Towards a neutron and X-ray reflectometry environment for the study of solid–liquid interfaces under shear

Abstract

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 $$7.0\times {}10^{2}$$ 7.0 × 10 2 $$\hbox {s}^{-1}$$ 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 $$7.0\times {}10^{2}$$ 7.0 × 10 2 $$\hbox {s}^{-1}$$ 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 $$24.3^{+9.9}_{-10.2}$$ 24 . 3 - 10.2 + 9.9 Å under direct shear at $$7.0\times {}10^{2}$$ 7.0 × 10 2 $$\hbox {s}^{-1}$$ s - 1 and $$25.8^{+4.4}_{-5.2}$$ 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 $$3.0\times {}10^{3}$$ 3.0 × 10 3 $$\hbox {s}^{-1}$$ s - 1 .

Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide

“…This can be quantified by comparing the natural logarithm of Z for modelling the substrate with (ln Z = 804.8 ± 0.5) and without (ln Z = −177.0 ± 0.5) the adventitious layer, where models with greater Bayesian evidences are preferable. The presence of adventitious material at the iron oxide–dodecane interface has been reported previously, 21 and comparable layers have been found at interfaces between materials of high and low surface energy. 61–64 The details of this model, including the parameterisation of the adventitious layer and the magnetisation of the iron layer, and the subsequent results, are given in the ESI †…”

“…In recent experimental work, a cell has been developed that allows the interfacial structures of adsorbed films to be studied under shear conditions using either X-ray or neutron reflectometry. 21 In the initial demonstration of the cell, GMO was studied at the interface between n -dodecane and planar iron oxide (hematite, Fe 2 O 3 ) surfaces. It was found that GMO forms a layer approximately 25 Å thick, which does not alter significantly between quiescent and shear conditions (shear rate 700 s −1 ).…”

Uniform Polyester-Based Nanoparticles Assembled via Living Crystallization-Driven Self-Assembly as Friction-Reducing Agents in Engine Oil

“…n -Alkane solvents have been utilized in multiple reports as a substitute solvent for heavy base oils in lubricant studies. − Therefore, we initially investigated the self-assembly properties of the BCPs in these solvents to gain a better understanding of the system. Three n -alkanes, n -octane, n -decane, and n -dodecane were selected to discern how alterations to the solvent choice may affect the resulting micelle properties.…”

Neutron Reflectometry under High Shear in Narrow Gap for Tribology Study

“…Regarding for polymer additives, the temperature dependence of the thickness and density of the adsorbed layer formed under static states has been evaluated 1 . In contrast, few operando analyses have been conducted in the shear eld 15 , and the change in the structure of the adsorbed layer formed by additives at the sliding surfaces has not been clari ed.…”

“…However, damage to the metal lm due to friction during neutron re ectometry causes operando analysis to fail. Therefore, when Armstrong et al analyzed the structure of an adsorbed layer of glycerol monooleate (GMO) under shear conditions, they set the gap between the roller and at disk to as much as 200 µm 15 . Re ectometry experiment have also been performed with a commercially available rheometer installed in a re ectometer, but the minimum gap between the cone and plate is typically on the order of 100 µm, which does not correspond to the typical oil lm thickness in tribological conditions, and the shear rate was only around 10 3 s − 1 15,18-21 .…”