INVESTIGATIONS ON ALKALINE EARTH AZIDES.
Final technical rept. May 66-Apr 67,
TECHNISCHE HOCHSCHULE GRAZ (AUSTRIA) INSTITUT FUER PHYSIKALISCHE CHEMIE
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The mechanism of thermal decomposition of anhydrous BaN32 is discussed from the view of the energy level diagram and the experimental kinetic laws. Nucleation proceeds according to a first order law and is associated to exciton formation. Nucleus growth proceeds via an electron transfer mechanism. For powdered material of uniform particle size the same kinetic laws and activation energies have been found as for single crystals. The t4-law is valid the longer the smaller the particles and also the Avrami-Erofeyev equation holds the better the smaller the crystals. Doping of BaN32 with Na or Cr3 less than 300 ppm accelerates the decomposition rate without changing the activation energies. The mechanism of decomposition seems to remain unchanged. In the presence of more Cr3 greater than 400 ppm a new decomposition product was found. A new apparatus is described for determination of the heat of solution of BaN32. 1,5 H20 below room temperature and thermochemical data of this compound are discussed. Two methods for determination of activity coefficients of BaN32-solutions are described and a value of alpha 0,260 is given. This value enables the calculation of free reaction enthalpies. The phase diagram CaN32 - water is described and two new hydrates were characterized. The lattice parameters, stability ranges, solubilities and thermochemical data of all compounds are given.
- Inorganic Chemistry