Effects of particle size regulation on the structure and electromagnetic wave loss mechanism of coal gasification fine ash

Coal gasification fine ash (CGFA) is a byproduct of coal gasification technology, contains approximately 40% carbon content traditionally considered difficult to utilize effectively in construction materials. However, this carbon exhibits excellent electromagnetic (EM) properties and, if properly developed, could impart excellent EM protective functionality to human settlement. This study systematically investigated the influence of particle size on the structure and EM wave loss mechanisms of CGFA by processing the material into three distinct size fractions via ball milling: Group A (D 0.9 = 249.1 μm), Group B (D 0.9 = 51.7 μm), and Group C (D 0.9 = 10.0 μm). The results indicate that the specific surface area of CGFA is dominated by its porous carbon structure. Reducing particle size leads to destruction of the pore structure and consequently to a decrease in specific surface area. Larger carbon particles exhibit superior electrical conductivity, their abundant porosity and higher specific surface area provide more interfaces, thereby significantly enhancing resistive loss and polarization loss. However, this also causes imbalanced impedance matching in CGFA/paraffin composites, which limits their EM wave absorption performance. As particle size decreases, impedance matching is optimized, among the samples, the group C specimen (30 % loading, 15 mm thickness) achieved the best reflection loss of −27.66 dB at 5.8 GHz. These findings demonstrate that particle size modulation can effectively tune the EM loss mechanisms of CGFA to meet different engineering requirements. • Electromagnetic: EM, Coal gasification fine ash: CGFA • 1.Evolution of Pore Characteristics in Porous Carbon During the Ball-Milling Process • 2.Effective of CGFA particle size and pore characteristics on EM wave loss mechanisms. • 4.Provided a new method for the high-value utilization of CGFA. • 4.A theoretical basis for the application of CGFA in EM protection building materials.