Biomedical Engineering Reference
In-Depth Information
Ban et al . [3] investigated the etching behavior of titanium
in concentrated sulfuric acid at 60°C for 0.25, 0.5, 1, 3, and 8 h
(Fig. 9.4). The etching reveals grain boundaries and the crystal
grains are well visible. On the surface are etched pores with
diameter less than 1 μm. The depth of the etched grain boundaries
and pores increases with etching time [3].
Figure 9.5 Surface roughness R a and R z , and weight loss of Ti after etching
in 48% H 2 SO 4 in the range from RT to 90 °C for 0.25-8 h [3].
The surface roughness and weight loss of the Ti increase with
the acid temperature and etching time (Fig. 9.5) [3]. A signiicant
difference occurs between the acid temperature and the etching
time for roughness and the weight loss. The etching of Ti in
concentrated H 2 SO 4 involves the following reactions:
TiO 2 + 2H 2 SO 4 Ti(SO 4 ) 2 + 2H 2 O
(9.1)
Ti + 2H 2 SO 4 Ti(SO 4 ) 2 + 2H 2
(9.2)
Ti + H 2 TiH 2
(9.3)
Surface roughness is strongly correlated with weight loss.
At the beginning of the etching, the formation rate exceeds the
rate of TiH 2 dissolution, and the relative amount of TiH 2 on the Ti
surface increases. The dissolution rate of TiH 2 also increases with
time, because the surface area increases with the increase in surface
roughness due to the etching.
 
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