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The structural evolution of a carbon microcoil (CMC) induced by a direct current was studied using a scanning tunneling microscope-transmission electron microscope work station. We found that the CMC got broken when a high-density current was passed through, and it was partially transformed into hollow graphitic spheres, double-walled carbon nanotubes, and fullerenes. A transformation process involving pore formation, high temperature induced graphitization, and closure of dangling bonds is proposed. The driving force of the structural evolution is considered to be the high temperature effect and electromigration effect brought by the current, and the graphitic crystallites composing the CMCs tend to reconstruct to form carbon nanomaterials with enhanced structural integrity when a high-density direct current is applied. (C) 2008 Elsevier Ltd. All rights reserved.