温度相关的微波频率下氯化钠水溶液介电特性

针对NaCl水溶液(0.001–0.5 mol/L)介电特性, 实验调查了频率(200–6.25 GHz), 温度(293–353 K)、 浓度相关复介电常数. 结果表明: 频率增大的过程中虚部呈逐渐减小的趋势, 高温使离子扰动增大, 破坏了溶液内部水分子四面体结构和氢键构象而使介电常数实部减小. 与纯水相比, 溶液的损耗角正切在高温353 K低频区下降明显. 同时发现2.45和5.8 GHz的复介电常数随温度变化的温度窗效应, 温度窗效应导致微波加热时耗散功率的振荡变化, 温度分布不均匀现象在实验中得以证实.关键词：微波复介电常数介电特性高温探头

Temperature dependent dielectric of aqueous NaCl solution at microwave frequency

Dielectric properties of aqueous NaCl solution, which are dependent on temperature (293-353 K), with a concentration in a range of 0.001-0.5 mol/L at microwave frequencies ranging from 200 MHz to 6.25 GHz are studied experimentally. The results indicate that imaginary part decreases with frequency increasing, and tetrahedral structure of H₂O and hydrogen bond of aqueous NaCl solution is broken by high temperature, leading to the decreasing of real part of dielectric. The loss angle tangent in solution obviously decreases in a low frequency zone at 353 K compared with that in pure water. Temperature window effect that complex dielectric increases or decreases with temperature varying at 2.45 GHz and 5.8 GHz, thereby leading to the oscillation of dissipation power in microwave heating process and the nonequilibrium distribution of temperature is also confirmed.