Wong Sing Yee, <br/><br/>
Influence of particle size variations on electromagnetic absorption performance in bacomn hexaferrites/carbon hybrid composites / 
Wong Sing Yee 
 - xvii, 95 pages :  illustrations ; 
<br/><br/> Faculty of Industrial Sciences and Technology 
<br/><br/>Final Year Report (Bachelor of Applied Science in Material Technology) -- Universiti Malaysia Pahang Al-Sultan Abdullah - 2025 
<br/><br/>Include bibliographical reference 
<br/><br/> 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. 
<br/><br/><label>ISBN: </label>THE0010451 (Local) 
<br/><br/><label>Subjects--Corporate Names: </label><br/>Faculty of Industrial Sciences and Technology--Dissertations
<br/><br/><label>Subjects--Topical Terms: </label><br/>Universities and colleges--Dissertations<br/>Theses--Dissertations