TiF(3)-doped NaH/Al mixture was hydrogenated into Na(3)AlH(6) and NaAlH(4) complex hydrides by reactive ball-milling at room temperature through the optimization of milling duration and hydrogen pressure. The analysis of the preparation of NaAlH(4) samples during reactive ball-milling process has been performed by XRD and TG/DSC. It has been found that Na(3)AlH(6) was formed under 0.5 MPa hydrogen pressure and 30 h milling duration, while NaAlH(4) was formed under 0.8 MPa hydrogen pressure and 45 h milling duration. The process of preparing NaAlH(4) by ball-milling was found accomplished via two reaction steps, namely: (1) NaH + Al + H(2) Na(3)AlH(6) and (2) Na(3)AlH(6) + Al + H(2) -> NaAlH(4). As the hydrogen pressure and milling duration increase, the synthetic yield of NaAlH(4) and its corresponding dehydriding capacity are both increased. With increased hydrogen pressure (0.8-3 MPa) and milling duration (45-60 h), the cell volume of Na(3)AlH(6) decreases while that of NaAlH(4) increases gradually. The abundance of Na(3)AlH(6) phase decreases from 57.76 (x = 0.8, y = 45) to 8.69 wt.% (x = 3, y = 60), and the abundance of NaAlH(4) phase increases from 20.63 (x = 0.8, y = 45) to 86.50 wt.% (x = 3, y = 60). All the samples prepared in this way have fairly good activation behavior and fast hydriding/dehydriding reaction kinetics, which are capable of absorbing 4.26 wt.% hydrogen at 120 degrees C and desorbing 4.12 wt.% hydrogen at 150 degrees C, respectively. The improvement of hydriding/dehydriding properties is ascribed to the favorable microstructure and ultrafine particle features of nanosized NaAlH(4) formed during ball-milling at the optimum synthetic condition. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.