Surface interactions between nanodiamonds and glass in magnetorheological finishing (MRF).

摘要

Magnetorheological finishing (MRF) is a deterministic sub-aperture polishing process. The process uses a magnetorheological (MR) fluid that consists of micron-sized, spherical, magnetic carbonyl iron (CI) particles, non-magnetic polishing abrasives, water and stabilizers. Material removal occurs when the CI and non-magnetic polishing abrasives shear material off the surface being polished.;In this work we focus on building a better understanding of the MRF process. Material removal is possible using a non-magnetic polishing abrasive free MR fluid. We study how this occurs and how removal changes with the addition of non-magnetic polishing abrasives. Specifically we study nanodiamonds in the MR fluid. Nanodiamonds can be engineered to achieve varying properties that allow us to learn more about the MRF process.;We introduce a new MRF material removal rate model. This model contains terms for the near surface mechanical properties of glass, drag force, polishing abrasive size and concentration, chemical durability of the glass, MR fluid pH and the glass composition. We validate individual terms in our model separately and then compare the entire model to an existing MRF material removal model. All of our experimental data were obtained using nanodiamond MR fluids and a set of six optical glasses.;We discuss the role of nanodiamonds in the polishing zone by examining the residual surface texture inside MRF spots. We show evidence that the CI particles in the abrasive free MR fluid remove material with a micro-gouging mechanism and, as nanodiamonds are added to the system, the mechanism changes to a micro-lateral-fracture mechanism, which is more efficient in removing material. Finally, we modify a conventional model for surface roughness for use with MRF.