Materials Chemistry and Physics 113 (2009) 57–62 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Synthesis and characterization of copper nanofluid by a novel one-step method S. Ananda Kumar a,∗ , K. Shree Meenakshi a , B.R.V. Narashimhan b , S. Srikanth b , G. Arthanareeswaran c a Department of Chemistry, Anna University, Chennai 600025, Tamilnadu, India b National Metallurgical Laboratory, Taramani, Chennai 600112, India c Department of Chemical Engineering, National Institute of Technology, Trichy 620015, India article info Article history: Received 24 February 2008 Received in revised form 30 May 2008 Accepted 1 July 2008 Keywords: X-ray diffraction topography Visible and ultraviolet spectrometers Fourier transform infrared spectroscopy Thermal conductivity abstract This paper presents a novel one-step method for the preparation of stable, non-agglomerated copper nanofluids by reducing copper sulphate pentahydrate with sodium hypophosphite as reducing agent in ethylene glycol as base fluid by means of conventional heating. This is an in situ, one-step method which gives high yield of product with less time consumption. The characterization of the nanofluid is done by particle size analyzer, X-ray diffraction topography, UV–vis analysis and Fourier transform infrared spectroscopy (FT-IR) followed by the study of thermal conductivity of nanofluid by the transient hot wire method. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Cooling has become one of the top technical challenges faced by hi-tech industries such as microelectronics, transportation, manufacturing and metrology. There is a strong need in these industrial fields to develop heat transfer fluid [1,2] with sig- nificantly higher thermal conductivity than pure fluids. It is a well-known fact that crystalline solids have a higher thermal con- ductivity by one to three orders of magnitude than traditional fluids like water, ethylene glycol, oil, etc. Therefore fluids contain- ing suspended solid particles are reasonably expected to have a higher thermal conductivity than pure fluids. Nanofluids [3], con- taining metallic or non-metallic particles have attracted a great deal of research attention due to their higher heat transfer effi- ciency. Nanofluids having suspensions [4,5] of nanometer sized parti- cles have been proposed as a route for surpassing the performance of heat transfer liquids that are currently available [6]. Recent exper- iments on nanofluids have indicated that a significant increase in thermal conductivity could be achieved when compared with liquids without nanoparticles or larger particles [7–10]. For exam- ple 0.3 vol.% copper nanoparticles dispersed in ethylene glycol is ∗ Corresponding author. Tel.: +91 22203158; fax: +91 22203543. E-mail address: sri anand 72@yahoo.com (S.A. Kumar). reported to increase its inherent poor thermal conductivity by 40% [7]. At present copper nanofluids are prepared by dispersing copper nanoparticles in the base fluid [8]. This is a step-by-step method, which involves agglomeration that takes place during the process of drying, storage and transportation of nanoparticles. Agglomera- tion will result in settlement and clogging of the microchannels and hence the thermal conductivity of the nanofluids will be decreased. There are several other methods that are similar to one-step physical method, in which copper vapour is directly con- densed into nanoparticles by contact with a flowing low vapour pressure liquid [7] but this method appears to be cost ineffective. By polyol process [11], monodispersed, non-agglomerated cop- per nanoparticles are obtained since polyol acts as solvent and reducing agent. However, the major drawback of this method is that solution of the copper salt should be heated to its boiling point and kept under refluxing conditions for a long time [12]. In the aqueous chemical reduction method, though the rate of the reaction is high, the agglomeration problem exists, as a conse- quence, a decrease in the thermal conductivity of the nanofluid is observed in most cases [13]. Hence the development of a new and novel method for the preparation of a copper nanofluid is inevitable. With all these ideas in mind, an attempt has been made in the present investigation to synthesize copper nanofluid by a novel one-step method using copper sulphate as a source for copper nanoparticles, ethylene glycol as base fluid and sodium 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.07.027