Thermal Expansion of Electrodeposited Nanoscale Multilayers of Invar with Copper

Nanoscaled, compositionally modulated multilayer alloys of NiFe in the Invar range and Cu were electroplated into an array of cylindrical microrecesses in polymethylmethacrylate in diameter, tall, with a center-to-center spacing of . Deposition conditions were determined using a rotating Hull cell and linear sweep voltammetry. The presence of the nanoscale multilayers was confirmed by transmission electron microscopy and the thermal expansion of the multilayer microposts was measured over the range from . As deposited, the multilayer alloy exhibited a negative coefficient of thermal expansion (CTE); for a thick Cu layer the CTE was up to and more negative for higher temperatures. To the best of the authors' knowledge this is the first observation of a room temperature, negative CTE in multilayered-Invar alloys. After thermal cycling, the alloy had a small positive CTE of up to , comparable to that of bulk Invar ( , and no increase of the CTE was observed for temperatures up to .