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

Abstract

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.

Molecular Dynamics Simulations of Perfluoropolyether Lubricant Degradation in the Presence of Oxygen, Water, and Oxide Nanoparticles using a ReaxFF Reactive Force Field

“…In the case of dry-air -treated silica nanoparticles, all four nanoparticles are bonded to each other and two water molecules are formed, while in wet-air-treated silica nanoparticles three nanoparticles are bonded to each other and no water molecule is formed. All of these results reveal that the presence of silica nanoparticles, in any form, makes D4OH strands more degradable, which is consistent with previous experimental results for other metal oxides . The order of influence of silica nanoparticles on D4OH degradation is as follows: untreated nanoparticles > dry-air-treated nanoparticles > wet-air-treated nanoparticles.…”

“…With increasing demands of data storage requirements, the computer hard disk drive (HDD) industry has experienced major improvements in data storage performance over the past few decades. Currently, the storage capacity of HDDs has increased from less than 1 Mbit/in 2 to approximately 1 Tbit/in 2 . − Heat-assisted magnetic recording (HAMR) has the potential to achieve a storage capacity of 50 Tbit/in 2 , but it faces many challenges . In HAMR recording, a pulsed laser is used to write on the magnetic medium at elevated temperature.…”

“…Furthermore, it is well known that, in the presence of metals and metal oxides, rapid degradation of PFPEs takes place at temperatures below their decomposition temperatures . Among different metal oxides that are present in the hard disks, the effects of some oxides such as ZrO 2 , Al 2 O 3 , and Fe 2 O 3 on lubricant degradation have been investigated experimentally. − Different mechanisms have been suggested for the catalytic lubricant degradation.…”

A Reactive Force Field Study on the Interaction of Lubricant with Diamond-Like Carbon Structures

“…Hard disk drive (HDD) technology has experienced a continuous increase in data storage capacity from 0.002 Mbit/in 2 to approximately 1 Tbit/in 2 in today’s hard disk drives. − The target of the new generation of hard disks is to reach an areal density as high as 50 Tbit/in 2 . To achieve this goal, further reduction in the space between the read head and the magnetic disk is required.…”

“…Noble et al show that lubricant functional end groups play an essential role in lubricant spreading on DLC. Some researchers used MD to study degradation of lubricant in the presence of DLC. − ,− Nath and Wong used coarse-grained MD to investigate thermal decomposition of different PFPE lubricants on a DLC surface. In another research work, Li et al applied MD simulation coupled with a coarse-grained bead–spring polymer model to study lubricant depletion.…”