A novel, simple and fast method for preparation of graphitic nanostructures such as nanofibers and nanospheres which uses a standard microwave oven is described. In this method polystyrene is used as carbon source and a solid metal such as nickel or iron provides both the trigger to initiate the plasma, as well as a source for sputtering catalyst particles which are required for formation of nanofibers. The mechanism of this process is discussed through analysis of different properties of the resulting products, by examining the effect of changing the microwave processing time and the nature of the metallic trigger/catalyst source. The effect of morphology of nanoparticles (nanofibers vs. nanospheres), as well as the effect of trigger/catalyst material and the deposition method on electron field emission properties of these samples, are also investigated. (C) 2011 Elsevier B.V. All rights reserved.