Analysis on the Physical Evidence Characteristics of the Simulated Electromagnetic Waves Involved in Cases Derived From Core‐Shell Superparamagnetic Ni‐Zn Ferrite@Polypyrrole Microspheres Absorbing Materials

ABSTRACT

Homogeneous superparamagnetic core‐shell microspheres based on Ni‐Zn ferrite@polypyrrole (NZFO@PPy) were firstly fabricated. Based on the introduction of the electromagnetic wave absorbing materials, the physical evidence characteristics of the simulated electromagnetic waves involved in cases were analyzed, and finally the specific expressive forms of the simulated electromagnetic waves involved in cases as physical evidence were analyzed. The shell thickness of the NZFO@PPy microspheres could be controlled through adjusting the ratio of pyrrole/Ni‐Zn ferrite (Py/NZFO). The effects of conductivity (or Py/NZFO ratio), volume fraction (of NZFO@PPy/paraffin containing NZFO@PPy composites), and layer thickness on electromagnetic wave absorbing properties were investigated at room temperature in the frequency range of 2–18 GHz. As a result, the sample with the Py/NZFO ratio of 40 exhibited the optimal reflection loss of −37.34 dB at 25% volume fraction when the thickness was 2 mm. The optimal bandwidth corresponding to RL < −10 dB (over 90% electromagnetic wave absorption) covers 3.92 GHz (from 10.82 to 14.74 GHz). Particularly, the core‐shell NZFO@PPy microspheres presented excellent dielectric loss (0.2 < tan δ _e < 0.4) due to the existence of PPy shell. Analysis results show that the simulated electromagnetic waves involved meet the requirements of relevance and availability as physical evidence.