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Abbasi S.,Ferdowsi University of Mashhad | Abbasi S.,Esfarayen University of Technology | Zebarjad S.M.,Shiraz University | Baghban S.H.N.,Ferdowsi University of Mashhad | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2016

The effects of temperature and concentration on the flow behavior and viscosity of nanofluids containing TiO2 nanoparticles, pristine MWCNTs, oxidized MWCNTs and decorated MWCNTs with TiO2 nanoparticles are experimentally investigated. The results of rheological characteristics of nanofluids revealed that nanofluid of TiO2 nanoparticle and MWCNT-TiO2 exhibits shear thickening or dilatant behavior. In contrast, nanofluids containing pristine and oxidized MWCNTs depict the shear thinning or pseudoplastic behavior. Also results demonstrated that the rheological characteristics of nanofluids are functions of temperature and concentration, whereas the viscosity of all prepared nanofluids decreases with increasing the temperature and decreasing the concentration. In addition, the results show that the oxidation of MWCNTs in nitric acid leads to the reduction in viscosity. The rheological behavior of decorated MWCNTs illustrates that viscosity decreases by increasing the attached TiO2 nanoparticles. TEM results show that TiO2 nanoparticles successfully attached to the outer surface of oxidized MWCNTs. © 2015 Akadémiai Kiadó, Budapest, Hungary. Source

Khosravi I.,Ferdowsi University of Mashhad | Yazdanbakhsh M.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute
Materials Chemistry and Physics | Year: 2011

In this paper, nanospinels NiMnxFe2-xO4 (x = 0.05, 0.1, 0.3, 0.5, 0.7, and 1) were prepared by sol-gel method in the presence of nitrate-metal-ethylene glycol (EG) polymerized complex. The nanospinels were characterized using thermogravimetry analysis (TGA), X-ray powder diffraction (XRD), Fourier infrared spectroscopy (FTIR), and transmission electron microscope (TEM). The adsorption of an azo dye, reactive blue 5 (RB5), from water was determined using the prepared nanospinels. The effect of operational parameters such as the initial dye concentration, the concentration of nanospinels, temperature, and pH on the degradation of dye was investigated. The adsorption process follows second-order kinetics and Arrhenius behavior. Two common models, the Langmuir and Freundlich isotherms were used to investigate the interaction of dye and nanospinels. The isotherm evaluations revealed that the Freundlich model provides better fit to the experimental data than that of the Langmuir model. The photocatalytic degradation of RB5 at pH 1 under UV irradiation was examined. The results showed that the degradation of RB5 dye follows merely an adsorption process. © 2011 Elsevier B.V. All rights reserved. Source

Abareshi M.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Mojtaba Zebarjad S.,Ferdowsi University of Mashhad | Khandan Fadafan H.,Golestan University | Youssefi A.,Par e Tavous Research Institute
Journal of Magnetism and Magnetic Materials | Year: 2010

Magnetite Fe3O4 nanoparticles were synthesized by a co-precipitation method at different pH values. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electronic microscopy. Their magnetic properties were evaluated on a vibrating sample magnetometer. The results show that the shape of the particles is cubic and they are superparamagnetic at room temperature. Magnetic nanofluids were prepared by dispersing the Fe3O4 nanoparticles in water as a base fluid in the presence of tetramethyl ammonium hydroxide as a dispersant. The thermal conductivity of the nanofluids was measured as a function of volume fraction and temperature. The results show that the thermal conductivity ratio of the nanofluids increases with increase in temperature and volume fraction. The highest enhancement of thermal conductivity was 11.5% in the nanofluid of 3 vol% of nanoparticles at 40 °C. The experimental results were also compared with the theoretical models. © 2010 Elsevier B.V. All rights reserved. Source

Hadadian M.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute
Journal of Nanoparticle Research | Year: 2014

Highly stable graphene oxide (GO)-based nanofluids were simply prepared by dispersing graphite oxide with the average crystallite size of 20 nm, in polar base fluids without using any surfactant. Electrical conductivity, thermal conductivity, and rheological properties of the nanofluids were measured at different mass fractions and various temperatures. An enormous enhancement, 25,678 %, in electrical conductivity of distilled water was observed by loading 0.0006 mass fraction of GO at 25 °C. GO–ethylene glycol nanofluids exhibited a non-Newtonian shear-thinning behavior followed by a shear-independent region. This shear-thinning behavior became more pronounced at higher GO concentrations. The maximum ratio of the viscosity of nanofluid to that of the ethylene glycol as a base fluid was 3.4 for the mass fraction of 0.005 of GO at 20 °C under shear rate of 27.5 s−1. Thermal conductivity enhancement of 30 % was obtained for GO–ethylene glycol nanofluid for mass fraction of 0.07. The measurement of the transport properties of this new kind of nanofluid showed that it could provide an ideal fluid for heat transfer and electronic applications. © 2014, Springer Science+Business Media Dordrecht. Source

Arbab-Zavar M.H.,Ferdowsi University of Mashhad | Chamsaz M.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute | Aliakbari M.,Ferdowsi University of Mashhad
Microchemical Journal | Year: 2013

A new flow injection method coupled to an electrochemical hydride generator with atomic absorption spectrometry was proposed for determination of cadmium. The influence of the experimental parameters such as cathode material, catholyte type, sample volume, catholyte flow rate, temperature of the atomizer, catholyte concentration, carrier gas flow rate, electrolytic current and cathode surface area on the analytical response was studied. Under the optimized conditions, the calibration curve was linear in the range of 2-50ngmL-1 of Cd. A concentration detection limit (3σb, n=9) of 0.61ngmL-1 Cd and a relative standard deviation of 5.1% (RSD, n=9) for 20ngmL-1 Cd were obtained. The potential interferences from various ions were also evaluated. The accuracy of the method was verified by the determination of cadmium in a certified reference material. The calculated concentration of Cd in CRM was found to be in good agreement with the certified value. © 2012 Elsevier B.V. Source

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