Study On Preparation Of Alumina Abrasive, Stability Of Polishing Slurry And Its Polishing Properties

Sapphire has high hardness?Mohs hardness of 9?,excellent corrosion resistance and good optical and mechanical properties,so it is widely used in high-tech fields such as solid-state lasers,precision anti-friction bearings,infrared windows,and semiconductor chip substrates.With the rapid development of technology,the sapphire surface flatness requirements are getting higher and higher,and chemical mechanical polishing?CMP?is the most common surface processing technology at present,and it is recognized as the only polishing method that can achieve global flattening.Chemical mechanical polishing to achieve smooth surface of sapphire has become a research hotspot.Polishing pastes and polishing abrasives play an important role in CMP and have a direct impact on the quality of sapphire polishing.In this paper,the polishing slurry with good stability and polishing performance was obtained by dispersing alumina abrasive in silica sol.The spherical alumina abrasives with particle diameters of 320 nm,500 nm and1.0?m were prepared by homogeneous precipitation method.The alumina abrasives with irregular morphology of 320 nm were prepared by direct precipitation method,and the particle size and morphology were different.The alumina is polished to sapphire,and the spherical alumina having a particle size of 1.0?m has a better polishing effect.The morphology and composition of the samples were characterized by scanning electron microscopy?SEM?and X-ray diffraction?XRD?.The dispersion stabilityof the polishing slurry was examined by Zeta potential,and the surface roughness of the sapphire before and after polishing was examined by atomic force microscopy?AFM?.The main results are as follows:Dispersing the alumina abrasive in the silica sol,the stability of the system is obviously improved,and the polishing performance of the sapphire is also obviously improved.It is found that the polishing performance of the polishing slurry is positively correlated with the stability of the slurry.The optimum polishing slurry prepared by the experiment using alumina as the abrasive was prepared by the following conditions:the concentration of alumina was 10.0 wt%,the silica sol having a particle diameter of 5 nm and 0.02 wt%was used as a dispersing agent,and the pH of the polishing slurry was adjusted to 10,Stir vigorously for 0.5 h;polishing the sapphire with the prepared polishing slurry.The surface roughness of the polished sapphire was reduced from 0.992 nm to 0.272 nm,and the material removal rate was15.16 nm·min^-1,which was compared with water as a dispersion medium.The polishing effect of the polishing slurry is significantly improved.?2?The experimental conditions for the preparation of spherical alumina with different particle sizes by single factor experiment are as follows:using 92°C water bath,using aluminum sulfate octahydrate as aluminum salt,and using urea with a ratio of material to Al³⁺of 20 as precipitation the initial pH of the reagent and reaction system is 3-4.The pH of the reagent adjustment system is not added during the reaction,and PEG2000 is used as a dispersant with 0.8wt%?water quality?,mechanically stirred for 2h,and aged for 1.5h to prepare dispersion,Good dispersion with good sphericity of alumina.Controlling the above conditions,adjusting the Al³⁺concentration can obtain spherical alumina with different particle sizes:when the Al³⁺concentration is 0.001 moL·L^-1,the alumina particle size is 320 nm,and when the Al³⁺concentration is 0.002 moL·L^-11 The particle size of alumina is 500 nm.When the concentration of Al³⁺is 0.005 moL·L^-1,the particle size of alumina is 1.0?m.When the concentration of Al³⁺is increased to 0.1 moL·L^-1,the particle size of alumina is not obvious.The increase is still about 1.0?m.When the concentration of Al³⁺is 0.5moL·L^-1,the particle size of alumina does not increase significantly,and the sphericity deteriorates and agglomeration occurs.?3?The optimum experimental conditions for obtaining irregular morphology alumina by orthogonal test are:Al³⁺concentration is 0.05 mol·L^-1,Al salt type is NH₄Al?SO₄?₂·9H₂O,PEG2000 mass fraction is 1.0wt%,the precipitant is NaOH,and the pH of the system is controlled to 6-7.Moreover,the irregular alumina obtained by the experimental conditions has good dispersibility and a particle size of about 320nm.?4?Experiments were carried out to investigate the polishing effect of spherical alumina with particle size of 320 nm and 1?m and irregular morphology of alumina with particle size of 320 nm on sapphire.The results show that the removal rate of sapphire polishing material by spherical alumina with particle size of 320nm is28.94nm·min^-1,the surface roughness of polished sapphire is 0.251nm,and the removal rate of spherical alumina to sapphire with particle size of 1.0?m.The surface roughness of the sapphire after polishing is 25.63 nm·min^-1,and the surface roughness of the sapphire with a particle size of 320 nm is 15.98 nm·min^-1.The surface roughness of the sapphire after polishing is 0.295 nm.The surface roughness of sapphire after polishing is consistent with the requirement of sapphire as substrate?less than 0.3nm?.The spherical alumina with particle size of 320nm has the highest material removal rate and the best polishing effect.The spherical alumina with particle size of 1.0?m The polishing effect is second,and the irregular morphology of alumina-polished alumina has a relatively poor polishing effect on sapphire.Although spherical alumina with a particle size of 320 nm has the best polishing effect on sapphire,the optimum polishing abrasive for this topic is because the Al³⁺concentration in the preparation process is too low(0.001 moL·L^-1),which is not suitablele for industrial production.So the spherical alumina with a particle size of1.0?m as the best polishing abrasive was choosed.?5?Production of 1.0?m spherical alumina as an abrasive,and polishing slurry is prepared by the preparation method of the best polishing slurry of the subject.The economic evaluation of the annual production of 500t polishing slurry shows that the production of the process has great economic benefits on the basis of meeting relevant environmental protection requirements,so the production process is feasible.