Study On Key Technology Of Nano Colloid Jet Polishing Of Single Crystal Silicon

X-ray free electron laser(XFEL)system and infrared laser system are important strategic resources,which are of great significance to national defense.With the development of XFEL system and infrared laser system,higher requirements are put forward for the transmission quality and stability of laser beam line.The researches show that the performance of XFEL system and infrared laser system is influenced by the material of reflector,accuracy and quality of optical surface.Single crystal silicon is widely used as substrate material because of its excellent physical and chemical properties.At present,single crystal silicon reflector is mainly formed by ultra-precision grinding,magnetorheological polishing and ion beam finishing.During the process,metal pollution still remains on the optical surface,which affect the reflector's performance.In this paper,the nano colloid jet polishing technique is selected as the research object.Flow field simulation is carried out to explore the influence of nozzle structure parameters on flow field,and the cone-straight nozzle is applied in jet polishing process.Based on the simulation results,the nano colloid jet process inhibition experiment is carried out to explore the evolution of metal pollution defects which generated in ion beam process,and the technique is proved to be effective.Finally,technical experiment is carried out to analyze the evolution of intrinsic surface.After polishing,roughness value and pollution concentration decrease,and the laser load capacity is improved.The paper is formed by following three aspects:1.Based on the theories of computer hydrodynamics,the simulation of jet polishing is studied,and the influence of structure parameters on the flow field is explored.According to the simulation result,the structure parameters of nozzle are optimized,which laid the foundation for carrying out technique experiment.2.According to material removal mechanism,the theoretical models of nano colloid jet polishing is established.The introduction of metal pollution is also studied.Based on the theories,the research on the suppression of metal pollution defects under nano colloid jet polishing process is carried out to verify its feasibility.3.Through nano-indentation experiment,the critical load of material is found and the processing parameters are optimized.Based on the optimized parameters,the experiment of nano colloid jet polishing technique in the elastic domain was carried out to explore the evolution of surface roughness and metal element concentration.It is verified that nano colloid jet polishing technique can improve the laser loading capacity of single crystal substrate.