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Influence of Mechanical Stirring on the Crucible Dissolution Rate and Impurities Distribution in Directional Solidification of Multicrystalline Silicon

Abstract

In this study, time dependent three-dimensional numerical simulations were carried out using the STHAMAS3D software in order to understand the effects of forced convection induced by mechanical stirring of the melt, on the crucible dissolution rate and on the impurities distribution in multicrystalline silicon (mc-Si) melt for different values of the diffusion coefficient.

Numerical simulations were performed on a pilot scale furnace with crucible dimensions of 38x38x40cm3. The computational domain used for the local 3D-simulations consists of melt and crystal.

The dissolution rate was estimated from the total mass of impurities that was found in the silicon melt after a certain period of time. The obtained results show that enhanced convection produced by a mechanical stirrer leads to a significant increase of the dissolution rate and also to a uniform distribution of impurities in the melt.

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Lectures on Stirring, Mixing and Transport
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Deposition time and annealing effects on morphological and optical properties of ZnS thin films prepared by chemical bath deposition

Abstract

Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 °C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 〈2 0 0〉 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10−4 Ω·cm−1 to 2.7 × 10−4 Ω·cm−1.

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Synthesis and characterization of small size fluorescent LEEH caped blue emission ZnTe quantum dots

ZnCl 2 (2.77 mM) into 10 mL of deionized water and 185.67 mg of LEEH (0.1 mM) into 10 mL of deionized water. These two solutions were mixed together and stirred at 45 °C for half an hour. Stirring of this solution and the solution (NaHTe + Na 2 B 4 O 7 ) was completed at the same time and the both solutions were mixed immediately and further stirred for 2 h at 80 °C. The chemical reaction for the formation of ZnTe NCQD is: (2) NaHTe + ZnCl 2 → 80 ∘ C , 2 h,LEEH ZnTe + NaCl + HCl $${\rm{NaHTe}} + {\rm{ZnC}}{{\rm{l}}_2}\buildrel {{\rm{8}}{{\rm{0}}^ \circ }{\rm

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Carrier recombination in sonochemically synthesized ZnO powders

few dozens of nm to ∼130 µm. In this work, the samples of ZnO powders are marked as SC1, SC2 and SC3 respectively. Subsequently, these samples are compared according to their stirring time of 1 min, 60 min and 120 min, respectively. Photoluminescence (PL) spectra and decays were recorded at room temperature using a monochromator MDR-4 and a photomultiplier tube FEU-79 with a computer data acquisition system. PL decays were analyzed with use of a digital oscilloscope GDS-806S with a time resolution of 1 µs. An N 2 laser with the wavelength of λ = 337.2 nm (3.67 eV

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A new geometrical model for mixing of highly viscous fluids by combining two-blade and helical screw agitators

the performance of anchor impellers for stirring shear-thinning fluids in a cylindrical vessel. J. Hydrodyn. 28(4), 669–675. DOI: 10.1016/S1001-6058(16)60671-6. 7. Ameur, H., Kamla, Y., Hadjeb, A., Arab, I.M. & Sahel, D. (2016). Data on mixing of viscous fluid by helical screw impellers in cylindrical vessels. J. Data Brief. 8, 220–224. DOI: 10.1016/j.dib.2016.05.036. 8. Havlica, J., Jirounkova, K., Travnickova, T. & Kohout, M. (2015). The effect of rotational speed on granular flow in a vertical bladed mixer. Pow. Technol. 280, 180–190.DOI: 10.1016/j

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Influence of different formulations and process parameters during the preparation of drug-loaded PLGA microspheres evaluated by multivariate data analysis

Abstract

The main objective of this study was to evaluate the influence of the formulation and process parameters on PLGA microparticles containing a practically insoluble model drug (ibuprofen) prepared by the o/w solvent evaporation method. Multivariate data analysis was used. The effects of altered stirring speed of a mechanical stirrer (600, 1000 rpm), emulsifier concentrations (PVA concentration 0.1 %, 1 %) and solvent selection (dichloromethane, ethyl acetate) on microparticle characteristics (encapsulation efficiency, drug loading, burst effect) were observed. It was found that with increased stirring speed, the PVA concentration or the use of ethyl acetate had a significantly negative effect on encapsulation efficiency. In addition, ethyl acetate had an adverse effect on the burst effect, while increased stirring speed had the opposite effect. Drug load was not affected by any particular variable, but rather by the interactions of evaluated variables.

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Parametric optimization of rice bran oil extraction using response surface methodology

Abstract

Use of bran oil in various edible and nonedible industries is very common. In this research work, efficient and optimized methodology for the recovery of rice bran oil has been investigated. The present statistical study includes parametric optimization, based on experimental results of rice bran oil extraction. In this study, three solvents, acetone, ethanol and solvent mixture (SM) [acetone: ethanol (1:1 v/v)] were employed in extraction investigations. Response surface methodology (RSM), an optimization technique, was exploited for this purpose. A five level central composite design (CCD) consisting four operating parameter, like temperature, stirring rate, solvent-bran ratio and contact time were examined to optimize rice bran oil extraction. Experimental results showed that oil recovery can be enhanced from 71% to 82% when temperature, solvent-bran ratio, stirring rate and contact time were kept at 55°C, 6:1, 180 rpm and 45 minutes, respectively while fixing the pH of the mixture at 7.1.

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In vitro evaluation of anticancer activity of sodium hyaluronate-titanium dioxide bionanocomposite

Abstract

The purpose of the current research is to optimize the synthesis of sodium hyaluronatetitanium dioxide nanocomposite with the highest anticancer activity. To this end, the Taguchi method was followed to design nine experiments with different ratios of sodium hyaluronate biopolymer, titanium dioxide nanoparticles and stirring times. The results of scanning electron microscopy (SEM) confirmed the synthesis of the nanoparticle and nanocomposite. The comparison of anticancer activity level of synthesized nanocomposites using MTT assay showed that the nanocomposite synthesized in the conditions of experiment 9 (8 mg/ml of titanium dioxide nanoparticles, 2 mg/ml of sodium hyaluronate biopolymer and 60 min stirring time) had the maximum anticancer activity against Michigan Cancer Foundation-7 (MCF-7) cell line. According to the results, the Taguchi method can be employed as an effective and useful strategy to save time and cost in order to determine the optimal conditions for the synthesis of sodium hyaluronate-titanium dioxide nanocomposite with the most favorable anticancer activity.

Open access
Synthesis and anticancer properties of bacterial cellulose-magnesium oxide bionanocomposite

Abstract

Given the increase in global mortality rate due to various types of cancer, the present study aimed to develop optimal conditions for the synthesis of cellulose-magnesium oxide nanocomposite with favorable anticancer activity. For this purpose, the Taguchi method was used to design nine experiments with varied ratios of cellulose biopolymer, magnesium oxide nanoparticles and different stirring times. The scanning electron microscopy (SEM) images confirmed the formation of cellulose-magnesium oxide nanocomposite. The anticancer activity level of nine nanocomposites studied was evaluated using MTT assay on Michigan Cancer Foundation-7 (MCF-7) cell line. The nanocomposite synthesized in experiment 9 (8 mg/ml of magnesium oxide, 2 mg/ml of cellulose and stirring time of 60 min) showed the highest growth inhibitory activity on the cancer cells. Based on the attained results,e cellulose-magnesium oxide nanocomposite synthesized in optimal conditions can be used as an eligible anticancer agent.

Open access