Ultrasonic preparation, stability and thermal conductivity of a capped copper-methanol nanofluid

• Published in: Ultrasonics sonochemistry 2019-07, Vol.55, p.25-31
• Main Authors: Graves, J.E., Latvytė, E., Greenwood, A., Emekwuru, N.G.
• Format: Article
• Language: English
• Subjects: Copper nanoparticles; Methanol; Nanofluids; Nanorefrigerant; Particle size; Thermal conductivity; Thermofluids; Ultrasonic dispersion; Zeta potential
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2019.02.028

•A short-chain, capped copper-methanol nanofluid was prepared with the aid of an ultrasonic probe.•Higher ultrasonic processing amplitudes gave the lowest z-average value.•The capping agent formed a dense layer around the particle and increased stability.•The nanofluid had an enhanced thermal conductivity of 9% over the base fluid. This paper describes a two-step method to prepare novel copper-methanol nanofluids capped with a short chain molecule, (3-Aminopropyl)trimethoxysilane (APTMS). Two commercial nanopowders were dispersed at various powers using a 20 kHz ultrasonic probe into solutions of methanol and the capping agent. Ultrasonic energy input was measured by calorimetry with z-average diameters, intensity and number size distributions recorded by a dynamic light scattering technique. The stability of the dispersion was monitored visually, and quantified by recording the zeta potential. Dispersions of the bare powder were used as a control. Absorption spectroscopy was used to confirm the presence of the capping agent. The thermal conductivities of 0 to 10% wt./vol. (1.1% vol.) dispersions of the capped copper-methanol nanofluid were determined using a C-Therm analyzer. Optimum ultrasonic de-agglomeration conditions gave dispersions with a z-average particle size of