Yang Yun1, Andrew J. Gellman2, Min Li1, Jun Wang1, Diana Liao1, Lorenz Kampschulte1, and Eric I. Altman1. (1) Chemical Engineering Department, Yale University, 100 Howe St, Apt. 302, New Haven, CT 06511, (2) Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213
Two projects are presented in this poster. The surface chemistry of carbon overcoats focuses on the oxidation kinetics and the vapor phase lubrication of carbon overcoats. Hydrogenated amorphous carbon (a-CHx) overcoat and perfluoropolyalkylether (PFPE) lubricant have been used as the protection and lubrication layers for magnetic hard disk platters for years. However, the oxidation kinetics and the effect of the oxidation on the bonding of the PFPE lubricant with a-CHx have not been studied carefully. Our results show that although the surfaces of a-CHx are heterogeneous in nature, the a-CHx oxidation kinetics in O2 can be predicted by a Langmuir-Hinshelwood reaction with a relatively low rate constant for oxidation. Furthermore the oxidation of the a-CHx surface is demonstrated to be able to intensify the hydrogen bonding of the PFPE hydroxyl endgroups and the a-CHx surface for the first time. Although this effect has been assumed to exist it has not been observed directly or quantified. These results imply that the oxidation of the fresh a-CHx may be a means to control or tailor the surface properties to optimize the properties of the lubricant-overcoat interface in hard disks.
The goal of the lithium niobate (LiNbO3) project is to determine the magnitude of the effect of the ferroelectric poling direction on surface catalytic chemistry. Large differences in 2-propanol reaction on the positive and negative faces of LiNbO3 (0001) faces are observed in temperature programmed desorption (TPD) experiments. On the negative face, only molecular desorption is observed, predominantly in peaks at ~380 and ~500 K. In contrast, 2-propanol desorbs from the positive face in a single peak at ~600 K, and evidence that some of the adsorbed 2-propanol undergoes oxidative dehydrogenation to acetone is observed. The adsorption of acetic acid is also being studied. The results indicate that adsorption strength can be dramatically altered by changing the ferroelectric polarization and suggest that oxidation reactions can be turned on and off by switching the polarization direction.