Dielectric Characteristics of Poplar Powder under High-Frequency Electric Field

Dielectric properties of poplar tree powder were measured at frequencies from 5 to 30 MHz. The effects of moisture content, frequency, and bulk density on the dielectric constant and dielectric loss factor were analyzed. The polar groups of wood powder were characterized by infrared spectroscopy to reveal the response mechanism of wood powder in the high-frequency electric field. The results showed that, in general, wood powder's dielectric constant and dielectric loss factor increased with increasing bulk density and moisture content. In the moisture content range from 0 to 24%, the dielectric constant epsilon' of wood powder decreased with the frequency increase with 5 MHz as the maximum value of e'. When the moisture content was 0 <= w < 20%, wood powder's dielectric loss factor epsilon'' varied as a quadratic function with increasing frequency, corresponding to a maximum value of epsilon'' at 13.4 to 17.7 MHz. When the moisture content was >20%, the dielectric loss factor e'' of wood powder decreased linearly with increasing frequency, and the maximum value of epsilon" was 5 MHz. The infrared spectrum showed that the polar groups in the wood powder were mainly -OH, C=O, C-O, and -CH, with the highest percentage of -OH.