In this study, we developed the electrical impedance method which simultaneously measures the thickness and breakdown ratio of oil films in elastohydrodynamic (EHD) line contacts within thrust needle roller bearings. Initially, we theoretically demonstrated that the oil film thickness and breakdown ratio can be simultaneously measured using the complex impedance that is produced when an AC voltage is applied to EHD line contacts. To verify the measurement accuracy of the electrical method, we monitored the oil film thickness of a thrust needle roller bearing and compared it with the theoretical value. The results revealed that the oil film thickness was thinner than the theoretical value immediately after starting the test, with the breakdown ratio being greater than 0 (indicating mixed lubrication); however, the breakdown ratio decreased over time, and the oil film thickness nearly matched the theoretical value one hour after starting the test, when it is believed that running-in wear is complete (i.e., breakdown ratio ≈ 0). Furthermore, following the test, after examining the race surface, we confirmed that running-in wear had indeed occurred. These results suggest that the developed method can monitor the lubrication conditions in EHD line contacts, such as those in thrust needle roller bearings, in detail.

9H-9-Silafluorene with two alkoxy groups underwent dehydrocoupling in the presence of [Pt(dmpe) 2 ] (dmpe: 1,2-bis(dimethylphosphino)ethane) to produce tetrasilaplatinacyclopentanes having four silafluorenylene units. Ligand exchange of the persilylated platinacycles with non-substituted silafluorene released tetrasilane dihydrides with two pairs of π-stacked biphenylene units. [Ni(dmpe) 2 ] catalyzes the dehydrogenative polycondensation of 2,7-dibutoxy-9H-9-silafluorene to produce the poly(1,1-silafluorene).

The catalytic polymerization of silafluorenes with [Ni(dmpe) 2 ] (dmpe = 1,2-bis(dimethylphosphino)ethane) afforded 2,7-dibutoxy-9H-9-silafluorene polymers with a narrow polydispersity (M w /M n < 1.1). In an open vessel, the polymerization ceased shortly after complete consumption of the monomer, but transfer of the reaction mixture into a closed system resumed the polymer growth. Polymerization in a closed system with occasional removal of the evolved H 2 furnished soluble polymers with a maximum molecular weight of M n = 3860. Treatment of a 2,7-dibutoxy-9H-9silafluorene tetramer with [Ni(dmpe) 2 ] resulted in the initial formation of a mixture of monomers and trimers, which subsequently transformed into oligomers (Si 1 −Si 9 ). This polymerization involves a preferential dehydrogenative condensation between the monomer and an oligomer relative to that between oligomers, while the presence of H 2 regenerates the monomer after its consumption and thus promotes further polymer growth.