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dc.contributor.advisorBiswas, S K
dc.contributor.authorKumar, Deepak
dc.date.accessioned2011-07-01T05:08:30Z
dc.date.accessioned2018-07-31T05:50:01Z
dc.date.available2011-07-01T05:08:30Z
dc.date.available2018-07-31T05:50:01Z
dc.date.issued2011-07-01
dc.date.submitted2010
dc.identifier.urihttp://etd.iisc.ac.in/handle/2005/1257
dc.identifier.abstracthttp://etd.iisc.ac.in/static/etd/abstracts/1637/G23835-Abs.pdfen_US
dc.description.abstractIn case of metalworking operations, the purpose of lubrication is served by a complex mixture of two or more phases, these mixtures are known as metalworking fluids (MWFs). For many decades oil-in-water emulsions have been used as metalworking fluids. The particular advantage of using oil-in-water emulsion in metalworking operations is that it combines the cooling property of water and the lubrication property of the oil. To explain the lubrication mechanism for oil-in-water emulsions as metalworking fluids a variety of models and theories has been proposed. To understand the lubrication mechanism, the role of each ingredient in the tribological process needs to be studied. In the present study a model for lubrication which determines force and proximity regimes of droplets based on the droplet size distribution is proposed. Dynamic light scattering (DLS) is used to characterize the emulsions. The small droplets are found to be the ones which enhance lubricity. DLVO (Derjaguin-Landau-Verwey-Overbeek) theory is used to validate the results. The concentration and type of surfactant is found to be the performance controlling parameter. A further analysis of the three interfacial energetics; oil/water, oil/substrate, water/substrate, is studied in the presence and absence of surfactants with the help of a Goniometer, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM). Such energetics reflects the rate at which the excess surfactant molecules accumulate at the water/oil interface and desorb into the phases. The tribological response is recorded using AFM and the nanotribometer (NTR). Frictional response of the chemisorbed self-assembled monolayer of surfactant (sodium oleate) on the steel substrate reflects that a tribofilm helps in lubricating the contact under boundary lubrication by creating a low shear strength material. Water being the continuous phase in oil/water emulsion a thin water layer adjacent to steel substrate is always present. This thin layer on the solid substrate acts as a barrier to the lubricating oil droplets to reach the metal surface. The focus of the present work is also to investigate conditions which permit the disjoining of the water film to allow the oil to lubricate the metal substrate. AFM is used to study the interaction force between an oil droplet and the steel substrate through water. An oil encapsulated SiO2 colloidal probe used to simulate the oil droplet. The charge regulatory status of the substrates and interfaces are found to be critical in mapping the force characteristics when DLVO interaction is considered. The condition for activation of non-DLVO (hydration, hydrophobic, capillary) forces are also identified and found to be dependent on the physical states of surfaces. Disjoining of the thin film can be controlled by selecting surfactants based on interfacial energetics and attractive force characteristic can be achieved to facilitate lubrication.en_US
dc.language.isoen_USen_US
dc.relation.ispartofseriesG23835en_US
dc.subjectNanotribologyen_US
dc.subjectLubricantsen_US
dc.subjectFrictionen_US
dc.subjectLubricationen_US
dc.subjectEmulsionen_US
dc.subjectSodium Oleateen_US
dc.subjectSteel Substrateen_US
dc.subjectThin Water Filmen_US
dc.subjectMetalworking Fluids (MWFs)en_US
dc.subjectOil Filmen_US
dc.subject.classificationMachine Engineeringen_US
dc.titleNanotribology Of Emulsified Lubricantsen_US
dc.typeThesisen_US
dc.degree.namePhDen_US
dc.degree.levelDoctoralen_US
dc.degree.disciplineFaculty of Engineeringen_US


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