Determination of the Tribological Fundamentals of Solid Lubricated Ceramics. Part 3: Molecular Engineering of Rutile (TiO2-x) as a Lubricious Oxide.
Abstract
A study was conducted to (a) confirm a Hughes hypothesis correlating the oxygen stoichiometry of rutile Magneli phases (Ti sub n O sub 2n-1) with their tribological behavior, and (b) show feasibility of controlling the stoichiometry (and thus the tribological performance) by doping specifically with Cu2+/Cu1+ and other selected cations. Variable temperature (from R.T. to 1000 deg C) SEM tribometry completed on fully stoichiometric, single crystal and polycrystalline rutile samples and other polycrystalline specimens reduced into narrow stoichiometric ranges confirmed that the shear strength and the resultant friction are highly dependent on oxygen-content-controlled development of various crystallographic shear planes (the TinO2n-1 Magneli phases). However, the high sensitivity of these phases to structural changes induced by the variation of the sample temperature and the partial pressures of oxygen around the sample render the rutile polymorph of TiO2.00 a tribooxidatively unstable material. Polycrystalline rutile was subsequently doped with cations predicted to stabilize or fail to stabilize stoichiometry. X-ray diffraction combined with four-point electrical conductivity measurements of model rutile compositions doped with CuO indicated the predicted the feasibility of generating chemically induced crystallographic shear planes through the creation of a Ti-Cu bronze equivalent in behavior to a TiO18.9 Magneli phase. SEM tribhometry, combined with other high temperature tribotests performed with an engineering-type friction and wear bench tester, demonstrated the enhanced tribooxidative stability of the copper-doped, TiOi1.89-like doped lubricious oxide prototype.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1994
- Accession Number
- ADA295170
Entities
People
- M. N. Gardos
Organizations
- Hughes Aircraft Company