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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Critical Shape for the Growth of Grain Boundary Twin Embryos in Mg and Mg Alloys: Crystal Plasticity Modeling

Application of polycrystalline hexagonal close packed (HCP) metals in engineering designs has been constrained by their anisotropic responses due to twinning and limited plasticity. In deformation, twins most often initiate at grain boundaries (GBs), and thicken and propagate across the grain. In this work, the GB twin embryos in Mg and Mg alloys, and the conditions that influence their propagation are investigated. Using a micromechanical crystal plasticity model, the role of embryo shape on the driving forces prevailing at the embryo boundaries that could support its expansion is studied. The modeled embryos are either planar, extending more in the shear direction than normal to the twin plane, or equiaxed. Results show that the thinner the embryo, the greater the driving forces for both thickening and forward propagation. Alloys with low prismatic-to-basal critical resolved shear stress (CRSS) ratios promote embryo thickening and large CRSS values for the slip mode that primarily accommodates the twin shear encourage propagation. The neighboring grains with orientations that enable local accommodation of the embryo twin shear by pyramidal slip promote forward propagation but have little effect on thickening. When two like embryos lie along the same GB, their paired interaction promotes forward propagation but hinders thickening.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A New Recycled Al–Si–Mg Alloy for Sustainable Structural Die Casting Applications

The use of secondary aluminum for structural components in the automotive industry is limited by the high Fe contents in recycled alloys which often result in the formation of brittle β-Al 5 FeSi phase which reduces the ductility of aluminum castings. In this study, a new secondary Al-Si-Mg alloy with high Fe content (about 0.44 wt.%) was developed for die casting applications. Based on thermodynamic modeling, manganese was added to obtain a designed Fe-to-Mn ratio of 2 which successfully suppressed the formation of β-Al 5 FeSi phase, by forming α-Al 15 (Fe,Mn) 3 Si 2 phase with rounded or hexagonal morphology. Additionally, a fine needle-like π-Al 8 FeMg 3 Si 2 phase was also formed within the eutectic regions. The new recycled alloy showed comparable mechanical properties in as-cast and heat treated (T5 and T6) conditions to three major primary die cast alloys (≤ 0.2 wt.% Fe) with similar composition. Ductility up to 7.4% from tensile elongation was achieved in as-cast recycled alloy due to the modification and refinement of α-Al 15 (Fe,Mn) 3 Si 2 by Mn and Sr additions. Tensile elongation was further improved to 9.1% after T6 treatment as a result of dissolution of π-Al 8 FeMg 3 Si 2 phase, defragmentation of α-Al 15 (Fe,Mn) 3 Si 2 and the spheroidization of Si phase. This new alloy provides a promising path for increasing usage of recycled aluminum with high Fe content in structural die castings for automotive and other applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Physical origins of the varying performance and unusual transport behaviors among thermoelectric A Mg 2 Sb 2 materials ( A = Ca, Sr, Sm, Yb, and Mg)

Contrary to the similar thermoelectric performance among both AZn 2 Sb 2 and AMg 2 Bi 2 compounds, their isostructural counterparts, AMg 2 Sb 2 , can exhibit thermoelectric figure of merit values that vary by orders of magnitude with different A elements. Here, we reveal physical origins accounting for the significantly differing performance among AMg 2 Sb 2 -based compounds (A = Ca, Sr, Sm, Yb, and Mg) through comprehensive analyses, where it is shown that the dispar- ities in performance at the macroscale essentially originate from the widely varying activation energies that equal amounts of dopant can induce. Meanwhile, a few unusual transport behaviors regarding electrical conductivity, carrier concentration, or lattice thermal con- ductivity among these compounds have been identified, and we also present their rationales in depth. Furthermore, this mechanism-focused study can not only promote further understanding of the complex transport behaviors in condensed matter but be instrumental in rationally tun- ing the physical properties of materials as well.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Salt Effects on Li-Ion Exchange Kinetics of Na 2 Mg 2 P 3 O 9 N: Systematic In Situ Synchrotron Diffraction Studies

The kinetics and thermodynamics of solid-state ion exchange of Li+ into Na2Mg2P3O9N were investigated using in situ synchrotron X-ray diffraction methods for a series of Li-containing salts, allowing systematic trends with general applicability to ion exchange reactions to be elucidated. The collection of data for a wide range of reaction conditions was enabled through the use of a novel multiwell sample environment which leverages the ability of the synchrotron beamline to rapidly (similar to 1 s) collect high-quality data suitable for monitoring reaction progress. From these data, it was possible to resolve the influence of salt choice and salt concentration on the ion exchange reaction kinetics. Furthermore, by carrying out experiments at different temperatures, initial estimates of activation energies were obtained. It was generally found that the ion exchange reaction kinetics strongly depended on the salt chosen as the ion source rather than being primarily determined by the ion mobility of the ceramic.

Cosby, Monty R.↗
DOE OSTI2023

X-ray imaging of liquid-liquid Mg cavitation

The coupling of dynamic loading platforms with synchrotron light sources have enabled experiments examining void formation in optically opaque materials. Much like spallation in a solid, cavitation occurs when rarefaction waves collide within a liquid. The resulting deformation leads to a complex flow field with numerous voids. It has been suggested that compaction of such a structure may be a significant source of ejecta (i.e. shallow bubble collapse). Experiments imaging supported and unsupported shocks interacting with a free surface in shock melted Mg with synchrotron radiation are presented. Here, the results are used to examine the structure of a cavitation plane that forms in the unsupported case and provide an estimate of the porosity within this region.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Mechanisms of Water-Stimulated Mg 2+ Intercalation in Vanadium Oxide: Toward the Development of Hydrated Vanadium Oxide Cathodes for Mg Batteries

As lithium-ion batteries approach their theoretical limits for energy density, magnesium-ion batteries are emerging as a promising next-generation energy storage technology. However, progress in magnesium-ion battery research has been stymied by a lack of available high capacity cathode materials that can reversibly insert magnesium ions. Vanadium Oxide (V 2 O 5 ) has emerged as one of the more promising candidate cathode materials, owing to its high theoretical capacity, facile synthesis methods, and relatively high operating voltage. This review focuses on the outlook of hydrated V 2 O 5 structures as a high capacity cathode material for magnesium-ion batteries. In general, V 2 O 5 structures exhibit poor experimental capacity for magnesium-ion insertion due to sluggish magnesium-ion insertion kinetics and poor electronic conductivity. However, several decades ago, it was discovered that the addition of water to organic electrolytes significantly improves magnesium-ion insertion into V 2 O 5 . This review clarifies the various mechanisms that have been used to explain this observation, from charge shielding to proton insertion, and offers an alternative explanation that examines the possible role of structural hydroxyl groups on the V 2 O 5 surface. While the mechanism still needs to be further studied, this discovery fueled new research into V 2 O 5 electrodes that incorporate water directly as a structural element. The most promising of these hydrated V 2 O 5 materials, many of which incorporate conductive additives, nanostructured architectures, and thin film morphologies, are discussed. Ultimately, however, these hydrated V 2 O 5 structures still face a significant barrier to potential applications in magnesium-ion batteries. During full cell electrochemical cycling, these hydrated structures tend to leach water into the electrolyte and passivate the surface of the magnesium anode, leading to poor cycle life and low capacity retention. Recently, some promising strides have been made to remedy this problem, including the use of artificial solid electrolyte interphase layers as an anode protection scheme, but a call to action for more anode protection strategies that are compatible with trace water and magnesium metal is required.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on Mg(AlB14)2 by Materials Project

Mg(AlB14)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to sixteen B atoms. There are a spread of Mg–B bond distances ranging from 2.33–2.91 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to twelve B atoms. There are a spread of Mg–B bond distances ranging from 2.45–2.73 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded in a 6-coordinate geometry to fourteen B atoms. There are a spread of Al–B bond distances ranging from 2.04–2.60 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to twelve B atoms. There are a spread of Al–B bond distances ranging from 2.05–2.49 Å. In the third Al site, Al is bonded in a 6-coordinate geometry to fourteen B atoms. There are a spread of Al–B bond distances ranging from 2.08–2.61 Å. In the fourth Al site, Al is bonded in a 10-coordinate geometry to ten B atoms. There are a spread of Al–B bond distances ranging from 2.18–2.69 Å. There are fifty-six inequivalent B sites. In the first B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.72–1.85 Å. In the second B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.84 Å. In the third B site, B is bonded in a 6-coordinate geometry to one Mg, one Al, and four B atoms. There are a spread of B–B bond distances ranging from 1.72–2.01 Å. In the fourth B site, B is bonded in a 6-coordinate geometry to one Mg, one Al, and four B atoms. There is one shorter (1.77 Å) and one longer (1.78 Å) B–B bond length. In the fifth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.77–1.84 Å. In the sixth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.76–1.85 Å. In the seventh B site, B is bonded in a 6-coordinate geometry to six B atoms. There are a spread of B–B bond distances ranging from 1.73–1.84 Å. In the eighth B site, B is bonded in a 8-coordinate geometry to one Mg, one Al, and six B atoms. There are a spread of B–B bond distances ranging from 1.77–1.84 Å. In the ninth B site, B is bonded in a 8-coordinate geometry to one Mg, one Al, and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.85 Å. In the tenth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.85 Å. In the eleventh B site, B is bonded in a 8-coordinate geometry to two Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.85 Å. In the twelfth B site, B is bonded in a 6-coordinate geometry to one Mg, one Al, and six B atoms. There are a spread of B–B bond distances ranging from 1.73–1.81 Å. In the thirteenth B site, B is bonded in a 6-coordinate geometry to one Mg, one Al, and six B atoms. There are a spread of B–B bond distances ranging from 1.80–1.83 Å. In the fourteenth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is one shorter (1.80 Å) and one longer (1.82 Å) B–B bond length. In the fifteenth B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. There are a spread of B–B bond distances ranging from 1.79–1.82 Å. In the sixteenth B site, B is bonded in a 6-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.73–1.81 Å. In the seventeenth B site, B is bonded in a 6-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.82 Å. In the eighteenth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There is two shorter (1.76 Å) and one longer (1.85 Å) B–B bond length. In the nineteenth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.75–1.81 Å. In the twentieth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. The B–B bond length is 1.77 Å. In the twenty-first B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is one shorter (1.76 Å) and one longer (1.79 Å) B–B bond length. In the twenty-second B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. The B–B bond length is 1.75 Å. In the twenty-third B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.74–1.84 Å. In the twenty-fourth B site, B is bonded in a 8-coordinate geometry to two Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.80–1.84 Å. In the twenty-fifth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There is three shorter (1.78 Å) and one longer (1.85 Å) B–B bond length. In the twenty-sixth B site, B is bonded in a 7-coordinate geometry to one Mg, two Al, and four B atoms. There is one shorter (1.75 Å) and one longer (2.05 Å) B–B bond length. In the twenty-seventh B site, B is bonded in a 7-coordinate geometry to one Mg, two Al, and four B atoms. There is one shorter (1.75 Å) and one longer (1.81 Å) B–B bond length. In the twenty-eighth B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. The B–B bond length is 1.79 Å. In the twenty-ninth B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. There are a spread of B–B bond distances ranging from 1.77–1.82 Å. In the thirtieth B site, B is bonded in a 6-coordinate geometry to two Al and four B atoms. There is one shorter (1.74 Å) and one longer (2.07 Å) B–B bond length. In the thirty-first B site, B is bonded in a 6-coordinate geometry to two Al and four B atoms. There is one shorter (1.75 Å) and one longer (1.80 Å) B–B bond length. In the thirty-second B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There is one shorter (1.75 Å) and one longer (1.81 Å) B–B bond length. In the thirty-third B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is two shorter (1.78 Å) and one longer (1.79 Å) B–B bond length. In the thirty-fourth B site, B is bonded in a 8-coordinate geometry to one Mg, one Al, and six B atoms. The B–B bond length is 1.81 Å. In the thirty-fifth B site, B is bonded in a 8-coordinate geometry to one Mg, one Al, and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.86 Å. In the thirty-sixth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.84 Å. In the thirty-seventh B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.84 Å. In the thirty-eighth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There are a spread of B–B bond distances ranging from 1.78–1.85 Å. In the thirty-ninth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.79–1.82 Å. In the fortieth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is one shorter (1.74 Å) and one longer (1.83 Å) B–B bond length. In the forty-first B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is one shorter (1.78 Å) and two longer (1.83 Å) B–B bond length. In the forty-second B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. There is one shorter (1.77 Å) and one longer (1.80 Å) B–B bond length. In the forty-third B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There are a spread of B–B bond distances ranging from 1.76–1.83 Å. In the forty-fourth B site, B is bonded in a 6-coordinate geometry to one Al and six B atoms. There is one shorter (1.72 Å) and two longer (1.80 Å) B–B bond length. In the forty-fifth B site, B is bonded in a 6-coordinate geometry to one Al and six B atoms. There is one shorter (1.78 Å) and one longer (1.83 Å) B–B bond length. In the forty-sixth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. There is two shorter (1.79 Å) and one longer (1.84 Å) B–B bond length. In the forty-seventh B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. There is one shorter (1.77 Å) and two longer (1.81 Å) B–B bond length. In the forty-eighth B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. The B–B bond length is 1.78 Å. In the forty-ninth B site, B is bonded in a 8-coordinate geometry to two Al and six B atoms. Both B–B bond lengths are 1.79 Å. In the fiftieth B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. In the fifty-first B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. The B–B bond length is 1.88 Å. In the fifty-second B site, B is bonded in a 7-coordinate geometry to one Mg and six B atoms. Both B–B bond lengths are 1.79 Å. In the fifty-third B site, B is bonded in a 6-coordinate geometry to two Al and four B atoms. There is one shorter (1.73 Å) and one longer (2.00 Å) B–B bond length. In the fifty-fourth B site, B is bonded in a 6-coordinate geometry to two Al and four B atoms. The B–B bond length is 1.82 Å. In the fifty-fifth B site, B is bonded in a 7-coordinate geometry to one Al and six B atoms. In the fifty-sixth B site, B is bonded in a 6-coordinate geometry to six B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(B3O8)2 by Materials Project

Mg(B3O8)2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of two Mg(B3O8)2 ribbons oriented in the (0, -1, 1) direction. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a distorted hexagonal planar geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 2.03–2.08 Å. In the second Mg site, Mg is bonded in a distorted octahedral geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 2.00–2.54 Å. There are six inequivalent B sites. In the first B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.55 Å. In the second B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.55 Å. In the third B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.54 Å. In the fourth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.37–1.39 Å. In the fifth B site, B is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.37 Å) and two longer (1.38 Å) B–O bond length. In the sixth B site, B is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.34 Å) and one longer (1.49 Å) B–O bond length. There are sixteen inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the second O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the fourth O site, O is bonded in a single-bond geometry to one B atom. In the fifth O site, O is bonded in a single-bond geometry to one B atom. In the sixth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. The O–O bond length is 1.31 Å. In the seventh O site, O is bonded in a single-bond geometry to one Mg atom. In the eighth O site, O is bonded in a single-bond geometry to one Mg atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Mg and one O atom. In the tenth O site, O is bonded in a trigonal non-coplanar geometry to three B atoms. In the eleventh O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the twelfth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fourteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fifteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the sixteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(B3O8)2 by Materials Project

Mg(B3O8)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two Mg(B3O8)2 sheets oriented in the (1, 0, 0) direction. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 6-coordinate geometry to six O atoms. There are two shorter (2.02 Å) and four longer (2.04 Å) Mg–O bond lengths. In the second Mg site, Mg is bonded in a distorted octahedral geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 1.99–2.36 Å. There are six inequivalent B sites. In the first B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.43–1.55 Å. In the second B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.54 Å. In the third B site, B is bonded to four O atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.55 Å. In the fourth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.34–1.48 Å. In the fifth B site, B is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.37 Å) and one longer (1.38 Å) B–O bond length. In the sixth B site, B is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.34 Å) and one longer (1.50 Å) B–O bond length. There are sixteen inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the second O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Mg and one B atom. In the fourth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. The O–O bond length is 1.33 Å. In the fifth O site, O is bonded in a single-bond geometry to one B atom. In the sixth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. The O–O bond length is 1.32 Å. In the seventh O site, O is bonded in a single-bond geometry to one Mg atom. In the eighth O site, O is bonded in a distorted single-bond geometry to one Mg and one O atom. In the ninth O site, O is bonded in a distorted linear geometry to one Mg and one O atom. In the tenth O site, O is bonded in a trigonal non-coplanar geometry to three B atoms. In the eleventh O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the twelfth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fourteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fifteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the sixteenth O site, O is bonded in a bent 120 degrees geometry to two B atoms.

36 MATERIALS SCIENCE↗