Raman spectra of solutions of dimethyl sulphoxide (DMSO) in carbon tetrachloride (CCl4) and water are reported for both parallel and perpendicular polarizations in the S=O stretching region. The various bands obtained were subjected to Gaussian band fittings. It was observed that the bands for solutions in CCI4 may be fitted satisfactorily by considering four components and those for solutions in water may be fitted by considering five components. It is inferred that the band at ca 1070 cm-' observed in the spectra of DMSO in CCI, belongs to the S=O stretching mode of free DMSO, whereas the two bands observed at ca 1058 cm-' and ca 1040 cm-' belong to out-of-phase and in-phase S=O stretchings of the cyclic dimer. The low-frequency band at ca 1025cm-' is assigned to linear dimer/higher polymers. Aqueous solutions of DMSO show an additional band at ca 1010 cm-' due to DMSO hydrogen-bonded with water.

The present studies highlight the applications of N M R spectroscopic techniques for unravelling the unique structural features present in base oils responsible for imparting lubricant properties. The viscosity-temperature and viscosity-pressure properties of base oils of API groups I-N; such as viscosity, viscosity index, pour point, elastohydrodynamic film thickness, and pressure-viscosity coefficient, have been correlated with the detailed hydrocarbon composition of base oils with a n emphasis on the various types of methyl branched structures. Molecular dynamics parameters, such as diffusion coefficient and energy of activation, estimated from the N M R spectral studies have provided evidence of the factors responsible for the different viscosity-temperature or viscosity-pressure characteristics of base oils.

Graphene was prepared in hydrocarbon oil medium in a mechano-chemical process.The resulting dispersion is a mixture of multilayered and single layer graphene as revealed from High Resolution Transmission Electron Microscope (HRTEM) and Selected Area Electron Diffraction (SAED) studies. The dispersion yielded significant increase in thermal conductivity with respect to base oil. The inclusion of the graphene dispersion in grease instead of traditionally used graphite improved the thermal conductivity value considerably, without deteriorating the tribological properties achieved from the pristine graphite system. A fully formulated lubricant inhibited with the said graphene dispersion showed excellent thermal dissipation and reduction in coefficient of friction over the neat lubricant. Spectroanalytical studies of the used test specimen of tribological rig bear signature peak of graphene film, thus proving the lubrication efficiency of graphene in hydrocarbon medium. …………………………………………………………………………………………………..

It has been well recognized that the chemical composition of the base oil is primarily responsible for its physicochemical properties such as viscosity, viscosity index (VI) and pour point etc., which in turn influence the performance of the finished formulation. Hence, it is very essential to determine the chemical composition of the base oil to understand the physicochemical properties. The paper highlights an experimental and computational protocol for the simultaneous determination of physicochemical properties (viscosity index and pour point) and carbon type analysis (C A , C P , C N , and isoparaffin carbon content, I P ) of base oils from their IR spectral features. IR spectra of 60 base oils of different origin and processing schemes are recorded using the horizontal attenuated total reflectance accessory with ZnSe windows. Partial least-squares (PLS) technique has been applied to construct the mathematical models which correlate the IR spectral features with the experimentally determined values (using NMR and standard ASTM tests). The regression coefficients are found to be in the range 0.80-0.95.

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