Data Storage Systems Center

It has become difficult to find the optimum lubricant that meets all the requirements for ultra-small head-media spacing in hard disk drives (HDDs) [1]. Hence, a mixture of lubricants may be a feasible and promising alternative for future HDDs. In this project, molecular dynamics (MD) simulations with a bead-spring model [2] are employed to examine the nanoscopic structure, conformation, and dynamics of single component as well as binary mixture lubricant films via analyzing the anisotropic radius of gyration and the self-diffusion coefficient. We also examined ‘compression and tension processes’ of single component lubricant films. Our simulation results indicate that compression and tension processes show hysteresis in normal stress profiles. Functional PFPEs exhibit extra relaxation mode due to strong interaction among functional endgroups. The static conformation and mobility change by systematically tuning the volume fraction may provide the criteria for the optimal lubricant selection. From this, we found that binary mixture monolayer can be more suitable as a disk lubricant in comparison to the single component [3].

[1] J. Gui, IEEE Trans. Magn., 39, p.716 (2003). [2] Q. Guo, S. Izumisawa, D.M. Phillips, and M.S. Jhon, J. Appl. Phys., 93, p.8707 (2003). [3] P.S. Chung, H. Chen, and M.S. Jhon, J. Appl. Phys., 103, 561891 (2008).

It becomes more and more difficult to find the enhanced lubricant that meets all the requirements for ultra-small head-media spacing hard disk drives (HDDs) [1]. The mixture of lubricants may become feasible and promising alternative for future HDD. In this project, molecular dynamics (MD) simulations with a bead-spring model [2] are employed to examine the detailed structure, conformation, and dynamics of single component and binary mixture lubricant films by analyzing the anisotropic radius of gyration and the self-diffusion coefficient. We also examined ‘compression and tension process’ of single component lubricant films. Our simulation results indicate that compression and tension process shows history dependent normal stress profile. Functional PFPE exhibits additional mode of relaxation due to the strong interaction between functional endgroups. We also found that the binary mixture monolayer can be more suitable as a disk lubricant in comparison with the single component [3]. The conformation and mobility change by tuning the volume fraction may provide the criteria for the optimal lubricant selection.

[1] J. Gui, IEEE Trans. Magn., 39, p.716 (2003). [2] Q. Guo, S. Izumisawa, D.M. Phillips, and M.S. Jhon, J. Appl. Phys., 93, p.8707 (2003). [3] P.S. Chung, H. Chen, and M.S. Jhon, J. Appl. Phys., May 2006 (scheduled).

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