7 TH EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS) Copyright  2017 by Batonneau and Beauchet. Published by the EUCASS association with permission. Synthesis, characterization and treatment of alane (aluminium hydride, AlH 3 ) Zaki El Sayah, Rachid Brahmi, Romain Beauchet, Yann Batonneau, Charles Kappenstein Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), CNRS – UMR7285, Université de Poitiers, 4 rue Michel Brunet, bât B27, TSA 51106, 86073 Poitiers cedex 9, France zaki.el.sayah@univ-poitiers.fr; rachid.brahmi@univ-poitiers ; romain.beauchet@univ-poitiers.fr ; yann.batonneau@univ-poitiers.fr ; charles.kappenstein@univ-poitiers.fr Abstract This paper presents preparation methods of alane (α-AlH 3 ), which is known as the most stable form among its seven polymorphs. They showed the importance of both careful washing with an acidic solution or inorganic compound, and of moisture and impurities removal. The characterization of structure and morphology of α-AlH 3 thus synthesized and treated showed that solid obtained is a white powder with an onset decomposition temperature of 151 °C which can be produced at ca. 12 g per batch with a yield of nearly 98 %. 1. Introduction Aluminum hydride (AlH 3 ) which is well-known as alane, is a promising hydrogen and energy storage material that is proposed for different uses such as rocket fuel, explosive, reducing agent in alkali batteries and as hydrogen source for low temperature fuel cells. Aluminum hydride is considered as one of the most interesting additives in space propulsion because of its capability of releasing hydrogen during decomposition and/or combustion and its high density, which makes this material an excellent candidate if it can be safely and cheaply produced.[1]-[2]. Aluminum hydride is a metastable crystalline solid at room temperature, it decomposes by an endothermic reaction to generate aluminum and H 2 gas as reported in the following equation [3]: AlH 3  Al + 3/2 H 2 The formation of a passivation layer of alumina on its surface can protect it from its decomposition and from the environment. This attractive material for hydrogen storage has a hydrogen content of 10.1 wt. % [4] and volumetric hydrogen capacity of 0.148 g/mL, which is twice as much as the value of liquid hydrogen (0.070 g/mL) [3]-[4]. Aluminum hydride presents at least seven different polymorphic crystal structures (α, α’, β, γ, δ, ε crystalline phases, and solvated solid  phase), -AlH 3 being the most stable (H f ° = -11.4 kJ mol -1 ) [5] which is interesting for space propulsion applications. The best described alane phases are α, β and γ [8]-[10] with regard to their structures, morphologies and synthesis conditions which are presented in Table 1. Aluminum hydride structure published by Turley and Rinn in 1969 possesses a trigonal space group, R  c, for α-AlH 3 crystals with a hexagonal shape for its unit cell and lattice parameters a = 4.449 Å and c = 11.804 Å [9]. The structure of α-AlH 3 shows that the corners of the hexagonal unit cell are formed of AlH 6 octahedra whereas H bridges connect two octahedrons to each other. The unit cell of AlH 3 is composed of atoms of aluminum (Al) and hydrogen (H) linked between each other by single bonds of different distances: 1.715 Å (Al–H), 2.418 Å (H–H) and 3.236 Å (Al–Al) and a volume of 33.5 Å 3 per AlH 3 unit cell [10] as reminded in Figure 1. DOI: 10.13009/EUCASS2017-478