Effects of functional end-groups on nano-tribology characteristics of ultra-thin liquid lubricant films in hard disk drives

This paper describes the effects of functional end-groups on lubricant redistribution of ultra-thin liquid lubricant films in hard disk drives. In the experiments, the spreading characteristics of ultra-thin liquid lubricant films have been investigated by using the disks with two kinds of lubricants which have different end-groups. In other words, the tested lubricants were conventional Zdol and novel cyclotriphosphazene-terminated PFPE lubricant. It was found that the mobility of novel lubricant film is lower than that of conventional Zdol and these characteristics depend on the interactions between the end-groups of the lubricants and carbon surfaces. The effect of molecularly thin lubricant films on nano-spacing flying head slider hysteresis behavior for touch-down and take-off process has been studied and the dynamic interactions between the slider and the tested lubricants films in near contact regime have been clarified. In addition, the behavior of two kinds of lubricants films for contact sliders also has been investigated. It could be observed that the lubricant film thickness instability occurs as a result of slider-disk contacts for the tested lubricants. Their unstable lubricant behavior depends on the chemical structure of functional end-group. Therefore, it may be concluded that the functional end-groups play a very important role and affect the tribological performance of lubricants in head-disk interface.