Thermal decomposition behavior of calcium borohydride Ca(BH4)2

Kim, Jae‐Hun; Jin, Seon‐Ah; Shim, Jaesool; Cho, Young Whan

doi:10.1016/j.jallcom.2007.07.097

Cited by 114 publications

(125 citation statements)

References 21 publications

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“…This value shows good agreement with that predicted by Equation 1. The presence of two endothermic peaks corresponding to dehydrogenation suggests the formation of intermediate compounds, which is confirmed by the powder X-ray diffraction (XRD) analyses of the dehydrogenated products that were heated to approximately 663 K [78] and after the plateau in the PCT profile measured at 593 K [79]. The intermediate compound is suggested to be a CaB 2 H x compound having a HgCl 2 -type structure with Pnma symmetry according to the high-resolution synchrotron radiation powder XRD measurement [81].…”

Section: Fundamentals Of Hydrogen Storage Propertiessupporting

confidence: 82%

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Recent Progress in Metal Borohydrides for Hydrogen Storage

et al. 2011

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Abstract:The prerequisite for widespread use of hydrogen as an energy carrier is the development of new materials that can safely store it at high gravimetric and volumetric densities. Metal borohydrides M(BH 4 ) n (n is the valence of metal M), in particular, have high hydrogen density, and are therefore regarded as one such potential hydrogen storage material. For fuel cell vehicles, the goal for on-board storage systems is to achieve reversible store at high density but moderate temperature and hydrogen pressure. To this end, a large amount of effort has been devoted to improvements in their thermodynamic and kinetic aspects. This review provides an overview of recent research activity on various M(BH 4 ) n , with a focus on the fundamental dehydrogenation and rehydrogenation properties and on providing guidance for material design in terms of tailoring thermodynamics and promoting kinetics for hydrogen storage.

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Section: Fundamentals Of Hydrogen Storage Propertiessupporting

confidence: 82%

“…Experimentally, approximately 9.0 mass% of hydrogen was released when Ca(BH 4 ) 2 was heated to 800 K [78][79][80]. This value shows good agreement with that predicted by Equation 1.…”

Section: Fundamentals Of Hydrogen Storage Propertiessupporting

confidence: 77%

Recent Progress in Metal Borohydrides for Hydrogen Storage

et al. 2011

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“…-, and γ-Ca(BH 4 ) 2 are usually found and the proportion of each phase is very sensitive to the preparation condition. 26,[32][33][34][35][36] Several in situ XRD experiments have shown that R-and γ-Ca(BH 4 ) 2 transform to -Ca(BH 4 ) 2 upon increasing temperature. Theoretical work based on density functional theory 26,27,37 supports this experimental observation that R-Ca(BH 4 ) 2 is stable at low temperatures and -Ca(BH 4 ) 2 at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

Decomposition Reactions and Reversibility of the LiBH₄−Ca(BH₄)₂ Composite

et al. 2009

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LiBH 4 is one of the promising candidates for hydrogen storage materials because of its high gravimetric and volumetric hydrogen capacity. However, its high dehydrogenation temperature and limited reversibility has been a hurdle for its use in real applications. In an effort to overcome this barrier and to adjust the thermal stability, we make a composite system LiBH 4 -Ca(BH 4 ) 2 . In order to fully characterize this composite system we study xLiBH 4 + (1 -x)Ca(BH 4 ) 2 for several x values between 0 and 1, using differential scanning calorimetry, in situ synchrotron X-ray diffraction, thermogravimetric analysis, and mass spectrometry. Interestingly, this composite undergoes a eutectic melting at ca. 200°C in a wide composition range, and the eutectic composition lies between x ) 0.6 and 0.8. The decomposition characteristics and the hydrogen capacity of this composite vary with x, and the decomposition temperature is lower than both the pure LiBH 4 and Ca(BH 4 ) 2 at intermediate compositions, for example, for x ≈ 0.4, decomposition is finished below 400°C releasing about 10 wt % of hydrogen. Partial reversibility of this system was also confirmed for the first time for the case of a mixed borohydride composite.

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“…It is possible that these differences in the Raman spectra obtained at these two temperatures are due to the phase transformation of α-Ca(BH 4 ) 2 to α -Ca(BH 4 ) 2 which reportedly occurs when α-Ca(BH 4 ) 2 is heated, and continues up to ≈495 K. 30 No α-Ca(BH 4 ) 2 -related features are observed in spectra recorded at 433 K and above. This is attributed to the transformation of the α-Ca(BH 4 ) 2 phase to the β-Ca(BH 4 ) 2 phase which occurs in the ≈440 to ≈573 K range, 30,31 and possibly to the continued transformation to the α -Ca(BH 4 ) 2 phase. The spectra obtained at 433-648 K all show a broad, asymmetric feature with a shoulder on the high wavenumber side.…”

Section: In Situ Raman Spectroscopic Measurementsmentioning

confidence: 99%

“…No features are observed in the spectra obtained at 698 and 748 K. This is attributed to the decomposition of Ca(BH 4 ) 2 which is expected in the ≈620 and ≈770 K range. 30,31 To illustrate high-pressure rehydrogenation using the optical cell, the reversible nano-LiBH 4 -LiNH 2 -MgH 2 powder system was cycled in situ. The Raman spectra in the region of the N-H stretches for the as-milled powders are shown in Fig.…”

Section: In Situ Raman Spectroscopic Measurementsmentioning

confidence: 99%

Optical cell for combinatorial in situ Raman spectroscopic measurements of hydrogen storage materials at high pressures and temperatures

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Srinivasan

et al. 2011

Review of Scientific Instruments

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Articles you may be interested inAn optical cell is described for high-throughput backscattering Raman spectroscopic measurements of hydrogen storage materials at pressures up to 10 MPa and temperatures up to 823 K. High throughput is obtained by employing a 60 mm diameter × 9 mm thick sapphire window, with a corresponding 50 mm diameter unobstructed optical aperture. To reproducibly seal this relatively large window to the cell body at elevated temperatures and pressures, a gold o-ring is employed. The sample holderto-window distance is adjustable, making this cell design compatible with optical measurement systems incorporating lenses of significantly different focal lengths, e.g., microscope objectives and single element lenses. For combinatorial investigations, up to 19 individual powder samples can be loaded into the optical cell at one time. This cell design is also compatible with thin-film samples. To demonstrate the capabilities of the cell, in situ measurements of the Ca(BH 4 ) 2 and nano-LiBH 4 -LiNH 2 -MgH 2 hydrogen storage systems at elevated temperatures and pressures are reported.

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Thermal decomposition behavior of calcium borohydride Ca(BH4)2

Cited by 114 publications

References 21 publications

Recent Progress in Metal Borohydrides for Hydrogen Storage

Recent Progress in Metal Borohydrides for Hydrogen Storage

Decomposition Reactions and Reversibility of the LiBH₄−Ca(BH₄)₂ Composite

Optical cell for combinatorial in situ Raman spectroscopic measurements of hydrogen storage materials at high pressures and temperatures

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Thermal decomposition behavior of calcium borohydride Ca(BH4)2

Cited by 114 publications

References 21 publications

Recent Progress in Metal Borohydrides for Hydrogen Storage

Recent Progress in Metal Borohydrides for Hydrogen Storage

Decomposition Reactions and Reversibility of the LiBH4−Ca(BH4)2 Composite

Optical cell for combinatorial in situ Raman spectroscopic measurements of hydrogen storage materials at high pressures and temperatures

Contact Info

Product

Resources

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Decomposition Reactions and Reversibility of the LiBH₄−Ca(BH₄)₂ Composite