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A novel neutron and X-ray reflectometry sample environment is presented for the study of surface-active molecules at solid–liquid interfaces under shear. Neutron reflectometry was successfully used to characterise the iron oxide–dodecane interface at a shear rate of 7.0 × 10 2 s - 1 using a combination of conventional reflectometry theory coupled with the summation of reflected intensities to describe reflectivity from thicker films. Additionally, the structure adopted by glycerol monooleate (GMO), an Organic Friction Modifier, when adsorbed at the iron oxide–dodecane interface at a shear rate of 7.0 × 10 2 s - 1 was studied. It was found that GMO forms a surface layer that appears unaltered by the effect of shear, where the thickness of the GMO layer was found to be 24. 3 - 10.2 + 9.9 Å under direct shear at 7.0 × 10 2 s - 1 and 25. 8 - 5.2 + 4.4 Å when not directly under shear. Finally, a model to analyse X-ray reflectometry data collected with the sample environment is also described and applied to data collected at 3.0 × 10 3 s - 1 . [ABSTRACT FROM AUTHOR]

Theadsorption behavior of a model additive, hexadecylamine, ontoan iron surface from hexadecane oil has been characterized using polarizedneutron reflectometry, sum-frequency generation spectroscopy, solutiondepletion isotherm, and X-ray photoelectron spectroscopy (XPS). Theamine showed a strong affinity for the metal surface, forming a densemonolayer at relatively low concentrations; a layer thickness of 16(±3) Å at low concentrations, increasing to 20 (±3)Å at greater amine concentrations, was determined from the neutrondata. These thicknesses suggest that the molecules in the layer aretilted. Adsorption was also indicated by sum-frequency generationspectroscopy and XPS, the latter indicating that the most dominantamine–surface interaction was via electron donation from thenitrogen lone pair to the positively charged iron ions. Sum-frequencygeneration spectroscopy was used to determine the alkyl chain conformationorder and orientation on the surface. [ABSTRACT FROM AUTHOR]