I am confused that when we do microwave sintering of ceramics, basically, the frequency is fixed either 915 or 2450 MHz. How can we control the heating rate? Am I right that we control it by input power? Moreover, how can power control the heating operation and does it affect to frequency?
Starting with a fixed oven setup (frequency, cavity volume, amount of sample, etc.), the heating rate during a microwave sintering depends on the permittivity of considered substance(s). For example, for some kind of ceramic materials, it is often observed that some thermal runaway happens during a microwave heating. As consequence, it is very difficult to have a uniform heating and so, a homogeneous sintered product.
Permittivity study of a substance have to be carried out, in order to better understand the behaviour of substance under microwave irradiation. This study is often carried out for different frequency because frequency affects the thermal response of substance.
Anyway, by monitoring power (for example, increasing it slowly) it is possible to control sintering process. It becomes more easy if your microwave oven have a temperature feedback, that automatically control input power.
Hi Stafano, thank you so much for giving me an explanation. Now I do understand more about this.
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