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12 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the tetragonal P4_2 space group. The structure is three-dimensional. Ca2+ is bonded in a 10-coordinate geometry to ten H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.30–2.49 Å. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is one shorter (1.22 Å) and three longer (1.23 Å) B–H bond length. There are four inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ca2+ is bonded to twelve H+0.50+ atoms to form CaH12 cuboctahedra that share edges with four equivalent CaH12 cuboctahedra and edges with six equivalent BH4 tetrahedra. There are a spread of Ca–H bond distances ranging from 2.32–2.60 Å. B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with three equivalent CaH12 cuboctahedra. There is two shorter (1.22 Å) and two longer (1.23 Å) B–H bond length. There are two inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Ca2+ is bonded to twelve H+0.50+ atoms to form distorted CaH12 cuboctahedra that share corners with two equivalent CaH12 cuboctahedra, edges with three equivalent CaH12 cuboctahedra, and edges with six BH4 tetrahedra. There are a spread of Ca–H bond distances ranging from 2.33–2.62 Å. There are two inequivalent B3- sites. In the first B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with three equivalent CaH12 cuboctahedra. There is two shorter (1.22 Å) and two longer (1.23 Å) B–H bond length. In the second B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with three equivalent CaH12 cuboctahedra. All B–H bond lengths are 1.23 Å. There are eight inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fifth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the sixth H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the seventh H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the eighth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the tetragonal P4_2/m space group. The structure is three-dimensional. Ca2+ is bonded in a 10-coordinate geometry to ten H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.29–2.49 Å. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is two shorter (1.22 Å) and two longer (1.23 Å) B–H bond length. There are three inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Ca2+ is bonded in a 12-coordinate geometry to twelve H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.29–2.75 Å. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is one shorter (1.22 Å) and three longer (1.23 Å) B–H bond length. There are four inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight H+0.50+ atoms. There are four shorter (2.31 Å) and four longer (2.42 Å) Ca–H bond lengths. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. All B–H bond lengths are 1.22 Å. There are two inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the tetragonal P-4 space group. The structure is three-dimensional. Ca2+ is bonded in a 10-coordinate geometry to ten H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.29–2.49 Å. B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is three shorter (1.22 Å) and one longer (1.23 Å) B–H bond length. There are four inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Ca(BH4)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Ca2+ is bonded in a 10-coordinate geometry to ten H+0.50+ atoms. There are a spread of Ca–H bond distances ranging from 2.33–2.52 Å. There are two inequivalent B3- sites. In the first B3- site, B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. All B–H bond lengths are 1.23 Å. In the second B3- site, B3- is bonded in a tetrahedral geometry to four H+0.50+ atoms. There is two shorter (1.22 Å) and two longer (1.23 Å) B–H bond length. There are eight inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Ca2+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one Ca2+ and one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the fifth H+0.50+ site, H+0.50+ is bonded in a distorted L-shaped geometry to one Ca2+ and one B3- atom. In the sixth H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom. In the seventh H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent Ca2+ and one B3- atom. In the eighth H+0.50+ site, H+0.50+ is bonded in a distorted water-like geometry to one Ca2+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ca-dimers, solvent layering, and dominant electrochemically active species in Ca(BH4)2 in THF

Abstract Divalent ions (Mg, Ca, and Zn) are being considered as competitive, safe, and earth-abundant alternatives to Li-ion electrochemistry, but present challenges for stable cycling due to undesirable interfacial phenomena. We explore the formation of electroactive species in the electrolyte Ca(BH 4 ) 2 ∣THF using molecular dynamics coupled with a continuum model of bulk and interfacial speciation. Free-energy analysis and unsupervised learning indicate a majority population of neutral Ca dimers and monomers with diverse molecular conformations and an order of magnitude lower concentration of the primary electroactive charged species – the monocation, $${\rm{CaBH}}_{4}^{+}$$ CaBH 4 + – produced via disproportionation of neutral complexes. Dense layering of THF molecules within ~1 nm of the electrode surface strongly modulates local electrolyte species populations. A dramatic increase in monocation population in this interfacial zone is induced at negative bias. We see no evidence for electrochemical activity of fully-solvated Ca 2+ . The consequences for performance are discussed in light of this molecular-scale insight.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Ca(BH4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effect of Salt Concentration on the Interfacial Solvation Structure and Early Stage of Solid–Electrolyte Interphase Formation in Ca(BH 4 ) 2 /THF for Ca Batteries

The Ca 2+ solvation structure at the electrolyte/electrode interface is of central importance to understand electroreduction stability and solid–electrolyte interphase (SEI) formation for the novel multivalent Ca battery systems. Here, using an exemplar electrolyte, the concentration-dependent solvation structure of Ca(BH 4 ) 2 -tetrahydrofuran on a gold model electrode has been investigated with various electrolyte concentrations via electrochemical quartz crystal microbalance with dissipation (EQCM-D) and X-ray photoelectron spectroscopy (XPS). For the first time, in situ EQCM-D results prove that the prevalent species adsorbed at the interface is CaBH 4 + across all concentrations. As the salt concentration increases, the number of BH 4 – anions associated with Ca 2+ increases, and much larger solvated complexes such as CaBH 4 + ·4THF or Ca(BH 4 ) 3 – ·4THF form at the interface at high concentrations prior to Ca plating. Different interfacial chemistries lead to the formation of SEIs with different components demonstrated by XPS. High electrolyte concentrations reduce the solvent decomposition and promote the formation of thick, uniform, and inorganic-rich (i.e., CaO) SEI layers, which contribute to improved Ca plating efficiency and current density in electrochemical measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Fabrication and characterization of nanoscale magnesium diboride and tetraboride for propulsion and hydrogen storage applications

Abstract: Boron-loaded propellants have the potential to dramatically increase the performance of solid fuel ramjets, ducted rockets, and hybrid rocket engines. However, difficult ignition of boron decreases the combustion efficiency of these propellants. One approach to solving this problem involves the use of magnesium diboride, MgB2, which ignites easier than boron. Magnesium tetraboride, MgB4, potentially offers greater energetic performance as B has a higher energy density than Mg. However, the effect of the higher boron/metal ratio on the ignition and combustion is unclear. Nanoscale MgB2 particles and quasi 2D structures are promising propellant ingredients, but the oxidation and combustion properties of nanoscale MgB4 remain unknown. Nanoscale magnesium borides are also of interest as precursors for the synthesis of magnesium borohydride, Mg(BH4)2, a promising hydrogen storage material, but hydrogenation of MgB4 has not been studied yet. The objectives of the present work included synthesis, purification, and high-energy ball milling of MgB2 and MgB4 powders as well as investigation of their hydrogen uptake, thermal decomposition, oxidation, and combustion. The powders were fabricated by combustion synthesis and by heating in a tube furnace. The latter method was superior in the synthesis of MgB4. Oxide impurities in the synthesized powders were removed by acid leaching. Nanoscale powders were obtained by ball-mill exfoliation. The hydrogen intake of the obtained magnesium borides was examined at 700 bar and 300 ℃ and did not reveal any advantage of MgB4 over MgB2. Their thermal decomposition and oxidation were investigated with thermogravimetric analysis (TGA), while their combustion was studied using laser ignition and high-speed video recording. TGA has confirmed prior observations of multistep decomposition of magnesium borides, where each step involves formation of a boride with a higher B/Mg ratio and evaporation of formed magnesium. The oxidation rates of the borides are much higher than that of boron at temperatures over 1200 °C for MgB2 and over 900 °C for MgB4. The burning rates of non-milled MgB₂ and MgB₄ powders were much higher than for the used submicron boron. Milling the MgB₂ and MgB₄ powders further increased their burning rates. The milled MgB4 burned 7.5 times faster than submicron boron.

Combustion of metals, Solid fuels, Propellants, Hy↗