Corrosion behaviour of AlN for self-cooled Li/V blanket application

Corrosion behaviour of Aluminum nitride (AlN) as a candidate material for insulating coating for V/Li blanket was investigated by corrosion experiments in liquid lithium (Li) up to 1073 K for 1000 h. High purity AlN samples decreased their weights after the sintering test in Li in contact with vanadium alloy over 973 K, while those in Li not in contact with the vanadium alloy survived up to 1073 K. Nitrogen dissolution from AlN into the liquid Li and absorption of dissolved nitrogen by vanadium alloy are considered to be a corrosion mechanism. Small decreases of electrical resistance were observed after the sintering tests over 873 K because of the conductive corrosion layer on the surface caused by the nitrogen dissolution. In the cases of low purity AlN samples sintered over 973 K, large weight decreases were explained by fragile grain boundary caused by oxygen dissolution. The oxygen dissolution may also results in the resistivity decrease even at 723 K. Therefore, decrease of oxygen impurity in AlN and addition of nitrogen in liquid Li are considered to give a possible solution to the Li/AlN corrosion problem in the Li/AlN/V alloy blanket system.