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Comparison of the thermochemical and mechanochemical transformations in the 2NaNH2–MgH2 system

Pireddu, Giovanni and Valentoni, Antonio and Bonatto Minella, Christian and Pistidda, Claudio and Milanese, Chiara and Enzo, Stefano and Mulas, Gabriele Raimondo Celestino and Garroni, Sebastiano (2015) Comparison of the thermochemical and mechanochemical transformations in the 2NaNH2–MgH2 system. International journal of hydrogen energy, Vol. 40 (4), p. 1829-1835. ISSN 0360-3199. eISSN 1879-3487. Article.

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DOI: 10.1016/j.ijhydene.2014.11.145

Abstract

We focus on the chemical transformations involved in the 2NaNH2 + MgH2 system subjected to thermal and mechanical inputs. Transformations occurring on the powder mixture during thermochemical and echanochemical processes are described by ex-situ X-ray powder diffraction (XRPD), FT-IR spectroscopy, differential scanning calorimetry and manometric measurements. In the thermally activated samples, the reaction take place through the fast formation of Mg(NH2)2 and NaH via metathesis reaction between NaNH2 and MgH2 at 125 °C. FT-IR analysis confirms the presence of unreacted NaNH2 and a new Na-amide phase that could be ascribable to tetramide, Na2Mg(NH2)4. At higher temperature, the formation of new imide-amide phase is detected, stables up to 300 °C. On the other hand when the initial mixture is subjected to mechanochemical processing for longer milling time (50 h), only Mg(NH2)2 and NaH are produced. The hydrogen desorption reaction of the as-milled Mg(NH2)2–NaH mixture starts at 100 °C together with the formation of the NaMg(NH2)(NH) imide-amide phase, equally to the initial mixture.

Item Type:Article
ID Code:10614
Status:Published
Refereed:Yes
Uncontrolled Keywords:Hydrogen storage materials, Sodium amide, Magnesium hydride, metathesis reaction, mechanochemical transformation
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:Elsevier
ISSN:0360-3199
eISSN:1879-3487
Copyright Holders:© 2014, Hydrogen Energy Publications, LLC. Published by Elsevier L.
Deposited On:14 Jan 2015 11:35

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