Ishida T, Makino T
Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki, Kagawa, 761-0795, Japan
J Colloid Interface Sci. 1999 Apr 1;212(1):144-151. doi: 10.1006/jcis.1998.6029.
By the use of a time domain reflectomery method, dielectric measurements were carried out on silica, alumina, and silica-alumina gel suspensions (five types with composition varying between 0.3 < Si/Al atomic ratio <0.8) in the frequency range of 100 kHz to 20 GHz. For all the gels, a relaxation peak due to bound water was observed. This peak locates at around 1-10 MHz, indicating that the peak is a decade or 10 decades lower than those of biological polymers such as an aqueous DNA solution. The silica and alumina gels have a different bound water structure, judging from the fact that the peaks are different in their locations and shapes between the two gels. The silica-alumina gels exhibit two different peaks other than the peak of bulk water. The sum of the relaxation strength on the two peaks is proportional to the monolayer capacity obtained from water vapor isotherms. The shape of the one peak holds that of the silica gel, whereas the other retains that of alumina gel, and furthermore the ratio of the relaxation strength on the former peak to that on the latter depends on Si/Al atomic ratio. It is suggested that both peaks are caused by the orientation of bound water molecules. Copyright 1999 Academic Press.
通过使用时域反射法，在100 kHz至20 GHz的频率范围内，对二氧化硅、氧化铝和硅铝凝胶悬浮液（五种类型，硅/铝原子比在0.3 < Si/Al < 0.8之间变化）进行了介电测量。对于所有凝胶，均观察到了由于结合水引起的弛豫峰。该峰位于1 - 10 MHz左右，这表明该峰比诸如DNA水溶液等生物聚合物的峰低一个数量级或十个数量级。从两种凝胶的峰在位置和形状上不同这一事实判断，二氧化硅凝胶和氧化铝凝胶具有不同的结合水结构。硅铝凝胶除了出现大量水的峰之外，还表现出两个不同的峰。这两个峰的弛豫强度之和与从水蒸气等温线获得的单层容量成正比。其中一个峰的形状与二氧化硅凝胶的峰相同，而另一个峰的形状与氧化铝凝胶的峰相同，此外，前一个峰的弛豫强度与后一个峰的弛豫强度之比取决于硅/铝原子比。有人认为这两个峰都是由结合水分子的取向引起的。版权所有1999年学术出版社。
