Investigation of charcoal and activated charcoal for microwave absorbers.

The effects of the microwave heating process and the behaviour as absorbent materials of charcoals obtained from Eucalyptus urograndis wood, macauba endocarp, and lignin, in the activated and non‐activated forms, were investigated. The dielectric properties were measured with the coaxial probe method, and the values of loss tangent obtained for all the materials characterize them as absorbers. Heating tests were performed with materials in the raw form and also mixed with sand, a transparent material to microwave radiation. A factorial design of experiments was performed, and the effect of microwave power and mass concentration of materials over heating rate was studied. Both factors had a significant and positive influence on the heating rate of the seven analyzed materials. The carbon activation process increased the absorption and heating potential, due to the greater surface area and porosity generated by the process. The highest values of heating rate were obtained in the tests carried out with Eucalyptus‐activated carbon. [ABSTRACT FROM AUTHOR]