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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.


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.


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.


Goharshadi E.K.,Ferdowsi University of Mashhad | Abareshi M.,Ferdowsi University of Mashhad | Mehrkhah R.,Ferdowsi University of Mashhad | Samiee S.,Ferdowsi University of Mashhad | And 3 more authors.
Materials Science in Semiconductor Processing | Year: 2011

A convenient microwave method in preparation of zinc oxide nanoparticles (ZnONPs) using an ionic liquid, trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}-imide, [P66614][NTf2], as a green solvent is described in this paper. To the best of our knowledge, there is no report for synthesizing any nanoparticle using this ionic liquid. Trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}-imide has low interface tension and thus it can enhance the nucleation rate, which is favorable to the formation of smaller ZnONPs. The fabricated ZnONPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis spectroscopy. The XRD pattern reveals that the ZnONPs have hexagonal wurtzite structure. The strong intensity and narrow width of ZnO diffraction peaks indicate that the resulting nanoparticles are of high crystallinity. The synthesized ZnONPs show direct band gap of 3.43 eV. The UVvis absorption spectrum of ZnONPs dispersed in ethylene glycol at room temperature revealed a blue-shifted onset of absorption. © 2010 Elsevier Ltd. All rights reserved.


Yazdanbakhsh M.,Ferdowsi University of Mashhad | Khosravi I.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute
Journal of Hazardous Materials | Year: 2010

For the first time, nanoparticles of zinc chromite, spinel ZnCr2O4 have been fabricated by the thermal decomposition of Zn-Cr gel prepared by sol-gel method in the presence of oxalic acid as a chelating agent. It was shown that the well-crystallized spinel structure is formed after calcination at 450°C. The nanospinel has been characterized by differential thermal analysis (DTA), X-ray powder diffraction (XRD), infrared spectroscopy (IR), and transmission electron microscope (TEM). The average particle size is approximately 13nm according to the TEM image. The nanoparticles of zinc chromites showed excellent adsorption properties towards reactive dye, reactive blue 5 (RB5). The adsorption studies have been carried out for contact time, different pH values, different temperatures, and adsorbent doses. The investigation of removal kinetics of RB5 indicates that the removal process obeys the rate of second-order kinetic equation. The results indicate that the Langmuir adsorption isotherm fitted the data better than the Freundlich. Also, the photocatalytic degradation of RB5 using spinel ZnCr2O4 under UV irradiation at pH=1 has been also examined. The results showed that the degradation of RB5 dye follows merely an adsorption process. © 2010 Elsevier B.V.


Karimi-Nazarabad M.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute
Journal of Molecular Liquids | Year: 2016

In this work, for the first time, particle shape effect on transport properties of nanofluids of tungsten oxide nanoparticles (NPs) in glycerol was investigated. For this purpose, WO3 NPs with different shapes using two methods of hydrothermal and microwave in the presence and absence of sodium chloride were prepared. The TEM images showed that the method of preparation and presence or absence of NaCl influence the morphology and shape of WO3 NPs. For mass fraction of 0.5, a maximum of 46.9% and minimum of 11.7% reduction in viscosity of glycerol were observed for the nanofluids having the maximum spherical and polygonal-shape NPs, respectively. The results showed that the viscosity of glycerol and the nanofluids decreases exponentially with increasing temperature. The effect of temperature on the viscosity of nanofluids with polygonal shape NPs was greater than those of other shapes. The thermal conductivity of glycerol and suspensions of WO3 NPs in glycerol was measured at different temperatures. The maximum and minimum enhancements in thermal conductivity were observed for the samples containing the greatest and lowest values of spherical and polygonal-shape NPs, respectively for all temperatures. A maximum of 6.7% enhancement in the thermal conductivity of glycerol at 40 °C was observed when the NPs with a mass fraction of 0.5, prepared by hydrothermal method, was added. The thermal conductivity ratio of nanofluids increases with raising temperature linearly. © 2016 Elsevier B.V.


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.


Moosavi M.,Ferdowsi University of Mashhad | Goharshadi E.K.,Ferdowsi University of Mashhad | Youssefi A.,Par e Tavous Research Institute
International Journal of Heat and Fluid Flow | Year: 2010

ZnO nanofluids have been prepared by dispersing ZnO nanoparticles in the ethylene glycol (EG) and glycerol (G) as the base fluids. Ammonium citrate, as a dispersant, has been used to improve the dispersion of nanoparticles and suppressing formation of particle clusters to obtain stable suspensions.The thermal conductivity of ZnO nanofluids has been measured as a function of the volume fraction and temperature. The thermal conductivity of ZnO/EG and ZnO/G nanofluids increases nonlinearly up to 10.5% and 7.2%, respectively, as the volume fraction of nanoparticles increases up to 3. vol.%. The thermal conductivity of a ZnO nanofluid increases nonlinearly with increasing the temperature at a constant volume fraction of nanoparticles.For the first time, we have measured the viscosity and surface tension of ZnO nanofluids. The viscosity ratio of nanofluids increases with increasing concentration and decreasing the temperature. The surface tension ratio of suspensions containing solid particles increases with increasing the volume fraction of the solid nanoparticles.The experimental data for thermal conductivity and viscosity have been compared with some existing theoretical models. © 2010 Elsevier Inc.


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
Talanta | Year: 2012

A novel electrochemical hydride generation (ECHG) system working in flow-injection (FI) mode was developed for determination of cadmium coupled to an electrically heated quartz tube atomizer (QTA) by atomic absorption spectrometry (AAS). A Plackett-Burman experimental design for screening has been used to evaluate the influence of several variables on the analytical response. Then, the significant parameters such as the concentration of NaCl in catholyte, applied electrolytic current and flow rate of carrier gas have been simultaneously optimized using a central composite design (CCD). Under the optimized conditions, the detection limit (3σ b, n=9) was found to be 0.51 ng mL -1 Cd and the relative standard deviation (RSD) for nine replicate analyses of 20 ng mL -1 Cd was 6.5%. The calibration curve was linear in the range of 2-50 ng mL -1 of Cd. The potential interferences from various ions were also evaluated. The analysis of a reference material showed good agreement with the certified value. The proposed method was successfully applied to the determination of Cd in tap water sample. © 2012 Elsevier B.V. All rights reserved.


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
Analytical Sciences | Year: 2012

Electrochemical hydride generation (EcHG) as a sample introduction system for determination of zinc was developed. It was directly coupled to an electrically heated quartz tube atomizer (QTA) atomic absorption spectrometry (AAS) system. The hydride generator is a laboratory-made semi-batch electrolytic cell that consists of a lead-tin alloy cathode and a platinum anode. The effects of typical parameters on the generation efficiency of the technique, such as types of cathode material and catholyte and anolyte solutions, were studied. The influences of numerical experimental operating parameters on the analytical signal were evaluated in detail and optimum conditions were obtained. The analytical figures of merit for the developed method were determined. The calibration curve was linear up to 300 ng mL -1 of Zn. A concentration detection limit (3σ, n = 9) of 11 ng mL -1 Zn and a relative standard deviation of 5.0% (RSD, n = 9) for 200 ng mL -1 Zn were accessed. In addition, the susceptibility of interference from various ions was evaluated. The accuracy of the method was verified by determination of Zn in a certified reference material and in tap water. The achieved concentrations were found to be in good agreement with both the certified value and the data obtained using flame AAS. © The Japan Society for Analytical Chemistry.

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