pore volume of MA under Taguchi optimal condition were 323.5 m2 g−1 and 0.551 cm3 g−1, respectively, by conducting confirmation test. Furthermore, the confirmation test showed high SBET of MA (363.4 m2 g−1), which was in a good agreement with calculated SBET result (431.25 m2 g−1) by a quadratic model under RSM optimal condition. Moreover, 3D response surface plots and 2D contour plots of desirability have been discussed to visualize the influence of input factors on response variable. It is also concluded that RSM shows more appropriate (12.33% higher SBET than TM) and efficient optimal condition with determining a quadratic function as the relationship between SBET and synthesis parameters. 相似文献
This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a drug, on the physico-mechanical and antibacterial properties as well as drug release behavior of poly(vinyl alcohol), PVA, hydrogels prepared by electron beam irradiation. The formation of spherical chitosan particles in nanoscale size prepared by an ionic gelation method was confirmed by FTIR and UV spectroscopy, and scanning electron microscopy analyses. The drug release kinetic studies from drug loaded chitosan nanoparticles (DLCNPs) at pH = 7.4 revealed a linear and steady release behavior over long period of time. The theoretical analysis of the swelling kinetic data, using Peppas’s model showed that the swelling kinetic is governed by Fickian diffusion for all the prepared hydrogels, however, the water diffusion coefficient, and therefore, the swelling content were lower for the hydrogels loaded with DLCNPs as compared to the ones with the neat drug. In agreement with these results, the hydrogels containing DLCNPs exhibited a more controlled drug release behavior with significantly stronger antibacterial activity. The tensile mechanical properties of the hydrogels not affected by the DLCNPs were found to be suitable for wound dressing applications. 相似文献
The potential energy profile of the reaction between dimethyl disulfide and OH? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10?10?cm3?molecule?1?s?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH3S?(OH)SCH3 decomposing rapidly to yield CH3S?+CH3SOH. 相似文献
A silane moisture-cured polyolefin elastomer/linear low-density polyethylene (LLDPE) blend was prepared through a two-step silane-grafting method (Sioplas Process) in an industrial scale twin-screw extruder. The silane-grafted compound was used to make wire and cable coatings. In this work, the effect of some interactive parameters on quality of the products prepared by the above method has been studied, while so far, there have been less experimental investigations. The volume resistivity of cross-linked compound was changed from 2.96 × 1014 to 7.41 × 1014 Ω cm with increasing LLDPE component by maximum 10 wt%. Surface morphology of the product was corrected with reduction in benzoyl peroxide (BPO) concentration from 0.2 wt% to 0.13 wt%. BPO at this level acted as an initiator in grafting reaction of vinyl trimethoxysilane. The curing condition and specimen preparation method by injection molding and/or extrusion were factors which influenced the hot-set test results at 200 °C. The results of tensile and elongation studies showed a maximum value of 9 MPa and 397% for the tests, after 6 h curing. With increases in curing time at a specified temperature, the gel content of the cross-linked compound was increased and reached its maximum value. The maximum gel content values were found to be approximately 60%, 80%, and 82% at temperatures of 25, 60, and 85 °C, respectively. The hardness, density, and tear strength of the samples did not vary significantly with the curing temperature.
Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of
the tube wall is assumed to be adiabatic (presenting a tube of a solar collector). Heat conduction mechanism through the tube
wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate
hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle
mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed
at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient
as well as on the wall shear stress is seen. 相似文献
In this study, La3+, Ce3+ and Sm3+ were removed from a solid matrix using supercritical CO2 which contained bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a chelating agent and tributylphosphate (TBP) as a co-extractant. The fractional factorial design, 25−1, was employed to optimize the SFE of these ions from spiked filter paper matrices. Effect of five experimental factors: amount of Cyanex 301, flow rate, temperature, pressure and amount of TBP and each factor at two levels on the SFE of these ions were studied and optimized. The results showed that these ions could be quantitatively extracted from the solid matrix at amount of Cyanex 301 of 0.14 g, flow rate of 4 ml min−1, 313 K, 250 bar and amount of TBP of 30 μl. Finally, by employing a regression analysis a model was proposed. Results showed that obtained recoveries are similar to those predicted by the model. 相似文献
In this study, the effect of fluorine content on the mechanical properties of the novel poly (?-caprolactone)/nano-fluoridated hydroxyapatite nanocomposite scaffolds was investigated. Poly (?-caprolactone)/nano-fluoridated hydroxyapatite (PCL-FHA) scaffolds were produced by solvent casting/particulate leaching method. The fluoridated hydroxyapatite nanopowders had a chemical composition of Ca10(PO4)6OH2−xFx (where x values were selected equal to 0.5, 1, 1.5 and 2.0). Various weight percentages (10, 20, 30 and 40) of the FHA were added to the PCL. Sodium chloride (NaCl) particles having diameter of 300-500 μm were used as porogen. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to identify the phase structure and functional groups of obtained scaffolds. Mechanical properties of the prepared scaffolds were also determined. Results showed that the compressive strength of scaffolds increases with decreasing the weight percent of fluorine in FHA. 相似文献