Performance of different PFPEs under HAMR condition Mohammad - - PowerPoint PPT Presentation

Performance of different PFPEs under HAMR condition

Mohammad Soroush Ghahri Sarabi Department of Mechanical Engineering, UC Berkeley CML Sponsors Meeting 2014

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Outline

n Governing Equation and Problem definition n Specifications of Z-tetraol 2200 n Simulation Results n Conclusion n Future Study

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Problem Definition

n

Disjoining and Laplace pressure gradients work as restoring force

n

Evaporation is affected by disjoining pressure

From Joanna Dahl’s Thesis

Parameter Value FWHM 20 nm Tmax 350 C UD 5 m/s Lube thickness 0.5, 0.7, 1.2, 1.4 nm Ts 2ns

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Z-tetraol Disjoining Pressure

n

Z-dol has steeper curves compared to Z-tetraol

n

So, Disjoining pressure derivative for Z-tetraol is less compared to the one for Z-dol

n

Therefore, disjoining pressure gradients for Z-tetraol are weaker than the one for Z-dol

n

This means less restoring force

n

However, the absolute value of disjoining pressure is more for Z-tetraol and therefore we expect less evaporation

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Z-tetraol Viscosity

n

Bulk viscosity of Z-tetraol is higher than Z-dol specially near room temperature

n

For Film viscosity model we use Eyring’s rate theory that Karis uses as follows:

n

Where:

n

For Z-dol:

n

For Z-tetraol:

n E E

vis vis

µ − Δ = Δ

∞ ,

µ = − AVl 6πh3 mol KJ Evis / 7 . 34

, =

Δ

∞

mol KJ Evis / 8 . 50

, =

Δ

∞

µ = − AVl 12π(h+ d0)3

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Results: Flow Under HAMR Condition

n Z-tetraol has smaller deformations compared to Z-dol

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Results: Lubricant Recovery

Recovery Time 1.2 nm Initial Thickness 1.4 nm Initial Thickness

Z-dol 10.2 µs 28.2 µs Z-tetraol 2.0 ms 5.0 ms

n Two cases were studied, 1.2

and 1.4 nm initial lube thickness

n There is a significant

difference between recovery time of Z-tetraol compared to Z-dol, Almost a factor of 200

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Results: Evaporation

n

Z-tetraol has less lubricant evaporation compared to Z-dol

n

This behavior is expected because Z-tetraol has higher disjoining pressure

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Conclusion

n Under HAMR condition Z-tetraol exhibits less

deformation, smaller trough and side ridges. This is expected because of higher viscosity and lower fluid mobility of Z-tetraol compared to Z-dol

n Z-tetraol needs more time to recovery compared to Z-

• dol. This was expected because of less mobility of Z-

tetraol and also weaker restoring forces (i.e. disjoining and Laplace pressure gradient)

n Z-tetraol has less evaporation compared to Z-dol due

to stronger disjoining pressure in Z-tetraol

Soroush Sarabi & David B. Bogy Computer Mechanics Laboratory January 2014

Future Study

n Study the behavior of Z-tetraol for various laser spot

sizes and maximum temperatures

n Study the behavior of Multidentate functionalized

lubricants (e.g. ZTMD)

n Add the viscoelastic terms to our model in order to

• btain a more accurate result

n Study the effect of viscoelastic terms in behavior of

fluid

n Determine effective IMF constants for ABS modeling

in presence of HAMR lubricant