Sintering is carried out for ferrite materials in microwaves. I want to know the physical interaction between the molecule of the ferrite (magnetic oxide) and the microwave so that I could adjust the power etc. in my sintering process.
Microwave owens work at 2.45 GHz. There are no specific data that show how much of its energy is transferred in which frequency and corresponding temperature.
The physics behind a chemical synthesis are the absorbance of power by your reactants and triggering the molecules by increasing thermal vibrations.
But for a chemical process, it is not easy to say exact power in watts during experiment since there is no specific device for microwave synthesis of nanomaterials. By doing experiments, you should see that reaction is not only dependent to the power that owen radiates. But catalyzers you mixed with nitrate salts for example, provide you a matrix in order to reach required reaction temperature. Ignition rate can be controlled by these catalyzers, I derived this information according to my experiments during my master thesis. By setting the amount in different stoichiometries it is easy the find best crystalline structure. Low heating creates impurities so residues will not satisfy you in XRD analysis, and overheating burns the products.
The link is a pretty comprehensive paper on this issue. From a macro point of view I think all you need is the "insertion loss" and the loss tangent of the material. If you have a VNA in transmission line mode (i.e., with an appropriate test fixture) you can get these from the S parameters. This will at least tell you how much power is going into sample.
Cheers
http://www.academia.edu/2031790/Synthesis_and_characterizations_of_microwave_sintered_ferrite_powders_and_their_composite_films_for_practical_applications
Dear John, Your answer and the reference has provided a real help. Thanks a lot.
Very interesting question indeed. Interaction of microwaves with the ferrites or materials in general, is not yet fully understood. There is no direct relation between microwave power and the temperature of the sample. This arises out of two fundamental difficulties.One : microwave heating is attributed primarily to dielectric properties , however there are some recent reports on the heating effects on account of the magnetic properties too. So the exact heating mechanism is still unknown. Two: The non-thermal effects of microwaves make it even more complex. This complexity associated with the microwave interaction with materials make it a very attractive option for research although it comes with inherent difficulties.
It is definitely possible to calculate S parameters, but from a practical point of view it wont be of much use keeping in view the unknowns in microwave-material interaction.
In order to use microwave radiation for heating materials, one needs to begin with optimization of the requirements of specific system. The theoretical explanation of microwave-material interaction is still incomplete. So, I suggest that you move ahead with the process of optimization of power-time-temperature for your system. Are you sintering only powder or some solid body of ferrites? If it is body, what are the dimensions?
It is difficult to understand how microwave radiation interact with ferrite material in a sintering process. I have prepared bismuth ferrite by using the microwave heating process. The result was different from the conventional heating process. Here is the link of the reference.
https://www.researchgate.net/publication/246546714_Microwave_hydrothermal_synthesis_of_perovskite_BiFeO3_nanoparticles_An_insight_into_the_phase_purity_during_the_microwave_heating_process
Article Microwave Hydrothermal Synthesis of Perovskite BiFeO3 Nanopa...
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