Basic Principles of Microwave-Promoted Growth

Traditional heating methodologies rely on the transfer of energy from hotter to colder in-contact interfaces ultimately employing one or more of the known heat transfer mechanisms conduction, convection and/or radiation. 

Microwaves (MWs) correspond to a fraction of the electromagnetic spectrum including a range of frequencies from approximately 0.3 (L-band of the microwave spectrum) to 300 GHz (D-band). As a rule, with the aim to avoid band interferences, microwave apparatus for domestic or chemical applications are allowed to operate at an established frequency window either of 0.915 GHz or 2.45 GHz (S-band of microwave spectrum). 

When electric fields of electromagnetic waves interact with a polarizable medium (dielectric) three main effects may be 

Dielectric polarizability depends on the facility of a material to polarize in response to electric fields it is expressed by the permittivity e which, generally speaking, represents a measure of the resistance that is encountered in the dipole or charge reorganization. In fact, the permittivity (resistivity) will almost always be dependent on the frequency of the applied field and on the viscosity of the reactive environment to some extent, thus it has the form of a complex value. When the frequency irradiation is low, dipole/charges re-orientation is regularly in phase with the applied field coherently re-displacing themselves alternatively in the field 

All these factors reveal actively significative from the point of view of fast and mass heating, reaction rates 1-2 orders higher than through traditional heating approaches and moreover for energy saving [194,199]. 

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