Study of Surface Films of Overbased Amorphous and Crystalline Calcium Carbonates by XPS and AES~©

摘要

The roll of the carbonate size and morphology (amorphous or crystalline) in an overbasedrndetergent on the surface rheology in a tribometer was invesigated. From XPS analysis ofrnthe wear scars produced in the Reichert test, it appears that OBCaS (amorph) and OBCaSrn(cryst) both form thin layers of CaCO3 on top of a thicker layer of CaO (from CaCO3rndecomposition) on the surface of the test piece. Additionally, we examined thernmorphology of the Ca and S films using Auger Electron Spectroscopy (AES). In thernpresence of sulfurized olefin, additional AES analysis reveals that a layer of both S andrnCa cover the surface, where the Ca is more prevalent and evenly coated and the S isrnmottled and lower in concentration. From AES analysis of selected regions, the surfacerneither possessed high S or high Ca concentrations, but never both together. We havernshown that crystalline overbased sulfonate detergents product possesses excellentrnReichert test results over the conventional amorphous overbased materials, andrnsubsequent X-Ray Photoelectron Spectroscopy (XPS) analysis revealed that thicker Carnand S films were observed on test specimen containing crystalline OB sulfonaterncompared to amorphous OB sulfonate.