Rice Husk Ash an Agro‐Waste Recycled Value Added Product in Epoxy for Microwave Absorption

ABSTRACT Rice husk is a major agricultural waste generated every year globally. Its open‐air burning produces rice husk ash (RHA), which has a severe impact on soil, air, and human health. However, the use of its fine particles in the polymer matrices can make value addition. In the present research, the RHA was coated with 0.2, 0.5, and 1.0 wt.% graphene nanoplatelets (GNP). These GNP‐coated RHA (G@R) were reinforced into the epoxy matrix. The electrical, electromagnetic (EM), and microwave absorption properties of G@R‐filled epoxy (EP/G@R) nanohybrids were then investigated. The direct current (DC) electrical conductivity and dielectric constant of neat epoxy increased with increasing G@R loading, and the highest values obtained are 9.5 × 10 −4 and 5.14, respectively, at 30 wt.% G@R. The real ( ε ′) and imaginary parts ( ε ″) of the complex permittivity of G@R‐filled EP nanocomposites increased marginally with increasing G@R content. The nanocomposite with 30 wt.% 1G@R and lower thickness (2.5 mm) exhibited excellent microwave absorption in the X‐band with wide absorption bandwidth. The maximum reflection loss (RL max ) is −19.53 dB at 11.87 GHz, and the absorption bandwidth (< −10 dB) is 3.08 GHz (9.32–12.4 GHz).