Sanjay R. Dhakate

Polymer nanocomposite foam filled with carbon nanomaterials as an efficient electromagnetic interference shielding material

Increasing use of the latest electronic gadgets in modern society causes rapid growth in electromagnetic pollution, which leads to detrimental effects on the function of highly sensitive precision electronic equipment as well as on human life. Mitigating this effect requires efficient electromagnetic radiation shielding materials, which should be lightweight, corrosion resistant and cost-effective. In this review article, we have presented lightweight polymer composite foams filled with carbon nanofibers, carbon nanotubes and graphene as efficient electromagnetic radiation shielding materials. It is seen that the low loading of multiwalled carbon nanotubes with uniform dispersion in polymer, uniform cell size of pore and controlled dielectric constant results in the attenuation of electromagnetic radiation by absorption phenomena. Flexible graphene–polymer composite foam derived using the chemical vapor deposition technique demonstrates a specific shielding effectiveness of ∼333 dB cm3 g−1, which is the highest value among those reported in literature. The SE is mostly dominated by the absorption of electromagnetic radiation, which is due to the multiple reflection of radiation inside the cells of the composite foam. Moreover, different carbon nanomaterial, such as carbon nanofibers and few layer graphene-filled polymer composite foams, with varying content of conducting filler are reported in this review. Their use in different applications, their future prospective and the challenges ahead are discussed in this review.

Dynamic mechanical properties of multiwall carbon nanotube reinforced ABS composites and their correlation with entanglement density, adhesion, reinforcement and C factor

The dynamic mechanical properties of multiwalled carbon nanotube (MWCNTs) reinforced acrylonitrile butadiene styrene (ABS) high performance composites, which were prepared using a micro twin screw extruder with a back flow channel that enabled proper dispersion of MWCNTs into the polymer matrix are studied in detail. The dynamic characteristics of the MWCNTs/ABS composites, such as storage, loss modulus and damping factor were significantly affected by the incorporation of MWCNTs. The dynamic mechanical properties of polymers strongly depend on the adhesion of MWCNTs and polymer and entanglement density of the polymer chains in the presence of MWCNTs. Herein, the entanglement density and C-factor of MWCNTs/ABS composites are evaluated using the dynamic mechanical properties results obtained from a dynamic mechanical analyser and correlated with their mechanical properties. The entanglement density of the MWCNTs/ABS composites increased from 4.31 × 104 mol m−3 (pure ABS) to 7.6 × 104 mol m−3 (5 wt% MWCNTs/ABS composites). C-factor measures the effectiveness of the filler on the modulus of the composites, which decreased from 1.086 (1 wt% MWCNTs/ABS composites) to 0.78 (5 wt% MWCNTs/ABS composites), and beyond this loading, the value of C-factor began to increase; this showed that the utilization of 5 wt% MWCNTs in the ABS matrix is sufficient for their effective use. The “b” factor increased from 6.16 (1 wt% MWCNTs/ABS composites) to 7.625 (5 wt% MWCNT/ABS composites) and after that started to decrease. A larger value of “b” strengthens the MWCNTs/ABS matrix interaction. In addition, Cole–Cole analysis was carried out to understand the phase behaviour of the composites.

CVD growth of continuous and spatially uniform single layer graphene across the grain boundary of preferred (111) oriented copper processed by sequential melting–resolidification–recrystallization

The properties of the catalyst used for CVD growth have a significant influence on the quality of the graphene grown. Single crystallinity or preferred (111) orientation with a smooth surface is the most essential criterion for the growth of high quality graphene on a copper substrate. Herein, the effective strategy of pre-heat treatment of the copper substrate for the growth of improved quality single layer graphene is demonstrated. The sequential melting, resolidification and recrystallization with a controlled slow cooling rate leads to preferred (111) oriented grain growth in the copper substrate, which was confirmed with XRD studies. The grain growth evolution and strain relaxation, correlated with surface smoothening, were inferred from AFM studies. The Raman spectroscopy measurement signifies the improved quality of the CVD grown graphene which is almost free from the multilayer patches that are usually associated with the routine CVD growth process. The Raman mapping carried out directly on the graphene/copper surface reveals spatial continuity and uniformity of graphene quality across the copper grain boundaries over a large area, which signifies the importance of the strain relaxed improved surface morphology with a uniform catalytic and crystallographic environment of the underlying surface. The electrical characterization corroborates the result of improved quality of graphene grown on recrystallized copper. Hence, a feasible process of high quality graphene growth was achieved with a simple but effective strategy of preheat treatment involving melting, resolidification and recrystallization of the copper substrate.