Flyability Failures Due to Siloxanes at the Head-Disk Interface Revisited

Guo, Xuan; Raman, V.; Karis, T.; Yao, Yi Zhao

doi:10.1109/tmag.2007.893418

Cited by 10 publications

(8 citation statements)

References 1 publication

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“…The figure shows that the inplane nitrogen atom accumulates considerable negative charge. This is determined from the series of figures which show that as the interaction energy is increased from 0.04 to 0.07 e/a 0 3 (where e is the elementary charge: 1.60 x 10 −19 C; and a 0 is the Bohr radius: 5.29 x 10 −11 m), the excess negative charge is increasingly isolated on the in-plane ring nitrogen atom. Figure 7 shows the ESP mapped onto the total electron density of the model CTP.…”

Section: The Electronic Structure Of Some Star Polymer Coresmentioning

confidence: 99%

“…End-functionalized linear perfluoropolyethers (PFPEs) have long served rigid magnetic media as the boundary lubricant of choice for tribological robustness related to head wear and contamination in the hard disk drive (HDD) [1][2][3]. During the last decade, several significant changes to the HDD have imposed on the chemical design of future boundary lubricant films.…”

Section: Introductionmentioning

confidence: 99%

“…The central branch point is often referred to as the "core." Possible cores include sp 3 carbon, aromatic and non-aromatic rings, and cyclotriphosphazene [13,14]. Examples of some PFPEs based on the star architecture are shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Perfluoropolyether Boundary Lubricants Based on the Star Architecture

2018

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Star PFPE (perfluoropolyether) polymers based on an aromatic benzene core and a non-aromatic cyclotriphosphazene (CTP) core are investigated as boundary lubricant films on rigid magnetic media. The effect of the benzene and CTP cores on head-disk spacing are measured by the changes in the acoustic emission signal as a function of head-disk spacing at similar lubricant film thicknesses. The earlier head-disk contact observed with the CTP core is attributed in part to its larger size perpendicular to the plane of the disk surface. The adhesion of the benzene and CTP cores to the underlying carbon film is investigated by ab initio quantum chemistry. The nonaromatic nature of the CTP ring and the lack of steric accessibility to the CTP core nitrogen atoms prevent good adhesive interactions with the underlying carbon film. Conversely, the π-electrons of aromatic benzene create a quadrupole moment in the direction perpendicular to the plane of the benzene that can interact with the underlying carbon surface and hence provide weak adhesion. Electron-withdrawing and-donating substituents on the benzene ring can be used to exert a "push-pull" effect on the π-electrons to alter the strength of the intermolecular interactions to specific functional groups of the underlying carbon surface. These effects are visualized by mapping the electrostatic potential of the benzene core as a function of electron-withdrawing and-donating substituents and computing model dimer optimized geometries and intermolecular interaction energies. Finally, the thermal stability of the star PFPE polymers are quantified by measuring the evaporation rate of thin films (11 Å) as a function of time at the HDD temperature (~ 60°C). Thermogravimetric analyses (TGA) of the neat polymers also provide direction for improvement of the synthetic lubricants.

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Section: The Electronic Structure Of Some Star Polymer Coresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Perfluoropolyether Boundary Lubricants Based on the Star Architecture

2018

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“…A small amount of siloxane adsorbed on the disk may be picked up by the flying head, accumulated there over time, and converted tribologically into silicon oxides, which stick to the head as solid smears, causing the drive to fail. 35,36 It has been found that a PFPE lubricant (Zdol at 19 Å ) reduces the adsorption energy of a model siloxane compound (dodecamethylcyclohexasiloxane) on a carbon overcoat. 37 To determine the effectiveness of 24TMD in reducing siloxane adsorption, it is useful to compare the amount of siloxane adsorption on disks with variable lubricant thickness at a constant siloxane exposure.…”

Section: Siloxane Adsorptionmentioning

confidence: 99%

A multidentate lubricant for use in hard disk drives at sub-nanometer thickness

Guo

Marchon

Wang

et al. 2012

Journal of Applied Physics

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We describe a second generation of multidentate lubricant structures for use on a magnetic media in a hard disk drive. Building on earlier work where a perfluoropolyether (PFPE) chain with hydroxyl bonding moieties were placed in the middle of the chain as well as on chain ends, creating a structure with two PFPE sub-units for enhanced tribological performance under very low head-disk spacing, this paper focuses on a PFPE chain composed of three, even shorter PFPE subunits. Experimental data focusing on surface characterization of sub-nanometer thickness films, as well as tribological performance, are presented that confirm the high confinement level achieved with the lubricant structure. Molecular dynamics calculations are also discussed, that are consistent with a molecular film of high stiffness, leading to a denser, more compact structure. This approach could pave the way to achieving the sub-nanometer head-disk clearance level, presumed necessary for storage densities exceeding the terabit per square inch density landmark.

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“…1,2 Siloxanes are particularly pernicious in the HDD environment due to their transformation into silicon oxide smears and particles. 3,4 Frequently, the ultrathin boundary lubricant film that is topically applied to the underlying carbon film of the rigid magnetic disk surface is manipulated (surface energy, film thickness, and coverage) to reduce the contamination adsorption. 3,4 Far less attention appears to have been paid to the possible role of the underlying carbon film itself in mediating contamination adsorption.…”

Section: ■ Introductionmentioning

confidence: 99%

Study of Siloxane Adsorption on Hard Disk Media Surface

Fan

Waltman

2020

Langmuir

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Siloxane adsorption on disk surfaces is investigated as a function of lubricant film thickness and carbon film composition through several analytical technologies including FTIR, XPS, TOF-SIMS, GC−MS, and Candela OSA. Disk parameters that govern the propensity for siloxane adsorption are identified. Lubricant film coverage, taken as the fractional monolayer thickness, is found to be the most significant determinant. Siloxane adsorption decreases with increasing lubricant film coverage. The nitrogen content of the underlying carbon film is also found to be a determinant for submonolayer lubricant films: On the one side, siloxane adsorption on carbon films increases with increasing atom % nitrogen in carbon films. On the other side, the lubricant monolayer film thickness increases with increasing atom % N in carbon films, i.e., lubricant film coverage decreases with increasing atom % N. Thus, increasing atom % N in carbon films leads to increasing siloxane adsorption.

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Flyability Failures Due to Siloxanes at the Head-Disk Interface Revisited

Cited by 10 publications

References 1 publication

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

A multidentate lubricant for use in hard disk drives at sub-nanometer thickness

Study of Siloxane Adsorption on Hard Disk Media Surface

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