Absence of the Structural Phase Transition in Ammonia Borane Dispersed in Mesoporous Silica: Evidence of Novel Thermodynamic Properties

The occurrence of the structural phase transition of NH3BH3 dispersed in mesoporous silica was studied by anelastic spectroscopy and differential scanning calorimetry. Both measurements indicate that the structural phase transition is suppressed in the sample in which ammonia borane covers only the internal surface of the scaffold. Such a drastic change in the main features of this compound indicates that novel thermodynamic properties can be obtained by means of the fine dispersion of NH3BH3 at a monolayer level.