Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)

1999 ◽  
Vol 593 ◽  
Author(s):  
C.S. Bhatia ◽  
C.-Y. Chen ◽  
W. Fong ◽  
D.B. Bogy
Keyword(s):  
Thermal Desorption ◽  
High Vacuum ◽  
Catalytic Decomposition ◽  
Ultra High Vacuum ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Desorption Temperature ◽  
Carbon Coated ◽  
Two Distinct Temperatures ◽  
Carbon Overcoats

ABSTRACTTribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated A1203-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated A1203/TiC sliders, forming CF3 (69) and C2F5(119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation

Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)

1999 ◽  
Vol 594 ◽  
Author(s):  
C. S. Bhatia ◽  
C.-Y. Chen ◽  
W. Fong ◽  
D. B. Bogy
Keyword(s):  
Thermal Desorption ◽  
Wear Track ◽  
High Vacuum ◽  
Catalytic Decomposition ◽  
Ultra High Vacuum ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Desorption Temperature ◽  
Two Distinct Temperatures ◽  
Carbon Overcoats

AbstractTribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carboncoated Al2O3-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated Al2O3/TiC sliders, forming CF3 (69) and C2F5 (119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation.

The Decomposition Mechanisms and Thermal Stability of ZDOL Lubricant on Hydrogenated Carbon Overcoats

1999 ◽  
Vol 122 (2) ◽  
pp. 458-464 ◽  
Author(s):  
Chao-Yuan Chen ◽  
Jianjun Wei ◽  
Walton Fong ◽  
David B. Bogy ◽  
C. Singh Bhatia
Keyword(s):  
Frictional Heating ◽  
High Vacuum ◽  
Catalytic Decomposition ◽  
Ultra High Vacuum ◽  
Carbon Overcoat ◽  
Disk Interface ◽  
Decomposition Mechanisms ◽  
Carbon Coated ◽  
Chemical Studies ◽  
Carbon Overcoats

Tribo-chemical studies of the head/disk interface (HDI) were conducted using hydrogenated CHx carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated Al2O3-TiC sliders and thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. The friction and catalytic decomposition mechanisms as well as the thermal behavior of ZDOL are described, and data demonstrating the chemical reactions of the lubricant and carbon overcoat are also presented. During the sliding at the carbon-coated slider/ZDOL lubricated CHx disk interface, frictional heating is the primary decomposition mechanism of ZDOL. [S0742-4787(00)01902-0]

Effects of Backbone and Endgroup on the Decomposition Mechanisms of PFPE Lubricants and Their Tribological Performance at the Head-Disk Interface

2000 ◽  
Vol 123 (2) ◽  
pp. 364-367 ◽  
Author(s):  
Chao-Yuan Chen ◽  
David B. Bogy ◽  
C. Singh Bhatia
Keyword(s):  
Removal Rate ◽  
Catalytic Decomposition ◽  
Degradation Process ◽  
Catalytic Degradation ◽  
Carbon Surface ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Pfpe Lubricant ◽  
Carbon Coated ◽  
Chemical Studies

Tribo-chemical studies of the lubricant endgroup effect on the tribology of the head-disk interface were conducted using carbon disks coated with PFPE lubricant. The studies involved drag tests with uncoated and carbon-coated Al2O3-TiC sliders in an ultrahigh-vacuum (UHV) tribochamber. The UHV drag tests show that a good lubricant should have one active OH endgroup and one nonactive endgroup. The active one insures the lubricant is adsorbed very well onto the disk carbon surface, resulting in a lower removal rate of the lubricants during the contact sliding. The nonactive one prevents the catalytic decomposition of the lubricant in the presence of the Al2O3 surface of the uncoated slider. The studies also demonstrate that the catalytic degradation process of ZDOL in the presence of Lewis acid occurs most readily at the acetal units -O-CF2-O within the internal backbones (CF2O and CF2CF2O) instead of the endgroup functionals. Therefore, demnum, without any acetal units, experiences less catalytic degradation with the uncoated Al2O3/TiC sliders as compared to ZDOL.

Reconstructions upon thermal desorption in ultra high vacuum of InSe covered Si(111) surfaces

1998 ◽  
Vol 5 (4-6) ◽  
pp. 919-926 ◽  
Author(s):  
F. Proix ◽  
V. Panella ◽  
S. El Monkad ◽  
A. Glebov ◽  
J.P. Lacharme ◽  
...  
Keyword(s):  
Thermal Desorption ◽  
High Vacuum ◽  
Ultra High Vacuum

Thermal Desorption Spectroscopy Study on the Hydrogen Behavior in a Plasma-Charged Aluminum

2016 ◽  
Vol 879 ◽  
pp. 1220-1225
Author(s):  
Toshiaki Manaka ◽  
Masaya Aoki ◽  
Goroh Itoh
Keyword(s):  
Thermal Desorption ◽  
Pure Aluminum ◽  
High Vacuum ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Gas ◽  
Ultra High Vacuum ◽  
Trap States ◽  
Intergranular Cracking ◽  
High Hydrogen ◽  
Gas Plasma

Hydrogen in aluminum has been known to be the cause of blister and pore. Some aluminum alloy is susceptible to stress corrosion cracking, which is based on intergranular cracking arisen from hydrogen embrittlement. The behavior of hydrogen in aluminum has not been fully understood yet. Hydrogen gas plasma enables to introduce high hydrogen concentrations into specimen without Al (OH)3 layer on the surface of specimen. In this paper, we have investigated the behavior of hydrogen in a plasma charged aluminum by means of thermal desorption spectroscopy, a method to evaluate the amount and trap states of hydrogen. Cold-rolled pure aluminum were annealed, electro-polished and charged with hydrogen gas plasma. Immediately after hydrogen gas plasma charging, TDS tests were performed under ultra-high vacuum. The hydrogen desorption spectrums obtained by TDS tests had three peaks corresponding to the co-diffusion of hydrogen-vacancy pair, dislocation and pore. Compared to a sample without charging, in a plasma charged sample, the amount of hydrogen trapped in vacancies especially increased.

scholarly journals Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

2018 ◽  
Vol 612 ◽  
pp. A88 ◽  
Author(s):  
N. F. W. Ligterink ◽  
C. Walsh ◽  
R. G. Bhuin ◽  
S. Vissapragada ◽  
J. Terwisscha van Scheltinga ◽  
...  
Keyword(s):  
Gas Phase ◽  
Thermal Desorption ◽  
High Vacuum ◽  
Protoplanetary Disk ◽  
Ultra High Vacuum ◽  
Indirect Pathway ◽  
Cold Environments ◽  
Chemical Modelling ◽  
Phase Chemistry ◽  
The Impact

Context. Methanol is formed via surface reactions on icy dust grains. Methanol is also detected in the gas-phase at temperatures below its thermal desorption temperature and at levels higher than can be explained by pure gas-phase chemistry. The process that controls the transition from solid state to gas-phase methanol in cold environments is not understood. Aims. The goal of this work is to investigate whether thermal CO desorption provides an indirect pathway for methanol to co-desorb at low temperatures. Methods. Mixed CH3OH:CO/CH4 ices were heated under ultra-high vacuum conditions and ice contents are traced using RAIRS (reflection absorption IR spectroscopy), while desorbing species were detected mass spectrometrically. An updated gas-grain chemical network was used to test the impact of the results of these experiments. The physical model used is applicable for TW Hya, a protoplanetary disk in which cold gas-phase methanol has recently been detected. Results. Methanol release together with thermal CO desorption is found to be an ineffective process in the experiments, resulting in an upper limit of ≤ 7.3 × 10−7 CH3OH molecules per CO molecule over all ice mixtures considered. Chemical modelling based on the upper limits shows that co-desorption rates as low as 10−6 CH3OH molecules per CO molecule are high enough to release substantial amounts of methanol to the gas-phase at and around the location of the CO thermal desorption front in a protoplanetary disk. The impact of thermal co-desorption of CH3OH with CO as a grain-gas bridge mechanism is compared with that of UV induced photodesorption and chemisorption.

Tribochemical Study of Hydrogenated Carbon Coatings With Different Hydrogen Content Levels in Ultra High Vacuum

1997 ◽  
Vol 119 (3) ◽  
pp. 437-442 ◽  
Author(s):  
Xiaohan Yun ◽  
David B. Bogy ◽  
C. Singh Bhatia
Keyword(s):  
Hydrogen Content ◽  
High Vacuum ◽  
Carbon Films ◽  
Ultra High Vacuum ◽  
Carbon Overcoat ◽  
Carbon Coatings ◽  
Disk Interface ◽  
Atomic Structures ◽  
Chemical Factors ◽  
Friction Measurements

Hydrogenated carbon films (CHx) with different hydrogen content percentages have been examined. Drag tests on CHx coated disks, using 50 percent Al2O3/TiC sliders, with and without carbon coating on the slider air bearing surfaces (ABS), were conducted in an ultra high vacuum chamber equipped with a mass spectrometer. Mass fragments of lubricant released from the head disk interfaces were recorded in real time along with friction measurements. The results show that a higher hydrogen content in the carbon overcoat can improve wear durability by reducing the friction coefficient and affecting the chemical reactions between the sliders and the lubricant. A carbon overcoat on the slider ABS can protect Z-dol lubricant from catalytic reaction with the Al2O3 in the slider material. The wear durability at the head disk interface is controlled by combined mechanical and chemical factors, which are defined by the atomic structures of the contacting surfaces.

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