Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

Abstract

This paper presents a study about the characterization of dielectric properties (dielectric constant $${\varepsilon }_{r}$$ ε r and dielectric-loss constant $$\mathrm{tan}\delta$$ tan δ ) of samples derived from two different biomass types: rice husk ash (RHA) and annoni grass ash (AGA).The procedure is carried out using the resonant cavity method along with a vector network analyzer. For this purpose, four different ashes were produced, by burning rice husk and annoni grass at two different temperatures and burning times: 400 °C/30 min (RHA40030 and AGA40030) and 800 °C/5 h (RHA8005h and AGA8005h). These ashes were combined with Bakelite to produce cylindrical samples with diameter of 30 mm and thickness of 4.5 mm, which were characterized considering the frequency in the test band for 5G technologies ($${f}_{o}=3.5$$ f o = 3.5 GHz). Experimental results showed that the samples burnt at high temperature showed very high $$\mathrm{tan \delta }$$ tan δ when compared to the samples burnt at low temperature, mainly for AGA8005h. These values are $$\mathrm{tan \delta }=$$ tan δ = 0.1690 and 1.4900 for RHA8005h and AGA8005h, respectively. The resulting dielectric constants are $${\varepsilon }_{r}$$ ε r = 3.87 for RHA8005h and $${\varepsilon }_{r}$$ ε r = 15.14 for AGA8005h). These very high dielectric loss tangent, indicate that these materials exhibit formidable properties for electromagnetic energy absorption, hence allowing the application as radiation-absorbent material (RAM).