Z-dol and carbon overcoat: the bonding mechanism

Kasai, Paul H.

doi:10.1007/s11249-006-9056-1

Cited by 13 publications

(6 citation statements)

References 21 publications

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“…The phenomenon of the temporal change of the contact angles can be explained by dynamic behavior of the lubricant molecules on the disk surface. Lubricant molecules having hydroxyl end groups adhere to the carbon overcoat at chain end via (1) hydrogen bonding with the hydroxyl units of the carbon surface, or (2) formation of a bona fide chemical bond reacted with a dangling bond shielded inside the carbon layer 12) . The contact angles of disks coated with A20H/Z-dol mixture and those coated with Z-tetraol have been reported to be 66° and 86°, respectively 6) .…”

Section: Resultsmentioning

confidence: 99%

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Water Contact Angle: Time Dependence and Lubricant Dynamics on Hard Disk Media

Wakabayashi¹,

Kasai²

2008

Tribology Online

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The water contact angles of disks coated with Z-tetraol and A20H decreased gradually with time, starting from the initial value of approximately 105° and approaching a value below 100° in 20 seconds. The cause of temporal change was the interaction between the polar end groups of lubricant molecules and water molecules of the droplet. In the measurement environment, a part of the polar end groups was attracted to a polar droplet from the carbon surface. The contact angle consequently decreased. However, on the robust lubricant films prepared by using the ester lubricants with long-UV (254 nm) irradiation, the temporal changes were not observed. It attests to the formation of chemical bonds without polar end groups. It is proposed that the temporal change of the contact angles reflected dynamic behavior of the lubricant molecules on the disk surface.

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Section: Resultsmentioning

confidence: 99%

“…This process is based on the decarboxylation of carboxylic acids or of their esters with long-UV (254 nm) irradiation 11) . The irradiation of these lubricants with long-UV generates the perfluoro-poly-ether chains terminated with the radical ends 12) .…”

Section: Methodsmentioning

confidence: 99%

Water Contact Angle: Time Dependence and Lubricant Dynamics on Hard Disk Media

Wakabayashi¹,

Kasai²

2008

Tribology Online

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“…This means that the bonding is accelerated by the heat treatment process. One of the features of bonding will be PFPE bonding which occurs when a hydrogen atom is transferred from the hydroxyl end to a dangling bond on the DLC surface 13) . In addition to bonding, hydrogen bonding between the hydroxyl end of the PFPE and an amine terminated sites on the DLC surface may occur because the desorption energy between the hydroxyl end and an amine terminated sites is higher than that between the hydroxyl end and an oxidized site on the DLC surface 5,6) .…”

Section: Discussionmentioning

confidence: 99%

Effect of Heat Treatment Temperature on PFPE Molecules Bonded on DLC Surface

et al. 2008

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Based on the demand of extremely increased area density for magnetic data storage, the contact recording systems have been proposed, in which stronger and thinner hard coatings and lubricant films for the head disk interface (HDI) are desired. In this study, two lubrication methods, i.e., the vacuum vapor deposition and dip-coating methods are evaluated and compared in order to satisfy the demands from the HDI development. Perfluoropolyether (PFPE) is applied to the diamond-like carbon (DLC) surface. The advantage of the vacuum vapor deposition is to prevent contamination of the DLC surface from the atmosphere because of no exposed samples to the atmosphere. In contrast, the advantage of dip-coating method is to thicken the bonded layer of the PFPE by heat treatment. We discuss the adsorption mechanism between the PFPE molecules and DLC surface for each method. In addition, a simple reaction model based on the Arrhenius equation is developed and compared to the experimental results. We concluded that the reaction will be dominated by covalent bonds and hydrogen bonding. Furthermore, the reaction model can well express the experimental results. The remarkable destruction of the DLC film by the heat treatment are not seen in the samples heat treated at a temperature from 353 to 423 K while the remarkable destruction are seen in the samples treated from 423 to 473 K.

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“…The affinity of Z-tetraol is clearly inferior to that of Z-SA2 during the first week but appears to improve with time. The improved affinity is attributed to the thermal bonding attained between hydroxyl unit(s) of Z-tetraol and dangling bonds in the carbon overcoat [8].…”

Section: Spin-off Testmentioning

confidence: 99%

Disk Lubricants for Spontaneous Adsorption and Grafting to Carbon Overcoat by UV Irradiation

Kasai¹,

Wakabayashi²

2010

Tribol Lett

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A molecular orbital study was performed to elucidate the p-p charge transfer interaction between perfluoropolyether (PFPE) lubricants possessing phenylic endgroups and the carbon overcoat of magnetic hard disks. It is revealed that the phenylic unit and the graphitic segment of the carbon attract each other leading to spontaneous adsorption. The strength of this interaction increases in the order of: an unsubstituted phenyl group \ a phenoxy unit \ a p-methoxy-phenoxy unit. A molecular dynamics calculation revealed that alkyl-phenyl ether, on capture of an electron, would dissociate to yield the phenoxide anion and the alkyl radical. It is thus predicted that PFPE lubricants with an end-group possessing a phenoxy unit would spontaneously adsorb on the carbon overcoat, and that irradiation of disks coated with such lubricant with short UV (185 nm), thus generating photo-electrons, would result in facile detachment of phenoxy groups and grafting of PFPE molecular chains to the carbon surface at the chain terminus. Four new PFPE lubricants, Z-SA1 and Z-SA2 based on the Fomblin Z type backbone, and D-SA1 and D-SA2 based on the Demnum backbone were synthesized, where SA1 and SA2 indicate end-groups possessing a phenoxy unit and a p-methoxy-pheoxy unit at the x-position, respectively. Disks coated with these lubricants were tested for (1) spin-off rate, (2) diffusion over the disk surface, (3) facility for photo-grafting by UV, (4) water contact angle (before and after UV exposure), (5) the catalytic degradation, and (6) the on-track time-to-failure test. A TOF-SIMS study of disks coated with D-SA1 and D-SA2 was performed to elucidate the disposition of lubricant molecular chains due to spontaneous adsorption and the effect of UV irradiation. All the experimental results were found to be in good accord with predictions given by the molecular orbital study. In the time-to-failure test, disks coated with Z-tetraol, Z-SA1, and Z-SA2 were compared. The durability was found to increase in the order of Z-tetraol \ Z-SA1 \ Z-SA2.

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Z-dol and carbon overcoat: the bonding mechanism

Cited by 13 publications

References 21 publications

Water Contact Angle: Time Dependence and Lubricant Dynamics on Hard Disk Media

Water Contact Angle: Time Dependence and Lubricant Dynamics on Hard Disk Media

Effect of Heat Treatment Temperature on PFPE Molecules Bonded on DLC Surface

Disk Lubricants for Spontaneous Adsorption and Grafting to Carbon Overcoat by UV Irradiation

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