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Saba, Costandy S.; Forster, Nelson H.

doi:10.1023/a:1014081523491

Cited by 54 publications

(65 citation statements)

References 16 publications

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“…In this context, it is interesting to note that PAO bond cleavage in one of the most commonly used additives, tricresyl phosphate [12][13][14], would deposit a substituted phenolate species, which, since it has no hydrogen, cannot desorb as an aldehyde and would lead to further carbon deposition on the surface [23]. In addition, CAO bond cleavage would result in the corresponding substituted phenyl species depositing surface carbon in a similar fashion as butyl groups do from TBP.…”

Section: Discussionmentioning

confidence: 99%

“…It is generally agreed that AW films containing a relatively hard polyphosphate glass are formed by reaction with the phosphorus in the additive. Chlorine- [8,9], sulfur- [10,11] and phosphorus-containing [12][13][14][15][16] molecules are all used as EP additives. It has been demonstrated previously that chlorinated hydrocarbons function by reactively forming a FeCl 2 film [17][18][19] at the high temperatures (>1000 K [20]) encountered at the solid-solid interface during EP applications.…”

Section: Introductionmentioning

confidence: 99%

“…Sulfur-containing additives decompose to form FeS under EP conditions, and FeS 2 at the lower temperatures found in less severe AW applications [21]. Phosphorus-containing EP additives often consist of phosphite or phosphate esters with formulae P(OR) 3 or O@P(OR) 3 respectively, where R is a hydrocarbon species or hydrogen [12][13][14][15][16]. One role of the hydrocarbon functionalities is to solubilize the molecule in the base oil.…”

Section: Introductionmentioning

confidence: 99%

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Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

et al. 2005

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The chemistry of tributyl phosphate on Fe 3 O 4 was studied in ultrahigh vacuum using temperature-programmed desorption (TPD) and Auger spectroscopy. A portion of the tributyl phosphate desorbs intact with an activation energy of $120 kJ/mol. The remainder decomposes either by PAO bond scission to deposit surface butoxy species or appears to dehydrogenate desorbing C 2 or C 3 compounds and depositing hydrogen and carbon on the surface. The resulting hydrogen reacts either with the oxide to desorb water or with butoxy species yielding 1-butanol. The remaining butoxy species are stable up to $600 K where they decompose to desorb butanal via hydride elimination where again the hydrogen reacts with butoxy species to form 1-butanol or with the oxide to form water. The carbon deposited onto the surface further reduces the oxide to desorb as CO above $750 K, although a small amount of carbon is detected on the surface using Auger spectroscopy. Substantially larger amounts of carbon are deposited onto the surface when Fe 3 O 4 is exposed to tributyl phosphate at 300 K, where an Auger depth profile reveals that the carbon is located at the surface while the PO x species formed by tributyl phosphate decomposition diffuse rapidly into the oxide layer, leading to a film structure in which graphitic carbon is deposited onto a phosphorus-containing oxide layer.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

et al. 2005

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“…The concept of lubricating high temperature bearing surfaces with organic vapors has existed for at least forty years, and as such, the surface reaction chemistry and macrotribological performance of a number of candidate materials has been extensively studied. [24][25][26][27][28][29][30][31][32] Vapor phase lubrication occurs via three distinct forms: (a) organic films that are intentionally reacted with a surface to form a solid lubricating film, (b) vapors which condense to form a lubricating liquid film on the surface of interest, and (c) light weight hydrocarbon vapors deposited onto hot catalytic nickel surfaces.…”

Section: Qcm Studies Of "Real World" and Model Lubricantsmentioning

confidence: 99%

“…Studies of TCP uptake at elevated temperature on iron oxide containing materials have revealed the reaction films to be highly lubricious [27] polymers that can withstand temperatures in excess of 600 C. While much progress has been achieved in recent years concerning the chemical nature of the reaction films, the exact mechanisms underlying of the lubricity of TCP remain to be established. [32] Modern nanotribological techniques can be brought to bear on these issues by examining in detail the properties of a known (macroscopic-scale) vapor phase lubricant. The knowledge gained is extremely likely to be applicable to NEMS/MEMS operations as well.…”

Section: Qcm Studies Of "Real World" and Model Lubricantsmentioning

confidence: 99%

Scanning Tunneling Microscope-Quartz Crystal Microbalance Studies of "Real World" and Model Lubricants

Krim

Abdelmaksoud

Borovsky

et al. 2004

ACS Symposium Series

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Abstract:Applications of the Quartz Crystal Microbalance (QCM) for studies of tribology at atomistic time and length scales are described herein. Employing QCM as the sole technique, we report measurements on vapor phase lubricants for "real world" applications, and rare-gas systems that are of more fundamental interest. We also report on QCM measurements that have been recorded in conjunction with a Scanning Tunneling Microscope (STM). The QCM-STM apparatus allows unique and detailed investigations of a simple nanomechanical system formed by a contacting tip and surface. Both STM images of the contact and the response of the QCM are monitored throughout the course of the measurements, which are performed at realistic sliding speeds of over 1 m/s.

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Pressure‐assisted decomposition of tricresyl phosphate on amorphous FeO using hybrid quantum‐classical simulations

et al. 2022

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The moving components of combustion engines are operated under harsh conditions of high pressures and temperatures. Extreme‐pressure anti‐wear additives, such as tricresyl phosphate (TCP), are mixed with base oil to prevent wear through the formation of a lubricant film on the substrate. We studied the effect of liquid pressure on the decomposition pathway of TCP in base oil molecules (2,5‐dimethylhexane) using hybrid quantum‐classical simulations with density functional theory for electrons. At a temperature of 300 K, we found that: (i) bond‐breaking barrier energies of both the OC and PO bonds of TCP decrease monotonically as the liquid pressure increases; (ii) the bond‐breaking barrier energy of PO is lower than that of OC at pressures of 0 and 2.0 GPa, but is higher at a pressure of 5.0 GPa; and (iii) the applied pressure significantly lowers the bond‐breaking barrier energies of both OC and PO when the PO bond of TCP is directed upward from the substrate. These findings are explained by the inhomogeneous distribution of base oil molecules around TCP and the steric repulsion of the PO bond of TCP. These results indicate that the internal structures of the lubricant films are pressure‐dependent.

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Untitled

Cited by 54 publications

References 16 publications

Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

Reaction of tributyl phosphate with oxidized iron: surface chemistry and tribological significance

Scanning Tunneling Microscope-Quartz Crystal Microbalance Studies of "Real World" and Model Lubricants

Pressure‐assisted decomposition of tricresyl phosphate on amorphous FeO using hybrid quantum‐classical simulations

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