Tribochemistry and Morphology of P-Based Antiwear Films

Dorgham, Abdel; Neville, Anne; Morina, Ardian

doi:10.1007/978-3-319-99897-8_6

Cited by 4 publications

(6 citation statements)

References 179 publications

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“…However, if the DDP tribofilms contain iron cations, i.e. consists of iron phosphate, the phosphate chains will undergo depolymerisation, which will result ultimately in the formation of short chains [1,24]. The XAS results could not conclude the presence of iron due to the convoluted noise in the data.…”

Section: Discussionmentioning

confidence: 93%

“…Zinc dialkyldithiophosphate (ZDDP) is used extensively in lubricating oils to protect contacting surfaces rubbing against each other by forming on them thin layers of a protective tribofilm [1][2][3]. However, this additive decomposes to form zinc, sulphur and phosphorus-based products, mainly in the form of zinc (thio)phosphate [4,5], which pose an environmental hazard especially to catalytic converters leading to increased harmful emissions [6].…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, extensive studies were performed in order to find a proper replacement to ZDDP with a similar antiwear performance [1,2]. One of the steps taken was to reduce or eliminate zinc, sulphur and phosphorus one-by-one while aiming at maintaining the same functionality.…”

Section: Introductionmentioning

confidence: 99%

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Tribochemistry evolution of DDP tribofilms over time using in-situ synchrotron XAS

Dorgham

Azam

Wang

et al. 2021

Tribology International

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Tribochemistry evolution of DDP tribofilms over time using in-situ synchrotron XAS

Dorgham

Azam

Wang

et al. 2021

Tribology International

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“…The reason behind this can be related to the type of the phosphate composing the main bulk of the triboreactive film. In the case of the ZDDP films, predominantly zinc phosphate of relatively long chain length is formed 3,6,7,10,13 compared to iron phosphate of short chain length in the case of DDP films [36][37][38] . Thus, the type of cations available during the decomposition of the additive appears to not only affect the composition but also the structure and possibly the flowability behaviour of the formed film.…”

Section: Formation Of Films With Congested Morphologymentioning

confidence: 99%

“…It all starts with rubbing, which occurs between contacting surfaces such as in the cylinder/piston geometry in a typical internal combustion engine (ICE), as demonstrated in Figure 1. Due to rubbing at high temperature, the molecules of ZDDP additive (Zn[(RO) 2 PS 2 ] 2 ) in the lubricating oil start to self-and trans-alkylate (Figure 1b), which involves the migration of alkyl groups from the O to S atoms [5][6][7] . The additive then adsorbs to the steel substrate as either unreacted molecules or as linkage isomers (Zn[O 2 P (SR) 2 ] 2 ) 8 .…”

Section: Introductionmentioning

confidence: 99%

Nanoscale viscosity of triboreactive interfaces

et al. 2021

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It has been long speculated that the good antiwear properties of the nano-thin triboreactive interfaces might have a rheological origin that can greatly influence their friction, lubrication and antiwear characteristics, which account for nearly one quarter of the worldwide total energy consumption. However, the measurement of the nanoscale viscosity of such tribological interfaces is still a challenging task. This is mainly due to their ultralow thickness, i.e. typically < 150 nm, high viscosity and reactivity, which make the currently used bulk, interfacial or micro-gap rheological techniques inadequate. Here we demonstrate two methods, i.e. creep and squeeze flow, that can be used to quantify the viscosity of triboreactive films in-situ as they form and ex-situ after formation. Films generated from the zinc and ashless dialkyldithiophosphate (ZDDP and DDP) antiwear additives were analysed as model systems because of their industrial and academic importance. The results confirm that the formed tribofilms behave as molten glass with an average viscosity ranging from 2 × 10 11 to 7 × 10 12 Pa.s. During its formation, the molten glass showed rich intrinsic rheological properties that allowed them to maintain local order on the nanoscale through the motion and reconfiguration of single and multiple patches within the formed film, which can significantly predetermine its superior antiwear properties. The findings of this study open future opportunities for optimising the nano-flowable glass to efficiently control the lubrication of tomorrow's engines without the need of any environmentally harmful oil additives.

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An Assessment of the Effect of Relative Humidity on the Decomposition of the ZDDP Antiwear Additive

et al. 2021

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The effect of relative humidity on the decomposition reaction of zinc dialkyldithiophosphate (ZDDP) additive under boundary lubrication regime has been investigated using Raman spectroscopy and atomic force microscopy (AFM). The ZDDP tribofilms were formed using the pin-on-disc tribometer at 30 and 90% relative humidity, which was controlled using a custom-made humid chamber. The results suggest that relative humidity does not change only the length of the phosphate chains but also their affinity towards the available cations. At low relative humidity, zinc pyrophosphate to polyphosphate chains were formed compared to predominantly shorter iron orthophosphate chains at high relative humidity. In addition, relative humidity altered the structure of the mature tribofilm. At low relative humidity, the tribofilm had a patchy structure with average thickness of 140 nm and fractal dimension of 2.17. However, at high relative humidity, the tribofilm had a thin dendritic structure with average thickness of 85 nm and fractal dimension of 2.34. This means that the structure is more complex with a larger number of nesting self-similar structures at all scales. This is significant in making the transition from descriptive towards quantitative information of the tribofilm structure.

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Tribochemistry and Morphology of P-Based Antiwear Films

Cited by 4 publications

References 179 publications

Tribochemistry evolution of DDP tribofilms over time using in-situ synchrotron XAS

Tribochemistry evolution of DDP tribofilms over time using in-situ synchrotron XAS

Nanoscale viscosity of triboreactive interfaces

An Assessment of the Effect of Relative Humidity on the Decomposition of the ZDDP Antiwear Additive

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