The corrosion behaviors of ceramics (Si-SiC, SiC, Si
3N
4, Al
2O
3, ZrO
2) were examined in boiliing 95 wt% sulfuric acid by measuring weight change, concentration of dissolved ions in the sulfuric acid, 4-point bending strength and apparent hardness calculated from Load-Depth curve obtained by Micro- Indentation technique. The corroded surface and the fracture surface of the specimens were analyzed by SEM and EPMA. The corrosion behaviors of these ceramics were divided into 3 types; (1) Si-SiC and SiC showed excellent corrosion resistance because of protective oxide films which developed during immersion, (2) the bending strength, apparent hardness of Si
3N
4 and Al
2O
3 decreased with increasing immersion time because of corroded layers produced during immersion, and (3) the bending strength of ZrO
2 decreased with remarkable weight loss. The thickness (T) of oxide films and corroded layer produced on Si-SiC, SiC, Si
3N
4 and Al
2O
3 was evaluated from the depth (d) which was determined by the slope change on Depth-Load/Depth curve. The relationship between T and d was described as T≈10d. The bending strengths of Si
3N
4 and Al
2O
3 were evaluated from thickness (T) of corroded layer and K
Ic obtained before immersion. As a result, the bending strengths of Si
3N
4 and Al
2O
3 could be determined with both the K
Ic and the equivalent crack length (a
e) to 20d.
抄録全体を表示