Historical review of advanced materials for electromagnetic interference (EMI) shielding: Conjugated polymers, carbon nanotubes, graphene based composites

Electromagnetic (EM) interference (EMI) “an off-shoot of explosive growth of electronics and telecommunications” is becoming an alarming issue for modern society. It may degrade the EM device performance or may adversely affect human health. Recently, polymer based blends and composites have emerged as powerful solution for efficient suppression of EM noises; thanks to the unique combination of electrical, thermal, dielectric, magnetic and/or mechanical properties, possessed by them. This review focuses on the basics of EMI shielding/microwave absorption, various techniques for measurement of shielding effectiveness, theoretical aspects of shielding, governing equations. In addition, different strategies and potential materials for handling of EMI have also been discussed with special reference to polymer based blends and composites especially those based on carbon nanotubes (CNTs), graphene and intrinsically conducting polymers (ICPs)

Graphene-Based Composites and Hybrids for Water Purification Applications

The increasing water demand and the worldwide shortage of clean water call for new technologies for wastewater treatment, of which sorption is recognized as simplest and efficient method for all major water pollutants, including heavy metal ions, organic dyes and organic solvents. In this context, graphene, an atomically thin two-dimensional hexagonal arrays of carbon atoms, and its analogs have been visualized as ultimate materials for the separation of pollutants from water due to properties such as superhydrophobicity, superoleophilicity, chemical-environmental-thermal stability, chemical manipulability, controllable morphology, texture, porosity and accessible surface area, facile processing, low density, biocompatibility and low-cost synthesis from a variety of abundant carbonaceous precursors. This chapter begins with an introduction of water purification, related processes and fundamentals of adsorption and absorption phenomenon. The next section emphasizes the importance and advantages of graphene as sorbent, brief about its synthesis, types of graphene-based composites/hybrid systems and their synthesis strategies. The last section throws light on the performance of graphene-based foams, aerogels and composites/hybrids for the separation of metal ions, organic dyes and various oils/organic solvents, supported by comprehensive literature account. Finally, the chapter concludes with the comments on the current status, major challenges and future scope in the direction

A Historical Review of Electrode Materials and Electrolytes for Electrochemical Double Layer Supercapacitors and Pseudocapacitors

The supercapacitor is one of the most promising alternatives to other popular energy storage solutions, viz., rechargeablebatteries and capacitors. They are considered the bridge between batteries (high energy density) and capacitors (high powerdensity) because of their fast charge/discharge capacity, high specific power/energy, and good service-life, which makethem the most promising candidate for future energy storage/redistribution systems as well as hybrid electric vehicles. In thepast, much progress has occurred in electrode materials, electrode architecture, electrolytes, separators, and deviceconfiguration. This review article discusse the basics of electrochemical super capacitors, storage principal, deviceconfiguration, electrode materials, and electrolytes, including the coverage of the comprehensive literature account of theadvancements in the area; and, finally, the discussion on technological challenges in the development of commerciallyviable next-gen supercapacitor devices

Determination of defect density, crystallite size and number of graphene layers in graphene analogues using X-ray diffraction and Raman spectroscopy

In this study, X-ray diffraction and Raman spectroscopic techniques have been wielded for determination of number of graphene layers per domain, crystallite size, interlayer spacing and defect density in bulk samples of chemically synthesized graphitic oxide (GrO) and reduced GrO (RGrO). Particularly, the ready to use and general mathematical equations have been presented for obtaining above mentioned parameters directly using the full width half maxima (FWHM) of XRD peaks and intensity ratios of Raman D- and G-bands. The results reflect that upon reduction, crystallites shrink in dimensions ultimately leads to decrease in number of graphene layers per domain and apparent increase in defect density

Carbon Nanotube-Based Polymer Composites: Synthesis, Properties and Applications

The present chapter covers the designing, development, properties and applications of carbon nanotube-loaded polymer composites. The first section will provide a brief overview of carbon nanotubes (CNTs), their synthesis, properties and functionalization routes. The second section will shed light on the CNT/polymer composites, their types, synthesis routes and characterization. The last section will illustrate the various applications of CNT/polymer composites; important properties, parameters and performance indices backed by comprehensive literature account of the same. The chapter concludes with the current challenges and future aspects

Stunted root development: a rare dental complication of Stevens-Johnson syndrome

Stevens-Johnson syndrome (SJS) is a severe cutaneous reaction seen rarely in clinical practice. Most often, it occurs as an adverse reaction to certain drugs. When it affects children at a very young age, arrested tooth root development may also be seen. We present a case of a 13 year old boy who suffered from SJ syndrome at the age of 7 years. Incomplete root development was observed in all teeth, as demonstrated by panaromic radiography. Clinical features of this condition and its management are further discussed. We aim to emphasise on the need for dental practitioners to be aware of the potential dental complications of SJS and enable them to recognise and manage the condition at the earliest so as to avoid any undesirable sequelae

Effect of controlled doping on electrical properties and permittivity of PTSA doped polyanilines and their EMI shielding performance

Emeraldine base (EB) has been protonated with different concentration of para-toluene sulfonic acid (PTSA) to form doped polyanilines (PANIs). These samples have been characterized by various techniques and a detailed correlation between dopant concentration and structural, thermal, electrical and electromagnetic properties has been established. The FTIR/UV-Visible and EPR spectra confirm the formation of polarons as proto-generated charge carriers whose concentration follows the dopant concentration trend. It was also observed that increase in doping level leads to systematic improvement of electrical conductivity (1.2x1(-9) to 5.3 S/cm) as well as complex permittivity (epsilon'similar to 5.5 & epsilon"-0.6 to epsilon'similar to 22.3 & epsilon"similar to 24.6) with parallel improvement of electromagnetic (EM) radiation blocking capacity from -3.8 dB (for EB) to -23.9 dB (for 1.0 M PTSA doped Sample). Further, the attenuation was found to be critically dependent on dopant concentration, complex permittivity and electrical conductivity revealing that both polarization as well as conduction is important for achieving high attenuation. It was also observed that reflection is main phenomenon at low doping level whereas absorption becomes increasingly important at higher doping levels and extends dominant contribution towards total attenuatio

Designing of epoxy composites reinforced with carbon nanotubes grown carbon fiber fabric for improved electromagnetic interference shielding

In this letter, we report preparation of strongly anchored multiwall carbon nanotubes (MWCNTs) carbon fiber (CF) fabric preforms. These preforms were reinforced in epoxy resin to make multi scale composites for microwave absorption in the X-band (8.2-12.4GHz). The incorporation of MWCNTs on the carbon fabric produced a significant enhancement in the electromagnetic interference shielding effectiveness (EMI-SE) from -29.4 dB for CF/epoxy-composite to -51.1 dB for CF-MWCNT/epoxy multiscale composites of 2 mm thickness. In addition to enhanced EMI-SE, interlaminar shear strength improved from 23 MPa for CF/epoxy-composites to 50 MPa for multiscale composites indicating their usefulness for making structurally strong microwave shields. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported Licens

Ultrafast adsorption of organic dyes by activated-carbon@Fe3O4 nanoscale composites: An effective solution for water purification

Superparamagnetic (SPM) Fe3O4 nanoparticles (NPs) decorated activated charcoal (AC) skeletal (AC@Fe3O4) type nanoscale composites (NCs) have been prepared by a scalable and facile approach involving impregnation of AC with stable dispersion of SPM Fe3O4 NPs followed by controlled vacuum drying. These NCs exhibit coupled magnetic character and porosity which can be easily optimized by controlling weight ratio of two phases. The electron microscopy images show the presence of clustered Fe3O4 particles present all over the surface of porous AC particles and prevalence of meso-pores, which provides the channels for ingress and immobilization of sorbent moieties. The magnetometry and nitrogen adsorption measurements reveal that magnetic character increases whereas porosity decreases with the increase in Fe3O4 NP loading. These NCs have been demonstrated for purification of water containing methylene blue (MB) dye as an impurity. The porosity of these composites allow rapid adsorption (<1 min) of MB with good removal efficiency (> 99%) and their magnetic behaviour helps in instantaneous separation of MB adsorbed NC particles by the application of external magnetic field. The sorbent can be reused several times after proper regeneration with retention of more than 95% of the original adsorption capacity