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Magnetic recording disk carbon overcoats are lubricated with nanometer-thick films of perfluoropolyether lubricant. It is well-known that lubricant thickness redistribution takes place due to air shear stress oscillation at air bearing resonant frequencies and also due to shear stress oscillation induced by disk topography waves on test tracks. We extended this work to demonstrate correlation between surface topography and lubricant redistribution on whole disk surfaces. Lubricant moguls are shown to form over regions of the disk surface which have topography waves that are half the slider length, and the lubricant thickness peak is out-of-phase down track from the topography peak height. There is a critical relative humidity above 20% beyond which moguls are readily formed by the slider flying at 10 nm without thermal fly-height control. The significance of the lubricant redistribution for drive magnetic performance has long been the subject of debate. The slider flying height modulation measured by magnetic head media spacing was in good agreement with the dynamic air bearing simulation based on the measured disk surface topography. Measured head media spacing image data on the same disk surface before and after lubricant redistribution had the same length scale as the correlation between topography and lubricant thickness variation. These results demonstrate that lubricant thickness redistribution on the order of atomic diameters can degrade magnetic performance, and that the surface topography waves alone can degrade areal density by as much as 2%.

Some words and phrases used by health care providers may be perceived as insensitive by patients, which could negatively affect patient outcomes and satisfaction. However, a distinct concept that can be used to describe and synthesize these words and phrases does not exist. The purpose of this article is to propose the concept of language sensitivity , defined as the use of respectful, supportive, and caring words with consideration for a patient's situation and diagnosis. Examples of how language sensitivity may be lacking in nurse–patient interactions are described, and solutions are provided using the RESPECT ( R apport, E nvironment/Equipment, S afety, P rivacy, E ncouragement, C aring/Compassion, and T act) model. RESPECT can be used as a framework to inform and remind nurses about the importance of sensitivity when communicating with patients. Various approaches can be used by nurse educators to promote language sensitivity in health care. Case studies and a lesson plan are included. J Contin Educ Nurs. 2017;48(11):517–524.

Diblock copolymers, comprised of two distinct homopolymers covalently bonded together at one end, undergo a transition on cooling from a state in which the segments of the blocks are homogeneously mixed to one in which they are segregated locally. This microphase separation is driven by the enthalpy of unfavourable interactions between segments. Here, the microphase separation of a diblock copolymer melt on heating is reported. Similar in nature to the lower critical solution temperature seen in polymer mixtures, this lower critical ordering transition is driven by entropic factors-specifically, by a negative volume change on mixing of the blocks. The transition to the microphase-separated state alters the rheological and mechanical properties of the copolymer markedly, the material gaining a non-zero equilibrium modulus above the ordering transition. This suggests potential technological applications of these copolymer systems as \"smart\" materials.

As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10 000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10–135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface.

Perfluoropolyethers (PFPEs) are widely used as lubricants on magnetic recording media. The mobility of the PFPE on the protective carbon overcoat of the media is widely accepted to be intimately coupled to the resulting tribological performance. The flow properties of molecularly thin films of nonpolar PFPEZ and polar PFPE Zdol fractions on solid surfaces were investigated by measuring the spreading profiles. The spreading of Zdol exhibits terraced profiles with the formation of a molecular foot, a shoulder and a vertical step. To describe these features of Zdol spreading, we measured the Zdol thickness dependence of the surface energy, which is then used to calculate the thickness dependence of the disjoining pressure. The polar component of the Zdol surface energy exhibits oscillations as a function of PFPE thickness. The resulting oscillations in the disjoining pressure can be used to qualitatively describe the origins of terraced spreading. The characteristic Zdol spreading profile and surface energy oscillations of Zdol are attributed to molecular layering induced by polar interactions between the Zdol end-groups and the surface. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26-28, 1998

Water adsorption isotherms were measured with two different types of perfluoropolyether lubricants, Zdol 4000 and Ztetraol 2000, on thin film magnetic recording disks. The adsorption isotherm provides the average water film thickness (areal density) as a function of relative humidity. The water film thickness was measured while varying the relative humidity (RH) in the range from dry air to 85%. The water film thickness for both types of lubricants increased with RH, and was independent of temperature between 20° and 50°C. The water film thickness at saturation RH was typically 0.44 nm (16/nm 2 ) for Zdol and 0.25 nm (9/nm 2 ) for Ztetraol. Friction measurements were performed on the same set of disks up to 70% RH. The maximum friction increased with RH, more for Zdol than for Ztetraol, and the friction with Ztetraol was much less than with Zdol. Brief exposure to condensing RH dramatically altered the friction and acoustic emission even at relatively high slider flying height. The altered frictional properties were associated with liquid nanodroplets formed on the disks during the brief condensation. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28-May 1, 2003

As magnetic recording slider size and flying height evolve to smaller dimensions, previously insignificant levels of contamination begin to play a role in slider media tribology. This article describes a new type of contamination. Liquid nanodroplets on disks originate with electrostatic deposition of hygroscopic ultrafine particles, also referred to as cloud condensation nuclei (CCN). On lubricated disks, the CCN equilibrate with atmospheric moisture and become partially overcoated with disk lubricant, which acts as a fluorocarbon surfactant. Dark-field microscopy measured deposition rates of 0.001 to 0.006 #/mm 2 /sec on initially clean disks exposed to ambient air in nonconductive cassettes. Tapping mode atomic force microscopy determined that the sites were deformable nanodroplets 70 to 300 nm in diameter and up to 150 nm high. From AFM profiles, the contact angle of the spherical capped nanodroplets with the disk was between 40 and 90 degrees. Nanodroplet contamination is characterized, and its effect on friction, acoustic emission, and slider smears is demonstrated. A surface chemical thermodynamic model is developed and employed to estimate that the average initial dry nucleus diameter is 110 nm. The estimated size range and composition of the initial nuclei are consistent with those well known in the atmospheric sciences. Nanodroplets were absent from disks that were stored in a CCN-free environment, and the deposition rate was reduced 10× by air ionizer or conductive cassette.

The magnetic recording industry predominantly uses Zdol to lubricate the carbon overcoat of magnetic recording disks. Zdol comprises a perfluoropolyether chain terminated with hydroxyl end groups that are capable of reversibly bonding to the carbon overcoat. Contact start/stop (CSS) tests were done to investigate the effects of Zdol lubricant bonding, thickness, and relative humidity on durability. The durability improved with increasing thickness of fully bonded or mobile Zdol. The durability decreased with increasing initial bonded fraction and with decreasing relative humidity. The bonded fraction increased with time during the tests at elevated temperature and low relative humidity. Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1-4, 2000

This article critically reviews the fundamental scientific tools, as well as constructs cohesive schemes for potential applications, relevant to the molecularly-thin liquid film technology. Our focus is to understand the nanoscale dynamic behavior of thin lubricant films, relevant to the emerging field of nanotechnology, especially for achieving durability and reliability in the nanoscale devices. Our goal is to present a unified and hybrid description of perfluoropolyether (PFPE) experiment, mesoscopic interpretation, microscopic simulation tools, and molecular design tools available up to now. The experimentation and theory for the physicochemical properties of ultra-thin PFPE films are used to examine liquid film in the sub-monolayer to multilayer regime. Methods for extracting spreading properties from the scanning microellipsometry (SME) for various PFPE/solid surface pairs and the surface rheological characterization of PFPEs are examined. The interrelationships among SME spreading profiles, rheology, surface energy, and tribology, are given. Mesoscopic theories, including thermodynamics of evaporation and flow, stability analysis, microscale mass transfer, and capillary waves are introduced to describe thin PFPE film dynamics. Estimation of thin film viscosity enhancement from vapor pressure suppression by dispersion force is reviewed. The method for experimental derivation of lubricant spreading profiles from contact angles is summarized. The implications of capillary waves, or thermal fluctuations, at the surface of polymeric lubricant films are also discussed. The lattice-based, simple reactive sphere Monte Carlo (MC) technique for examining the fundamentals of PFPE dynamics is illustrated. An off-lattice based bead–spring MC model is also introduced to capture a detailed internal structure of the PFPE molecules, and the molecular dynamics method is implemented for a full-scale nanostructural analysis of PFPE ultra-thin films. By systematically tuning the endgroup strengths of PFPE, we examined the physicochemical properties for thin liquid films of the various PFPE/solid surface pairings. These tools accurately describe the static and dynamic behavior of ultra-thin liquid films consistent with experimental findings and thus are suitable for examining the fundamental mechanisms of lubrication in nanoscale devices. Application of the next generation head–disk interface design in information storage device is briefly considered.