The influence of friction stir processing parameters and the subsequent evolution of microstructures and cor-rosion behaviour of Al–SiC surface composites fabricated in the presence of graphitic flakes are presented in this paper. The circumferential shear stress exerted by the rotating tool exfoliates the graphite flakes into few-layered graphene during processing. These graphene flakes preferentially occupy both the grain boundaries and the SiC–Al interface during recrys-tallization. The potentiodynamic polarization test, in 3.5 wt% sodium chloride (NaCl) solution, is conducted for samples processed at various tool rotational speeds and it is found that the presence of this thin graphitic layer at these locations reduces the intergranular and interfacial corrosion to a great extent. The tool rotational speed has a significant influence on processing, and samples fabricated at an optimum tool rotational speed of 2200 rpm shows better corrosion resistance and mechanical properties as compared to that at lower and higher speeds. Raman spectroscopic analysis, X-ray diffraction studies and microhardness tests corroborate the experimental results and the proposed mechanisms.

The impact of reinforcing multi-walled carbon nanotubes (MWCNT) and uni-directional carbon fibre fabric (UCFF) in the epoxy polymer matrix on the electromagnetic interference shielding efficiency (EMI SE) is studied in the X-band frequency range (8–12 GHz). The increase in the weight percentage (wt%) of pristine MWCNT increases the EMI SE of the nanocomposites. Inclusion of UCFF, as a layer, enhances the EMI SE of the structure to a great extent giving an EMI SE of around 75 dB at 12 GHz for UCFF-sandwiched 5 wt% MWCNT–epoxy composite. The layered structure, epoxy–MWCNT/UCFF/epoxy–MWCNT introduces heterogeneity and this results in a SE much higher than the individual contributions of MWCNT and UCFF. The analysis suggests that the presence of thin layer of UCFF absorbs the radiation apart from inducing multiple scattering enhancing the absorption within the MWCNT– epoxy region.