The Dispersion Stability Of CeO₂ Nanoparticles In Surfactant System

Because of having lots of functional characters, CeO₂ nanoparticles have been applied widely in many fields of high technology. Recent investigation shows that CeO₂ nanoparticles can be used as CMP slurry to polish IC chip. As abrasive particles for silicon wafer and silica dielectric layer in CMP process, CeO₂ nanoparticles have more advantages of higher smoothness, higher velocity and better selectivity than SiO₂ nanoparticles.In CMP technology, abrasive particles which disperse fully in the liquid is the premise to ensure the quality of CMP.In this paper, surface charge potential and dispersion property of CeO₂ nanoparticles in the water under different conditions are researched furtherly. In the acidic water, it shows that surface of CeO₂ nanoparticles has positive charge and Zeta potential is most at pH 4 or so. While in the alkalescent water, surface of CeO₂ nanoparticles has negative charge, and absolute value of Zeta potential is most at pH 11 or so,pH_IEP of CeO₂ is about 6.7.In this paper, the synergistic effect of the surfactant mixture was studied by the Zeta potential, adsorption experiment and settling experiment. After researching, it was found that CeO₂ particles have different surfactant electrical property in different pH value or mixture surfactant system, by which the dispersion stability was affected. Isoelectric point and Zeta potential was changed obviously by adding mixture surfactant. After adding the mixture surfactant that was made of Tween 80 and CTAB. The Zeta potential of CeO₂ particles was changed to be positive value under wide range pH value. Isoelectric point of Zeta potential move to lower pH value in the system that was added the mixture surfactant of Tween 80 and SDBS. CeO₂ particles have good adsorption property for these two kinds mixture surfactants. But the shapes of adsorption isotherm of them have different. The dispersion stability of CeO₂ particles in mixture surfactant system was improved obviously compare of no surfactant. The synergistic effect of mixture surfactant of Tween 80 and SDBS on CeO₂ slurry was more obviously than the other one. Affect of mixture surfactant on dispersion stability was decided by interact of single surfactants.