Characteristics of Nanofluids Made from Solgel Synthesized-Al<sub>2</sub>O<sub>3</sub> Nanoparticles Using Citric Acid and PEG as Organic Agent and Bauxite as Raw Material

Abstract

Nanofluids have great attention in the world due to big potential to replace conventional fluids that have been used in some systems such as automotive, nuclear reactors, solar heating, building heating, and industry. Utilization of indigenous raw material in production of nanoparticles is a key to reach real application of the nanofluids. The aim of this study is to know the effect of combination of organic agent in solgel synthesis on characteristic of Al2O3nanoparticles and nanofluids made of them. In this study, Al2O3nanoparticles have been synthesized from local bauxite using solgel method with citric acid and PEG 4000 as chelating and capping agent. Nanofluids with pH 10 were prepared from the nanoparticles. Raw material of Al (OH)3was extracted from the bauxite. Powder of Al (OH)3was diluted in water, and citric acid and PEG 4000 was added into the solution to form a sol. The sol was heated to form a xerogel, and then calcined at 900°C for 3 hours to get the Al2O3nanoparticles. From the synthesis we got gamma-Al2O3nanoparticles with crystallite size of 4.0-4.6 nm. From the characterization data of the nanofluids it was known that the nanofluids with concentration of Al2O3nanoparticles of 0.025 vol % to 0.1 vol% possessed relatively high zeta potential of-39.2 mV to-40 mV, and good critical heat flux (CHF) enhancement of 13% to 74%. The nanofluids had large potential to be applied as coolant for External Reactor Core Cooling System (ERVCS), ECCS (Emergency Core Cooling System), electronics, automotive, metal forming and solar heating system.