| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
The corrosion behavior and strength degradation of structural ceramics in high-temperature and high-pressure water vapor, which coexists with the high-temprtature and high-pressure water, have been studied. The porpose of this study is to clarify the corrosion reaction and the forms of corrosion for typical non-oxide and oxide ceramics in such environments, to evaluate the corrosion resistance and the environmental strength for these ceramics, and to present the suggestions for the material design and the material improvement.
Silica glass and silicon carbide ceramics were used as the test samples.Corrosion tests were conducted hydrothermally in saturated water vapor at 300ﾟC for 1-10 d. The weight change before and after corrosion of the sample, XRD analysis of the surface for the corroded sample, the solution analysis by ICP-AES,SEM observation and EDX analysis of the corroded sample, and the fracture strength of the sample before and after corrosion by 3-point bending test, were measured.
The following results were obtained.
(1) Corrosion rates of silica glass and sic ceramics in saturated water vapor at 300ﾟC is higher than those in water.
(2) Intergranular corrosion proceeded in the SiC ceramics by preferential attack at the grain boundaries.
(3) The fracture strength of silica glass agter corrosion rised up with increasing duration time, because the viscosity of silica glass was reduced due to the permeation of water. The fracture strength of SiC ceramics after corrosion was reduced by about 80% of the initial strength.
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