To observe the time-dependent two-dimensional (2D) images of spatial distribution of chemically/physically modified lubricant molecules on the metal surface during friction motion, a new in situ technique has been developed by combining the 2D fast-imaging Fourier-transform infrared-attenuated total reflection spectrometer with the temperature-controlled friction equipment containing lubricant agent. Using this new instrument, the time-dependent changes in lubricant molecules, for example, cis-trans isomerization, stress-induced molecular deformation, etc., can be detected successfully. The characteristic features of this instrument have been demonstrated in a detailed and concrete manner by demonstrating the experimental data measured for oleic acid and tricresyl phosphate.
By using our newly developed in situ Fourier transform infrared attenuated total reflection (FTIR-ATR) measurement system, the physicochemical property changes of n-alkane on the metal surface have been measured during repeatedly reciprocated friction motion. It was found that the friction force induced the phase transition of liquid n-alkane from melt to rotator phase and orthorhombic phase. In the severer friction condition, it was clarified that the conformational disorder was induced even in the orthorhombic phase by applying the shear stress. From these results, a phase diagram of n-alkane as a function of temperature and friction shear force has been constructed for the first time.
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