the method of the invention produces nickel structures from nickel - coated polymer substrates . the nickel - coated polymer substrate has a nickel outer layer and initially has a temperature where the outer nickel layer lacks burst openings . rapidly exposing the nickel - coated polymer substrate to a temperature of at least about 600 ° c . thermally decomposes the polymer substrate and bursts holes through the outer nickel layer . the gases resulting from the thermally decomposed polymer substrate escape through the holes through the outer nickel layer to leave a nickel structure . finally , annealing the nickel structure increases strength of the nickel structure to produce a ductile foam product .