Dependency of structural change and polishing efficiency of meso-silica/ceria core/shell composite abrasives on calcination temperatures

Abstract

The structural design and controlled synthesis of abrasive particles provide a helpful solution for achieving high-efficiency and defect-free polishing. The ceria-based composite abrasives featuring mesoporous silica ( m SiO2) cores and ceria (CeO2) nanoparticle shells were annealed at controlled temperatures ranging from 500 to 1250 °C. The structural changes of the as-obtained m SiO2/CeO2 composites were characterized by powder X-ray diffraction (XRD), porosity measurements, transmission electron microscopy (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. The relationships between the calcination temperature and the finishing performance for silicon oxide layers of the m SiO2/CeO2 particles as abrasives were further explored in terms of surface roughness and material removal rate. XRD and XPS analyses indicated that an enhanced calcination temperature resulted in an improved CeO2 crystallinity and an increased Ce3+ concentration at the surfaces of CeO2 particles. As revealed by TEM and SEM observations, the core/shell structure of the composite particles was destroyed after calcination at temperatures above 950 °C, which might result from the amorphous-to-crystalline phase transformation of the m SiO2 cores (confirmed by XRD). Surface roughness analysis by atomic force microscopy revealed that the m SiO2/CeO2 abrasives with a well-defined core/shell structure (CP-500 to -950) presented a surface finish of 0.17–0.31 nm. In our experiments, the CP-500 to -950 abrasives also exhibited an enhanced removal rate as the calcination temperature increased. The crystallinity and surface property of the CeO2 particles in the shells were found to play a key role in oxide polishing processes. This present work will provide essential experimental and theoretical basis for the design and fabrication of ceria-based novel composite abrasives in efficient and damage-free finishing applications.