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Blow-Off Flow of Nano PFPE Liquid Film at Hard Disk Surfaces

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Abstract

Blow-off test was conducted for two different types of perfluoropolyether (PFPE): non-functional PFPE Z25 and functional PFPE Zdol3000. The film thickness of PFPE during the blow-off test was monitored intermittently in terms of ellipsometry. It is found that the two types of PFPE show completely different rheological behavior; micro-slip at the hard disk surface was observed for the non-functional PFPE Z25, while there was no micro-slip for the functional PFPE Zdol3000. Experimental results were analyzed theoretically, and it is found that micro-slip velocity of Z25 decreases steeply at first with the increases in the distance from the front end and then reaches a constant value, the film thickness in the front region increases with time due to the different micro-slip velocity, and a pileup layer is formed in the region. The pileup layer has a much lower viscosity than the original layer.

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Abbreviations

C :

Height of the micro-channel

L :

Length of the micro-channel

h f :

Film thickness of lubricant

H f :

Dimensionless film thickness of lubricant

\( H_{\text{f}}^{\text{i}} \) :

Film thickness up to the ith layer

pi, pa:

The input pressure and atmosphere pressure of the blow gas

Q :

Flow rate of lubricant film per unit width

T :

Dimensionless time

v :

Velocity of lubricant film

v e :

Velocity of moving coordinate

v s :

Slip velocity of lubricant film at a solid surface

V s :

Dimensionless slip velocity

X :

Dimensionless × coordinate

ηf :

Viscosity of lubricant film

λ:

Micro-slip length

Λs :

Dimensionless parameter defined as (\( \eta_{\text{f}} v_{{{\text{s}}_{0} }} /\tau_{\text{a}} h_{{{\text{f}}_{0} }} \))

Λe :

Dimensionless parameter defined as (\( \eta_{\text{f}} v_{\text{e}} /\tau_{\text{a}} h_{{{\text{f}}_{0} }} \))

Λ:

Dimensionless parameter

τ:

Shear stress

τa :

Shear stress at the surface of lubricant film

ζf :

Dimensionless viscosity

\( \zeta_{\text{f}}^{\text{i}} \) :

Dimensionless viscosity of the ith layer

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Authors and Affiliations

  1. Department of Mechanical Engineering, Saga University, 1 Honjo-machi, Saga-shi, Saga, 840-8502, Japan

    Bo Zhang & Akira Nakajima

  2. Fujitsu Laboratories LTD, 10-1 Morinosato-Wakamiya, Atsugi, 243-0197, Japan

    Hiroshi Chiba

Authors
  1. Bo Zhang
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  2. Hiroshi Chiba
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  3. Akira Nakajima
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Correspondence to Bo Zhang.

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Zhang, B., Chiba, H. & Nakajima, A. Blow-Off Flow of Nano PFPE Liquid Film at Hard Disk Surfaces. Tribol Lett 39, 193–199 (2010). https://doi.org/10.1007/s11249-010-9636-y

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  • DOI: https://doi.org/10.1007/s11249-010-9636-y

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