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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Al(BH4)3 by Materials Project

Al(BH4)3 is Protactinium-like structured and crystallizes in the orthorhombic Pna2_1 space group. The structure is zero-dimensional and consists of four Al(BH4)3 clusters. Al3+ is bonded to six H+0.50+ atoms to form distorted AlH6 pentagonal pyramids that share edges with three BH4 tetrahedra. There is two shorter (1.77 Å) and four longer (1.78 Å) Al–H bond length. There are three inequivalent B3- sites. In the first B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share an edgeedge with one AlH6 pentagonal pyramid. There is two shorter (1.20 Å) and two longer (1.27 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 an edgeedge with one AlH6 pentagonal pyramid. There is two shorter (1.20 Å) and two longer (1.27 Å) B–H bond length. In the third B3- site, B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share an edgeedge with one AlH6 pentagonal pyramid. There is two shorter (1.20 Å) and two longer (1.27 Å) B–H bond length. There are twelve inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the third H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom. In the fourth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the fifth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the sixth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom. In the seventh H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the eighth H+0.50+ site, H+0.50+ is bonded in an L-shaped geometry to one Al3+ and one B3- atom. In the ninth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom. In the tenth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom. In the eleventh H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom. In the twelfth H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to one B3- atom.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Aluminum Borohydride Ammines as Fuels for Hybrid Rocket Motors: Theoretical Performance and Particle Synthesis

The aluminum borohydride ammines, Al(BH4)3·XNH3, are a family of complexes between aluminum borohydride and ammonia for which up to six moles of ammonia can be complexed per mole of aluminum borohydride. Two of these complexes, the diammine (X = 2) and hexammine (X = 6) are of particular interest for use in hybrid rocket motors as additives and stand alone fuels. This study compares these compounds against other metal hydride for their potential as additives to increase the regression rate of solid fuel grains. The theoretical performance of the diammine as a stand alone fuel paired with non-toxic oxidizers is also investigated. The low temperature and good performance of these combinations make them of interest for low cost orbital maneuvering thrusters. Finally, the synthesis process for Al(BH4)3·6NH3 is discussed and TGA/DSC results are presented.

hybrid rockets↗
NASA NTRSDate not supplied

Aluminum borohydride ammines as fuels for hybrid rocket motors: theoretical performance and particle synthesis

The aluminum borohydride ammines, Al(BH4)3·XNH3, are a family of complexes between aluminum borohydride and ammonia for which up to six moles of ammonia can be complexed per mole of aluminum borohydride. Two of these complexes, the diammine (X = 2) and hexammine (X = 6) are of particular interest for use in hybrid rocket motors as particle additives and stand alone fuels. This study compares these compounds against other metal hydrides for their potential to increase the regression rate of solid fuel grains. The theoretical performance of the diammine as a stand alone fuel paired with non-toxic oxidizers is also investigated. The low temperature and good performance of these combinations make them of interest for low cost orbital maneuvering thrusters. Finally, results on the synthesis of Al(BH4)3·6NH3 and its thermal characterization are presented.

hybrid rockets↗
DOE OSTI2021

A New Complex Borohydride LiAl(BH4)2Cl2

A new mixed alkali metal–aluminum borohydride LiAl(BH4)2Cl2 has been prepared via mechanochemical synthesis from the 2LiBH4–AlCl3 mixture. Structural characterization, performed using a combination of X-ray powder diffraction and solid-state NMR methods, indicates that the LiAl(BH4)2Cl2 phase adopts a unique 3D framework and crystallizes in an orthorhombic structure with the space group C2221, a = 11.6709(6) Å, b = 8.4718(4) Å, c = 7.5114(3) Å. The material shows excellent dehydrogenation characteristics, where hydrogen evolution starts at Tons = 70 °C, releasing approximately 2 wt.% of nearly pure (99.8 vol.%) hydrogen and a very small amount (~0.2 vol.%) of diborane. When compared to halide-free mixed alkali metal–aluminum borohydrides, the presence of Al‒Cl bonding in the LiAl(BH4)2Cl2 structure likely prevents the formation of Al(BH4)3 upon decomposition, thus suppressing the formation of diborane.

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

Materials Data on Li2AlB5(H19N3)2 by Materials Project

Li2(BH4)3(BH4)2Al(NH3)6 crystallizes in the trigonal P-3c1 space group. The structure is two-dimensional and consists of two Al(NH3)6 clusters; four BH4 clusters; and two Li2(BH4)3 sheets oriented in the (0, 0, 1) direction. In each Al(NH3)6 cluster, Al3+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Al–N bond lengths are 2.04 Å. N3- is bonded in a distorted trigonal non-coplanar geometry to one Al3+ and three H+0.74+ atoms. All N–H bond lengths are 1.03 Å. There are three inequivalent H+0.74+ sites. In the first H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one N3- atom. In the second H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one N3- atom. In the third H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one N3- atom. In each BH4 cluster, B3- is bonded in a tetrahedral geometry to four H+0.74+ atoms. All B–H bond lengths are 1.23 Å. There are two inequivalent H+0.74+ sites. In the first H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one B3- atom. In the second H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one B3- atom. In each Li2(BH4)3 sheet, Li1+ is bonded in a 6-coordinate geometry to six H+0.74+ atoms. There are three shorter (2.03 Å) and three longer (2.28 Å) Li–H bond lengths. B3- is bonded in a tetrahedral geometry to four H+0.74+ atoms. All B–H bond lengths are 1.23 Å. There are two inequivalent H+0.74+ sites. In the first H+0.74+ site, H+0.74+ is bonded in a single-bond geometry to one Li1+ and one B3- atom. In the second H+0.74+ site, H+0.74+ is bonded in a water-like geometry to one Li1+ and one B3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Atomic Layer Deposition for Materials-Based H2 Storage: Mg(BH4)2 as a Case Study

To meet the requirements for vehicular solid-state hydrogen (H2) storage, novel materials such as metal borohydrides have increasingly been investigated, in particular, magnesium borohydride (Mg(BH4)2). While these materials have a high H2 capacity (> 14 wt%), poor hydrogenation-dehydrogenation cyclability and material degradation, (e.g., loss of boron), need to be overcome. Prior research has indicated that nano-encapsulation and chemical additives can address these challenges. Therefore, we pursued these two strategies simultaneously with atomic layer deposition (ALD) on Mg(BH4)2. We investigated the use of metal-oxides (e.g., Al2O3, TiO2, CeO2), Pt- group metals (e.g., Pd, Ru) as well as pulsing only one precursor molecule (e.g., Al(CH3)3, BBr3, TiCl4), and assessed these modified Mg(BH4)2 in terms of their H2 storage properties. This presentation will also present the benefits and limitations of using vapor-phase techniques to modify the properties of Mg(BH4)2.

atomic layer deposition↗
DOE OSTI2021

Al2O3 Atomic Layer Deposition on Nanostructured γ-Mg(BH4)2 for H2 Storage

In the context of the growing hydrogen (H 2 ) economy, the demand for H 2 storage materials is high, and metal borohydrides are of particular interest. Magnesium borohydride, Mg(BH 4 ) 2 , has one of the highest hydrogen capacities of all known metal hydrides (14.9 wt % H) but suffers from high operating temperatures, slow kinetics for (de)hydrogenation, and the loss of capacity upon cycling. Strategies to address these challenges include nanoencapsulation and the use of chemical additives. This work is the first to utilize these two strategies simultaneously by using atomic layer deposition (ALD). For this new approach to modify borohydrides, we chose the well-studied Al 2 O 3 ALD process using trimethylaluminum and water. Although there has been limited use of aluminum-based additives for Mg(BH 4 ) 2 , we demonstrate that the low-temperature H 2 capacity was doubled, desorption kinetics were increased by a factor of 3, and 100 cycles of Al 2 O 3 suppressed the release of diborane compared to the uncoated Mg(BH4)2. We identified that the use of trimethylaluminum and water in the ALD process affected the decomposition pathway and that the Al 2 O 3 film growth is dominated by infiltration due to the high porosity of the ..gamma..-phase Mg(BH 4 ) 2 . From these results, the potential of ALD as a method to functionalize solid-state H 2 storage materials is inferred, and recommendations for future ALD processes are presented.

08 HYDROGEN↗
DOE OSTI2020

Materials Data on Na4Al3Ge3B(HO3)4 by Materials Project

Na4Al3(GeO4)3BH4 crystallizes in the cubic P-43n space group. The structure is three-dimensional and consists of two BH4 clusters and one Na4Al3(GeO4)3 framework. In each BH4 cluster, B3- is bonded in a tetrahedral geometry to four equivalent H1+ atoms. All B–H bond lengths are 1.23 Å. H1+ is bonded in a single-bond geometry to one B3- atom. In the Na4Al3(GeO4)3 framework, Na1+ is bonded in a 3-coordinate geometry to three equivalent O2- atoms. All Na–O bond lengths are 2.35 Å. Al3+ is bonded to four equivalent O2- atoms to form AlO4 tetrahedra that share corners with four equivalent GeO4 tetrahedra. All Al–O bond lengths are 1.77 Å. Ge+3.33+ is bonded to four equivalent O2- atoms to form GeO4 tetrahedra that share corners with four equivalent AlO4 tetrahedra. All Ge–O bond lengths are 1.76 Å. O2- is bonded in a trigonal planar geometry to one Na1+, one Al3+, and one Ge+3.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na4Al3Si3B(HO3)4 by Materials Project

Na4Al3(SiO4)3BH4 crystallizes in the cubic P-43n space group. The structure is three-dimensional and consists of two BH4 clusters and one Na4Al3(SiO4)3 framework. In each BH4 cluster, B3+ is bonded in a tetrahedral geometry to four equivalent H1+ atoms. All B–H bond lengths are 1.23 Å. H1+ is bonded in a single-bond geometry to one B3+ atom. In the Na4Al3(SiO4)3 framework, Na1+ is bonded in a trigonal non-coplanar geometry to three equivalent O2- atoms. All Na–O bond lengths are 2.36 Å. Al3+ is bonded to four equivalent O2- atoms to form AlO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.76 Å. Si+1.33+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent AlO4 tetrahedra. All Si–O bond lengths are 1.64 Å. O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si+1.33+ atom.

36 MATERIALS SCIENCE↗