Low Temperature Hybrid Processing Technology of Fine Electronic Ceramics

The present paper reports the synthesis of a high-performance microwave absorbing material using a simple, cost-effective and scalable method by encapsulating barium strontium titanate (BST) and expanded graphite (EG) in a polyaniline (PANI) matrix. One of the formulations (higher content of BST) shows shielding effectiveness due to absorption of more than 50 dB (>99.9999% attenuation) with minimum reflection loss (#1 dB) in the Ku-band (12.4-18 GHz) frequency range. Another formulation (higher content of EG) shows a total shielding effectiveness of more than 81 dB with a reflection loss of 10 dB. In order to probe the relationship between the observed shielding response and the electromagnetic attributes, dielectric and permeability parameters have been calculated from the measured scattering parameters (S 11 , S 22 , S 12 , S 21 ) using the Nicolson-Ross-Weir algorithm. The synthesised formulations were characterized thoroughly using XRD, FTIR, TGA, UV, Raman spectroscopy, SEM and HRTEM. A. IntroductionElectromagnetic interference (EMI) among various devices such as cellular phones, televisions, weather radars, TV picture transmission, and telephone microwave relay systems 1 is the side-effect of the vast development in electronics and communication industries. Shielding at higher frequency, especially microwave radiation, continues to be a serious concern to ensure unperturbed performance of electronic items and to avoid any adverse effects on human health. To overcome this problem, lightweight EMI shielding materials are needed to protect the workspace and environment from radiation from computers and telecommunication equipment, as well as for protection for sensitive circuits. Conventionally, there are two ways of EMI shielding, either by complete reection or by total absorption of the radiation. Metals are generally employed for reection-based shielding, 2,3 but in the quest of absorptionbased shields, materials should possess optimum conductivity along with a high dielectric value.When electromagnetic radiation is incident on a shield, part of the incident wave is absorbed, some is reected from the surface and the rest is transmitted through the shield. Hence, the total EMI shielding effectiveness (SE T ) is the sum of the contributions from absorption (SE A ), reection (SE R ) and transmission or multiple reections (SE M ). However, when SE T > 10 dB, SE M can be ignored.4,5 Furthermore, the effective absorbance (A eff ) can be described as A eff ¼ (1 À R À T)/(1 À R) with respect to the power of the effectively incident EM wave inside the shielding material, where R and T are the reectance and transmittance coefficients. For a material, the skin depth (d) is the distance up to which the intensity of the EM wave decreases to 1/e of its original strength. d is related to the angular frequency, relative permeability and total conductivity, s T ¼ (s dc + s ac ). According to EM theory, for electrically thick samples (t > d), the frequency (u) dependence of far eld losses can be expressed in terms of...

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“…34-0411. 20 The XRD pattern of EG shows a sharp peak at 2q ¼ 26. 3 , which corresponds to the (002) crystal plane.…”

Section: Surface Morphologymentioning

confidence: 99%

“…34-0411. 20 The XRD pattern of EG shows a sharp peak at 2q ¼ 26.3 , which corresponds to the (002) crystal plane. 16 The nanocomposites show the characteristic peaks of BST and EG and their intensity increases monotonically with the increase in their content.…”

Section: Surface Morphologymentioning

confidence: 99%