Effect of copper oxide on microwave heating of copper powder

The microwave heating of compacted Cu powder was examined using a 2.45 GHz microwave generator. The microwave heating of compacted Cu powder was quite anomalous. In the early irradiation stage, the temperature increased gradually with increasing time. After reaching similar to 200 degrees C, abrupt temperature rise and drop occurred. Then the temperature increased again and remained almost unchanged in the late stage of microwave irradiation. The time from which the abrupt temperature rise began and the time at which the peak temperature was attained were shorter by the addition of CuO powder particle which has a large dielectric loss. The microwave heating of compacted Cu powder was also significantly enhanced by the formation of thick Cu oxide film on the surface of the Cu powder particles. Such behaviour due to Cu oxide was similar to the effect of a catalyst in a chemical reaction.