Preparation and Characterization of Spherical Magnetorheological Composite Abrasives Based on Two Different Titanium Sources

Abstract

Magnetorheological finishing (MRF) is one of the key technologies for the efficient and precise planarization of surfaces. While maintaining magnetic properties, improving the corrosion resistance of magnetic particles and their synergy with abrasives plays an important role in improving the efficiency and quality of magnetorheological finishing. In this work, TiO2 and TiH2 powders were used as titanium sources to prepare two Fe-Ti-O magnetorheological composite powders, labelled as A and B, through an in-situ oxidation-reduction process. Subsequently, diamond grits (0.5μm, 5wt%) were added into the Fe-Ti-O magnetorheological composite powders and spherical magnetorheological composite abrasives (SAs) with particle size ranged from 2-12μm were prepared by a spray granulation process. The effects of TiO2/TiH2 addition on the microscopic morphology, phase composition, microhardness, density, magnetic properties, particle sizes, specific surface areas and corrosion resistance of A, B and SAs were investigated. The results indicate that A and B are composed of two phases, Fe and Fe2TiO4, which have a unique "Ferrero" structure. The microhardness, density, saturation magnetization and corrosion potential of B were 525 HV, 5.125 g/cm3, 131 emu/g and -0.841 VSCE respectively, which were higher than those of A. The results of the magnetorheological finishing of single crystal silicon wafers demonstrate that the efficiency of the magnetorheological slurry (MRS-B) is approximately 6.3 times that of MRS-A. It has been demonstrated that B is a more suitable base material for SAs, which possess a high degree of sphericity and a high degree of particle size concentration. The Raman spectra of SAs demonstrated that the preparation process did not result in the carbonization of the diamond grits. The magnetic properties (Ms=104.1 emu/g, Hc=133.12 Oe, Mr=5.88 emu/g) of SAs meets the requirements for magnetorheological finishing and positions them as ideal candidates for the magnetorheological finishing of third-generation semiconductor SiC wafers.

Keywords: Magnetorheological finishing, spherical abrasive, TiO2/TiH2, corrosion resistance, Fe-Ti-O composite powder