Title

Performance improvement in the grinding of ceramics via the Rebinder effect

Date of Completion

January 1999

Keywords

Engineering, Materials Science

Degree

Ph.D.

Abstract

The Rebinder effect, or the dependence of the hardness of a ceramic material on its environment, was investigated for aluminum oxide and silicon nitride in aqueous environments of varying pH. Significant Rebinder effects were found for both materials. A maximum in hardness (Knoop microhardness) was found at the pH of zero zeta potential (surface charge). Observations were consistent with a mechanism for the Rebinder effect, proposed by Westwood, (Westwood, A. R. C. and Goldheim, D. L., J. Appl. Phys., 39 [7] 3401–3405 (1968)) in which hardness is governed by dislocation motion. ^ Prior attempts to apply the Rebinder effect have considered the low speed process of drilling. These attempts have been successful in the laboratory but unsuccessful in the field due to the overall inefficiency of this process. This work extends the application of the Rebinder effect to grinding, a high speed process. Although grinding forces were measured, the focus of this study was on part quality improvement rather than a reduction in energy consumption. Grinding forces, surface finish, and post grinding flexural strength were shown to be dependent on coolant pH in the grinding of alumina. These data are consistent with mechanisms involving brittle/ductile or brittle/brittle (e.g. intergranular → transgranular) transitions depending on the aggressiveness of the grinding parameters. ^