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1.
《Tribology International》2003,36(4-6):305-309
Surface reactions on magnetic recording disks have been studied during sliding with ceramic sliders in the main chamber of TOF-SIMS. Chemical change of lubricant oil in the wear track was observed by the chemical image of TOF-SIMS. The magnetic disk surface was covered with perfluoroalkyl polyether lubricant (Fomblin Zdol). The Si tip slider surface was covered with Al2O3, DLC, TiN or c-BN coating. Experimental conditions were as follows: 0.8 mN of load and a sliding speed of 0.01 m/s. Lubricant oils were decomposed with Al2O3 and TiN slider surfaces. Metal (Al, Ti) fluorides were detected by TOF-SIMS in the sliding track. Material transfer occurred by chemical wear of slider material. From TOF-SIMS observation, the decomposition of lubricant molecules was initiated at the end group of molecules (-CF2CH2OH). On the other hand, DLC and c-BN sliders suppressed the decomposition reaction of PFPE oils. In conclusion, hard and chemical inert materials such as DLC and c-BN are suitable for a long-life HDI. 相似文献
2.
X-1P, a cyclic phosphazene lubricant, is studied and compared with polar perfluoropolyether (PFPE) lubricant Z-Dol. Contact
angles of lubricants are measured on different solid surfaces. Contact start-stop (CSS), drag, and ball-on-flat tests are
performed and the results are discussed. Drag tests under high vacuum are also performed and discussed. Experimental results
show that lubricant X-1P exhibits lower static friction and higher durability than lubricant Z-Dol, especially at high humidity.
Higher durability is also observed for X-1P under the high vacuum condition compared with lubricant Z-Dol. Diamond-like carbon
(DLC) overcoat on the Al2O3–TiC slider surface lowers friction and prolongs durability, especially for lubricant Z-Dol at high humidity, whereas for
X-1P, there is no benefit of DLC. X-1P as an additive shows some improvement in durability at high humidity as compared to
lubricant Z-Dol.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The Effect of Phosphazene additives to passivate and stabilize lubricants at the head/disk interface
There have been a number of applications for lubricant additives in the disk drive media area, the first of which was for pseudo-contact recording with inductive heads (tri-pad sliders) in an effort to stabilize the head/disk interface and minimize lube decomposition under hot/wet conditions. A number of additives have been tried which include antioxidants as well as Lewis bases, the latter in an effort to passivate the catalytic activity of the Lewis Acid sites on the slider which results in the decomposition of the perfluoropolyether (PFPE) lubricants such as Z-Dol, AM and Z-Tetraol. In addition to this passivation action of the phosphazene toward catalytic decomposition of the lubricant, it has recently been reported that the use of X-1P (a cyclic phosphazene) also enhances reflow of the lube, increasing the durability of the head disk interface. In this regard there are still a number of unanswered questions that pertain to the mechanism of the interaction of the X-1P with the lubricant and/or carbon to cause this increase in mobility of the lubricant resulting in the enhanced durability.There are numerous technical issues associated with the use of the various additives with the main one being compatibility between the additive and the PFPEs as well as the carbon surfaces on which they are coated. These issues include bonding, phase separation of the components, and the transfer mechanism for the additive to the slider where the passivation is required.In this paper, we will look at the interaction of the X-1P with the carbon overcoat on the media in an effort to try to better understand the mechanism of such an interaction and its effect on the mobility of the lubricant as well as the amount of bonded lube on the disks. 相似文献
4.
This paper, with the concepts of hydrogen bonding interaction and tribo-emission, develops a new approach of the mechanism
of perfluoropolyether (PFPE) lubricant degradation at the head–disk interface. The role of lubricant X-1P in tribological
performance is also described. The mechanism is as follows: (1) at the interface, there exist hydrogen atoms with partial
positive charge and oxygen atoms with partial negative charge; (2) hydrogen bonding interactions at the sliding interface
result in high friction which depletes the lubricant film at some sites; (3) low energy electrons are emitted from the sites
with solid–solid asperity contact, inducing C–O bond scission through the interaction of low-energy electrons with PFPE lubricant
molecules. Carbon overcoat on Al2O3–TiC surface passivates the interaction between water and PFPE lubricant molecules. Hydrogen bonding interactions are minimized
during the presence of lubricant X-1P. The new approach well explains experimental results in part I of the paper.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Lubricant accumulation on the slider’s surface of a hard disk drive (HDD) has a detrimental effect on its read/write performance. Air flow through the slider-disk clearance moves some of the lubricant from the air-bearing surface (ABS) toward the slider’s lateral walls where it accumulates. In this article, we show by numerical simulations that the lubricant accumulation characteristics are strongly dependent on the slider’s flying height, skew angle and ABS design. The lubricant flow on the slider’s surface is quantified numerically. Air shear stress, air pressure and disjoining pressure are used as driving forces in the simulations. The lubricant thickness profile and volume evolution are calculated for two states of the HDD: operating and at rest. In the first state, lubricant is driven by air shear stress toward the trailing edge of the slider where it accumulates on the deposit end. In the second state, lubricant from the deposit end flows back into the ABS driven by the action of disjoining pressure. Lubricant accumulation on the four lateral walls of the slider is taken into account. The lateral walls are unfolded to study the flow using a two-dimensional lubrication model. The effects of flying height, skew angle and slider design on the accumulation removal of lubricant from the ABS are determined for the two states of the drive. 相似文献
6.
To increase the recording density of hard disk drives (HDD), head and disk surfaces must be very flat. This will make the friction between them large when liquid bridges are formed. This is a result of Laplace pressure in the liquid bridge. Therefore, the study of Laplace pressure in real HDD interface is of an interest for head-disk interface engineers. However, Laplace pressure of perfluoropolyether (PFPE) lubricant on carbon coated thin-film disk surface was not clear until now.We measured Laplace pressure between transparent flat pins and carbon coated thin-film disks with laser texturing. Using laser textured disks, we could control the distance between two surfaces precisely by the bump height. The friction coefficient between the pin and the disk surfaces was determined when the interface was fully wet by liquids. It was 0.16 and 0.1 for water and a PFPE lubricant. The Laplace pressure was then calculated using the friction force and liquid wet area when the interface was partially wet by a liquid. The liquid wet area was measured by the observation of the contact point through the transparent pins.The results showed that the Laplace pressure at the lowest bump height (11 nm) was about 2.8 MPa for the PFPE lubricant. Results agreed well with calculated curves. We consider that PFPE acts as liquid down to 11 nm. 相似文献
7.
PFPE lubricants (Fomblin Z-dol) for hard disk surface lubrication have two hydroxyl groups, one at each end of the molecules, and form stable insoluble monolayers at the water surface. In this study, molecular weight-fractionated PFPE lubricant monolayers were transferred from the water surface to solid substrates such as a hydrophilized silicon wafer, gold-sputtered mica, and a hard disk after adjusting the two-dimensional density of the lubricant molecules. The molecular structures of the PFPE lubricant molecules at the solid surfaces were observed by the cryogenic non-contact AFM under ultra-high vacuum. At the hydrophilic silicon wafer surface we could observe a single lubricant molecule in a random coil sphere shape. However, at the non-polar gold surface we confirmed the formation of reversed micelle structures. At the hard disk surface we detected various sizes of reversed micelles of PFPE lubricant in a flat oval shape. 相似文献
8.
The adsorption characteristics and tribological properties of the perfluoropolyether (PFPE) lubricants Zdol and Z-Tetraol on amorphous nitrogenated CNx carbon are investigated as a function of solvent used to apply the lubricants. The solvents used in these studies include perfluorohexane, CF3CHFCHFCF2CF3 and C4F9OCH3. Deposition studies indicate that the applied thickness of PFPE films is strongly solvent-dependent that can be related to differences in the solubility parameters between the various lubricants and solvents. The results of ab initio computations on the molecular electronic structure of the solvent molecules show that their solvent power is correlated to their polarity and in particular to the acidity of the protons on the CF3CHFCHFCF2CF3 and C4F9OCH3 molecules. Tribological reliability, as measured by contact start-stop testing, slider-disk clearance, lubricant pickup by the slider, lubricant smearing on the disk surface, etc., is independent of solvent and is limited to the physical properties of the adsorbed lubricant film. The kinetics of lubricant mobility are charateristic of confined liquids that are independent of solvent as shown by lubricant flow profiles, bonding kinetics, and contact angle goniometry. 相似文献
9.
The micro-phase separation of the additive, cyclotriphosphazene (X-1P), in perfluoropolyether (PFPE) lubricant films on hard disk media was studied. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) indicated that the small spots appearing on the disk surface consisted predominantly of X-1P. Observation using an atomic force microscope (AFM) revealed the micro-phase separation process to be the sudden, continuous appearance of new spots some time after coating the film. Some spots grew over previous ones, while some spots dissolved. Finally, they stopped growing and the number of spots became saturated. The solubility of X-1P in the lubricant film increased in the order of ZDIAC, ZDOL2000, ZDOL4000 and Z03, and that in bulk lubricant increased in the order of Z03, ZDOL4000, ZDOL2000 and ZDIAC. The order of solubility of X-1P in the film did not correspond to that in the bulk. 相似文献
10.
The retention characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants and a phosphazene
additive, X-1P, were investigated in this study. The retention performance was evaluated by a drag test with a waffle head
sliding against the disk that was designed to mechanically wear out the lubricant layer. An IR beam was aligned on the test
track to directly measure the amount of PFPE lubricants and X-1P left on the media surfaces for determining the retention
characteristics of the lubricants. The drag test results show that under ambient and hot/wet conditions the media coated with
AM3001 PFPE lubricant have higher retention ratio on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene
additive X-1P was observed to strongly anchor on the surface and not easily removed as PFPE lubricants (ZDOL and AM3001).
The retention characteristics of X-1P are independent of lube combination, either AM or ZDOL lubricants. It is demonstrated
that X1-P exhibits a good antiwear property and excellent retention performance.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
M. Yanagisawa 《摩擦学汇刊》2013,56(3):629-635
Mobility of molecularly thin lubricant film is an important issue in understanding boundary lubrication mechanisms and to develop reliable magnetic disk media. Intra-molecular mobility for a perfluorinated poly ether (PFPE), which is used as a disk lubricant, with two hydroxyl groups on a sol-gel SiO2 surface, which is used for a protective overcoat for plated magnetic disks, was studied using nuclear magnetic resonance (NMR). Thin film viscosities for molecular segments were derived from a relaxation time. The viscosity for the hydroxyl segment is 1.8 to 11 times as much as that for a bulk lubricant at room temperature, and the viscosity rate increased with increasing temperature. For example, it increased 15 times at 100°C. The viscosities for the segments in a main chain were not different from that of bulk PFPE. A spin-off calculation for the molecularly thin lubricant film with thin film viscosity, derived from the NMR method, shows that there is no thickness decrease after seven years. 相似文献
12.
The tribological characteristics of vapor lubricated X-1P films on carbon coated disks were investigated as a function of lubricant thicknesses (0.2–2 nm) and compared with traditionally dip-coated X-1P and PFPE films. Glide and flyablity tests were performed and the lubricant redistribution in the ‘wear track’ was investigated using a surface reflectance analyzer (SRA). A critical lubricant thickness was found to exist for X-1P below which lubricant accumulation was observed, while lubricant loss was found to be present if the thickness of the lubricant film was greater than the critical thickness. 相似文献
13.
In order to minimize the stiction force caused by contact of the extremely smooth surfaces of head sliders and disks in hard disk drives, texture is usually applied on the disk surface. For future contact/near-contact recording, the stiction-induced high friction between slider and disk will become a problem. Texture on the slider/disk interface will still be an expected method to reduce friction. Recently, it was suggested to texture the slider surface. A protective coating is usually required on the textured slider surface to reduce wear of the texture. The results showed that texture on the slider surface was effective in reducing the friction between head sliders and disks. On the other hand, the texture and coating on the slider surface increase the spacing between the read/write element and the magnetic layer of the disk. The necessary and effective texture height and coating thickness are still not clear. In the present research, island-type textures with different heights (3–18 mn) were formed on slider surfaces by ion-beam etching. Amorphous carbon nitride (a-CNx) coatings of different thicknesses (0–50 nm) were coated on the textured slider surfaces as a protective overcoat. The friction and wear properties of these sliders were evaluated by constant-speed drag tests against hard disks coated with diamond-like carbon (DLC). The results show that 2 nm texture on a slider surface is sufficient for low (0.3–0.5) and stable friction of the slider against the disk in a drag test, and coatings thicker than 5 nm show similar wear resistances of the texture on slider surfaces. 相似文献
14.
Renguo Lu Hedong Zhang Yasunaga Mitsuya Kenji Fukuzawa Shintaro Itoh 《Tribology Letters》2014,54(3):237-247
To protect the interface against intermittent head–disk contact in hard disk drives, nanometer-thick perfluoropolyether (PFPE) films consisting of both “bonded” and “mobile” molecules are applied on the disk surfaces. Because of their different adsorption states and mobility, the bonded and mobile molecules are supposed to contribute differently to friction properties, which directly impact the stability of ultra-low flying head–disk interfaces. By measuring the friction force at light loads and low to high speeds as a function of bonded and mobile film thicknesses, we studied the contributions of bonded and mobile molecules to the dynamic friction of nanometer-thick PFPE films. We found that the friction coefficient of lubricant films without or with less bonded molecules increased as a power function of sliding speed, whereas that of lubricant films with more bonded molecules increased logarithmically with sliding speed. We suggest that these results can be explained by the following mechanisms: the dynamic friction of lubricant films without and with less bonded molecules is dominated by shear thinning behavior of mobile molecules, while that of lubricant films with more bonded molecules is governed by bonded molecules which lead to boundary lubrication. 相似文献
15.
R. J. Waltman N. Kobayashi T. Shimizu A. Inoue H. Deng Y.-C. Wu 《Tribology Letters》2009,33(2):137-142
We have investigated the resistance of a novel end-functionalized perfluoropolyether (PFPE) lubricant film to slider–disk
interactions caused by low-flying sliders. The PFPE lubricant is based on the CF2CF2CF2O main chain monomer unit. Both slider–disk interactions and the formation of lubricant moguls are significantly reduced compared
to the Fomblin Z backbone, (CF2O)
p
–(CF2CF2O)
q
. These results are interpreted on the basis of ab initio quantum chemical computations that show that the barrier to internal
rotation about the C–O bond in the CF2CF2CF2O monomer unit is significantly larger than in the CF2O monomer unit that is bordered by another CF2O monomer unit, ~8 kcal/mol compared to <2 kcal/mol, respectively. It is proposed that main chains containing CF2O monomer units will be very flexible and hence their physical properties will be more sensitive to adhesive and cohesive
interactions, while main chains containing CF2CF2O and CF2CF2CF2O monomer units will be comparatively stiffer and hence their physical properties will be less sensitive to adhesive and cohesive
interactions. 相似文献
16.
17.
The dewetting of perfluoropolyether (PFPE) films on amorphous nitrogenated carbon, CNx, is investigated. An optical surface analyzer is used to image perfluoropolyether films on CNx-overcoated magnetic recording disks. An autophobic dewetting transition is observed to result when the PFPE film thickness applied to the disk surface exceeds a critical value. This critical dewetting thickness is linearly dependent on the PFPE molecular weight. Addition of the phosphazine, X-1P, to the PFPE film reduces the critical dewetting thickness compared to that of the neat lubricant. Dewetting in these molecularly-thin PFPE lubricant films is shown to occur at thicknesses where the total disjoining pressure is negative. The impact of this autophobic dewetting on the performance of a head--disk interface is inferred from take-off height measurements conducted as a function of PFPE film thickness. A steep reduction in the slider--disk clearance is observed when the PFPE film is present at thicknesses in excess of the critical dewetting thickness. 相似文献
18.
Nagayoshi Kobayashi Hiroshi Tani Tsuyoshi Shimizu Shinji Koganezawa Norio Tagawa 《Tribology Letters》2014,53(1):43-49
In this study, the wear properties of a magnetic head slider on disks lubricated by ultra-thin perfluoropolyether (PFPE) lubricants with different molecular weights were evaluated by the continuous sliding of magnetic head sliders using the slider contact by the dynamic flying height control. Two types of PFPE lubricants (Z-tetraol and D-4OH) with different molecular weights were evaluated. Results show that the slider wear depended on the coverage of the lubricant film; i.e., the lubricant film with sufficient coverage reduced slider wear. The lubricant film with a low molecular weight (low-Mw), including a lubricant material with a Fomblin and Demnum main chain, exhibited better coverage on a diamond-like carbon surface. Sliders with a low-Mw lubricant film showed less wear than those of a high molecular weight (high-Mw), and the depletion of the low-Mw lubricant film was less than that of the high-Mw lubricant film. 相似文献
19.
In this paper, we describe the behavior of ultrathin liquid lubricant films for contact sliders in hard disk drives. In the experiments, the ultrathin liquid lubricant film behavior is investigated using Zdol and cyclotriphosphazene-terminated PFPE lubricant which have different end groups as a function of lubricant film thickness. The disks are examined with a scanning microellipsometer before and after contact slider experiments. It is found that the lubricant film thickness profiles almost do not change, when the lubricant film thickness is less than one monolayer. It can also be observed that lubricant film thickness instability due to dewetting occurs as a result of slider-disk contacts for the tested lubricants and the films undergo spontaneous redistributions, resulting in significantly nonuniform film thickness profiles, when the lubricant film thickness is thicker than one monolayer. In addition, it is found that the observed behavior of ultrathin liquid lubricant films for cyclotriphosphazine-terminated PFPE lubricant contrasts markedly with that for Zdol. The difference between cyclotriphosphazene-terminated PFPE lubricant and Zdol is only the functional end group. Therefore, it may be concluded that their unstable lubricant behavior depends on the chemical structure of functional end groups. 相似文献
20.
Lubricant pick-up by a low-flying slider is investigated for hydroxyl-terminated perfluoropolyethers as a function of the
number of hydroxyl (OH) groups and of film thickness on the surface of finished rigid disks. The total number of hydroxyl
(OH) groups per main chain is 2, 4, and 8 for Zdol, Z-Tetraol, and ZTMD, respectively. The amount of disk lubricant that is
picked up by the low-flying slider decreases with decreasing PFPE film thickness and increasing number of OH functional groups.
The results are discussed in terms of the disjoining pressure characterizing the lubricant film on the disk surface. 相似文献