Studying aluminum hydride by means of thermal analysis

• Published in: Russian Journal of Physical Chemistry A 2015-07, Vol.89 (7), p.1141-1145
• Main Authors: Milekhin, Yu. M., Koptelov, A. A., Matveev, A. A., Baranets, Yu. N., Bakulin, D. A.
• Format: Article
• Language: English
• Subjects: Chemical Thermodynamics and Thermochemistry; Chemistry; Chemistry and Materials Science; Physical Chemistry
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024415070250

Chemical reactions and physical transformations that occur upon heating aluminum hydride (AlH 3 , alane), stored for 25 years, in the temperature range of 50–1200°C in an atmosphere of nitrogen, argon, and air are studied by means of thermogravimetric analysis and differential scanning calorimetry. The heat of thermal decomposition and the hydrogen content are determined for the AlH 3 samples and are found to be 318 ± 25 J/g and 9.32 ± 0.24 wt %, respectively. It is established that the estimated enthalpy of formation of AlH 3 in stoichiometric composition (Δ f H ≈ −10.3 kJ/mol) agrees with the literature data. After the release of hydrogen, the mass of the precipitate increases by 0.5 ± 0.3%, relative to the initial mass of the AlH 3 samples; the most likely reason for this effect is the adsorption of nitrogen (argon) in the micropores and mesopores that form. Thermal phenomena associated with the crystallization of the amorphous aluminum that forms after hydrogen is released from the alane particles are analyzed. It is established that the aluminum contained in initial AlH 3 samples is almost completely transformed into aluminum nitride and oxide (AlN and Al 3 O 3 ) upon heating to 1200°C in nitrogen and air, respectively.