Study On Mechanism And Key Techniques Of Ion Implantation Surface Modification Method For Ultra-precision Machining

Brittle materials such as silicon, germanium, gallium phosphide（GaP）, lithium niobate（LiNbO₃） and silicon carbide（SiC） are widely used in high-tech fields. These materials are brittle in room temperature and easy to fracture in mechanical manufacturing process. Traditionally, they are machined using grinding and polishing, which are low in productivity and efficiency and difficult to maintain form accuracy. Ultra-precision machining with diamond tools has been suggested as a replacement which can make the production of brittle materials with nanometric surface finish and submicron level geometry accuracy possible. Mirror surfaces can be achieved by ductile cutting under certain conditions. However, the short tool life and low surface integrity are still critical issues in nanometric machining. Ion implantation surface modification has attracted significant interests recently. It can alter the mechanical behavior of the workpiece surface being machined. The use of surface modification through ion implantation thus provides a possible approach to reduce surface fracture and tool wear and increase the machining efficiency, hence prolong the tool life.In this thesis, molecular dynamics simulation was firstly used to study ultra-precision machining mechanism. Cutting force, work-piece lattice deformation, and potential energy changes in the cutting process was systematically investigated.Novel method of ion implantation surface modification for ultra-precision machining of hard and brittle single crystal materials were verified from both simulation and experiments. Meanwhile, annealing after implantation for minimizing damage was also discussed.The application of this method was explored in two perspectives: ion species and multi-implantation and has been used in manufacturing aspheric silicon lenses and THz generation apparatus.