By Dr Ioana Nuta, Univ. Grenoble Alpes, France.
The hydride system LiBH4 – MgH2 has shown interesting functionalities for hydrogen storage, as reported by reacting the complex hydride (LiBH4) with another compound of binary hydride (MgH2). In the frame of COSY project, high energy ball milling, either at ambient pressure or under high pressures of inert gas (e.g. Ar) or H2 atmosphere, was established as the preferential preparation method for Reactive Hydride Composites (RHC) in order to achieve sufficient mixing of the components of the composites. The systematic identification of the gaseous phase (composition and species) of these RHC will be useful for understanding the reactional mechanisms and their kinetics during the diffusion of hydrogen across the different interfaces of segregation in this kind of materials, i.e. by studying the evolution of the gas phase – pressure and composition – emitted by the complex hydrides during ball-milling. In this respect, a set-up was built in order to couple a high energy ball mill with a mass spectrometer working with an effusion Knudsen cell. A gas flow study (from molecular to viscous regimes) was done to propose a suitable architecture of the whole device (ball-mill, capillary tubing, tubes and pipes systems, effusion cell compartment, pumping system) compatible with the mass spectrometric detection in term of effused flows. Theoretical simulation of the flows and definition of their regimes nature at each stage of the pipes and vessels system will be explained. This study highlights the advantage of using a capillary for the connection between the mill and the spectrometer. Different working pressure conditions are associated to its length, meanwhile the diameter choice has been demonstrated to be too sensitive to be varied.
I. Nuta1, A. El Kharbachi1,2, L. Artaud1, H. Collas1, A.R. Yavari1, and C. Chatillon1
(1) Univ. Grenoble Alpes, CNRS, Grenoble INP*, SIMaP, 38000 Grenoble, France.
(2) Helmholtz Institute Ulm (HIU), Germany.
Funding by COSY (EU – RTN) “Marie Curie Actions “ (MRTN-CT-2006-035366).
Ioana NUTA graduated as chemical engineer at Polytechnica University of Bucharest in 1999. In 2005, she received her PhD from Orleans University (France) by studying molten salts by high temperature NMR. She occupied a postdoctoral position at research laboratory LCS (Caen, France) and at Bruker Elektronik (Karlsruhe, Germany) where she developed NMR instruments for catalysis process studies. Since 2007 she is CNRS research scientist/HDR at SIMAP (Grenoble, France) in thermodynamics of the gaseous phase of materials, mainly, for energy production and storage, by using Knudsen effusion method coupled with mass spectrometry and calorimetry.