Preparation And Performance Of PS/CeO₂ Nanocomposite Microspheres

When chemical mechanical polishing（CMP）technology is used to smooth the surface of the material,the selection of abrasive directly affects the surface quality of the polished material.Organic-inorganic composite material has the characteristics of organic polymer and inorganic material,and shows excellent polishing performance in CMP technology.In order to obtain ultra-smooth surface and improve the polishing rate,PS/CeO₂ composite microspheres with core-shell structure and PS/_mCeO₂ composite microspheres with meso-porous pores were synthesized in the microwave radiation environment.XRD,FT-IR,FESEM,TEM,AFM,laser particle size meter,Zeta potential meter and BET were used.The microstructure and properties of the samples were characterized.The polishing proper-ties of two kinds of composite abrasives were characterized by using KDP crystal as polish-ing object.The specific research contents and results are as follows:（1）Polystyrene（PS）microspheres were prepared by soap-free emulsion polymerization.The effects of initiator concentration,crosslinking agent and stabilizer dosage and micro-wave power on particle size,sphericity and surface morphology of PS microspheres were studied.FT-IR results showed that PS microspheres were prepared.FESEM diagram shows that the concentration of initiator has a great influence on the particle size of PS microspheres,the amount of crosslinking agent and stabilizer has a great influence on the monodispersity of PS microspheres,and the microwave power has a great influence on the surface morphol-ogy of PS microspheres.When the dosage of styrene was 20 ml,the initiator concentration was 6.06×10^-3 mol/L,the volume ratio of crosslinking agent to stabilizer was 2:1,and the microwave power was 300 W,PS microspheres with uniform particle size,good sphericity and smooth surface were prepared.The average particle size was about 240 nm,and the elastic modulus was 2.75 GPa.（2）Based on in situ chemical precipitation method,PS microspheres were coated with a layer of cerium nitrate.The effect of the amount of cerium nitrate on PS/CeO₂ composite microspheres was studied.FT-IR results showed the presence of CeO₂ in the composite mi-crospheres.XRD results also showed the presence of cerium dioxide in the samples,and cerium dioxide has a high degree of crystallinity.FESEM results showed that the prepared composite microspheres still maintained a high sphericity.TEM results showed that the pre-pared composite microspheres were core-shell structure,the lighter core was PS microsphere,and the darker shell was CeO₂.By adjusting the amount of cerium source to 0.8 g,2 g,3 g and 4.5 g,the composite microspheres with shell thickness of 10 nm,15 nm,20 nm and 25nm were obtained,respectively.By analyzing the AFM force curve,the elastic modulus of the composite microspheres with a shell thickness of 25 nm is 8.49 GPa.（3）Using cationic surfactant CTAB as template,PS/_mCeO₂ composite microspheres were prepared by liquid crystal template mechanism,and the effect of template dosage on the composite microspheres shell was studied.N₂ adsorption-desorption test results showed that the composite microspheres with a specific surface area of 39.62 m²/g and average pore size of 18.70 nm were prepared when the dosage of template agent was 0.88 g.The compo-site microspheres with surface area of 47.59 m²/g and average pore size of 18.10 nm were prepared when the dosage was 2.26 g.（4）The PS/CeO₂ composite microspheres and PS/_mCeO₂ composite microspheres were prepared into polishing abrasives respectively,and the surface of KDP crystal was polished.In the range of 5μm×5μm,Ra and RMS of PS/CeO₂ composite microspheres are 0.39 nm and 0.47 nm,respectively,and the material removal rate MRR is 137 nm/min.When PS/_mCeO₂ composite microspheres were used as polishing abrasive,Ra,RMS and MRR were 0.21 nm,0.26 nm and 172 nm/min in the range of 5μm×5μm.Compared with PS/CeO₂composite abrasives,PS/_mCeO₂ composite abrasives have better polishing performance and can effectively improve material removal rate while obtaining lower surface roughness.