Reaction of niobium with plasma-spray coated aluminium oxide

The interaction in an inert gas medium between plasma spray coated aluminium oxide and a niobium base preheated to 200-21000C was investigated. A zone of chemical contact with non-uniform phase compostion was observed in the Nb-Al2O3 vapour. The distribution of Nb, Al and O at the point of contact and in the barrier layer was established. The causes of darkening of the Al2O3 close to the area of contact with the base were examined. The adhesion between Nb and Al2O3 increases with preheating of the base as the thickness and continuity of the area of chemical contact increases. (author)