Lubrication of particulate magnetic recording media improves their mechanical durability in sliding and flying by several orders of magnitude compared with unlubricated media. Lubricant removal, degradation, and recovery were studied using microslit scanning Fourier transform infrared spectroscopy and microspot scanning X-ray photoelectron spectroscopy. These techniques measure the total and surface lubricant amounts in the porous film, respectively. Lubricant dynamics were compared for two physisorbed polyperfluoroalkylether lubricants of similar molecular weight but different molecular structure—Y with a CF3 side group and Z with linear chains. The bulk viscosity of Y was about ten times higher than the viscosity of Z. In sliding, the lubricant removal rate of Y was significantly higher than that of Z while in flying the removal rates were reversed. Removal rates in sliding were orders of magnitude higher than those in flying. Effective lateral diffusion coefficients estimated from the rate of lubricant reflow back to the depleted tracks were close to inversely proportional to the bulk viscosity. During sliding and flying both lubricants degraded as evidenced by chemically altered lubricant detected on the surfaces after dissolution of undegraded lubricant.
The Polyakov loop dependence of bulk viscosity of QCD matter
