液相化学反应介电常数的测量与气泡影响分析

Measurement of effective permittivity for solution chemical reaction and analysis of air bubble effect

溶液中化学反应的等效介电常数是微波化学研究中的重要内容,等效介电常数的精确测量是研究微波与化学反应系统相互作用的基础。介绍了一种对溶液中化学反应等效介电常数随时间微弱变化跟踪测量的方法并对测量中经常遇到的气泡影响进行了分析。最后制作了一批测量探头,该探头可以有效排除其中的气泡。通过测量得到的反射系数和遗传算法(GA)可以对等效介电常数的微小变化进行精确测量。对稀溶液中的皂化反应测量的结果证实了该测量方法的有效性。

One of fundamental studies in microwave chemistry is to measure effective permittivity of chemical reaction precisely. A combination of experiment with computational method to determine the effective permittivity of reaction that changes feebly with respect to time in dilute solution is introduced in this paper. A new type of slotted resonant coaxial sensor is designed to avoid the influence of air bubble in the experiment. To predict influence of air bubble, the electromagnetic field distribution near the sensor with air bubble and the reflection coefficient is calculated by employing FDTD method. A GA-based inverse calculation technique was used to determine the complex permittivity from the measured reflection coefficient. Finally, the method is used to determine the effective permittivity of dilute solution in a typical saponification reaction. The feasibility of the method is proven by the experimental results.