STUDIES ON HEXAFERRITE BASED NANOCOMPOSITES FOR RADAR/MICROWAVE ABSORPTION APPLICATIONS

Abstract

Radar is a sensitive detection tool and since its development, methods for reducing microwave reflections have been explored. In defense, the primary objective is to detect enemies' equipment/arms as early as possible in order to employ weapons effectively. In current, radar cross section (RCS) designs, shaping techniques are considered to be the first step of RCS control. The objective of shaping is to design the platform's surfaces and the edges to reflect or diffract the incident wave in directions away from the radar, and is primarily applied to establish a low RCS in the main threat sectors. However, the modification of an aircraft's shape is limited to certain aerodynamic principles and within last three decades, the shaping techniques have been applied excessively in the design of fighter aircrafts. Recent design approaches generally opt for a balance between shaping and other reduction techniques. Therefore, radar absorbing material (RAM) engineering has become an important area of research. Radar absorbing materials reduce the energy reflected back to the radar by means of absorption. Thus radar absorbing materials have become the essential part of defense system for their contribution to survivability of air vehicle. Like defense, these materials are equally important in industries for use as a commercial product for the electromagnetic interference (EMI) shielding. EMI is a specific type of environmental pollution which is caused by the - - - - - extensive use of electromagnetic (EM) waves in wireless communications such as EM waves of 0.8-1.2 GHz are used for mobile phones, 2.45 GHz for electronic ranges, 5.6-8.2 GHz (G-band) for synthetic aperture radar (SAR) or microwave communication on the ground, 8.2-12.4 GHz (X-band) and 12.4-18 (Ku-band) for SAR or electron spin resonance (ESR) apparatus. The emergence of nanoscience and nanotechnology opened the door for newer opportunities to further involve the functionality of electromagnetic absorber. The use of magnetic , non magnetic and composite of magnetic/non magnetic materials in polymer resin matrix system has become a subject of interest in engineering applications due to potential changes in physical, chemical, magnetic and dielectric properties of nanocomposite. These changes in the properties come from unique morphology, increased surface area, exchange interaction existing between hard and soft magnetic phases and quantum size effect associated with nano size particles. ii