Wong Sing Yee creator author. text my 2025 2025 monographic eng xvii, 95 pages : illustrations ; Microwave-absorbing materials are essential for radar stealth in military security and mitigating electromagnetic wave (EM) pollution caused by the widespread use of telecommunication devices. However, insufficient synergy between magnetic and dielectric losses and impedance mismatching constrain the absorption performance. This research was devoted to investigate the effect of particle size on the EM wave absorption properties of BaCoMn-hexaferrites (BCMFO) and BCMFO/activated carbon (AC) hybrid composites. The study aimed to enhance absorption by hybridizing high magnetic and dielectric losses of BCMFO and AC in a multilayer structure to minimize impedance mismatching. BCMFO was synthesized via the ball-milling with different milling times of 4, 8 and 12 hours to achieve varying particle sizes. Their effect on structural, microstructural and magnetic properties were analyzed, while electromagnetic absorption performance of BCMFO/AC with different thicknesses was measured in X-band frequency ranges. The smallest particle size of 0.20 μm, obtained after 4 h milling, demonstrated the lowest Ms, highest permeability, magnetic loss and negative RL. Conversely, the largest particle size of 0.30 μm from 12 h milling exhibited the lowest Hc, highest permittivity, and dielectric loss. Among the samples, the 1AC/1BCMFO(4) composite with a total thickness of 2 mm achieved the best absorption performance, attaining the highest negative RL of –16.66 dB and 90% absorption (< –10 dB) over a bandwidth of 1.86 GHz. The superior performance is attributed to improved impedance matching between magnetic and dielectric losses, enhanced interface polarization and hybridization of carbon. specialized Wong Sing Yee Faculty of Industrial Sciences and Technology Final Year Report (Bachelor of Applied Science in Material Technology) -- Universiti Malaysia Pahang Al-Sultan Abdullah - 2025 Include bibliographical reference Faculty of Industrial Sciences and Technology Dissertations Universities and colleges Dissertations Theses Dissertations THE0010451 (Local) https://umpir.ump.edu.my/id/eprint/45997 https://umpir.ump.edu.my/id/eprint/45997 UMPSA 260413 20260413120557.0 eng