油基-金纳米流体的制备及热稳定性

分别采用N-十六烷基-N-(羟乙基)-N,N-二甲基溴化铵(CHDAB)和丁烷-1,4-二(N-十六烷基-N,N-二甲基溴化铵)(G16-4-16)2种阳离子表面活性剂作为金属表面修饰剂,在石油醚/正丁醇/水混合体系中用KBH4还原HAuCl4制备出亲油性纳米金.其中,双子表面活性剂G16-4-16显示出更好的包裹分散作用,其包裹的纳米金粒径分布范围较窄,平均粒径为5.2 nm.将该纳米金颗粒分散在液态烷烃、甲苯和长链烷基醇等溶剂中可制成稳定的油基纳米流体.采用紫外-可见光谱法跟踪热稳定性随时间的变化,结果表明,该纳米流体显示了较好的热稳定性,在130℃稳定时间达20 h.采用点热源法测定了该纳米流体的导热系数,结果表明,50℃时添加质量分数1.5%的纳米金可以使其导热系数增大约17%.

Preparation and Thermal Stability of Oil-based Au Nanofluids

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%.