Formation of heterostructures with p-type oxides such as NiO and CuO is one of the effective methods for improving the photocatalytic performance of ZnO. Such systems are often synthesized through template-based growth techniques that involve many steps. We have prepared ZnO-NiO composites through a facile, template-free, low-temperature sonochemical route. High-resolution transmission electron microscopy analysis indicates the formation of ZnO-NiO heterostructures. Photocatalytic activity of ZnO-NiO nanocomposites in the decomposition of methylene blue dye under solar irradiation is found to be much larger than that of both pure ZnO (1.26 × 10 −2 min −1 ) and NiO (0.31 × 10 −2 min −1 ) establishing synergistic effects. The rate constant increases with increase in the percentage of NiO in the composite and is 6.00 × 10 −2 min −1 for sample with the highest percentage of NiO. Rate constants for the second and third runs are estimated to be 4.4 × 10 −2 and 4.2 × 10 −2 min −1 which are promising. The main mechanism of enhancement of photocatalytic activity of the composites is identified as the more effective separation of the photogenerated free charge carries due to the internal electric field at the ZnO-NiO interface. Sharp decrease in the relative intensity of the band-band emission of ZnO at ~ 380 nm in the case of composite samples and analysis of the relative position of the conduction band and valence band edges of ZnO and NiO support the proposed mechanism.

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The present work aimed at the simultaneous improvement in the mechanical and electromagnetic shielding properties of Fe3O4‐carbonaceous/epoxy composites by the reinforcement of two plies of carbon fiber into the epoxy‐filler matrix. In this study, Fe3O4‐activated carbon and Fe3O4‐activated charcoal composites were synthesized by co‐precipitation method and were introduced into the epoxy matrix with different weight percentage (5, 10, and 15 wt%). The BET surface area analysis revealed the high porosity in the Fe3O4‐activated charcoal composite than that of activated carbon composite. The Fe3O4‐activated carbon/epoxy composite showed better mechanical properties than the later. Both the composites showed nearly same EMI SE value. 10 wt% of the filler‐1/epoxy composite showed the highest shielding effectiveness (SE) value of −22.5 dB at 10 GHz whereas 15 wt% Fe3O4@charcoal/epoxy composite showed better SE value of −27.15 dB at 8.8 GHz. The obtained results were supported by the dielectric and magnetic loss tangent studies. The incorporation of carbon fiber enhanced the mechanical property by three times and the EMI SE value by ~15 dB. Thus, the carbon fiber reinforced Fe3O4/carbonaceous epoxy composites may be the potential electromagnetic shielding material for electronics and aircraft industries.