Ki-Yeon Park

Two-layered electromagnetic wave-absorbing E-glass/epoxy plain weave composites containing carbon nanofibers and NiFe particles

Two-layered radar-absorbing structures (RASs) were investigated for the broadband absorbing characteristics for the X-band (8.2–12.4 GHz) and Ku-band (12.0–18.0 GHz). E-glass/epoxy plain weave composites containing carbon nanofibers (CNFs) and submicron NiFe particles were fabricated and their complex permittivities and permeabilities measured in the range 2–18 GHz. The surface and absorbing layers of two-layered RASs consisted of the low and high lossy materials, respectively. Six kinds of two-layered RASs were designed through the parametric studies. The three kinds of specimens with wide absorption characteristics were selected for the experimental performance evaluations, and their results showed very broad 10 dB absorbing bandwidths of 8.9–9.7 GHz with thicknesses 3.15–3.43 mm.

Fabrication and electromagnetic characteristics of microwave absorbers containing carbon nanofibers and magnetic metals

The ultimate aim of this study is the development of microwave absorbers containing both dielectric and magnetic lossy materials. Carbon nanofibers (CNFs) were used as dielectric lossy materials and NiFe particles were used as magnetic lossy materials. Total twelve specimens for the three types such as dielectric, magnetic and mixed radar absorbing materials (RAMs) were fabricated. Their complex permittivities and permeabilities in the range of 2~18 GHz were measured using the transmission line technique. The parametric studies in the X-band (8.2~12.4 GHz) for reflection loss characteristics of each specimen to design the single-layered RAMs were performed. The mixed RAMs generally showed the improved absorbing characteristics with thinner matching thickness. One of the mixed RAMs, S09 with the thickness of 2.00 mm had the 10 dB absorbing bandwidth of 4.0 GHz in the X-band. The experimental results for selected specimens were in very good agreements with simulation ones in terms of the overall reflection loss characteristics and 10 dB absorbing bandwidth.

A Study on Electromagnetic Wave Absorbing Sandwich Structures

The object of this study is to design the Radar Absorbing Structures (RAS) having sandwich structures in the X-band () frequencies. Glass fabric/epoxy composites containing conductive carbon blacks and carbon fabric/epoxy composites were used for the face sheets. Polyurethane(PU) foams containing multi-walled carbon nanotube (MWNT) were used for the core. Their permittivities in the X-band were measured using the transmission line technique. The reflection loss characteristics for multi-layered sandwich structures were calculated using the theory of transmission and reflection in a multi-layered medium. Three kinds of specimens were fabricated and their reflection losses in the X-band were measured using the free space technique. Experimental results were in good agreements with simulated ones in 10dB absorbing bandwidth.㨊吀Ѐ㘹〻Ⰰ䉵楬摩湧Ⱐ捯湳瑲畣瑩潮⁡湤⁣楶楬⁥湧楮敥物湧