Functionalized Nano Carbon for excellent Microwave Absorption at GHz Frequency

Avanish Kumar Srivastava, Bhumika Samaria, Smita Soni, Anuj Shukla*, Umesh Kumar

Material Development Group, Defence Laboratory, Jodhpur 342011, India

DOI: 10.5185/amlett.2019.0027

Publication Date (Web): May 20, 2019

Corresponding author: Tel: (+91) 2912511363; Fax: (+91) 2912510260; E-mail: anuj.shukla@dl.drdo.in; avanish@dl.drdo.in

Graphical Abstract

In the present study, nano carbon (NC) was chemically functionalized by refluxing in nitric acid for 6 h to form acid functionalized NC (FNC). TEM, XRD, FTIR, Raman, N2 BET surface area and dc electrical conductivity characterizations confirm the functionalization and formation of surface oxygen functional groups, which in turn increase the hydrophilicity of FNC, thus rendering them solution processable. The basic framework of NC did not get change as confirmed from different characterization techniques. FNC were dispersed in an epoxy matrix by a solution blending method with different FNC loading levels (5, 7.0, 10, 12& 15 wt %). The FNC/epoxy composites were studied for electromagnetic properties in 8-12 GHz. Electromagnetic properties such as real and imaginary part of dielectric permittivity found increasing with increase of FNC loading. Reflection loss result of 10wt % of FNC composite shows RL >10 dB from 9.5 to12.0 GHz (absorption bandwidth~ 2.5 GHz) and effective absorption bandwidth (RL> 5dB) ~ 7 GHz (8-15 GHz).  As a kind of potential microwave absorption material, the FNC composites are light weight and show excellent microwave absorbing ability. Copyright © VBRI Press.

Abstract

In the present study, nano carbon (NC) was chemically functionalized by refluxing in nitric acid for 6 h to form acid functionalized NC (FNC). TEM, XRD, FTIR, Raman, N2 BET surface area and dc electrical conductivity characterizations confirm the functionalization and formation of surface oxygen functional groups, which in turn increase the hydrophilicity of FNC, thus rendering them solution processable. The basic framework of NC did not get change as confirmed from different characterization techniques. FNC were dispersed in an epoxy matrix by a solution blending method with different FNC loading levels (5, 7.0, 10, 12& 15 wt %). The FNC/epoxy composites were studied for electromagnetic properties in 8-12 GHz. Electromagnetic properties such as real and imaginary part of dielectric permittivity found increasing with increase of FNC loading. Reflection loss result of 10wt % of FNC composite shows RL >10 dB from 9.5 to12.0 GHz (absorption bandwidth~ 2.5 GHz) and effective absorption bandwidth (RL> 5dB) ~ 7 GHz (8-15 GHz).  As a kind of potential microwave absorption material, the FNC composites are light weight and show excellent microwave absorbing ability. © VBRI Press.

Keywords

Nano carbon, composite, dielectric loss, microwave absorption, lightweight absorber.

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