Formation Of Magnesium Hydride Research Articles

X-Ray absorption spectroscopy of transition metal–magnesium hydride thin films

Mixed metal thin films containing magnesium and a first-row transition element exhibit very large changes in both reflectance and transmittance on exposure to hydrogen gas. Changes in electronic structure and coordination of the magnesium and transition metal atoms during hydrogen absorption were studied using dynamic in situ transmission mode X-ray absorption spectroscopy. Mg K-edge and Ni, Co, and Ti L-edge spectra reflect both reversible and irreversible changes in the metal environments. A significant shift in the nickel L absorption edge shows it to be an active participant in hydride formation. The effect on cobalt and titanium is much less dramatic, suggesting that these metals act primarily as catalysts for formation of magnesium hydride.

Stress corrosion cracking of rapidly solidified magnesium-aluminum alloys

Stress corrosion cracking (SCC) of rapidly solidified magnesium-aluminum alloys in aqueous solutions of potassium chromate and sodium chloride was investigated using electrochemical techniques, constant displacement rate tests, and optical and electron microscopy. Microcrystalline alloys containing 1 and 9 wt% aluminum were prepared using a melt-spinning process which yields continuous ribbons 15–25 μm thick. Potential-pulse and scratched electrode experiments showed that repassivation kinetics are improved both by rapid solidification and increased aluminum content. The melt-spun alloys experienced relatively uniform attack, and repassivated more rapidly and more completely than their as-cast counterparts. Both failed by transgranular stress corrosion cracking (TGSCC) in aqueous 0.21 M K 2 CrO 4 containing 0.6M NaCl at displacement rates between 5 × 10 −5 and 9 × 10 −3 mm s −1. In 0.6M NaCl, TGSCC occurred only near 3.6 × 10 −3 mm s −1, while no stress corrosion was observed in chromate solution without chloride. Constant displacement rate tests in air after pre-exposure to the electrolyte indicated that TGSCC probably results from a hydrogen embrittlement process. Using reasonable estimates of the diffusivity of hydrogen in magnesium, analysis of the constant displacement rate and potential-pulse tests for Mg-9Al supports a model involving the formation of magnesium hydride ahead of the crack tip.

Neue Synthesen von Magnesiumhydrid / New Syntheses of Magnesium Hydride

A very easy and safe way for the production of Ni-doped magnesium hydride is reported. Another process, which is not requiring transition metals (e. g. nickel) has also been found as a means to ameliorate the kinetics of hydrogen uptake. MgH2 itself exerts a catalytic effect on the formation of magnesium hydride from the elements, i. e. by autocatalysis.

Les alliages terre rare-magnesium riches en magnesium et leur application au stockage de l'hydrogene

The LnMg 12, Ln 2Mg 17 and Ln 5Mg 41 alloys (Ln = La, Ce or mischmetal) have been investigated. The composition range and the stability of the various phases have been determined. They decompose during hydriding with formation of magnesium hydride and the corresponding rare-earth hydride. The study of absorption-desorption hydriding cycles at different temperatures and various pressures shows that these alloys could be used as high performance hydrogen storage materials.

Kinetic study of the reaction between hydrogen and magnesium, catalyzed by addition of indium

The kinetics of formation of magnesium hydride from pure activated magnesium and from some indium containing magnesium alloys has been studied. The experimental data fit the rate equation [(1−2α/3)−(1−α) 2/3] = Kt where α is the fraction of metal reacted at time t. The form of this rate expression indicates a three-dimensional diffusion-controlled reaction. The addition of small amounts of indium to magnesium lowers appreciably the activation energy of the process.

Effect of Group IIIA metal additives on the kinetics of magnesium hydride formation

Die Aktivierungsenergie der Hydrierung von Mg wird durch einen Zusatz von unter 1 Atom-% Al, Ga oder In erheblich herabgesetzt, nimmt aber mit wachsendem Ubergangsmetallgehalt der Legierung bis etwa zu dem fur reines Mg geltenden Wert zu.

Kinetics of Formation of Magnesium Hydride from Magnesium and Hydrogen

Kinetics of Formation of Magnesium Hydride from Magnesium and Hydrogen

Concerning the formation of magnesium hydride in the preparation of grignard reagents. The origin of 2-methylbenzhydrol in the reaction of methylmagnesium bromide with 2-methylbenzophenone

Concerning the formation of magnesium hydride in the preparation of grignard reagents. The origin of 2-methylbenzhydrol in the reaction of methylmagnesium bromide with 2-methylbenzophenone

The Magnesium-Hydrogen System1-3

The decomposition pressure of magnesium hydride was measured under conditions such that the precision and accuracy of the temperature and pressure measurements could be estimated and the composition of the solid phases determined. The diffusion of hydrogen through the walls of the apparatus and the solubility of hydrogen in the walls was considered. The apparatus and the method of making the measurements are described. The decomposition pressures were converted to fugacities hy use of the BeattieBridgeman equation of state for hydrogen and fitted to straight lines to give R ln f/sub H/sub 2/ = (-17,785 plus or minus 76)/T + 32.28 plus or minus 0.45 acd R ln f/sub D/sub 2/ = (- 17,480 plus or minus 110)/T + 32.48 plus or minus 0.17. Magnesium hydride, MgH/sub 2/, was found to be a stoichiometric compound within the limits of error of the measurements. The solubility of hydrogen in magnesium was found to increase from 2 atom% at 440 deg to 10 atom% at 560 deg . From these measurements thermodynamic functions for the formation of magnesium hydride and magnesium deuteride were estimated. (auth)