Electrostatic self-assembly design of core@shell structured Al2O3@C nanospheres towards high-efficiency and damage-free polishing sapphire wafer

Abstract A novel core@shell structured nanocomposite particles with carbon as soft shell and nanoAl2O3 as hard core were prepared by electrostatic self-assembly, and the subsequent hydrothermal and high temperature treatment. By adjusting concentration of nanoAl2O3, the average size of the composite particles vary from 750 nm to 150 nm, the corresponding to the thickness of the carbon shell in the range of 355–55 nm. On the basic of the TEM and Raman results, the shell materials were composed of the amorphous carbon. As confirmed by XPS, the Al2O3 @C composite particles had a stable structure, owing to the formation of the interfacial bonding between carbon shell and nanoAl2O3 after the carbonization process. Moreover, the nanoAl2O3 @carbon composite abrasive could lead to a decrease in the surface damage and roughness of the sapphire wafer compared with the nanoalumina abrasive, owing to the elastic effect coming from the amorphous carbon shell.