Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca
| Autor: | Torben R. Jensen, Steffen R. H. Jensen, Ulla Gro Nielsen, Elisabeth Grube |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Thermogravimetric analysis
Materials science chemistry.chemical_element 02 engineering and technology 010402 general chemistry Borohydride 01 natural sciences Hydrogen storage chemistry.chemical_compound Materials Chemistry Composite material Thermal decomposition Calcium hydride Hydride Magnesium Mechanical Engineering Magnesium borohydride Metals and Alloys 021001 nanoscience & nanotechnology In-situ powder X-ray diffraction 0104 chemical sciences chemistry Mechanics of Materials Reactive hydride composites 0210 nano-technology Diborane |
| Zdroj: | Grube, E, Jensen, S R H, Nielsen, U G & Jensen, T R 2019, ' Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH 4 ) 2-MH x, M = Li, Na, Mg, Ca ', Journal of Alloys and Compounds, vol. 770, pp. 1155-1163 . https://doi.org/10.1016/j.jallcom.2018.08.177 Grube, E, Jensen, S R H, Nielsen, U G & Jensen, T R 2019, ' Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH 4 ) 2-MH x, M = Li, Na, Mg, Ca ', Journal of Alloys and Compounds, vol. 770, no. January, pp. 1155-1163 . https://doi.org/10.1016/j.jallcom.2018.08.177 |
| DOI: | 10.1016/j.jallcom.2018.08.177 |
| Popis: | The reactivity and thermal decomposition of γ-Mg(BH4)2-MHx, M = Li, Na, Mg, and Ca composites has been examined with the objective of studying the hydrogen storage capability of the composites. The samples were prepared by manual grinding γ-Mg(BH4)2 with a metal hydride to obtain homogenous mixtures. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and simultaneous thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry was performed to analyse the decomposition mechanism, whereas solid-state 11B nuclear magnetic resonance spectroscopy and SR-PXD was used to investigate the decomposition products. Interestingly, substitution reactions take place between magnesium borohydride and lithium, sodium and calcium hydride forming the more stable metal borohydrides, M(BH4)x, M = Li, Na or Ca. The composite γ-Mg(BH4)2-LiH has a hydrogen release at T ∼380–420 °C, which indicates the formation of amorphous LiBH4 during decomposition. For the composites γ-Mg(BH4)2-NaH, formation of crystalline NaBH4 is observed by SR-PXD from T = 150–450 °C, and hydrogen release ascribed to NaBH4 is observed in MS data at T = 460–480 °C. γ-Mg(BH4)2-MgH2 composite decomposes as the individual constituents. β-Ca(BH4)2 is formed at T = 175–375 °C in the composites of γ-Mg(BH4)2-CaH2. Bragg diffraction from CaB6 at T > 370 °C is detected by SR-PXD for γ-Mg(BH4)2-CaH2 (1:0.5) but not for samples richer in CaH2. Release of diborane was not observed for any of the magnesium borohydride metal hydride composites. |
| Databáze: | OpenAIRE |
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