Sodium alanate

Hydrogen Absorption and Desorption Properties of Sodium Alanates... 

Bellosta von Colbe, J.M., B. Bogdanovic, M. Felderhoff, A. Pommerin, and F. Schuth, Recording of hydrogen evolution—a way for controlling the doping process of sodium alanate by ball milling, /. Alloys Compd., 370, 104-109, 2004. 

Streukens, G., B. Bogdanovic, M. Felderhoff, F. Schuth, Dependence of dissociation pressure upon doping level of Ti-doped sodium alanate—a possibility for "thermodynamic tailoring" of the system, Phys. Chem. Chem. Phys., 8(24), 2889-2892, 2006. 

Ahluwalia, R.K., Sodium alanate hydrogen storage system for automotive fuel cells, Int.. Hydrogen Energ, 32(9), 1251-1261, 2007. 

Overall the spheres were of good quality judging from images obtained and could be used for filling with sodium alanate. However, to confirm through wall open porosity formation across the spheres wall, approximately 900 A cross section was made across a sphere wall and SEM and elemental mapping was conducted and Fig. 3 shows the results obtained. 

The spheres which were soaked in the sodium alanate tetrahydrofuran solution were cracked open by applying a slight pressure and the interior of a cracked sphere was investigated and Fig.4 show s the interior of a cracked glass sphere. 

Two types of structures were seen a needle type bundled structure pointing inward towards the center of the sphere and surface bumps. The needle type structures overall were less than 10 pm in length and less than 1 pm in thickness. To confirm that these structures corresponded to sodium alanate. elemental mapping of the alanate s sodium and aluminum constitutes was made. As can be seen in Fig.5, the presence of intense sodium distribution was noted on the needle structures while the both the surface bumps and needle structures showed the presence of aluminum distribution. These results confirmed spheres filling with the alanate. While these needle structures are not usual for sodium alanate. it is speculated that the porous silica could have provided a nucleation surface for these unique structures formation. Nevertheless, since the samples were exposed to ambient air prior to the... 

Figure 5 Elemental mapping of the interior of a cracked hollow glass sphere following filling with sodium alanate...

Zaluska, A., Zaluski, L., Strom-Oslen, J.O. 2000. Sodium alanates for reversible hydrogen storage. J Alloys Comp 298 125-134. 

J.M.B.van Colbe, M. Felderhoff, B. Bogdanovic, F. Schiith, C. Weidenthaler, One-step direct synthesis of a Ti-doped sodium alanate hydrogen storage material , Chem. Commun. (2005) 4732. 

The sodium alanate hydride NaAlH is so far the most investigated and promising hydrogen storage material, at least on a short time scale (for reviews see [1-7]). 

G. Sandrock, K. Gross, G. Thomas, Effect of Ti-catalyst content on the reversible hydrogen storage properties of the sodium alanate , J. Alloys Compd. 339 (2002) 299-308. 

M.S.L. Hudson, D. Pukazhselvan, G. Irene Sheeja, O.N. Srivastava, Studies on the synthesis and dehydrogenation behavior of magnesium alanate and magnesium-sodium alanate mixture , Int. J. Hydrogen Energ. 32 (2007) 4933 938. 

It can be summarized that of all the complex aluminum hydrides presented in this chapter only NaAlH4 up till now partially fulfils the requirements for a storage material for mobile fuel cell applications. Over the last decade, the kinetics as well as the cycle stability of doped sodium alanates has been improved. Nevertheless, for application in a low-temperature fuel cell the storage capacity seems to be too low because only the first decomposition step (3.6 wt.% hydrogen) can be used. 

Sodium alanate (NaAll-14) remains so far the most studied complex hydride. It is found that NaAlH4 decomposes in several steps ... 

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