Surface morphology and molecular conformation for ultrathin lubricant films with functional end groups

Guo, Qian; Izumisawa, Satoru; Phillips, David M.; Jhon, Myung S.

doi:10.1063/1.1540169

Cited by 81 publications

(47 citation statements)

References 10 publications

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“…To simulate a nonfunctional lubricant molecule PFPE Z on a DLC substrate, a coarse-grained bead spring model [11,[49][50][51] is used, which neglects the detailed atomistic information while keeping the essence of molecular Energy, force…”

Section: Theoretical Formulation Of Nonfunctional Lubricant On the DLmentioning

confidence: 99%

Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

Nath

Wong

2014

Journal of Nanotechnology

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Perfluoropolyethers (PFPEs) are widely used as hard disk lubricants for protecting carbon overcoat reducing friction between the hard disk interface and the head during the movement of head during reading and writing data in the hard disk. Due to temperature rise of PFPE Zdol lubricant molecules on a DLC surface, how polar end groups are detached from lubricant molecules during coating is described considering the effect of temperatures on the bond/break density of PFPE Zdol using the coarse-grained bead spring model based on finitely extensible nonlinear elastic potential. As PFPE Z contains no polar end groups, effects of temperature on the bond/break density (number of broken bonds/total number of bonds) are not so significant like PFPE Zdol. Effects of temperature on the bond/break density of PFPE Z on DLC surface are also discussed with the help of graphical results. How bond/break phenomenonaffects the end bead density of PFPE Z and PFPE Zdol on DLC surface is discussed elaborately. How the overall bond length of PFPE Zdol increases with the increase of temperature which is responsible for its decomposition is discussed with the help of graphical results. At HAMR condition, as PFPE Z and PFPE Zdol are not suitable lubricant on a hard disk surface, it needs more investigations to obtain suitable lubricant. We study the effect of breaking of bonds of nonfunctional lubricant PFPE Z, functional lubricants such as PFPE Zdol and PFPE Ztetrao, and multidented functional lubricants such as ARJ-DS, ARJ-DD, and OHJ-DS on a DLC substrate with the increase of temperature when heating of all of the lubricants on a DLC substrate is carried out isothermally using the coarse-grained bead spring model by molecular dynamics simulations and suitable lubricant is selected which is suitable on a DLC substrate at high temperature.

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Section: Theoretical Formulation Of Nonfunctional Lubricant On the DLmentioning

confidence: 99%

Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

Nath

Wong

2014

Journal of Nanotechnology

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“…(5) where k = 40ε/σ 2 is the spring constant, r is the distance between two beads, r e = 1.3σ is the equilibrium bond length, and R 0 = 0.3σ is the maximum extension of the spring (1), (3) . Besides describing the motions of the beads, the Langevin equations is also employed for controlling the temperature of the lubricant like a thermostat, as shown in Eq.…”

Section: Methodsmentioning

confidence: 99%

“…The bead diameter σ is set to 0.7 nm corresponding to the diameter of the polymer chain (3), (4) . The model polymer consists of 10 beads to represent PFPE Zdol 2000…”

Section: Methodsmentioning

confidence: 99%

“…For the dispersive interaction between a bead and the head/tip, the 9-3 LJ potential is used, (2) For the attractive interaction between polar end and head/tip, the potential is used as, (3) where ε p = 2ε quantifies the strength of the interaction between end beads and the head, r c = 1.165σ is the critical distance of the interaction, d = 0.3σ is the decay length for the short range interaction (3) .…”

Section: Methodsmentioning

confidence: 99%

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Molecular Study of Dynamic Behavior between Head and Ultrathin Lubricant Film

Liu

Amemiya

Wong

et al. 2010

JAMDSM

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The lubricant, perfluoropolyethers (PFPEs), has been modeled and analyzed using molecular dynamics simulations based on a coarse-grained bead-spring model. An ultrathin lubricant film with a thickness of 1-2 nm is coated on a disk to lubricate the head disk interface (HDI) of hard disk drives (HDDs). The retention performance of the lubricant film is studied, which is important to avoid a direct contact between the head and disk. The replenishment performance is also studied, which is essential to repair the lubricant film ruptured by a contact of the head. Finally, the typical phenomenon of touch down-take off hysteresis during the contact between head and disk is confirmed and analyzed because of the nanoscopic interactions in the HDI.

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“…6 The coarse-grained PFPE molecule can be represented by the bead-spring model with bond stretching constraints, which can adequately capture chain conformational behavior at the larger molecular scale. 7 The force field was established by the Lennard Jones potential for the intermolecular interactions among all beads and finitely extensible nonlinear elastic (FENE) model for the intramolecular interaction between bonded beads.…”

Section: Non-equilibrium Molecular Dynamicsmentioning

confidence: 99%

Non-equilibrium responses of PFPE lubricants with various atomistic/molecular architecture at elevated temperature

2017

Self Cite

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Multiscale modeling of organic molecules contamination in head-disk interface under high thermal stress AIP Advances 7, 056514 (2017) During the operation of hard disk drive (HDD), the perfluoropolyether (PFPE) lubricant experiences elastic or viscous shear/elongation deformations, which affect the performance and reliability of the HDD. Therefore, the viscoelastic responses of PFPE could provide a finger print analysis in designing optimal molecular architecture of lubricants to control the tribological phenomena. In this paper, we examine the rheological responses of PFPEs including storage (elastic) and loss (viscous) moduli (G and G ) by monitoring the time-dependent-stress-strain relationship via non-equilibrium molecular dynamics simulations. We analyzed the rheological responses by using Cox-Merz rule, and investigated the molecular structural and thermal effects on the solid-like and liquid-like behaviors of PFPEs. The temperature dependence of the endgroup agglomeration phenomena was examined, where the functional endgroups are decoupled as the temperature increases. By analyzing the relaxation processes, the molecular rheological studies will provide the optimal lubricant selection criteria to enhance the HDD performance and reliability for the heat-assisted magnetic recording applications. © 2017 Author (s)

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Surface morphology and molecular conformation for ultrathin lubricant films with functional end groups

Cited by 81 publications

References 10 publications

Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

Study of the Thermal Decomposition of PFPEs Lubricants on a Thin DLC Film Using Finitely Extensible Nonlinear Elastic Potential Based Molecular Dynamics Simulation

Molecular Study of Dynamic Behavior between Head and Ultrathin Lubricant Film

Non-equilibrium responses of PFPE lubricants with various atomistic/molecular architecture at elevated temperature

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