Comparison of Microwave Absorption Properties Between BaTiO 3 /Epoxy and NiFe 2 O 4 /Epoxy Composites Yuksel Akinay , 1 Fatih Hayat, 1 Yasin Kanbur, 1 Hasan Gokkaya, 2 Safa Polat 1 1 Faculty of Engineering, Metallurgical and Materials Engineering, Karabuk University, Karabuk, Turkey 2 Faculty of Engineering, Mechanical Engineering, Karabuk University, Karabuk, Turkey Microwave absorption properties of Epoxy/Nickel Fer- rite (NiFe 2 O 4 ) and Epoxy/Barium Titanate (BaTiO 3 ) composites were investigated and compared in the 1– 14 GHz. Epoxy/filler particles (NiFe 2 O 4 and BaTiO 3 ) composites were prepared with 85/15 mixture ratios via Ultrasonic Probe Sonicator method in solution. The complex permittivity (E 0 -E 00 ) and permeability (l 0 -l 00 ) of the composites have been measured at different microwave frequencies in 1–14 GHz via vector network analyzer (Keysight N9926A). The reflection loss (R L ) of composites was calculated and evaluated from cam- plex permitivity and permeability. The obtained results show that both composites exhibit the large R L and broadband within the frequency range from 1 to 14 GHz for different thickness. Epoxy/BaTiO 3 showed a better microwave absorption at the range of 6–7.2 GHz for 7 and 6 mm, at the range of 7.4–9.1 GHz for 5 mm. However, the Epoxy/NiFe 2 O 4 exhibits the largest R L and the widest bandwidth than those obtained from Epoxy/BaTiO 3 composite. POLYM. COMPOS., 00:000–000, 2017. V C 2017 Society of Plastics Engineers INTRODUCTION Electromagnetic wave absorbing technology has received considerable attention, especially in studies of composite materials with different types of ferromagnetic or ferroelectric fillers [1, 2]. Therefore, these composites may be classified as magnetic or dielectric materials and have attracted intense interest due to their microwave absorption properties [3]. However, these microwave absorbers materials are also used as effective counter- measures against radar detection in the area of stealth technology for defense [4–10]. In recent years, microwave absorber composites are widely used in the frequency range of 1–20 GHz due to development of electronic and telecommunication systems [9]. Ferromagnetic and ferroelectric fillers such as Nickel ferrites (NiFe 2 O 4 ) and BaTiO 3 are generally used in microwave absorber composites. Hence, the magnetic and electrical properties of which the complex permeability and the permittivity, especially, are important in deter- mining their microwave characteristics [2]. Magnetic nanoparticle has drawn intense interest, because of good novel physiochemical properties, low cost and commer- cial availability [11–14]. Among these nanoferrite pow- ders, NiFe 2 O 4 is considered one of the most suitable powders for radar absorbing materials (RAMs) due to their high saturation magnetization, excellent chemical stability and corrosion resistance. NiFe 2 O 4 crystallizes in inverse spinel structure, that is, tetrahedral sites are occu- pied by Fe 31 ions and the octahedral sites by Ni 21 ions. Although presenting good absorbing properties, the NiFe 2 O 4 is too heavy [1]. Barium titanate (BaTiO 3 ) is well known as ferroelec- tric and piezoelectric material with a perovskite structure type ABO 3 . It exhibits a large dielectric relaxation at dif- ferent frequencies and magnetic properties linked to domain structure [15–17]. BaTiO 3 exhibits dielectric con- stant properties with high permittivity. The structure of BaTiO 3 is that the Ba 21 (A ions) and O 2– form a face center cubic with Ba 21 occupy the corner sites, and oxy- gen anions on the face centers. The Ti 41 and O 2– fitting octahedral structure with titanate ions locate in the center and O 2– on the face center [18]. BaTiO 3 is the most com- mon choice for ceramic filler material due to its widely availability [15]. In general microwave absorption proper- ties of BaTiO 3 depend on complex permittivity (E 0 -E 00 ) and complex permeability (l 0 -l 00 ) constant throughout the frequency range [19]. However, epoxy resins are one of the most important candidate thermoset due to having excellent electrical insulators, surface coatings, adhesives, and fiber-reinforced composites. There have been key interests in the area of electromagnetic interference shielding and microwave absorption for epoxy resins, Correspondence to: Yuksel Akinay; e-mail: yukselakinay@karabuk. edu.tr Contract grant sponsor: Scientific Research Projects Coordination Unit of Karabuk University; contract grant number: KBU-BAP-16/2-DR-080. DOI 10.1002/pc.24497 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2017 Society of Plastics Engineers POLYMER COMPOSITES—2017