Nutpool Materials

To increase their resistance to oxidation by oxygen and corrosion by molten steel, and to change the effect of their microstructure, some yttrium oxide additions have been used. Yttrium oxide, by helping the alumina sintering, increases the composite's densification and so its mechanical strength, and by increasing the grains cohesion, it allows us to change the hot-pressing programme to obtain a more isotropic composite. Also, by reaction with alumina, it forms yttrogarnet (YAG) which protects the composite from oxidation by forming a protective liquid phase at the surface, following the reaction with boron oxide formed by the boron nitride oxidation. However, this liquid phase is eroded by the molten steel and so, cannot increase the corrosion resistance, but it is possible to stop this corrosion by an addition of neodymium oxide.