Camshaft Surface Temperatures in Fired-Gasoline Engines

McGeehan, J. A.; Graham, John; Yamaguchi, E. S.

doi:10.4271/902162

Cited by 16 publications

(14 citation statements)

References 9 publications

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“…Except for the base oil effect in the screening formulation (Table I), all basic and neutral ZnDTPs, at the same P concentration, independent of the size or type of the R group, showed similar performance contradicting the Hanison assertion (8), (9). This result is also in contrast to the known dependence of wear inhibition performance on the nature of the R group (7). It should also be noted that other researchers attempted a similar study with the basic ZnDTP salt from isooctanol (20).…”

Section: The Harrison Assertion and The Equilibrium Between Basic Andcontrasting

confidence: 83%

The Relative Oxidation Inhibition Performance of Some Neutral and Basic Zinc Dithiophosphate Salts

Yamaguchi

Onopchenko

Francisco

et al. 1999

Tribology Transactions

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Recent engine testing on separate neutral and basic zinc dirhiophosphates (ZnDTPs) showed a drfference in valve train wear performance, with the neutral ZnDTP giving statistically better wear inhibition in Sequence VE rests. Since the literature was lacking on the oxidatiotl inhibition performance of the separate neutral and basic salts, we systematically examined the relative antioxidatlcy of several neutral and basic ZnDTP salts in various formulations. The results were dependent on the type of base oil and formulation used, and the presence of other additives. NMR Spectroscopy, coupled with Oxidator Bench Test studies, were used to reach these conclusions.

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Section: The Harrison Assertion and The Equilibrium Between Basic Andcontrasting

confidence: 83%

The Relative Oxidation Inhibition Performance of Some Neutral and Basic Zinc Dithiophosphate Salts

Yamaguchi

Onopchenko

Francisco

et al. 1999

Tribology Transactions

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“…b The cohesive energies from eq 11b. c See ref a. We consider results for alkyl secondary in this reference comparable to iPr; alkyl primary comparable to iBu; aryl comparable to Ph.…”

Section: The Dtp Film On α-Fe2o3mentioning

confidence: 99%

“…Generally, surface films may be formed by physical adsorption, chemisorption, and chemical reaction as temperature increased. On the basis of experimental observations, ,, adsorption is the initial step in antiwear film formation. It has been proposed 26 that the ZnDTP initially physisorbs on the surface and subsequently reacts with hydroxyl groups on the metal surface to form a chemisorbed Zn-depleted DTP layer.…”

Section: The Dtp Film On α-Fe2o3mentioning

confidence: 99%

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The SAM Model for Wear Inhibitor Performance of Dithiophosphates on Iron Oxide

et al. 1997

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Zinc dithiophosphate (DTP) molecules have long been used as wear inhibitor oil additives for automotive engines. In order to obtain an atomistic understanding of the mechanism by which these molecules inhibit wear, we examined the geometries, energetics, and vibrations of an oxidized iron surface [(001) surface of α-Fe2O3] using the MSX force field (FF) based on ab initio quantum chemistry (QC) calculations. The DTP molecules studied include (RO)2PS2 with R = methyl, isobutyl, isopropyl, and phenyl. The α-Fe2O3 surface is described using the generalized valence bond (GVB) model of bonding. The geometries, binding energies, and vibrational frequencies from ab initio calculations on simple clusters are used with the biased Hessian method to develop the MSX FF suitable for describing the binding of DTP molecules to the surfaces. We find that the cohesive energies for the self-assembled monolayers (SAM) of the DTP molecules on the Fe2O3 surface correlate with the antiwear performance observed in experimental engine tests. This suggests that the search for more effective and environmentally benign wear inhibitors can use the cohesive energies for SAM formation as a criterion in selecting and prioritizing compounds for experimental testing.

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“…[1][2][3] In particular the ZnDTPs derived from secondary alcohols (termed secondary alkyl) provide excellent valve train wear control in comparison to ZnDTPs derived from primary alcohols or phenols. 1 Although ZnDTPs have proved quite effective as wear inhibitors and have been in use for nearly 50 years, there is little molecular-level understanding of how they work. 4 Understanding the mechanism of action of ZnDTPs could reveal insights to developing more effective ones.…”

Section: Introductionmentioning

confidence: 99%

Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry

et al. 1996

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Zinc dithiophosphates (ZnDTPs) are ubiquitous lubricating oil additives in today's passenger car motor oils, providing the important functions of wear and oxidation inhibition. However, the molecular-level mechanism by which these materials reduce wear is not understood. As a first step in developing an understanding of this mechanism, we used ab initio quantum chemical methods to examine the structures, vibrations, and energetics of these systems. The results show that the two phosphorus-sulfur bonds of the dithiophosphate of ZnDTPs are equiValent and have character intermediate between single and double bonds. This contrasts with the paradigm of one double bond (PdS) and one single bond (P-S) often used. Vibrational studies of DTP systems lead to a strong IR transition at about 650 cm -1 and a weak transition at about 530 cm -1 . We find modes in good agreement with experiment, where the high-frequency mode is antisymmetric PS stretch (not PdS), while the lower mode is symmetric PS stretch (not P-S). On the basis of the ab initio calculation results, we used the biased Hessian method to develop a vibrationally accurate force field (FF) for ZnDTPs. This FF can be used to examine the binding of DTPs to metal and metal oxide surfaces.

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Camshaft Surface Temperatures in Fired-Gasoline Engines

Cited by 16 publications

References 9 publications

The Relative Oxidation Inhibition Performance of Some Neutral and Basic Zinc Dithiophosphate Salts

The Relative Oxidation Inhibition Performance of Some Neutral and Basic Zinc Dithiophosphate Salts

The SAM Model for Wear Inhibitor Performance of Dithiophosphates on Iron Oxide

Structures, Vibrations, and Force Fields of Dithiophosphate Wear Inhibitors from ab Initio Quantum Chemistry

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