After
treatment with isoamyl acetate solution, the coupons were dried in
a critical point dryer (13200-AB, SPI supplies, West Chester, PA,
USA) using carbon dioxide and coated with platinum (40 nm thick)
using sputter coating (Cressington 208HR, Cressington Scientific
Instruments, Watford, UK). The samples were visualized using a
Hitachi S-4700 scanning electron microscope (Hitachi Ltd., Tokyo,
Japan).