| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1990: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1989: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The change of surface structure of ion-beam irradiated three typical ceramics has been investigated to cralify the effect on (a) irradiation-produced micro-structures, (b) amorphous formation and (c) surface hardness.
In the case of single crystal of alumina (Al_2O_3), the surface hardness was increased by low dose of the irradiation, clarify with increasing of the dose, and finally saturated at higher doses. The microstructural observation can explain as follo13EA\ : ws ; the hardening at initial stage is caused by defect cluster formed with high number density, and the softening at higher doses is lead by the amorphous formation. This property of hardening is affected by the presence of grain boundaries, i.e. p13EA\ : olycrystals showed larger hardness and smaller softening. In the case, the amorphous formation started at grain boundaries. This phenomena can be explained that silica (SiO_2) located at grain boundaries is easy to tern to amorphous.
In the case of silicon nitride (Si_3N_4), which is a typical covalent-bonding materials, the properties of hardness were same, and the critical doses for amorphous formation was quite low.
In the case of zirconia (ZrO_2) which is a typical ionic-bonding materials, ion-irradiation produced only hardening. In this material defect clusters were formed, but amorphous was not produced during the irradiation.
These results can cralified that the modification of surface properties is caused by the amorphous formation from the accumulation of irradiation-defects, not by the increase of the internal stress.
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