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Journal ArticleDOI

Surfactant free magnetic nanofluids based on core-shell type nanoparticle decorated multiwalled carbon nanotubes

27 Sep 2011-Journal of Applied Physics (American Institute of Physics)-Vol. 110, Iss: 6, pp 064325
TL;DR: In this paper, the authors presented a novel magnetic nanofluid obtained by dispersing silicon dioxide (SiO2) coated on magnetite (Fe3O4) particle decorated multiwalled carbon nanotubes (MWNTs) in de-ionized water.
Abstract: Magnetic nanofluids consisting of fluids suspended with magnetic materials are of current interest and have potential applications in both energy related and biomedical fields In this paper, we present a novel magnetic nanofluid obtained by dispersing silicon dioxide (SiO2) coated on magnetite (Fe3O4) particle decorated multiwalled carbon nanotubes (MWNTs) (Fe3O4@SiO2/MWNTs) in de-ionized water As compared to a magnetite decorated MWNT based nanofluid, the present system shows better stability and thermal properties without the use of any surfactants Fe3O4/MWNTs and Fe3O4@SiO2/MWNTs have been synthesized via a simple chemical reduction technique and dispersed in de-ionized water via ultrasonication Dispersed de-ionized water based nanofluids containing Fe3O4/MWNTs with surfactant and Fe3O4@SiO2/MWNTs without surfactant show a thermal conductivity enhancement of 20% and 245%, respectively, for a volume fraction of 003% in the presence of magnetic field The enhancement in the thermal conductivity has
Citations
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Journal ArticleDOI
TL;DR: In this paper, the convective heat transfer coefficient and friction factor for fully developed turbulent flow of MWCNT-Fe3O4/water hybrid nanofluids flowing through a uniformly-heated-atconstant-heat-flux circular tube are estimated.

453 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis of hybrid nanoparticles, preparation of hybrid nanofluids, thermal properties, heat transfer, friction factor and the available Nusselt number and friction factor correlations are discussed.
Abstract: In the past decade, research on nanofluids has been increased rapidly and reports reveal that nanofluids are beneficial heat transfer fluids for engineering applications. The heat transfer enhancement of nanofluids is primarily dependent on thermal conductivity of nanoparticles, particle volume concentrations and mass flow rates. Under constant particle volume concentrations and flow rates, the heat transfer enhancement only depends on the thermal conductivity of the nanoparticles. The thermal conductivity of nanoparticles may be altered or changed by preparing hybrid (composite) nanoparticles. Hybrid nanoparticles are defined as nanoparticles composed by two or more different materials of nanometer size. The fluids prepared with hybrid nanoparticles are known as hybrid nanofluids. The motivation for the preparation of hybrid nanofluids is to obtain further heat transfer enhancement with augmented thermal conductivity of these nanofluids. This review covers the synthesis of hybrid nanoparticles, preparation of hybrid nanofluids, thermal properties, heat transfer, friction factor and the available Nusselt number and friction factor correlations. The review also demonstrates that hybrid nanofluids are more effective heat transfer fluids than single nanoparticles based nanofluids or conventional fluids. Notwithstanding, full understanding of the mechanisms associated with heat transfer enhancement of hybrid nanofluids is still lacking and, consequently it is required a considerable research effort in this area.

365 citations

Journal ArticleDOI
TL;DR: The preparation of nanofluids by various techniques, methods of stabilization, stability measurement techniques, thermal conductivity and heat capacity studies, proposed mechanisms of heat transport, theoretical models on thermal Conductivity, factors influencing k and the effect of nanoinclusions in PCM are discussed in this review.

341 citations


Additional excerpts

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Journal ArticleDOI
TL;DR: In this article, a numerical evaluation of three oxide-based nanofluids and their hybrids is proposed, which is a function of the Reynolds number, Prandtl number, and nanoparticle concentration.

180 citations

References
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Journal ArticleDOI
TL;DR: The use of Raman spectroscopy to reveal the remarkable structure and the unusual electronic and phonon properties of single wall carbon nanotubes (SWNTs) is reviewed comprehensively in this article.

3,835 citations

Journal ArticleDOI
TL;DR: In this paper, a transient hot-wire method was used to measure the thermal conductivity of a small amount of nanoparticles and the experimental results showed that these nanoparticles have substantially higher thermal conductivities than the same liquids without nanoparticles.
Abstract: Oxide nanofluids were produced and their thermal conductivities were measured by a transient hot-wire method. The experimental results show that these nanofluids, containing a small amount of nanoparticles, have substantially higher thermal conductivities than the same liquids without nanoparticles. Comparisons between experiments and the Hamilton and Crosser model show that the model can predict the thermal conductivity of nanofluids containing large agglomerated Al{sub 2}O{sub 3} particles. However, the model appears to be inadequate for nanofluids containing CuO particles. This suggests that not only particle shape but size is considered to be dominant in enhancing the thermal conductivity of nanofluids.

2,811 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the increase of thermal conductivity with temperature for nano fluids with water as base fluid and particles of Al 2 O 3 or CuO as suspension material.
Abstract: Usual heat transfer fluids with suspended ultra fine particles of nanometer size are named as nanofluids, which have opened a new dimension in heat transfer processes. The recent investigations confirm the potential of nanofluids in enhancing heat transfer required for present age technology. The present investigation goes detailed into investigating the increase of thermal conductivity with temperature for nano fluids with water as base fluid and particles of Al 2 O 3 or CuO as suspension material. A temperature oscillation technique is utilized for the measurement of thermal diffusivity and thermal conductivity is calculated from it

2,177 citations

Journal ArticleDOI
TL;DR: It is shown that NPs with predetermined dimensions and size-dependent properties can be synthesized by using a very delicate balance between the reaction conditions, the composition and the structure of microgel templates, and the concentration of NPs in the microgel.
Abstract: We report a strategy for the production of materials with structural hierarchy. The approach employs polymer microgels as templates for the synthesis of semiconductor, metal, or magnetic nanoparticles (NPs). We show that NPs with predetermined dimensions and size-dependent properties can be synthesized by using a very delicate balance between the reaction conditions, the composition and the structure of microgel templates, and the concentration of NPs in the microgel. Postheat treatment of microgels doped with semiconductor nanoparticles reduces NP polydispersity and allows control of their photoluminescence. Microgel templates are particularly beneficial in the synthesis of polymer microspheres heavily loaded with monodisperse superparamagnetic Fe3O4 NPs. Hybrid submicrometer-size microgels have promising potential applications in photonics, catalysis, and separation technologies.

608 citations

Journal ArticleDOI
TL;DR: In this article, the thermal conductivities of CNT-ethylene glycol and synthetic engine oil suspensions were investigated using a modified transient hot wire method, and the results showed that CNT nanofluids have noticeably higher thermal conductivity than the base fluid without CNT.

568 citations