Abstract:

Two cationic surfactants, N-cetyl-N-(hydroxyethyl)-N,N-dimethyl ammonium bromide(CHDAB) and 1,4-bis(cetyldimethylammonium) propane dibromide(G16-4-16), were used as surface-modified reagents for preparation of hydrophobic gold nanoparticles from reduction of HAuCl₄ with KBH₄ in mixture of petroleum ether/n-butanol/H₂O. The results show that gemini surfactant G16-4-16 is better for coating and dispersing, and the gold nanoparticles coated by the gemini surfactant G16-4-16 have a narrow size distribution with an average diameter of 5.2 nm. Stable nanofluids containing gold nanoparticles with hydrocarbon(toluene) as base liquids were prepared. The thermal stability of the nanofluids as a function of time was monitored using UV-Vis absorption method. It is shown that the gold nanofluid has good thermal stability, which has a stable time of 20 h at 130 ℃. The thermal conductivity of the gold nanofluids was performed by point heat source method. The enhancements of thermal conductivity of the gold nanofluids containing 1.5%(mass fraction) gold nanoparticles can reach 17%.

Key words: Nanofluid, Nano gold, Gemini surfactant, Thermal stability