Humidity Effects on PFPE Lubricant Bonding to a-CH_x Overcoats

Abstract

The continued reduction in the head-disk separation of magnetic data storage systems and the corresponding increase in the frequency of head-disk contacts will place severe stress on the lubricant and overcoat used to protect the surfaces of magnetic media. With decreasing fly heights, environmental conditions such as temperature and humidity that influence the lubricant-overcoat interactions become increasingly important to the tribological performance of the head-disk interface. It is essential to obtain a fundamental understanding of the molecular interactions at the lubricant-overcoat interface in order to maintain the reliability of future hard disk drives. The coadsorption of model fluoro alcohols and fluoro ethers with water was studied to gain a fundamental understanding of the effects of humidity on the bonding of perfluoropolyalkyl ether (PFPE) lubricants to amorphous hydrogenated carbon (a-CHx) overcoats. Temperature-programmed desorption experiments were performed using 2,2,2-trifluoroethanol (CF3CH2-OH) coadsorbed with water and perfluorodiethyl ether [(CF3CF2)2O] coadsorbed with water. The results indicate that the presence of water increases the desorption energy of CF3CH2OH on the a-CHx overcoat but decreases the desorption energy of (CF3CF2)2O on a-CHx overcoats. The implication of these results is that there is a net increase in the mobility of PFPE lubricant films when exposed to humid environments.

Electron stimulated decomposition of fluorocarbons on amorphous hydrogenated carbon (a-CHx) overcoats used in data storage media

“…As the coverage of (CF 3 CF 2 ) 2 O is increased, the peak desorption temperature decreases monotonically and the peak broadens. This behavior has been observed many times in studies of the adsorption of these compounds from various types of amorphous carbon films and is attributed to the heterogeneity of the surface [30,31]. As a consequence of the heterogeneity of the a-CH x surfaces, there is no clear resolution of the monolayer, and multilayer desorption features which would be resolved on homogeneous single crystalline surfaces [32,33].…”

Vacuum vapor deposition of PFPE molecules on CHxNy and CHxFy amorphous carbon surfaces

“…It is seen from the figure that both the CHxNy and CHxFy films consistently have a higher amount of Zdol bonding compared to the CHx film. The reason for this seems to come from the change in the bonding It is well known that the Zdol will strongly bond to the CHx film by some interaction such as a covalent bond, the interaction between the hydroxyl end groups of the Zdol molecule and the proton acceptor of the CHx film, and the interaction between the oxygen of the ether linkage of the Zdol main chain and the site of the CHx film which has a higher affinity (Shukla et al 2000;Lei and Gellman 2000;Lei et al 2001a, b;Waltman 2000). However, the oxygen of the ether linkage adsorbed on the high affinity site is displaced by the solvent rinsing, i.e., a water molecule is adsorbed instead of the oxygen of the ether linkage, because the desorption energy between the oxygen and the affinity site is lower than that between the water molecule and the site.…”

Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of Vapor-Phase Mercury Uptake by Carbonacoues Surfaces

“…The results obtained in this study can be compared to the TPD spectra of other polar organic adsorbates (alcohols and ethers) on HOPG, which showed first order monolayer and zero order multilayer desorption peaks. (123,124) In addition to using the simulation method described above to assess the desorption parameters, acetone TPD experiments were performed using different heating rates at 7L acetone exposure to independently determine acetone desorption parameters. (92) Figure 4-20 illustrates how the TPD peak amplitude grows and the peak location shifts to higher temperature as the heating rate increase.…”