785023.fig.002a
(a)
785023.fig.002b
(b)
785023.fig.002c
(c)
785023.fig.002d
(d)
785023.fig.002e
(e)
785023.fig.002f
(f)
785023.fig.002g
(g)
785023.fig.002h
(h)
Figure 2: SEM images showing the porous structure on anodic tungsten oxide when tungsten was anodized in 0.4 wt.% NaF electrolyte, at 25°C for 1 hr and voltages of (a) 20 V, (b) 40 V, (c) 60 V, (d) 80 V, (e) 100 V, (f) 120 V, (g) 140 V, and (h) 160 V were applied.