As the Palladium core in the arc reactor that kept Stark alive and powered the armor was slowly poisoning and killing him, with Stark unable to find a substitute for it. But later when Nick Fury handed him some of his father's old material; Tony found a hidden message in the diorama of the 1974 Stark Expo proves to be a diagram of the structure of a new element that proved to be the perfect substitute for Palladium, with no fear of poisoning. With the aid of his computer JARVIS, Stark synthesized it - revealing the element to be Vibranium, the same material used by Howard Stark to make Captain America's shield. Stark then had a new suit (Mark VI) developed, capable of channeling the power of the small, yet extremely powerful, new reactor.

Tony Stark's Vibranium Arc Reactor:
Parameters: Weight about 90 grams, thickness 14MM, diameter 82MM, working current 250MA

Switch through battery box

Handle time: 5-7 days