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Unsaturated fatty acids in alkane solution: adsorption to steel surfaces
KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
YKI, Institute for Surface Chemistry.
ThyssenKrupp Steel AG, Center of Materials Excellence, Surface Analysis.
YKI, Institute for Surface Chemistry.
Vise andre og tillknytning
2007 (engelsk)Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 21, s. 10598-10602Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The adsorption of the unsaturated fatty acids oleic, linoleic, and linolenic acid on steel surfaces has been investigated by means of a quartz crystal microbalance (QCM). Two different solvents were used, n-hexadecane and its highly branched isomer. viz.. 2.2,4,4,6,8,8-heptamethylnonane. The area occupied per molecule of oleic acid at 1 wt % corresponds to what is needed for adsorption parallel to the surface. At the same concentration, the adsorbed amount of linoleic acid and linolenic acid indicates that they adsorb in multilayers. The chemisorbed amount estimated from static secondary ion mass spectroscopy (SIMS) measurements was found to be similar for the three unsaturated fatty acids. In the case of linolenic acid, it was found that the presence of water significantly alters the adsorption, most likely because of the precipitation of fatty acid/water aggregates. Furthermore, static SIMS results indicate that the amount of water used here inhibits the chemisorption of linolenic acid.

sted, utgiver, år, opplag, sider
2007. Vol. 23, nr 21, s. 10598-10602
Emneord [en]
quartz-crystal microbalance, metal-substrate, frequency, liquid, films, isotherms, resonator, contact, oxide
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-17005DOI: 10.1021/la700909vISI: 000249948700027Scopus ID: 2-s2.0-35449008420OAI: oai:DiVA.org:kth-17005DiVA, id: diva2:335048
Merknad
QC 20100525Tilgjengelig fra: 2010-08-05 Laget: 2010-08-05 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Unsaturated Fatty Acids in Alkane Solution: Adsorption and Tribological Properties
Åpne denne publikasjonen i ny fane eller vindu >>Unsaturated Fatty Acids in Alkane Solution: Adsorption and Tribological Properties
2008 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Fatty acids and blends of fatty acids are used as friction modifiers and anti-wear additives in diesel fuels. A large part of some fatty acid blends are unsaturated fatty acids. Even though fatty acids have been thoroughly investigated, the adsorption and tribological behaviour of unsaturated fatty acids are no fully understood. The aim of this thesis was to investigate the influence of fatty acid unsaturation on the adsorption from alkane solution and the tribological properties, such as friction and wear scar characterization, of such systems.

To increase the fundamental understanding of the influence of the degree of fatty acid unsaturation the three fatty acids, oleic, linoleic and linolenic acid, have been studied. In boundary lubrication the amount of material and how well the material is bound to the surface can affect the friction and wear of the system. Thus, as a first step the adsorption of fatty acids onto steel surfaces was investigated with the quartz crystal microbalance (QCM). This technique is straight forward to used and is ideal for these samples that are difficult to investigate with optical techniques due to small differences in refractive index between the alkane solvent and fatty acid. To determine the chemical binding to steel surfaces static secondary ion mass spectroscopy (SIMS) has been used.

Next, the influence of fatty acid unsaturation on the friction and wear was determined. Two different studies were made, one on a molecular level with the tribological surfaces forces apparatus (T-SFA) and the other one with a technique used for determining friction and wear of diesel fuel additives. The T-SFA technique provides data from which the packing of the fatty acids at mica surfaces can be estimated as well as how the friction is altered due to the packing. For determining the friction and wear of steel surfaces the high frequency reciprocating rig (HFRR) and pin on disc apparatus (POD) were used. The HFRR is a standardized technique, where, if the settings specified in the ISO12156 protocol are used, a diesel fuel additive must provide an average wear scar radius less than 0.230 mm to pass. The wear scars received from the two techniques were further analysed with Raman spectroscopy and also a visual rating of the wear scars was performed.

As the project progressed, there was an increasing interest in the influence of water on the adsorption and lubricating properties of the fatty acids. Moisture uptake of the fatty acids was therefore determined gravimetrically as well as with nuclear magnetic resonance spectroscopy (NMR). The adsorption of the moist fatty acids onto steel surfaces was then investigated with QCM and static SIMS, while HFRR and POD were used for investigate the friction and wear.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2008. s. iv, 44
Serie
Trita-CHE-Report, ISSN 1654-1081 ; 2008:5
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-4616 (URN)978-91-7178-854-2 (ISBN)
Disputas
2008-02-15, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Veileder
Merknad
QC 20100824Tilgjengelig fra: 2008-01-28 Laget: 2008-01-28 Sist oppdatert: 2010-08-24bibliografisk kontrollert

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