Mechanochemical alloying of Mg(BH4)(2) with small amounts of metal chlorides (PdCl2, TiCl3, VCl3, MoCl3, RuCl3, CeCl3 and NbCl5) results in the formation of transition metal doped nanocomposites with different hydrogen desorption properties. The thermal decomposition properties of ball-milled as well as doped alpha-Mg(BH4)(2) have been studied. An amorphization reaction of Mg(BH4)(2) is induced by ball milling, nevertheless a partial recrystallization of the alpha phase takes place after heating up to 150 degrees C. The effect of ball milling Mg(BH4)(2) with each additive has been investigated in detail by using differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction. The onset temperature of Mg(BH4)(2) is lowered by more than 100 degrees C through the addition of Nb- or Ti chloride. Moreover, a mixed Ti-Nb-nanocomposite was also synthesized and investigated. The onset temperature of hydrogen evolution during decomposition of the mixed Ti-Nb-nanocomposite is considerably lowered by up to 125 degrees C. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.