Liquid-Mediated Adhesion at the Thin Film Magnetic Disk/Slider Interface

1990 ◽  
Vol 112 (2) ◽  
pp. 217-223 ◽  
Author(s):  
B. Bhushan ◽  
M. T. Dugger
Keyword(s):  
Thin Film ◽  
Normal Load ◽  
Water Film ◽  
Adsorbed Water ◽  
Disk Surface ◽  
Adhesive Force ◽  
Contact Duration ◽  
Asperity Contacts ◽  
High Concentrations ◽  
Magnetic Recording Heads

The adhesive force between magnetic-recording heads and thin film disks in a direction normal to the interface has been measured for a variety of loads, contact times, separation rates, and relative humidities with and without a layer of perfluoropolyether lubricant at the interface. At low humidities, the adhesive force due to the lubricant film alone is small for the lubricant thickness and disk surface roughness used. We find that the major component of the adhesive force between the slider and the disk in humid environments may be attributed to an adsorbed water film which can displace the lubricant (if the disk is lubricated) at sufficiently high loads, during tangential sliding, or after extended exposure to high concentrations of water vapor and create menisci around individual asperity contacts. The adhesive force was found to increase with contact duration on the unlubricated disk, but was essentially independent of contact duration on the lubricated disk. For both lubricated and unlubricated disks, the adhesive force increased with increasing relative humidity and loading rate, but was independent of applied normal load.

scholarly journals Negative friction coefficient in microscale graphite/mica layered heterojunctions

2020 ◽  
Vol 6 (16) ◽  
pp. eaaz6787 ◽  
Author(s):  
Bingtong Liu ◽  
Jin Wang ◽  
Shuji Zhao ◽  
Cangyu Qu ◽  
Yuan Liu ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Water Film ◽  
Underlying Mechanism ◽  
Positive Dependence ◽  
Asperity Contacts ◽  
Muscovite Mica ◽  
Different Temperatures ◽  
Negative Friction ◽  
Dynamics Simulations

The friction of a solid contact typically shows a positive dependence on normal load according to classic friction laws. A few exceptions were recently observed for nanoscale single-asperity contacts. Here, we report the experimental observation of negative friction coefficient in microscale monocrystalline heterojunctions at different temperatures. The results for the interface between graphite and muscovite mica heterojunction demonstrate a robust negative friction coefficient both in loading and unloading processes. Molecular dynamics simulations reveal that the underlying mechanism is a synergetic and nontrivial redistribution of water molecules at the interface, leading to larger density and more ordered structure of the confined subnanometer-thick water film. Our results are expected to be applicable to other hydrophilic van der Waals heterojunctions.

scholarly journals Relationship between Landform Development and Lake Water Recharge in the Badain Jaran Desert, China

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1999
Author(s):  
Da-Peng Yue ◽  
Jing-Bo Zhao ◽  
Yan-Dong Ma ◽  
Xiao-Gang Huang ◽  
Tian-Jie Shao ◽  
...  
Keyword(s):  
Water Film ◽  
Adsorbed Water ◽  
Water Source ◽  
Infiltration Rate ◽  
High Water ◽  
Badain Jaran Desert ◽  
Multi Stage ◽  
Water Recharge ◽  
Landform Development ◽  
Precipitation Events

Four distinctive but poorly documented landforms in the Badain Jaran megadunes were studied: arcuate steps, multi-stage fans, depressions formed by runoff erosion, and groundwater overflow zones around lakes. The development of these four landform types indicates the following: (1) The hydrological balance in the sand layers of the megadune areas is positive; (2) After evaporation and transpiration, precipitation is able to infiltrate the deep sand layers; (3) Precipitation is a source for the groundwater and for many of the lakes of the area. The groundwater recharge mechanism is characterized by intense precipitation events that provide a water source, high infiltration rate, shallow evaporation depth, and low water retention. These factors together enable the precipitation to be transformed into groundwater. The energy of gravity water and the high water film pressure of adsorbed water together provide the forces necessary for effective water recharge.

scholarly journals Moisture Induced Degradation of Porous Low-k Materials

2006 ◽  
Vol 914 ◽  
Author(s):  
Mikhail Baklanov ◽  
David O'Dwyer ◽  
Adam M Urbanowicz ◽  
Quoc Toan Le ◽  
Steven Demuynck ◽  
...  
Keyword(s):  
Water Film ◽  
Internal Surface ◽  
Hydrophobic Surface ◽  
Adsorbed Water ◽  
Bulk Water ◽  
Oh Groups ◽  
Film Bulk ◽  
Low K

AbstractInteraction of moisture with porous low-k films is evaluated by using in situ ellipsometry setup. The adsorbed water amount is calculated from change of refractive index measured during the adsorption. Pristine low-k films reversibly adsorb 2 - 5% of water that reflects presence of constitutive hydrophilic centrums. Plasma and thermal treatments increase the number of hydrophilic centrums. Once the amount of these centrums has reached a certain critical value sufficient to form a continuous water film, bulk water condensation is observed. Change of properties during the water adsorption in the damaged films is not fully reversible. Each additional adsorption cycle increases the dielectric function of the film because of decreasing porosity, increasing skeleton density and shrinkage. The pressure corresponding to the bulk condensation allows us to calculate internal contact angle (internal surface energy) of low-k materials. The water molecules adsorbed on separate OH groups play the role of a catalyst that hydrolyses the siloxane bridges initially present on hydrophobic surface.

Tribological Characteristics of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 Bulk Metallic Glass

1998 ◽  
Vol 554 ◽  
Author(s):  
Xi-Yong Fu ◽  
D. A. Rigney
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Normal Load ◽  
Disk Surface ◽  
Test System ◽  
Kelvin Probe ◽  
Material Transfer ◽  
Surface Appearance ◽  
Wear Rates ◽  
Lower Load

AbstractThe sliding characteristics of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass have been examined in vacuum and in air using a pin/disk geometry without lubrication. The counterface material was either the same metallic glass (self-mated) or 52100 steel. Normal load was 0.1–1 kgf. The test system was equipped for continuous measurement of friction force. In addition, a Kelvin probe allowed continuous monitoring of changes in the structure and chemistry of the disk surface. Post-test characterization included optical and electron microscopy, X-ray diffraction and EDS of worn surfaces and debris. Friction coefficients in both vacuum and air were typical of those expected for ductile materials, with values ranging from 0.4 to 0.9 (higher values with lower load). Wear rates and average debris size increased with load. Wear rates were larger in air than in vacuum. Wear surface appearance and chemical composition were influenced by plastic deformation, material transfer and environmental interactions. After tests in air, the wear tracks and debris had a granular appearance and oxygen concentrations were high. Changes in the Kelvin probe signal correlated well with visual observations and with concentrations of oxygen detected by EDS.

S1603-1-2 Effect of Ultraviolet Irradiation on Adhesive Force and Elongation of Monolayer Lubricant Films Coated on Magnetic Disk Surface

2009 ◽  
Vol 2009.5 (0) ◽  
pp. 203-204
Author(s):  
Yasuji OHSHIMA ◽  
Takashi SUMI ◽  
Hiroki Hoshida ◽  
Hedong ZHANG ◽  
Kenji FUKUZAWA ◽  
...  
Keyword(s):  
Ultraviolet Irradiation ◽  
Disk Surface ◽  
Adhesive Force ◽  
Magnetic Disk ◽  
Lubricant Films

Delamination of Ultra-Thin Diamond-Like Carbon Coatings on Magnetic Recording Heads Under Normal Loading

2013 ◽  
Author(s):  
Michael Price ◽  
Andrey Ovcharenko ◽  
Raj Thangaraj ◽  
Bart Raeymaekers
Keyword(s):  
Amorphous Carbon ◽  
Normal Load ◽  
Substrate Material ◽  
Adhesion Layer ◽  
Carbon Overcoat ◽  
Normal Loading ◽  
Carbon Coatings ◽  
Disk Interface ◽  
Recording Heads ◽  
Magnetic Recording Heads

Delamination between an ultra-thin amorphous carbon overcoat, a silicon adhesion layer, and permalloy substrate material of a hard drive recording head is studied during normal loading/unloading of the head disk interface. The effect of normal load and thickness of the silicon adhesion layer on delamination of the Si-permalloy and amorphous carbon-Si interfaces is quantified using a molecular dynamics model. No permanent delamination is found for contact pressures up to 100 MPa, except for the case where a silicon adhesion layer is absent.

Non-Equilibrium Thin-Film Flow in Rotating Disk and Cone

2008 ◽  
Author(s):  
Wallace Woon-Fong Leung
Keyword(s):  
Thin Film ◽  
Mammalian Cells ◽  
Flow Behavior ◽  
Experimental Tests ◽  
Rotating Disk ◽  
Disk Surface ◽  
Thin Film Flow ◽  
Liquid Stream ◽  
Highly Nonlinear ◽  
Rotating Cone

The acceleration of a continuous feed liquid stream in a film “down” the rotating cone and disk is of great interest in centrifuges [1, 2], thin-film reactors and process intensifiers. The mechanism of feed acceleration is determined by an interaction of several different effects. Circumferential viscous forces act to increase the angular momentum. The centrifugal field thus produced establishes a body-force component along the cone/disk surface, thereby driving the flow “down” toward larger radius. The longitudinal flow is however impeded by longitudinal resistance forces. These different effects compete with each other as the flow proceeds, never quite coming to an unchanging equilibrium state. An approximate integral method which was used to explore the “near-equilibrium” flow behavior in earlier work has been extended to investigate the case with large departure from equilibrium. The latter exhibits complicated highly nonlinear effect. Despite this, useful information can be obtained from the theoretical analysis. Experimental results on feed acceleration of liquid streams at various feed rates and rotation speeds in a rotating cone have been used to validate the study. The theoretical study with complementary experimental tests provides insights into how continuous liquid stream in form of a thin film is being accelerated using rotating cones and disks, and the associated shear rates involved. The latter has important bearing in processing shear-sensitive mammalian cells in biopharmaceutical separation with centrifuges and mass transfer in thin-film reactors.

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