Lubricant Transfer in Disk Drives

• Published in: Tribology letters 2012-12, Vol.48 (3), p.367-374
• Main Authors: Kasai, Paul H., Raman, Vedantham
• Format: Article
• Language: English
• Subjects: Alkali halides; Chemistry and Materials Science; Corrosion and Coatings; Disk drives; Disks; Droplets; Electrolytes; Encapsulation; Halides; Materials Science; Molecular dynamics; Nanotechnology; Original Paper; Particulates; Physical Chemistry; Surfaces and Interfaces; Theoretical and Applied Mechanics; Thin Films; Tribology
• ISSN: 1023-8883; 1573-2711
• DOI: 10.1007/s11249-012-0031-8

For disk drives with Z-tetraol-coated disks, the ingress of airborne solid particulates into the disk drive was found to result in disk-to-head lubricant transfer. In addition, high humidity was found to enhance the transfer process. Water soluble electrolytes such as alkali halides are most ubiquitous airborne solid particulates. Molecular dynamics calculations were performed to examine (a) the condensation process of H 2 O, (b) the effect of alkali halide on the process, (c) the difference between the end-groups of Z-dol and Z-tetraol. It was shown that the OH units of Z-tetraol end-groups would embed themselves into facial layer of water–electrolyte droplets, thus encapsulating and stabilizing the droplets, while the OH units of Z-dol would not do so. The lubricant transfer observed uniquely for Z-tetraol-coated disks is attributed to inorganic particulates such as NaCl entering the drive interior, landing on the disk surface, attracting water, and forming Z-tetraol encapsulated water–electrolyte droplets. These droplets are viscous and are readily picked up by the slider.