Synthesis and characterization of nano-alumina powder by milling of Al and MnO2 powder mixture

Abstract

There are extensive study on nano composites because of its outstanding mechanical properties when compared with the monolithic materials. The manufacturing of nano particles presents an increasing interest. There are two basic strategy for the synthesis of nano particles, they are bottom up and top down approach. Nano particles are built atom by atom in the bottom up approach. In the synthesis of nano particles, top down approach is most applied one. In this approach, bulk materials are broken down gradually into smaller sizes until they reach nano size. Ball milling is most widely used method for the top down approch. Ball milling process involves milling of constituent powders in a vial where mechanical deformation and chemical reactions takes place between the powders to form new phase. In the present study, constituent powder mixture of Al (1.845 μm) and MnO2 (0.75 μm) are subjected to high energy planetary ball milling to form new phase which is of nano alumina (Al2O3). Initially, Al and MnO2 powder mixture are taken in the ratio of 1:2.416 by weight for different milling duration of 120 min, 240 min and 360 min. The constant speed of the mill was maintained at 300 rpm. The powder mixture inside the mill subjected to impact force between ball to ball and between ball to wall of the container undergo cyclic deformation, cold welding and fracture ensures the generation of nano alumina particles in the range of 50 nm to 560 nm. The effect of mechanical alloying on the microstructure of the powder mixture have been studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and EDS. Toluene was used during milling appears effective process control agent to avoid severe agglomeration and to enhance milling effect.