The Department of Materials Engineering at the University of Technology awarded a PhD to researcher Lamis Salam Faeq on Thursday, 31/10/2024, in the Graduate Studies Hall in Building B for her thesis entitled:

“Development of Microwave Dielectric Materials with Low Loss Factor"

Abstract

The study aimed to obtain lightweight, high-performance materials for use in wireless communication and high-frequency applications. A composite material composed of ceramic reinforced with polymer was prepared to achieve a balance between the excellent dielectric properties of ceramics and the mechanical flexibility of polymers. Three types of crystalline structures (scheelite, wolframite, and perovskite) were added at 5% and 10% concentrations to three types of polymers: epoxy, polyurethane, and silicone rubber.The ceramic compounds were prepared using solid-state reactions and include Zn1-xCuxWO4 (x=0, 0.03), Ba1-xMgxWO4 (x=0, 0.4), Ba2MgWO6, Ba2ZnWO6, Bi2Mo0.5W0.5O6, (1-x)CaWO4-xNa2WO4 (x=0, 0.2, 0.4), and (Na0.5Bi0.5)(Mo0.5W0.5)O4 (x=0.5). Characterization techniques such as X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to study the crystal structure, phase formation, and surface of the oxidized materials. The dielectric properties of the composites were determined using a vector network analyzer (VNA) within the frequency range of 4-8 GHz. A mathematical model known as the Nicholson-Ross-Weir (NRW) model was used to convert the measured scattering parameters to dielectric constant and loss tangent. The results showed that composites containing 10% ceramics provided higher performance compared to 5%, especially in the frequency range of 7-7.98 GHz. These composites exhibit enhanced dielectric properties, frequency stability, and minimal signal loss, making them suitable for high-frequency applications.

The discussion committee consisted of Prof. Dr. Alaa Abdel Hassan Attia as Chairman and the membership of Prof. Dr. Ghazi Kamal Saeed, Prof. Dr. Hussein Alaa Jaber, Asst. Prof. Dr. Mayada Shanan Abdul, Asst. Prof. Dr. Alaa Abdul Mohammed. The thesis was supervised by Prof. Dr. Fadel Abbas Hashem, Prof. Dr. Saad Badri Hassoun. The thesis was scientifically evaluated by Prof. Dr. Shihab Ahmed Zidane, Asst. Prof. Dr. Hanaa Shukr Mahmoud, and linguistically by Asst. Prof. Dr. Gamal Jalal Daoud.