PHASE COMPOSITION OF CHOSEN MG-BASED MATERIALS DURING HYDROGEN SORPTION

1,2 ČERMÁK Jiří
Co-authors:
1 KRÁL Lubomír 1,3 ROUPCOVÁ Pavla
Institutions:
1 Institute of Physics of Materials AS CR, v.v.i., Zizkova 22, CZ-61662 Brno, Czech Republic, EU
2 CEITEC-Institute of Physics of Materials, AS CR, Zizkova 22, CZ-61662 Brno, Czech Republic, EU
3 CEITEC-Brno University of Technology, FME, IMSE, Technická 2896/2, CZ-616 69 Brno, Czech Republic, EU
Conference:
10th International Conference on Nanomaterials - Research & Application, Hotel Voronez I, Brno, Czech Republic, EU, October 17th - 19th 2018
Proceedings:
Proceedings 10th International Conference on Nanomaterials - Research & Application
Pages:
719-724
ISBN:
978-80-87294-89-5
ISSN:
2694-930X
Published:
28th February 2019
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
5 views / 2 downloads
Abstract

Phase transformation during hydrogen sorption was investigated in ten chosen magnesium-based hydrogen storage (HS) materials. Chemical composition of the materials consisted of Mg, as a principal hydrogen-binding element, additive X and amorphous carbon (CB), as an anti-sticking component. In order to assess the effect of X itself upon the structure, values of concentration of both X and CB were fixed to about 12 wt. %. The influence of X = Mg2Si, Mg2Ge, Mg17Al12, Mg5Ga2, NaCl, LiCl, NaF, LiF and two combinations Ni+Mg17Al12 and Ni+Mg2Si upon the changes in phase composition was tested. Phase content in HS materials was observed (i) after the intensive ball milling (BM), (ii) after the BM followed by hydrogen charging at 623 K and (iii) after the BM and one hydrogen charging/discharging cycle (C/D) at temperature 623 K. The study was carried out by SEM and XRD. It was found that, the C/D is approximately structurally reversible for X = Mg2Ge, Mg17Al12, NaF and LiF. However, additives X = Mg17Al12 and NaF decompose already during the BM. In alloys with combination of Ni with Mg17Al12, new phases NimAln are formed. Phase composition changed during C/D for X = Mg2Si Mg5Ga2 and Ni+Mg2Si due to equilibration of phases composition. Observed structure changes of HS materials with chloride ionic additives NaCl and LiCl are, most likely caused by the relatively strong affinity between Mg and Cl. Hydrogen storage capacity of all studied alloys was 6.0 ± 0.3 wt. % H2.

Keywords: Hydrogen storage, Mg alloys, carbon black
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