"Another hint: it might be possible to oxidize the FiberFrax by a pretreatment with sulfuric acid or nitric acid, two very well known oxidizers, that together are even stronger. A thorough post rinse with ultrapure water or an aprotic solvent might leave the ceramic fibers hungry for some reduction by nickel...."
This is very interesting, so if the ceramic is left active after the H2SO4/HNO3 treatment then exposure to a solution of nickel ions would result in NiO bound to the ceramic surface. This would be confirmed by the green coloration. Am I correct in interpreting your hint?
More frustration being rocking chair bound for me. The next step to fusion replication only requires a simply equipped lab. What fun it would be!