Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1279331 | International Journal of Hydrogen Energy | 2011 | 5 Pages |
Abstract
A systematic study of the structural phase transition of NH3BH3 and of its fully deuterated analogue was performed combining DSC and anelastic spectroscopy measurements. The transition is accompanied by a latent heat, and therefore is of the 1st order. On the deuterated sample the enthalpy variation is reduced of more than 20%, from 1.29 to 1.01Â kJ/mol and the transition is shifted by â¼1.5Â K toward higher temperatures. Both NH3BH3 and ND3BD3 display a temperature hysteresis between cooling and heating, thus denoting that the phase transition is of first-order. In addition, this hysteresis is extremely small (â¼0.5Â K) indicating that the coexistence region between the two phases is very narrow. During isothermal ageing, the transformation of the low-temperature orthorhombic phase into the high-temperature tetragonal one occurs with a time constant of â¼16Â min in NH3BH3 and â¼64Â min in ND3BD3, evidencing a drastic slowing down of kinetics in the deuterated compound.
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Physical Sciences and Engineering
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Authors
Oriele Palumbo, Annalisa Paolone, Pasquale Rispoli, Rosario Cantelli, Tom Autrey, Abhijeet Karkamkar, Maria Assunta Navarra,