Recycling red mud with raw coal to low-cost Fe/C/ceramic composite for efficient microwave absorption

Area of Science:

• Materials Science
• Environmental Science
• Electromagnetics

Background:

• Growing electromagnetic (EM) wave radiation pollution necessitates effective absorption solutions.
• Red mud (RM), a significant industrial solid waste, presents challenges for disposal and resource utilization.

Purpose of the Study:

• To develop cost-effective and high-performance EM wave-absorbing materials by recycling RM.
• To investigate the feasibility of using RM and raw coal (RC) to create Fe/C/ceramic composites.

Main Methods:

• Construction of Fe/C/ceramic composites via mechanical mixing of RM and RC, followed by carbothermal reduction.
• Optimization of calcination temperature (optimal at 900 °C for Fe formation) and RC:RM mass ratio.
• Characterization of EM wave absorption performance, including reflection loss (RL) and effective absorption bandwidth (EAB).

Main Results:

• Optimal Fe formation achieved at 900 °C.
• Composites with RC:RM ratios of 0.4:1 and 0.5:1 exhibited superior performance.
• A composite with RC:RM of 0.4:1 achieved a minimum RL of -41.6 dB and EAB of 3.2 GHz at 2 mm thickness.
• A composite with RC:RM of 0.5:1 achieved a maximum EAB of 4.2 GHz and RL of -25.3 dB at 1.5 mm thickness.

Conclusions:

• The developed composites demonstrate tunable and effective EM wave absorption capabilities.
• Good impedance matching and strong intrinsic attenuation, attributed to graphitized carbon, crystalline Fe, and defects, are key to performance.
• This work presents an economical method for preparing microwave absorbents and a viable route for RM utilization.