Synthesis and growth mechanism of 3D alpha-MnO2 clusters and their application in polymer composites with enhanced microwave absorption properties

alpha-MnO2 hollow-sphere-like clusters composed of nanotubes have been synthesized on a large scale by a simple hydrothermal method. The results show that the 3D hollow-sphere-like clusters are assembled by 1D nanotubes (HSC-nanotubes) with diameter of around 80-100 nm and length of around 2-3 mm. The influences of reaction time and temperature on the morphology of the final products are investigated, while the formation mechanism is also discussed. The alpha-MnO2 hollow-sphere-like clusters possess much better dielectric properties than the bulk material, which is directly related to their special nanostructures. Besides, the synthesized alpha-MnO2 hollow-sphere-like clusters were used as fillers in the fabrication of mu-MnO2/PVDF nanocomposites, which have excellent wave-absorption properties with low filler loading. The enhanced properties are caused by a synergic effect between alpha-MnO2 and PVDF, as explained in this research.