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At least 19 records

The Corrosion of Magnesium and of the Magnesium Aluminum Alloys Containing Manganese

The extensive use of magnesium and its alloys in aircraft has been seriously handicapped by the uncertainties surrounding their resistance to corrosion. This problem has been given intense study by the American Magnesium Corporation and at the request of the Subcommittee on Materials for Aircraft of the National Advisory Committee for Aeronautics this report was prepared on the corrosion of magnesium. The tentative conclusions drawn from the experimental facts of this investigation are as follows: the overvoltage of pure magnesium is quite high. On immersion in salt water the metal corrodes with the liberation of hydrogen until the film of corrosion product lowers the potential to a critical value. When the potential reaches this value it no longer exceeds the theoretical hydrogen potential plus the overvoltage of the metal. Rapid corrosion consequently ceases. When aluminum is added, especially when in large amounts, the overvoltage is decreased and hydrogen plates out at a much lower potential than with pure magnesium. The addition of small amount of manganese raises the overvoltage back to practically that of pure metal, and the film is again negative.

Boyer, J A

Structural and chemical evolutions of a magnesium vanadium oxide cathode under electrochemical cycling in magnesium batteries

The design of cathode materials that remain chemically and structurally stable during repetitive ion insertion and extraction poses a significant challenge in developing multivalent batteries. The cycling stability of traditional metal oxide-based cathode is challenged by sluggish diffusion of multivalent cations and parasitic reactivity at interfacial regimes, including the cathode electrolyte interphase layer (CEI). Understanding the reactions at the cathode-electrolyte interface, particularly those induced by non-stoichiometric surface layers, is a crucial design parameter for both cathode materials and electrolytes. Here, in this study, we employed multimodal analysis, including in situ and ex situ X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) to examine the surface reactions and subsequent structural and chemical evolutions of the CEI on high voltage magnesium vanadium oxide (MgV 2 O 4 ) spinel cathode during the Mg 2+ insertion/extraction processes. The results revealed that the presence of non-stoichiometric surface layers in the magnesium vanadium oxide cathode drive the decomposition of bis(trifluoromethanesulfonyl)imide (TFSI - ) anion, leading to the formation of the CEI layer. The CEI layer could inhibit the Mg 2+ ion transfer processes. Accompanying this reactivity-driven degradation, the magnesium vanadium oxide cathode undergoes pulverization, forming clusters of nanosized particles. This process likely improves cycling ability by creating new intercalation sites and shortening the diffusion pathway for the Mg 2+ cations. This study demonstrates that controlling surface stoichiometry and engineering morphological properties are critical design parameters for high performance cathodes for multivalent batteries.

25 ENERGY STORAGE

Evidence Connecting Mercury's Magnesium Exosphere to Its Magnesium-Rich Surface Terrane

Mercury is surrounded by a tenuous, collisionless exosphere where the surface of the planet is directly exposed to the space environment. As a consequence, impacts and space weathering processes are expected to eject atoms and molecules from the surface into the exosphere, implying a direct link between the exospheric composition and the planet's regolith material. However, observational evidence demonstrating this link has been elusive. Here we report that exospheric magnesium, a species recently discovered and systematically measured by the Mercury Surface, Space ENvironment, GEochemistry, and Ranging mission, is enhanced when observed over a portion of the planet's surface regolith rich in magnesium. These observations confirm a direct link between Mercury's magnesium exosphere and the underlying crustal surface composition, providing strong evidence supporting theoretical arguments that impact vaporization can directly supply material to the exosphere from the regolith of a rocky, airless body.

Mercury

Nondestructive spot test method for magnesium and magnesium alloys

A method for spot test identification of magnesium and various magnesium alloys commonly used in aerospace applications is described. The spot test identification involves color codes obtained when several drops of 3 M hydrochloric acid are placed on the surface to be tested. After approximately thirty seconds, two drops of this reacted acid is transferred to each of two depressions in a spot plate for additions of other chemicals with subsequent color changes indicating magnesium or its alloy.

Wilson, M. L.

Evidence Connecting Mercury's Magnesium Exosphere to its Magnesium-Rich Surface Terrane

Mercury is surrounded by a tenuous, collisionless exosphere where the surface of the planet is directly exposed to the space environment. As a consequence, impacts and space weathering processes are expected to eject atoms and molecules from the surface into the exosphere, implying a direct link between the exospheric composition and the planet's regolith material. However, observational evidence demonstrating this link has been elusive. Here we report that exospheric magnesium, a species recently discovered and systematically measured by the Mercury Surface, Space ENvironment, GEochemistry, and Ranging mission, is enhanced when observed over a portion of the planet's surface regolith rich in magnesium. These observations confirm a direct link between Mercury's magnesium exosphere and the underlying crustal surface composition, providing strong evidence supporting theoretical arguments that impact vaporization can directly supply material to the exosphere from the regolith of a rocky, airless body.

Mercury atmosphere

Evidence Connecting Mercury's Magnesium Exosphere to Its Magnesium‐Rich Surface Terrane

Mercury is surrounded by a tenuous, collisionless exosphere where the surface of the planet is directly exposed to the space environment. As a consequence, impacts and space weathering processes are expected to eject atoms and molecules from the surface into the exosphere, implying a direct link between the exospheric composition and the planet's regolith material. However, observational evidence demonstrating this link has been elusive. Here we report that exospheric magnesium, a species recently discovered and systematically measured by the Mercury Surface, Space ENvironment, GEochemistry, and Ranging mission, is enhanced when observed over a portion of the planet's surface regolith rich in magnesium. These observations confirm a direct link between Mercury's magnesium exosphere and the underlying crustal surface composition, providing strong evidence supporting theoretical arguments that impact vaporization can directly supply material to the exosphere from the regolith of a rocky, airless body.

Aimee W. Merkel

Graphene Activated Magnesium Diboride for Moderate Pressure and Temperature Hydrogenation to Magnesium Borohydride

The hydrogenation conditions of magnesium diboride (MgB2) to magnesium borohydride (Mg(BH4)2) can be significantly enhanced through the discovery of improved modifiers. This study demonstrates that the modification of MgB2 by mechanical milling with graphene nanoplatelets significantly reduces the hydrogenation conditions of MgB2 from 900 bar and 400 degrees C for pure MgB2 to 400 bar and 300 degrees C while achieving 77% conversion to Mg(BH4)2. The introduction of the graphene additives coupled with milling leads to a reduction of the temperature and pressure required for bulk hydrogenation by 100 degrees C and 500 bar, respectively, from that of pure MgB2. The identification of graphene additives that drastically improve the hydrogenation conditions of MgB2 represents an important step toward improving hydrogen uptake kinetics to Mg(BH4)2.

complex hydrides

Isotopically pure magnesium isotope-24 is prepared from magnesium-24 oxide

Apparatus is used to prepare isotopically pure magnesium isotope-24, suitable for use in neutron scattering and polarization experiments. The apparatus permits thermal reduction of magnesium-24 oxide with aluminum and calcium oxide, and subsequent vaporization of the product metal in vacuum. It uses a resistance-heated furnace tube and cap assembly.

Chellew, N. R.

Investigation of the Surface Chemistry of Magnesium and Magnesium Alloy Powders

Magnesium (Mg) and Mg alloy powders are generally difficult to sinter at atmospheric pressure in inert atmospheres purportedly due to the presence of powder particle surface oxide layers. To better understand sintering of Mg and Mg alloy powders, x-ray photoelectron spectroscopy (XPS) was performed to characterize the surface chemistry of gas atomized pure Mg and Mg alloys AZ91D and WE43 powders. These results are used to quantitatively determine the surface chemistry of these powders. Additionally, equilibrium thermodynamic modeling of these Mg/Mg alloys materials exposed to oxygen down to part per billion concentrations are presented for relative comparison to experimental XPS results. Analysis of these results are intended to improve sintering of Mg and Mg alloy powder materials through more quantitative knowledge of powder surface chemistry.

25 ENERGY STORAGE

High resolution observations of magnesium II 2800 A in Alpha Centauri A - The density of interstellar magnesium II and the stellar chromospheric profiles

The profiles are virtually identical with the solar profiles except for the presence of an absorption feature near line center in the h and k lines of Alpha Centauri A. It is found that this absorption feature can be explained by interstellar absorption of Mg II along the line of sight. The average density of Mg II is found to be 2.75 plus or minus 0.7 x 10 to the -7th/cu cm, in good agreement with the previously determined values in the solar vicinity in the direction of Alpha CMa and Alpha Lyr.

Oegerle, W. R.