Carbon Nanotubes based composites for electromagnetic absorption- A review

: Radar is a delicate detection device and since its evolution different techniques for reducing electromagnetic reflections have been discovered. This paper provide concise review on fundamentals of absorption which reduces radar cross section from stealth target with which radar cross section has effects to survivability and mission capability. The reduction of radar cross section depend on dielectric and magnetic properties of material. The first section reviews the Radar Absorbing Material (RAM) in order to provide a background on fundamentals, various stealth techniques for absorption and its properties at microwave frequencies. The second section reviews the Multi-Walled Carbon Nanotubes and its different composites by encapsulation of other metals, polymers or epoxies into it and its microwave absorption properties were studies at microwave frequencies. Multi-Walled Carbon Nanotubes based composites for microwave absorption are reviewed on the basis of various factors; material composition, reflection loss performance, thickness, complex permittivity, complex permeability, dielectric tangent loss, magnetic tangent loss, bandwidth, and frequency band.

Effect of Filler Concentration and Time Sonication of ZnO Composite for Radar Absorbing Material Applications

Effects of filler concentration and sonication time on the structure, morphology, reflection loss and absorption percentage of ZnO composite was investigated. The structure, morphology, reflection loss and absorption percentage of the composite was investigated using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Vector Network Analyzer (VNA). The ZnO composite was made by solution mixing method with the epoxy resin as a filler varied of 10 wt%, 20 wt%, and 30 wt%. The hardener was mixed to the ZnO composite by the composition of 2: 1. The sonication time was varied of 30, 45 and 60 minutes. The XRD showed that the crystal structure of ZnO composite was confirmed as a hexagonal structure and the structure was not change for all composite. The VNA results showed that the optimum reflection loss value was-9.37042 dB at the frequency of 12.3 GHz for the filler composition of 20 wt% and sonification time of 45 minutes. On the other hand, the minimum reflection loss value was-6.86845 dB at the frequency of 12.3 GHz for the filler composition of 10 wt% and sonification time of 45 minutes. In addition, the optimum absorption percentage was 18 % at a filler composition of 10 wt% with 60 minutes sonication time. This study demonstrates a promising method to improve a microwave absorption of ZnO composites.

Phase Transition of Fe₃O₄ Magnetic Material Based on Observation of Curie Temperature and Hysteresis Curve: Micromagnetic Simulation Study

Phase transition yesng happens to the material magnetite (Fe3O4) is an interesting phenomenon to study because it has many important applications, one of which is RAM (Radar Absorbing Material). The magnetic properties of nanomaterials are known to be influenced by their size. In this simulation research, the research objective was to analyze the temperature value of the Curie and the hysteresis curve of the Fe3O4 material with variations in the size of the material sample cube of 5 nm, 8 nm, 10 nm, 12 nm, and 15 nm. In this study, using a micromagnetic simulation method based on atomistic models with the Vampire program. The results showed that the Curie temperature value in the Fe3O4 material was influenced by variations in the size of the material. The Curie temperature values when the side sizes of the cube are 5 nm, 8 nm, 10 nm, 12 nm, and 15 nm, namely 650 K, 635 K, 650 K, 665 K and 645 K. The characteristics of the hysteresis curve for Fe3O4 material based on simulations at each material size (5 nm, 8 nm, 10 nm, 12 nm, and 15 nm) for several temperatures (0 K, 328 K, 473 K and 773 K) indicate that there is a change in the coercivity and field values. saturation.

Synthesis Polymer Matrix Composite Epoxy-FeNdB-Mn for Radar Absorbing Material Application

<p style="margin-bottom: 0in; line-height: 115%;" align="justify"><span style="font-family: Times New Roman, serif;">In recent years, applications using electromagnetic wave technology have grown rapidly. One of them is in the military field, the wave-absorbing material used to avoid detection such as aircraft, ships, or tanks requires a super thin absorbent material which has extraordinary absorption. One of the criteria for a wave absorbing material is a soft magnet and has a high Reflection Loss (RL). This research aims to see the effect of the addition of FeNdB and Mn on the synthesis of Polymer Matrix Composite (PMC) as a wave-absorbing material.</span><span style="font-family: Times New Roman, serif;">The FeNdB milling process and Mechanical Alloying (MA) with Mn were carried out using a Planetary Ball Mill (PBM) at a speed of 1000 rpm for 60 minutes. synthesis of PMC by varying the composition of epoxy resin with magnetic powder 95: 5; 90:10; 85: 5. Based on the characterization results, the optimum RL was obtained at a composition of 85: 5 with a value of -22.40 dB at a frequency of 10.40 GHz and the magnetic properties after the addition of Mn were obtained HcJ 0.116 kOe and Br 0.41 kG. PMC hardness increased with the increase of powder in the sample with the highest value of 29.2 HD Shore D and the adhesion decreased with the addition of powder in the sample with the lowest value of 1 MPa.</span></p>

Design of An Ultra-Thin and Broadband Absorption Materials For Middle-Temperature Applications

A radar absorbing material (RAM) is designed based on the magnetic ceramic and frequency selective surface (FSS). The phase composition and micromorphology were characterized, respectively. The complex permittivity and complex permeability of magnetic ceramic were tested and studied from 25 ℃ to 500 ℃ temperature. Based on the experimental and simulation results, the changes of reflection loss along with the structure parameters of RAM are analyzed at 500 ℃. The relationship of reflection loss varies with temperature are studied. The analytical results show that the absorption property of the RAM increases with the increase of temperature. An optimal absorption of RAM is obtained at 500℃. When the thickness of RAM is 1.5 mm, the reflection loss lower than -10 dB can be obtained in the frequency range from 8.2 ~ 16 GHz. More than 90% microwave energy can be consumed in the RAM which may be applied in the high temperature environment.

Wideband Radar Absorbing Structure Using Polyaniline-Graphene Nanocomposite

A wideband non-resonant absorber is proposed, and its radar cross section (RCS) reduction is investigated. A discussion on the functional materials available is followed by the design of an absorber on a Plexiglas substrate with polyaniline-graphene nanocomposite as layered square inclusions with thicknesses and conductivities scaled to golden ratio. The measured dielectric properties of polyaniline-graphene nanocomposites are used in the fullwave simulation. The design parameters have been identified and optimized using CST Microwave Studio. As designed structure is fabricated and the reflection is measured. The objective of the work is to demonstrate the use of non-metallic conducting polymer composites devoid of metals for radar absorbing material (RAM) structural designs. The structure is an all-polymer and electrically thin design with a potential to be 3D printed to suit the target object.