On the use of microwaves to measure porosity of materials

The measure of porosity is of great interest in different industrial fields related to materials, such as in polymers, ceramics and composite materials technologies. Two microwave based procedures are here considered and analyzed, using, respectively, or a reflection sensor or a resonator sensor. By modelling the porous material under test as two phase mixture, the theorical performances are derived and usefull choice criteria between the two procedures in relation to different experimental conditions are obtained. The proposed procedures are fully non-destructive, non-contact and suitable for a real-time control by means of simple processing techniques of the output signals.