Study of Molecular Conformation of PFPE Lubricants With Multidentate Functional Groups on Magnetic Disk Surface by Experiments and Molecular Dynamics Simulations

Tani, Hiroshi; Shimizu, Tsuyoshi; Kobayashi, N.; Taniike, Yoshihiro; Mori, Kazuya; Tagawa, Norio

doi:10.1109/tmag.2010.2042573

Cited by 7 publications

(10 citation statements)

References 12 publications

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“…Tersoff potential is used for the C-C interaction of the DLC structure. To resist diffusion of nonfunctional lubricant PFPE Z, functional lubricants such as PFPE Zdol and PFPE Ztetraol, and multidented functional lubricants such as ARJ-DS, ARJ-DD, and OHJ-DS synthesized by Tani et al [55] into DLC thin film during the simulation using coarse-grained bead spring model based on finitely extensible nonlinear elastic potential for lubricants, original DLC thin film is compressed into half of its original configuration in the , , and directions, respectively. To simulate nonfunctional and functional lubricant using the coarse-grained bead spring model based on finitely extensible nonlinear elastic potential and nonbonded potential LJ 12/6, DLC thin film is compressed [56] to obtain dimensional temperatures.…”

Section: Simulation Proceduresmentioning

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: Simulation Proceduresmentioning

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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“…Here, the bonding ratio is defined as the ratio of the coated lubricant thickness to the residual film thickness after rinsing the lubricantcoated surface with a solvent (Vertrel XF). The monolayer thickness of Z-dol2000 was approximately 1.4 nm, and that of Z-Tetraol was approximately 1.7 nm [17]. The monolayer thickness of Z-TMD was estimated to be of the same order as that of Z-dol2000 [18].…”

Section: Friction Testsmentioning

confidence: 89%

Dependence of Pin Surface Roughness for Friction Forces of Ultrathin Perfluoropolyether Lubricant Film on Magnetic Disks by Pin-on-Disk Test

Tani

Mitsuya

Kitagawa

et al. 2012

Advances in Tribology

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We fabricated supersmooth probes for use in pin-on-disk sliding tests by applying gas cluster ion beam irradiation to glass convex lenses. In the fabrication process, various changes were made to the irradiation conditions; these included one-step irradiation of Ar clusters or two-step irradiation of Ar and N2clusters, with or without Ar cluster-assisted tough carbon deposition prior to N2irradiation, and the application of various ion doses onto the surface. We successfully obtained probes with a centerline averaged surface roughness that ranged widely from 1.08 to 4.30 nm. Using these probes, we measured the friction forces exerted on magnetic disks coated with a molecularly thin lubricant film. Perfluoropolyether lubricant films with different numbers of hydroxyl end groups were compared, and our results indicated that the friction force increases as the surface roughness of the pin decreases and that increases as the number of hydroxyl end groups increases.

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“…Low MW PFPE is not a practical solution because there is a trade-off relationship between small monolayer thickness and evaporation loss. In order to reslove this trade-off issue, multidentate PFPE lubricant is developed which has several hydroxy (OH) groups at the intermediate positon along the PFPE main chain [6][7][8][9][10]. The conventional PFPEs such as Z-Dol and Z-Tetraol, have OH groups only at both terminals of the PFPE main chain.…”

Section: Introductionmentioning

confidence: 99%

Ionic Liquid Lubricant for Ultra-Low Head-Media Spacing in Hard Disk Drives

2020

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In order to attain high recording density in a hard disk drive, reduction of the head-media spacing (HMS) is crucial. The contribution of lubricant thickness to the HMS is a significant factor in performance. Because the lubricant thickness is on the order of angstroms, molecules of long-chain lubricants, such as perfluoroether, must lay parallel to the magnetic disk surface to reduce lubricant thickness. In this study, new lubricants were designed using ionic liquids (ILs). The ILs had smaller molecular weight than that of current perfluoropolyether (PFPE) lubricants but with lower evaporation loss. The molecular conformation of the ILs was controlled by two hydroxyl groups, which were placed in a cation moiety at both terminal ends (IL-1) or placed on one side of the cation (IL-2). The monolayer thickness of IL-1 and IL-2 was seen to be 0.6 nm and 1.2 nm, respectively. The adhesion force at a lubricant thickness of 1.0 nm decreased in the order: PFPE (Z-Dol 2000) > IL-2 > IL-1. The small adhesion force, which is one of the essential parameters for low flight of a magnetic head, was achieved by changing the molecular conformation of the IL.

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Study of Molecular Conformation of PFPE Lubricants With Multidentate Functional Groups on Magnetic Disk Surface by Experiments and Molecular Dynamics Simulations

Cited by 7 publications

References 12 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

Dependence of Pin Surface Roughness for Friction Forces of Ultrathin Perfluoropolyether Lubricant Film on Magnetic Disks by Pin-on-Disk Test

Ionic Liquid Lubricant for Ultra-Low Head-Media Spacing in Hard Disk Drives

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