Theoretical analysis of evaporation and re-adsorption of PFPE molecules on hard disk surface

Abstract

The collision density of the evaporated lubricant molecules in the air with the hard disk was analyzed based on the kinetic theory of gases. It is found that the collision density is quite high even for the ultralow vapor pressure of the lubricant perfluoropolyether used in hard disks. This suggests that the adsorption of the collided molecules may have significant contribution to the lubricant film replenishment. In addition, the adsorption of the lubricant molecules is also expected to reduce the potential barrier to the surface diffusion, and hence to promote the spreading process of lubricant film on hard disk surface. An adsorbing-spreading mechanism is proposed for the lubricant film replenishment in hard disks.

Adsorption of Fluorinated Ethers and Alcohols on Fresh and Oxidized Carbon Overcoats for Magnetic Data Storage

“…The desorption energy of CF 3 CH 2 OH is dependent on the degree of oxidation of the surface, while the interaction of (CF 3 CF 2 ) 2 O with a -CH x is independent of its degree of oxidation. The fact that the desorption energy of CF 3 CH 2 OH increases with oxidation of the surface is consistent with CF 3 CH 2 OH interacting with the surface via hydrogen bonding. − The results support the possibility of using surface oxidation to control the bonding and properties of lubricants such as Fomblin Zdol on the a -CH x surface. These fundamental studies help to probe the bonding mechanism of perfluoropolyalkylether lubricants with a -CH x film surfaces and also provide the types of insights needed to help design a vapor-phase lubrication process for disk surfaces.…”

“…In addition, the lubricants interact with the surface via van der Waals attractions. These are the interactions that give the current lubricants their desirable balance of properties on the surface. − As mentioned, in current disk fabrication, the surface of the a -CH x overcoat is exposed to air prior to application of the lubricant by dip-coating. Thus, the PFPE lubricant is interacting with a surface that is partially oxidized.…”