气相二氧化硅溶胶的介电弛豫行为研究

Study on the Dielectric Relaxation Behavior of Fumed Silica Suspensions

制备了不同浓度的亲水气相二氧化硅/水溶胶和憎水气相二氧化硅/乙醇溶胶,利用阻抗分析仪在102~107 Hz频率范围内测量了这些溶胶的介电谱.观察到分别位于104和105 Hz附近的2个介电弛豫行为,利用Cole-Cole公式对其进行了拟合并准确获得了这些弛豫的特征参数.结果发现,两种溶胶的介电弛豫行为均随气相二氧化硅浓度呈规律性变化.根据这些弛豫的特征及其随气相二氧化硅浓度的变化规律,确定了低频和高频弛豫分别来自于聚集体的对离子极化和界面极化,并进一步讨论了亲水和憎水气相二氧化硅分别在水和乙醇中的表面行为、分散状态及其随气相二氧化硅浓度的变化.

Colloidal suspensions of hydrophilic fumed silica in water and hydrophobic fumed silica in ethanol with different silica concentrations were prepared,and their dielectric spectra in the frequency range of 102 Hz to 107 Hz were measured by means of impedance analyzer.Two dielectric relaxation behaviors are observed locating in the vicinity of 104 Hz and 105 Hz in these spectra,they were then fit in line with Cole-Cole equation and characteristic parameters of these relaxations were accurately obtained.It is found that,the dielectric relaxation behaviors of both suspensions vary regularly with the concentration of silica.Based on the relaxation features and the regularity of the variation of the features with the silica concentration,it is confirmed that the low-and high-frequency relaxations are ascribed to counterion polarization and interfacial polarization of silica aggregate,respectively,furthermore,the surface behavior,the dispersing state,and their variation with the change of the concentration of silica of hydrophilic fumed silica in water and of hydrophobic fumed silica in ethanol were discussed in detail.