Microwave-Enhanced Solid State Reactions in Ionic Crystalline Solids

本研究项目的主要目标是分离和表征微波场增强效应对离子陶瓷中离子输运的影响。 调查将强调实验，以确定这种微波驱动力是否是一个占主导地位的机制负责增强固态扩散和界面化学反应。 测量将使用卤化物盐，一个14 GHz的微波源，和一个非谐振波导施加器。 将与俄罗斯科学院（下诺夫哥罗德）应用物理研究所的研究人员合作进行理论分析。 实验设计、实验施源器和实验操作将与罗克韦尔国际公司的研究人员合作完成。 计划进行两组实验：（1）测量微波对K+离子进入NaCl和Na+离子进入KCl的晶界扩散的影响，以及（2）测量微波对（伪）二元化合物形成的界面限制固态反应速率的影响。 在这两种情况下，将比较微波辐照和无微波样品的反应作为样品温度、微波场强度和电场极化的函数。 此外，PI计划微波加热陶瓷试样内的温度分布的实验研究。 这将解决微波加热/材料加工中精确测温的问题，以及微波加热玻璃和陶瓷中增强反应的报告是否可以（至少部分地）通过高达几百摄氏度的芯表面温差来解释。 具体而言，PI将表征内部温度梯度，由于倒置的温度分布通过微波加热的氧化物颗粒复合材料中的固态化合物形成的实验检查，其中在起始压块中的两个组分氧化物相反应形成一个或两个准二元化合物。 结果将进行比较的基础上的热传输和微波吸收模型的氧化物颗粒复合材料的预测。

The primary goal of this research project is to isolate and characterize a microwave-field-enhancement effect on ionic transport in ionic ceramics. The investigation will emphasize experiments to establish whether this microwave driving force is a dominant mechanism responsible for enhanced solid state diffusion and of interface chemical reactions. Measurements will made using halide salts, a 14 GHz microwave source, and a nonresonant waveguide applicator. Theoretical analyses will be conducted in collaboration with researchers from the Institute of Applied Physics, Russian Academy of Science (Nizhny Novgorod). Design of the experiments, the experimental applicator, and experimental operation will be completed in collaboration with a researcher from Rockwell International. Two sets of experiments are planned: (1) measurements of microwave effects on grain boundary diffusion of K+ ions into NaCl and Na+ ions into KCl, and (2) measurements of microwave effects on interface-limited solid-state reaction rates for (pseudo) binary compound formation. In both cases, th e reactions will be compared for microwave-irradiated and microwave-free samples as a function of sample temperature, microwave field strength, and electric field polarization. In addition, the PIs plan experimental studies of temperature distributions within microwave-heated ceramic specimen. This will address questions of accurate thermometry in microwave heating/materials processing and whether reports of enhanced reactions in microwave-heated glasses and ceramics can be (at least partially) explained by core-to surface temperature differentials of up to several hundred degrees Celsius. Specifically, the PIs will characterize internal temperature gradients due to inverted temperature profiles through the experimental examination of solid-state compound formation in microwave-heated oxide particulate composites in which the two component oxide phases in the starting compact react to form one or two quasi binary compounds. The results will be compared to predictions based on heat transport and microwave absorption modeling in oxide particulate composites.