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Feasibility of high pressure tribochemistry experiments from Raman study of lubricant additives at ambient conditions
2009 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this work a possibillity of studying ZDDP lubricant additive in-situ under high pressure in a diamond anvil cell (DAC) using Raman spectroscopy is examined. Pure ZDDP does not exhibit anti-wear properties whereas its presence in the lubricant results in forming a protective layer (tribo- film), the process which mechanism is still unknown. Therefore it is desirable to study chemical transformation of ZDDP in a solution at real tribological conditions, i.e. high pressure and temperature. Recent molecular dynamics simulations show cross-linking behaviour of the decomposition products of ZDDP under high pressure which may explain the mechanism of tribofilm formation thus making high pressure experimental verification of the model necessary. We use three different lasers and two different solvents to examine the possibillities of studying ZDDP solutions by Raman spectroscopy. The Raman spectrum of ZDDP in solid form was recorded and served as a reference for further experiments. The hydrocarbons - hexadecane and diethyleneglycoldibutylether (molecules with higher polarity) – were used as ZDDP solvents. Raman spectra of the solutions with different ZDDP concentrations were recorded and compared to the spectra of pure solvents and solid ZDDP. The signal from hydrocarbons is overlapping with that from the ZDDP in the solution which makes study of the latter in a DAC problematic. Nevertheless we demonstrate in this work feasibility of the tribochemical experiments in a DAC by showing that the unwanted contribution of the solvents to the Raman spectrum of ZDDP can be eliminated. Our experiments show that even more clear spectral separation can be made using an ethanol/methanol mixture as a solvent although in this system a chemical alteration of the ZDDP molecules may occur. The Raman peak with highest intensity in ZDDP spectrum is assigned to the bonds in the core of the ZDDP molecule. Following evolution of this peak at high pressure/temperature would provide information on the molecular structure changes – a first step to the tribofilm formation.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths, ZDDP, Diamond Anvil Cell, DAC, lubricant, additive, Raman, spectroscopy, hexadecane, diethyleneglycoldibutylether, high, pressure, cross-linkage, Anti-wear, tribo-film, methanol-, ethanol
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-58229ISRN: LTU-EX--09/147--SELocal ID: ed02976a-df2e-491e-94f7-fd4caee8b2bfOAI: diva2:1031617
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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