Carbon micro-coils with double helical/spiral forms were obtained by the Ni-catalyzed pyrolysis of acetylene at 700-850degreesC. There are two kinds of carbon coils: the carbon coils that are circular in fiber cross-section (circular coils) and flat or rectangular in fiber cross-section (flat coils). It was found that the circular coils with a large coil diameter of several dozen micrometers could be elastically extended up to 15 times the original coil length while that of the flat coils with small coil diameter of 3-6 mum was extended to only 1.5 times. The preparation conditions, morphology, growth mechanism and extension characteristics of the super-elastic coils were examined. (C) 2002 Elsevier Science B.V. All rights reserved.