First principles study of organophosphorus additives in boundary lubrication conditions: Effects of hydrocarbon chain length

Loehlé, Sophie; Righi, Maria Clelia

doi:10.1002/ls.1382

Cited by 20 publications

(28 citation statements)

References 59 publications

(109 reference statements)

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“…Ab initio MD simulations of trimethyl phosphite and tributyl phosphite confined and sheared between Fe(110) slabs showed that dissociation of both molecules proceeded along the same pathway at high load, but that more phosphorous was likely to be released with the smaller molecule because of the greater number of adsorbed molecules per unit area. 22,30 It was further shown that the energy of dissociation adsorption decreased as the number of detached methoxy groups increased. 31 Lastly, reactive MD simulations compared TCP with four alkyl phosphates (primary linear, primary branched, secondary, and tertiary).…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Tricresyl Phosphate on Ferrous Surfaces

et al. 2021

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Tricresyl phosphate (TCP) forms protective films on moving mechanical components through thermally driven decomposition and interactions with the ferrous surfaces of the components. These reactions are hidden from view in moving interfaces, but are known to be sensitive to both the surface material and the isomeric form of the TCP. Here, temperature-programmed reaction spectroscopy (TPRS) and gas chromatography-mass spectroscopy (GC-MS) are complemented by reactive molecular dynamics (MD) simulations to investigate the thermal decomposition of meta and para isomers of TCP reacting with ferrous materials. Key observations are that the primary decomposition product of TCP is cresol, more cresol is generated on Fe 2 O 3 than on Fe 3 O 4 , and that para-TCP isomers are more reactive than meta-TCP isomers. These trends are explained using the simulations to identify multiple reaction pathways leading to cresol formation. The likelihood of each pathway is quantified and correlated to surface material and TCP isomer trends in terms of energy barriers for the rate-limiting steps in the decomposition reactions.

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Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Tricresyl Phosphate on Ferrous Surfaces

et al. 2021

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“…Figure e,d shows the P and S elements appearing on the surface of wear are coming from P 888P DOSS. Besides the BEs of these elements are completely different from those of neat ILs indicating the formation of phosphorus or sulfur products decomposed from P 888P DOSS under rigorous condition, and then reacted with new born Mg surface to form a novel antiwear agent …”

Section: Resultsmentioning

confidence: 99%

Task‐Specific Oil‐Miscible Ionic Liquids Lubricate Steel/Light Metal Alloy: A Tribochemistry Study

Wang

Huang

et al. 2018

Adv Materials Inter

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In order to increase the solubility of ionic liquids in base oils and to improve the lubricating performance of light alloys, two new ionic liquids comprised of sulfonate base anion and phosphonium based cation are designed and synthesized. The difference between these two ionic liquids is the cation: One has only one organophosphate group (P88816DOSS) and the other has two organophosphate group (P888PDOSS). The copper strip corrosion test is used to evaluate the anticorrosion properties of new developed ionic liquids. Tribological properties of the ionic liquids are investigated by an optimal SRV‐IV oscillating tribometer. The results indicate that the new designed ionic liquids show very good solubility in traditional mineral‐based oils. P88816DOSS and P888PDOSS show excellent friction reduction, antiwear performance accompanied with effective anticorrosion properties for the mineral base oil. Surface analysis results show that the superior properties of P88816DOSS and P888PDOSS are attributed to surface chemical reactions between ionic liquids and light metal.

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“…29 The calculations showed that the mechanisms (a), (b), and (c) described above all have at least one exothermic reaction pathway. 29 In addition to static calculations, ab initio molecular dynamics (AIMD) simulations have also been used to investigate the dissociation of tri(methyl)phosphate, 30 tri(methyl)phosphite, 31 and tri(nbutyl)phosphite 32 confined between iron surfaces where load and sliding are applied. The AIMD simulations have given insight into the dissociation pathways of organophosphorus molecules inside tribological contacts.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

Ewen¹,

Latorre²,

Gattinoni³

et al. 2021

Preprint

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Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. An atomic-level understanding of phosphate ester tribofilm formation mechanisms is required to improve their tribological performance. A process of particular interest is the thermal decomposition of phosphate esters on steel surfaces, since this initiates polyphosphate film formation. In this study, reactive force field (ReaxFF) molecular dynamics (MD) simulations are used to study the thermal decomposition of phosphate esters with different substituents on several ferrous surfaces. The ReaxFF parameterisation was validated for a representative system using density functional theory (DFT) calculations. During the MD simulations on Fe 3 O 4 (001) and α-Fe(110), chemisorption interactions between the phosphate esters and the surfaces occur even at room temperature, and the number of molecule-surface bonds increases as the temperature increases from 300 to 1000 K. Conversely, on hydroxylated, amorphous Fe 3 O 4 , most of the molecules are physisorbed and some desorption occurs at high temperature. Thermal decomposition rates were much higher on Fe 3 O 4 (001) and particularly α-Fe(110) compared to hydroxylated, amorphous Fe 3 O 4. This suggests that water passivates ferrous surfaces and inhibits phosphate ester chemisorption, decomposition, and ultimately polyphosphate film formation. For the alkyl phosphates, thermal decomposition proceeds mainly through CO and C-H cleavage on Fe 3 O 4 (001). Aryl phosphates show much higher thermal stability, and decomposition on Fe 3 O 4 (001) only occurs through P-O and C-H cleavage, which require very high temperature. The onset temperature for CO cleavage on Fe 3 O 4 (001) increases as: tertiary alkyl < secondary alkyl < primary linear alkyl ≈ primary branched alkyl < aryl. This order is consistent with experimental observations for the thermal stability of antiwear additives with similar substituents. The simulation results clarify a range of surface and substituent effects on the thermal decomposition of phosphate esters on steel that should be helpful for the design of new molecules with improved tribological performance.

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First principles study of organophosphorus additives in boundary lubrication conditions: Effects of hydrocarbon chain length

Cited by 20 publications

References 59 publications

Thermal Decomposition of Tricresyl Phosphate on Ferrous Surfaces

Thermal Decomposition of Tricresyl Phosphate on Ferrous Surfaces

Task‐Specific Oil‐Miscible Ionic Liquids Lubricate Steel/Light Metal Alloy: A Tribochemistry Study

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

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