Friction and wear tests were conducted by sliding the (001) and (110) planes of single crystal rutile (TiO2-x) specimens against selected ceramic surfaces, in well-defined crystallographic directions. The purpose of the experiments was to investigate the environmental influences on anion vacancy formation, as related to a recent hypothesis connecting oxygen sub-stoichiometry with predictable variations in the tribological properties of rutile. The data were obtained with two entirely different test machines operating at various loads, speeds, temperatures, sliding directions and durations, as well as test specimen atmospheres. The results independently confirmed the predicted, anion vacancy-controlled formation of certain low and high lattice (strain) energy crystallographic shear systems (i.e., Magneli phases) and that their generation was overwhelmingly environment-dependent. The stoichiometry-controlled lattice energy of these rutile phases influences the surface and bulk shear strength of the oxide single crystal.

Effect of Anion Vacancies on the Tribological Properties of Rutile (TiO2-x). Part II. Experimental Evidence. Gardos, M.N., Hong, H.S., Winer, W.O.: Tribology Transactions, 1990, 33[2], 209-20