阳离子表面活性剂对纳米SiO_2流体稳定性的影响

Effect of Cationic Surfactants on the Stability of the Nano-SiO_2 Fluid

通过研究纳米SiO2/水纳米流体的稳定性建立了差示透光率法,并利用差示透光率法和重力沉降法研究了阳离子表面活性剂十四烷基三甲基溴化铵(TTAB)、十六烷基三甲基溴化铵(CTAB)和十八烷基三甲基溴化铵(OTAB)对纳米SiO2流体稳定性的影响。结果表明:阳离子表面活性剂吸附在纳米SiO2颗粒表面后促使纳米流体形成凝胶,且不同阳离子表面活性剂对2.5wt%SiO2纳米流体稳定性的影响均存在三个临界浓度C1、C2和C3,这三个临界浓度的大小与阳离子表面活性剂疏水链长密切相关,碳链越长,相应临界浓度越低,并提出了阳离子表面活性剂在纳米SiO2表面吸附后纳米颗粒之间的疏水缔合作用理论。

We researched the nano-SiO2/water nanofluid stability and established the method of differential transmittance. And then we studied the effect of different cationic surfaetants ： tetradecyl trimethyl ammonium bromide （TTAB）, cetyl trimethyl ammonium bromide （CTAB） and octadecyl trimethyl ammonium bromide （OTAB） on the nano-SiO2 fluid stability by using the method of differential transmittance and gravity sedimentation. The results showed that the surface of SiO2 nanopartieles after adsorbing cationic surfactant prompted nanofluid to form a gel, and there existed three critical concentrations C1, C2 and C3 by the type of cationic surfactant to 2.5wt% SiO2 nanofluid stability, and these three critical concentrations were closely related to the hydrophobic chain length , the longer the carbon chain, the lower the corresponding critical concentration. Finallly, we proposed a theory of hydrophobic associating interaction among the nano-SiO2 particles which its surface adsorbed cationic surfactants.