Phase stability and hydrogen desorption in a quinary equimolar mixture of light-metals borohydrides

Dematteis, Erika Michela; Santoru, Antonio; Poletti, Marco Gabriele; Pistidda, Claudio; Klassen, Thomas; Dornheim, Martin; Baricco, Marcello

doi:10.1016/j.ijhydene.2018.05.048

Cited by 21 publications

(28 citation statements)

References 64 publications

(62 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Only when the value of Δ H mix is close to zero, the different elements can randomly distribute in the system, and the solid solution phases can stable occur in the solid phase . In general, the mixing entropy of a system containing two different sublattices ( h presents one sublattice with a number of sites X , and k presents another sublattice with a number of sites Y ) can be defined as:

Δ S_{normalmix} = - R \{\frac{X}{X + Y} {false\sum}_{i = 1}^{N} x_{i}^{h} ln (x_{i}^{h}) + \frac{Y}{X + Y} \sum_{i = 1}^{N} x_{i}^{k} ln false(x_{i}^{k} false)\}

where R is the ideal gas constant, N is the element species in the individual sublattice, and

x_{i}^{h}

and

x_{i}^{k}

are the mole fractions of the i th element in the sublattice h and k , respectively. In HHC‐1, the values of X of carbon sublattice ( h ) and Y of metal sublattice ( k ) are equal to 1, and the value of

{false\sum}_{i = 1}^{N} x_{i}^{h} ln (x_{i}^{h})

of carbon sublattice is equal to 0.…”

Section: Resultsmentioning

confidence: 99%

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

et al. 2019

View full text Add to dashboard Cite

The formation possibility of (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C high-entropy ceramic (HHC-1) was first analyzed by the first-principles calculations, and then, it was successfully fabricated by hot-pressing sintering technique at 2073 K under a pressure of 30 MPa. The first-principles calculation results showed that the mixing enthalpy and mixing entropy of HHC-1 were −0.869 ± 0.290 kJ/mol and 0.805R, respectively. The experimental results showed that the as-prepared HHC-1 not only had an interesting single rock-salt crystal structure of metal carbides but also possessed high compositional uniformity from nanoscale to microscale. By taking advantage of these unique features, it exhibited extremely high nanohardness of 40.6 ± 0.6 GPa and elastic modulus in the range from 514 ± 10 to 522 ± 10 GPa and relatively high electrical resistivity of 91 ± 1.3 μΩ·cm, which could be due to the presence of solid solution effects. K E Y W O R D S electrical resistivity, first-principles calculations, high-entropy ceramics, mechanical properties, metal carbides

show abstract

Δ S_{normalmix} = - R \{\frac{X}{X + Y} {false\sum}_{i = 1}^{N} x_{i}^{h} ln (x_{i}^{h}) + \frac{Y}{X + Y} \sum_{i = 1}^{N} x_{i}^{k} ln false(x_{i}^{k} false)\}

where R is the ideal gas constant, N is the element species in the individual sublattice, and

x_{i}^{h}

and

x_{i}^{k}

{false\sum}_{i = 1}^{N} x_{i}^{h} ln (x_{i}^{h})

of carbon sublattice is equal to 0.…”

Section: Resultsmentioning

confidence: 99%

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

et al. 2019

View full text Add to dashboard Cite

show abstract

“…This not only suggests that (Hf 0.5 Zr 0.5 )B 2 solid solution with compositional uniformity can be stable, but also means that (Hf 0.5 Zr 0.5 )B 2 solid solution can be regarded as an ideal one . In addition, if a system involves two different sublattices: h sublattice with a number of sites X and k sublattice with a number of sites Y , the mixing entropy of the system can be defined as:

Δ S_{normalmix} = - R (\frac{X}{X + Y} \sum_{i = 1}^{N} x_{i}^{h} In(x_{i}^{h} false) + \frac{Y}{X + Y} \sum_{i = 1}^{N} x_{i}^{k} In (x_{i}^{h}))

where R is the ideal gas constant, N is the element species in the individual sublattice, and

x_{i}^{h}

and

x_{i}^{k}

are the mole fractions of the i th element in the h and k sublattices, respectively. In our case, (Hf 0.5 Zr 0.5 )B 2 solid solution consists of two different sublattices including boron sublattice ( h ) and metal sublattice ( k ).…”

Section: Resultsmentioning

confidence: 99%

Molten salt synthesis, characterization, and formation mechanism of superfine (Hf_xZr_1‐x)B₂ solid‐solution powders

Liu

Wen

et al. 2018

J Am Ceram Soc

View full text Add to dashboard Cite

High‐purity superfine (HfxZr1‐x)B2 solid‐solution powders with various chemical compositions (x = 0.2, 0.5, and 0.8) were successfully synthesized via molten salt synthesis technique at 1423 K using ZrO2, HfO2, and 20% excessive B as precursors within a KCl/NaCl molten salt for the first time. The results showed that the as‐synthesized solid‐solution powders exhibited the irregular polyhedral morphology with the average particle sizes of 170–185 nm and simultaneously possessed a single‐crystalline hexagonal structure and good compositional uniformity from nanoscale to microscale. In addition, their formation mechanisms were well interpreted by analyzing the thermodynamics of the possible chemical reactions in the molten salt.

show abstract

“…Recently, an explorative investigation of a quinary borohydride mixture showed a limited interaction of the different borohydrides in the LiBH 4 -NaBH 4 -KBH 4 -Mg(BH 4 ) 2 -Ca(BH 4 ) 2 system in the solid phase [193]. [179,180], no significant solubility in the orthorhombic and cubic phases is evidenced, while in the hexagonal phase limited solubility is detected at high temperatures.…”

Section: Solid Phasesmentioning

confidence: 99%

“…The Calphad method allows assessment of these parameters using a least square method and taking into account all available data on the system or pure compound from the available database or new experimental data [154]. Following the thermodynamic cycle described above, an estimation of the interaction parameter Ω for the liquid phase in the LiBH for the liquid phase in the LiBH 4 -NaBH 4 -KBH 4 system is reported in Table system is reported in Table For the quinary LiBH 4 -NaBH 4 -KBH 4 -Mg(BH 4 ) 2 -Ca(BH 4 ) 2 borohydride mixture, a multi-cation liquid phase has been observed for the first time, underling a strong interaction among borohydrides that could be related both to strong negative enthalpy of mixing or entropy effects [193]. Generally, in the liquid phase, a full solubility in the cation sublattice is observed, with a stabilization of the liquid mixture with respect to pure liquid borohydrides, as evidenced by the occurrence of eutectics or thermal minima.…”

Section: Liquid Phasementioning

confidence: 99%

Complex hydrides for energy storage

Milanese

Jensen

Hauback

et al. 2019

International Journal of Hydrogen Energy

147

View full text Add to dashboard Cite

In the past decades, complex hydrides and complex hydrides-based materials have been thoroughly investigated as materials for energy storage, owing to their very high gravimetric and volumetric hydrogen capacities and interesting cation and hydrogen diffusion properties. Concerning hydrogen storage, the main limitations of this class of materials are the high working temperatures and pressures, the low hydrogen absorption and desorption rates and the poor cycleability. In the past years, research in this field has been focused on understanding the sorption mechanism of the pristine and catalysed materials and on the characterization of the thermodynamic aspects, in order to rationally choose the composition and the stoichiometry of the systems in terms of hydrogen active phases and catalysts/destabilizing agents. Moreover, new materials have been discovered and characterized in an attempt to find systems with properties suitable for practical on-board and *Manuscript Click here to view linked References stationary applications. A significant part of this rich and productive activity has been performed by the research groups led by Experts of the International Energy Agreement Task 32, often in collaborative research projects. The most recent findings of these joint activities and other noteworthy recent results in the field are reported in this paper.

show abstract

Phase stability and hydrogen desorption in a quinary equimolar mixture of light-metals borohydrides

Cited by 21 publications

References 64 publications

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

Molten salt synthesis, characterization, and formation mechanism of superfine (Hf_xZr_1‐x)B₂ solid‐solution powders

Complex hydrides for energy storage

Contact Info

Product

Resources

About

Phase stability and hydrogen desorption in a quinary equimolar mixture of light-metals borohydrides

Cited by 21 publications

References 64 publications

First‐principles study, fabrication, and characterization of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high‐entropy ceramic

First‐principles study, fabrication, and characterization of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high‐entropy ceramic

Molten salt synthesis, characterization, and formation mechanism of superfine (HfxZr1‐x)B2 solid‐solution powders

Complex hydrides for energy storage

Contact Info

Product

Resources

About

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

First‐principles study, fabrication, and characterization of (Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C high‐entropy ceramic

Molten salt synthesis, characterization, and formation mechanism of superfine (Hf_xZr_1‐x)B₂ solid‐solution powders