Study On Preparation And Properties Of Polishing Slurry With Shear Thickening And Chemical Effect

With the development of modern electronic information,optoelectronics,semiconductor and other technologies,higher requirements are put forward for precision and ultra-precision machining technology.With the increasing of value precision and ultra-precision machining for high-end manufacturing industry,the efficient and low-cost polishing technology of optical crystals and semiconductors has become one of the key research directions in the field of ultra-precision machining.In this paper,based on the research of ultra-precision machining technology at home and abroad,the preparation and properties of polishing slurry with shear thickening and chemical compound effect are studied.Firstly,the characteristics,preparation process and performance test method of shear thickening and chemical effect compound polishing slurry are explored and analyzed,and a new test platform of shear thickening and chemical compound polishing is built.Based on the new test platform,the mechanical analysis of workpiece polishing process is carried out,and the critical shear rate prediction model and material removal model of shear thickening and chemical effect compound polishing slurry are established.Combined with the model,the high efficiency polishing experiment of the workpiece is carried out,and the new high performance polishing slurry is optimized.The main work is as follows:The basic principle of shear thickening and chemical composite effect and the mechanism of characteristic material removal are expounded.The main influencing factors of polishing were analyzed.A new type of LC-1 machining process system is built.The maximum speed of the driving spindle is 8000 rpm,and the polishing pressure is 10?150k Pa.The main components of the polishing solution are:cerium oxide,H₂O₂,polymethylmethacrylate,potassium hydroxide and citric acid.The influence of abrasive particle size,concentration,temperature and p H value on the rheological properties of polishing slurry was measured by digital rheometer.The results show that temperature has a great influence on the shear thickening effect,and the concentration of dispersed particles(abrasive and dispersed phase)has the second effect.When the particle size of dispersed phase is close to that of abrasive particle,the thickening effect of polishing slurry is better.On this basis,the influence of various factors on the critical shear stress is studied,and the prediction model of critical shear rate of polishing slurry is established.It is found that the critical shear rate increases with the increase of temperature,but decreases with the increase of abrasive content and p H value.The formula of friction resistance and shear rate in the process of polishing liquid movement is calculated and deduced theoretically,and the mechanical calculation model of surface force of workpiece in polishing process is established.The mechanism of shear thickening and chemical compound effect polishing slurry in polishing process was studied.Based on the characteristics of polishing slurry and processing technology system,the laws of kinematic and mechanical properties of abrasive particles were analyzed.A material removal model based on shear thickening theory and tribochemical theory was proposed to guide the subsequent actual production and processing technology.Through the polishing experiment of lithium niobate workpiece,the influence of abrasive content,p H value and oxidant concentration of polishing slurry on the surface quality of polishing workpiece is analyzed.With the increase of abrasive content,the surface polishing quality and material removal rate of lithium niobate become higher and higher.When the content of cerium oxide abrasive is 16 wt.%and polished for 80 min,the polishing effect is the best.Under different p H values,when p H value is 9.5,the surface roughness decreases fastest after polishing;when the content of oxidant is 1.2 wt%,the surface roughness of lithium niobate is smaller and the material removal rate is higher.