Search NASA⌕ Search

DOE OSTI · 1743194

Materials Data on Ho4HfAl15 by Materials Project

Abstract

Ho4HfAl15 is Uranium Silicide-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded to twelve Al atoms to form HoAl12 cuboctahedra that share corners with four equivalent HfAl12 cuboctahedra, corners with eight HoAl12 cuboctahedra, edges with twenty-four AlHo2Hf2Al8 cuboctahedra, a faceface with one HfAl12 cuboctahedra, faces with five HoAl12 cuboctahedra, and faces with twelve AlHo4Al8 cuboctahedra. There are a spread of Ho–Al bond distances ranging from 2.98–3.01 Å. In the second Ho site, Ho is bonded to twelve Al atoms to form HoAl12 cuboctahedra that share corners with twelve HoAl12 cuboctahedra, edges with twenty-four AlHo4Al8 cuboctahedra, faces with six HoAl12 cuboctahedra, and faces with twelve AlHo4Al8 cuboctahedra. There are a spread of Ho–Al bond distances ranging from 2.98–3.00 Å. Hf is bonded to twelve Al atoms to form HfAl12 cuboctahedra that share corners with four equivalent HfAl12 cuboctahedra, corners with eight equivalent HoAl12 cuboctahedra, edges with twenty-four AlHo2Hf2Al8 cuboctahedra, faces with two equivalent HoAl12 cuboctahedra, faces with four equivalent HfAl12 cuboctahedra, and faces with twelve AlHo2Hf2Al8 cuboctahedra. There are eight shorter (2.91 Å) and four longer (2.98 Å) Hf–Al bond lengths. There are six inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Hf and eight equivalent Al atoms to form AlHf4Al8 cuboctahedra that share corners with twelve AlHf4Al8 cuboctahedra, edges with eight equivalent HoAl12 cuboctahedra, edges with sixteen equivalent AlHo2Hf2Al8 cuboctahedra, faces with four equivalent HfAl12 cuboctahedra, and faces with fourteen AlHo2Hf2Al8 cuboctahedra. All Al–Al bond lengths are 2.91 Å. In the second Al site, Al is bonded to four equivalent Ho and eight Al atoms to form distorted AlHo4Al8 cuboctahedra that share corners with twelve AlHf4Al8 cuboctahedra, edges with four equivalent HoAl12 cuboctahedra, edges with four equivalent HfAl12 cuboctahedra, edges with sixteen AlHo2Hf2Al8 cuboctahedra, faces with four equivalent HoAl12 cuboctahedra, and faces with fourteen AlHf4Al8 cuboctahedra. There are four shorter (2.99 Å) and four longer (3.02 Å) Al–Al bond lengths. In the third Al site, Al is bonded to four equivalent Ho and eight Al atoms to form distorted AlHo4Al8 cuboctahedra that share corners with twelve AlHo4Al8 cuboctahedra, edges with eight HoAl12 cuboctahedra, edges with sixteen AlHo4Al8 cuboctahedra, faces with four equivalent HoAl12 cuboctahedra, and faces with fourteen AlHo4Al8 cuboctahedra. All Al–Al bond lengths are 2.99 Å. In the fourth Al site, Al is bonded to two equivalent Ho, two equivalent Hf, and eight Al atoms to form distorted AlHo2Hf2Al8 cuboctahedra that share corners with twelve AlHo2Hf2Al8 cuboctahedra, edges with four equivalent HoAl12 cuboctahedra, edges with four equivalent HfAl12 cuboctahedra, edges with sixteen AlHf4Al8 cuboctahedra, faces with two equivalent HoAl12 cuboctahedra, faces with two equivalent HfAl12 cuboctahedra, and faces with fourteen AlHf4Al8 cuboctahedra. All Al–Al bond lengths are 2.98 Å. In the fifth Al site, Al is bonded to four Ho and eight Al atoms to form distorted AlHo4Al8 cuboctahedra that share corners with twelve AlHo2Hf2Al8 cuboctahedra, edges with eight HoAl12 cuboctahedra, edges with sixteen AlHo4Al8 cuboctahedra, faces with four HoAl12 cuboctahedra, and faces with fourteen AlHo4Al8 cuboctahedra. All Al–Al bond lengths are 2.98 Å. In the sixth Al site, Al is bonded to four equivalent Ho and eight Al atoms to form distorted AlHo4Al8 cuboctahedra that share corners with twelve AlHo4Al8 cuboctahedra, edges with eight equivalent HoAl12 cuboctahedra, edges with sixteen AlHo4Al8 cuboctahedra, faces with four equivalent HoAl12 cuboctahedra, and faces with fourteen AlHo4Al8 cuboctahedra. All Al–Al bond lengths are 2.98 Å.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

2020-04-29. Materials Data on Ho4HfAl15 by Materials Project. https://doi.org/10.17188/1743194

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related reports

Cyclic moisture reactivation of calcium sorbents for long duration thermochemical energy storage

The transition to a flexible and reliable energy infrastructure, using electro-thermal energy generation technologies such as geothermal, concentrated solar power, and nuclear, usually demands simultaneous advancement of thermal energy storage (TES) to support on-demand electricity generation and industrial applications while mitigating the inherent intermittency of renewable energy sources and power outages from direct energy generation. Among TES technologies, thermochemical energy storage (TCES) based on calcium looping emerges as a compelling high-power energy storage candidate due to its high reaction enthalpy, compatibility with elevated operating temperatures, and abundance of low-cost materials. However, the long-term durability of calcium-based sorbents for TCES is hindered by surface sintering and particle aggregation, leading to performance degradation over repeated thermal cycles. This study explores a moisture hydration-based strategy to regenerate a degraded calcium sorbent and mitigate performance degradation for long duration TCES. The addition of moisture transforms calcium oxide into calcium hydroxide and produces intercalation water layers, associated with a regenerated surface area and reduced calcium oxide crystallite size. Both these effects are beneficial in restoring the sorbents' reactivity for carbonization. Additionally, an optimized hydration-assisted reactivation protocol balances the recovered energy storage capacity with heating penalty required for moisture removal from hydrated samples, resulting in an enhanced energy storage capacity up to 176% compared to benchmark sorbents that undergo cycling without reactivation after 60 cycles. In conclusion, these results highlight the potential of hydration-assisted reactivation to enhance the long-term performance of TCES, providing an effective pathway to advancing electro-thermal storage technologies.

36 MATERIALS SCIENCE↗