Paul Hug

Hydrogen–deuterium exchange experiments to probe the decomposition reaction of sodium alanate

NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of dopants on the sorption kinetics triggered the investigation of this empirical finding. In this paper, a short review of the state of the art is given. To gain further understanding of the mechanisms involved we label the interacting species during the sorption process. This was experimentally realized by hydrogen-deuterium exchange measurements during the decomposition of NaAlH(4) followed by thermogravimetry, Raman spectroscopy and mass spectrometry. By these experiments we are able to obtain specific information on the diffusing species and formation of intermediates. The activation energy of tracer diffusion in NaAlH(4) is found to be 0.28 eV. The results are evidence for a vacancy-mediated desorption process of NaAlH(4).

Hydrogen-deuterium exchange in bulk LiBH4

Because of its apparent simplicity, diffusion of hydrogen in solids can be regarded as a general model system for diffusion. However, only rudimentary knowledge exists for the dynamics of hydrogen in complex hydrides. Insight into the specific diffusion process is given by hydrogen-deuterium exchange experiments. Thermogravimetry and Raman spectroscopy are used to measure the hydrogen-deuterium exchange during the decomposition of LiBH4. At a temperature of 523 K the self-diffusion constant of deuterium in LiBH4 is estimated to be D approximately 7 x 10(-14) m(2) s(-1). A careful analysis of the Raman spectra shows that hydrogen is statistically exchanged by deuterium in LiBH4; i.e., the diffusing species is assumed to be the single hydrogen atom.

The effects of switching time and SrTiO3-xNy nanostructures on the operation of Al/SrTiO 3-x N y /Al memristors

The nanostructure and switching properties of the Al/SrTiO3-xNy/Al memristors have been investigated. It was found that the formation of stacking faults defects in the perovskite structure during plasma nitridation facilitates resistivity switching in Al/SrTiO3-xNy/Al memristors. From thermal emission measurements we observed local heating of the Al/SrTiO3-xNy anode interface (285oC) during switching when the interface becomes rectified due to the formation of locally undoped region. A model for resistivity switching and parameters affecting the memristor operation is discussed considering the electromigration theory. The I-V curves are analyzed taking into account the tunnel barrier formations and an inhomogeneous Schottky barrier modification at the anode interface.