The influence of nano-Fe on the electromagnetic shielding properties of nano-Fe/carbon fiber/LDPE composites

Nano-Fe/carbon fiber/Low-density polyethylene (LDPE) composites were prepared by melt compounding. The electromagnetic shielding properties of nano-Fe/CF/LDPE composites as a function of nano-Fe mass content were investigated. The data of DC electrical conductivity evidence percolation behavior of the composites, and percolation threshold descends with the increase of nano- Fe. When the CF/LDPE composites reach the percolation threshold (p_CF=0.10), "double percolation" appears in the nano-Fe/CF/LDPE composites as continuously adding nano-Fe into the CF/LDPE composites, and the percolation threshold of the "double percolation" is 0.10 mass fraction of CF and 0.08 mass fraction of nano-Fe, which result in at least 10³ orders of magnitude greater than that of CF/LDPE composites. The data of Initial DC permeability μ_r, coercivity H_c, saturation magnetization M_s and residual magnetization M_r of nano-Fe/CF/LDPE composites at the magnetic field intensity between -2500 G and 2500 G enhance with increasing addition of nano-Fe. The value of relative permeability decreases as the loading of nano-Fe is increased from 0.04 to 0.19 mass fraction in frequency ranges of 300 KHz-100 MHz. The EMI SE in frequency ranges of 300KHz-100MHz increase with the addition of nano-Fe, and mechanism of electromagnetic shield for nano-Fe/CF/LDPE composites is compound shielding mechanism with reflection loss R and absorption loss A. Absorption loss A increases significantly with increasing addition of nano-Fe from 0.04 to 0.19 mass fraction, and increasing trend of reflection loss R slow down as mass fraction of the fillers reach percolation threshold.