Activation of the SiC Surface for Vapor Phase Lubrication by Fe Chemical Vapor Deposition from Fe(CO)5

The feasibility is demonstrated of a new approach to the vapor phase lubrication of ceramics using organophosphorus compounds. The surface of SiC is shown to be unreactive for the decomposition of trimethylphosphite, (CH3O)3P, a simple model for organophosphorus vapor phase lubricants such as tricresylphosphate. In order to activate the surface of SiC it has been exposed to Fe(CO)5 at a temperature of 600 K. Chemical vapor deposition serves as a means of depositing Fe on the SiC surface. The Fe-modified SiC surface is then shown to induce the decomposition of adsorbed (CH3O)3P. The mechanism of (CH3O)3P decomposition is similar to that observed on Fe(110) surfaces modified by the presence of oxygen. It is initiated by P–O bond cleavage to produce adsorbed methoxy groups, CH3O(ad), which then decompose by β-hydride elimination resulting in H2, CO, H2CO, and CH3OH desorption. It is suggested that chemical vapor deposition of metals using high vapor pressure metal-containing compounds such as Fe(CO)5 can serve as a mechanism for continuous, in situ activation of ceramic surfaces for vapor phase lubrication in high temperature engines.