Synthesis of Fe-Co magnetic nanoparticles via reverse micelle method

• Main Author: Koh, Nicholas Jing Qin
• Other Authors: Raju V. Ramanujan
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials
• Online Access: http://hdl.handle.net/10356/76846
• Institution: Nanyang Technological University

Magnetic fluid based cooling is thermal management system, which operates owing to the principle of thermomagnetic convection (TMC). TMC takes place when the ferrofluid circulates in a device loop under the combined effect of thermal energy and externally applied magnetic field. During this process, the ferrofluid transfers the excess heat from the devices/equipments (heat load) to the heat sink. In this era, where energy crisis is one of the biggest problem, such cooling systems are of paramount importance as they cool the devices by carrying the waste heat from the heat load, without any external power requirement. The effectiveness of such cooling systems depend strongly on the type of ferrofluids used. Hence, these ferrofluids should be synthesized with nanoparticles, which possess superior magnetic property and greater thermal conductivity. Compared to oxide nanoparticles, the metallic/alloy based nanoparticles can fulfil the two aforementioned criteria. However, due to the difficulties in synthesizing metallic/alloy magnetic nanoparticles, the oxide magnetic nanoparticles are still widely used. To overcome these difficulties, reverse micelle techniques are adopted to prepare metallic magnetic nanoparticles for ferrofluid synthesis. Two variables that are crucial in reverse micelle are the concentration of AOT surfactants and Fe2+/Co2+ salt solution:AOT solution ratio. Different configurations of the two variables are tested to produce different samples of nanoparticles. The as-synthesized samples using higher AOT surfactant volume ratio and concentration had shown lesser signs of oxidation and higher presence of Fe-Co contents. However, this as-synthesized samples display lower saturation magnetization due the masking effect from the non-magnetic nanoparticle’s surfactant layer. The increment in the AOT surfactant concentration from 0.2M to 0.6M can also cause the decomposition onset temperatures to drop from 239oC to 217oC. Of all configurations, the assynthesized samples using 1:2 salt solution: AOT/solvent solution and 0.2M AOT/solvent solution display the greatest magnetization saturation and relatively good thermal stability. Hence, controlled amount of surfactant used is important in the synthesis metallic magnetic nanoparticles (MNPs).