Abbas Youssefi

Ferdowsi University Of Mashhad, Mashad, Razavi Khorasan, Iran

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Publications (31)47.27 Total impact

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    ABSTRACT: We report the thermal conductivity modeling of nanofluids containing decorated MWCNTs with TiO2 nanoparticles. Therefore we synthesis TiO2 nanoparticles and decorated MWCNTs with different amount of TiO2 nanoparticles. The experimental results show that the measured thermal conductivities of TiO2 nanofluids and MWCNTs nanofluids are higher than the predicted values by theoretical models. The comparison results of MWCNTs nanofluid and MWCNTs-TiO2 nanofluids reveal that the predicted values by Xue model are closer to the measure values. In addition, the results show that thermal conductivity of nanofluids containing of MWCNTs-TiO2 increases with respect to TiO2 content of hybrid. Keywords: MWCNT, TiO2 nanoparticles, thermal conductivity, nanofluid, modeling
    No preview · Article · Jan 2016 · Experimental Heat Transfer
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    Full-text · Dataset · Jan 2016
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    Full-text · Dataset · Jan 2016
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    ABSTRACT: Abstract 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 exhibit shear-thickening or dilatants 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 of viscosity. The rheological behavior of decorated MWCNTs illustrate that viscosity decreases by increasing the attached TiO2 nanoparticles. TEM results show that TiO2 nanoparticles successfully attached to the outer surface of oxidized MWCNTs. Keywords: MWCNT; TiO2 Nanoparticles; Flow behavior; Viscosity
    Full-text · Article · Jan 2016 · Journal of Thermal Analysis and Calorimetry
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    ABSTRACT: Synthesis of different phases of titania nanoparticles (TiO2) and decorated Multi-walled carbon nanotubes (MWCNTs) with various content of rutile titania have been performed. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The XRD results showed that the amount of precursor strongly influenced by phase transition of TiO2 nanoparticles. TEM images showed that the outer surface of MWCNTs modified with TiO2 nanoparticles. The selected-area electron diffraction (SAED) of TiO2 nanoparticles and MWCNTs-TiO2 revealed the polycrystalline structure of the samples. FTIR analysis confirmed the presence of oxygen containing groups on the surface of oxidized MWCNTs and TiO2 on the surface of decorated MWCNTs. Optical properties of samples measured using UV-Vis spectrophotometer and the achieved results demonstrated that dispersibility of oxidized and decorated MWCNTs is higher than that of pristine MWCNTs. The XPS results showed that TiO2 nanoparticles were covalently attached on the side walls of acid-treated multi-walled carbon nanotubes.
    Full-text · Article · Jan 2015 · Synthesis and Reactivity in Inorganic Metal-Organic and Nano-Metal Chemistry
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    ABSTRACT: Abstract 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 exhibit shear-thickening or dilatants 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 of viscosity. The rheological behavior of decorated MWCNTs illustrate that viscosity decreases by increasing the attached TiO2 nanoparticles. TEM results show that TiO2 nanoparticles successfully attached to the outer surface of oxidized MWCNTs. Keywords: MWCNT; TiO2 Nanoparticles; Flow behavior; Viscosity
    No preview · Article · Jan 2015

  • No preview · Article · Jan 2015
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    ABSTRACT: Abstract In this paper, we report for the first time the thermal conductivity behavior of nanofluids containing MWCNTs which decorated with different amount of TiO2 nanoparticles. For this purpose we synthesis the TiO2 nanoparticles and decorated MWCNTs with different amount of TiO2 nanoparticles using hydrolysis method. The samples are characterized by transmission electron microscopy (TEM). TEM image confirmed that the ends of MWCNTs successfully opened. Meainwhile acid treatment leads to the cutting of MWCNTs to the short length and the outer surface of MWCNTs successfully decorated withTiO2 nanoparticles. Measurements of thermal conductivity behavior of nanofluids were carried out in the range of temperature varying from 25 to 70 °C. The mass fraction of the TiO2 nanoparticles, MWCNTs and decorated multi walled carbon nanotubes with TiO2 nanoparticles in water is 0.25, 0.5, 1 and 1.5 %wt..The results of thermal conductivity behavior of nanofluids revealed that the thermal conductivity and enhancement ratio of thermal conductivity of MWCNTs-TiO2 at different amount of TiO2 nanoparticles are higher than those of TiO2 and MWCNTs nanofluids. Temperature and weight fraction dependence study also show that the thermal conductivity of all nanofluids increases with temperature and weight fraction. However the influence of temperature is more significant than that of weight fraction. Keywords: MWCNT, TiO2 Nanoparticles, Decoration, Thermal Conductivity
    No preview · Conference Paper · Jan 2015
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    Full-text · Article · Jan 2015
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    ABSTRACT: Abstract The aim of the current research is concentrated on the modification of multi-walled carbon nanotubes (MWCNT) using TiO2 nanoparticles at rutile phase. In order to elucidate the role of TiO2 content on photocatalyst behavior of MWCNTs, the hybrids were prepared with different amounts of TiO2 nanoparticles. the opening and functionalization of MWCNTs were carried out by oxidation with nitric acid solution. The samples were characterized by Fourier Transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). FTIR results show that functional groups such as carboxylic and hydroxyl groups have been successfully attached to the surface of nanotubes after acid treatment. The attaching these oxygen containing groups lead to easy dispersion of CNTs in polar solution. TEM results of oxidized MWCNTs illustrated opening of MWCNTs at the end tips. The micrographs taken from the modified carbon nanotubes prove that the surface of MWCNTs is decorated with nano-sized TiO2. The TEM results revealed that the average size of TiO2 nanoparticles which modified MWCNTs were 20nm. TGA results confermed that there was no obvious weight loss between 300 and 400℃, therefore there is no amorphous carbons in the raw samples The results obtained from thermal behavior of modified CNTs revealed that the hybrid with highest amount of TiO2 had the higher temperature of decomposition. Keywords: Physical behavior, MWCNT, TiO2, Thermal stability
    No preview · Conference Paper · Jan 2015
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    ABSTRACT: 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.
    Full-text · Article · Dec 2014 · Journal of Nanoparticle Research
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    ABSTRACT: In this paper, we report for the first time the statistical analysis of thermal conductivity of nanofluids containing TiO2 nanoparticles, pristine MWCNTs and decorated MWCNTs with different amount of TiO2 nanoparticles. The functionalized MWCNT and synthesized hybrid of MWCNT-TiO2 were characterized using transmission electron microscopy (TEM). TEM image confirmed that the ends of MWCNTs were opened during the oxidation of them in HNO3 and TiO2 nanoparticles successfully attach to the outer surface of oxidized MWCNTs. Thermal conductivity measurements of nanofluids were analyzed via two factor completely randomized design and comparison of data means is carried out with Duncan’s multiple range test. Statistical analysis of experimental data shows that temperature and weight fraction have a reasonable impact on the thermal conductivity of all tested nanofluids (α=0.05). The results also show that increasing temperature and weight fraction leads to the increasing of thermal conductivity.
    Full-text · Article · Oct 2014 · Bulletin of Materials Science
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    ABSTRACT: هدف از اين تحقيق، اتصال کووالانسی نانوذرات TiO2روی سطح نانولوله­های کربنی و بررسی پایداری و هدایت حرارتی نانوسيال می­باشد. نانولوله­های آرایش یافته با میکروسکوپ الکترونی عبوری (TEM) جهت اطمینان از اتصال نانوذرات TiO2 و طیف سنجی رامان جهت بررسی تغییرات میزان گرافیته شدن مورد بررسی قرار گرفتند. پایداری نانوسیال به کمک پتانسیل زتا بررسی گردید. تصاویر TEM نشان دهنده اتصال نانوذرات TiO2روی سطح نانولوله­ها می­باشد. طیف­سنجی رامان نشان­دهنده افزایش میزان عیوب ایجاد شده در ساختار نانولوله با افزایش میزان نانوذرات متصل شده می­باشد. نتایج حاصل از بررسی پایداری نانوسیال نشان داد که با افزایش میزان نانوذرات متصل شده، پایداری نانوسیال کمتر می­شود. همچنین نتایج بررسی ها نشان داد که دما و غلظت تاثیر معناداری بر روی میزان هدایت حرارتی نانوسیال دارند.
    Full-text · Article · Jan 2014
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    ABSTRACT: Synthesis of different phases of titania nanoparticles (TiO2) and decorated Multi-walled carbon nanotubes (MWCNTs) with various content of rutile titania have been performed. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The XRD results showed that the amount of precursor strongly influenced by phase transition of TiO2 nanoparticles. TEM images showed that the outer surface of MWCNTs modified with TiO2 nanoparticles. The selected-area electron diffraction (SAED) of TiO2 nanoparticles and MWCNTs-TiO2 revealed the polycrystalline structure of the samples. FTIR analysis confirmed the presence of oxygen containing groups on the surface of oxidized MWCNTs and TiO2 on the surface of decorated MWCNTs. Optical properties of samples measured using UV-Vis spectrophotometer and the achieved results demonstrated that dispersibility of oxidized and decorated MWCNTs is higher than that of pristine MWCNTs. The XPS results showed that TiO2 nanoparticles were covalently attached on the side walls of acid-treated multi-walled carbon nanotubes.
    No preview · Article · Nov 2013 · Synthesis and Reactivity in Inorganic Metal-Organic and Nano-Metal Chemistry
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    ABSTRACT: 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 2–50 ng mL− 1 of Cd. A concentration detection limit (3σb, n = 9) of 0.61 ng mL− 1 Cd and a relative standard deviation of 5.1% (RSD, n = 9) for 20 ng mL− 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.
    No preview · Article · May 2013 · Microchemical Journal
  • M H Arbab-Zavar · M Chamsaz · A Youssefi · M Aliakbari
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    ABSTRACT: 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.
    No preview · Article · Aug 2012 · Talanta
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    ABSTRACT: 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.
    No preview · Article · Jul 2012 · Analytical Sciences
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    ABSTRACT: 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.
    No preview · Article · Nov 2011 · Materials Chemistry and Physics
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    ABSTRACT: For the first time, nanoparticles of zinc chromite, spinel ZnCr(2)O(4) 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 13 nm 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 ZnCr(2)O(4) under UV irradiation at pH=1 has been also examined. The results showed that the degradation of RB5 dye follows merely an adsorption process.
    No preview · Article · Dec 2010 · Journal of hazardous materials
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    ABSTRACT: It is realized that the surface of biomedical metallic implants covered by fluorohydroxyapatite, [Ca10(PO4)6(OH, F)] (FHA) can create bioactivity of the implant and shorten healing time. In this work FHA, in the form of powders and of thin films on titanium substrates, were synthesized by sol-gel spin coating method, using calcium nitrate tetrahydrate (Ca(NO3)2)·4H2O, phosphorous pentoxide (P2O5) and ammonium fluoride (NH4F) to provide Ca-precursor, P-precursor and fluorine reagent, respectively. The FHA powders were calcined and thin films were fired at temperatures ranging from 500-800°C The constituent of both powders and thin films were confirmed as FHA using X-ray diffraction (XRD) and Fourier transform Infrared spectroscopy (FTlR). The thermal stability of FHA powders was studied by differential thermal analysis (DTA). The optimized calcination and firing temperature was 600°C Transmission electron microscopy (TEM) results with Debye-Scherrer equation gave the size of the FHA particles in nano-scale range. The films were found to be quite uniform and dense by SEM.
    Full-text · Article · Dec 2010