Abstract
In this study, real-time and in-situ permittivity measurements under intense microwave electromagnetic fields are proposed as a powerful technique for the study of microwave-enhanced thermal processes in materials. In order to draw reliable conclusions about the temperatures at which transformations occur, we address how to accurately measure the bulk temperature of the samples under microwave irradiation. A new temperature calibration method merging data from four independent techniques is developed to obtain the bulk temperature as a function of the surface temperature in thermal processes under microwave conditions. Additionally, other analysis techniques such as Differential Thermal Analysis (DTA) or Raman spectroscopy are correlated to dielectric permittivity measurements and the temperatures of thermal transitions observed using each technique are compared. Our findings reveal that the combination of all these procedures could help prove the existence of specific non-thermal microwave effects in a scientifically meaningful way.
Highlights
The benefits of using microwaves for heating materials are well-known and have been widely recognized over the last decades
Our findings allow for deeper theoretical insight into the high-temperature ultrafast interaction of materials with microwaves and its kinetics, and most importantly, provide a solid experimental basis which, for the first time, could assess the existence of thermal or non-thermal effects in upcoming microwave heating experiments leading to new developments in microwave technology
The experimental setup (Fig. 1) used in our study for microwave heating and in-situ permittivity measurements of dielectric samples consisted of a dual-mode microwave cylindrical cavity capable to heat and measure with two separate microwave systems without interferences
Summary
As to experimental research into microwave applications, the in-situ and real-time observation of dielectric properties of materials during microwave heating, together with the synchronous recording of other process parameters, recently described by Catala-Civera et al.[20] has provided the basis for a better understanding of the interaction of materials with electromagnetic fields. We propose real-time and in-situ permittivity measurements under intense microwave electromagnetic fields together with the simultaneous determination of dielectric properties and synchronous recording of some thermo-physical and mechanical properties as a powerful technique for the study of thermal processes in materials. Our findings allow for deeper theoretical insight into the high-temperature ultrafast interaction of materials with microwaves and its kinetics, and most importantly, provide a solid experimental basis which, for the first time, could assess the existence of thermal or non-thermal effects in upcoming microwave heating experiments leading to new developments in microwave technology
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call