Strength and ductility of as-plated and sintered CVD nickel foams

Low density, open cell nickel foams produced by chemical vapor deposition (CVD) are made for electrochemical applications. One process involves nickel carbonyl decomposition within a plater whereby nickel is deposited onto a reticulated polyurethane (PU) foam substrate. The as-plated nickel foams are then sintered in a partially reducing atmosphere at high temperature in order to enhance ductility. The high strength and brittleness of the as-plated foams presents a material handling challenge in manufacturing. As-plated foams are much stronger than sintered foams of the same density. Our analysis shows that the strengthening in the as-plated nickel foams is due to a combination of grain size, solid solution strengthening, dislocations and nano-porosity. Of these, the effects due to interstitial carbon are dominant. This is lost upon sintering. Foam ductility does not show the usual inverse trend with strength. Instead, foam ductility and bendability show little variation with carbon or sulfur level or with the level of nano-porosity, which are among the strongest strengthening sources in the foams.