Mg—Ni hydrogen storage composite having high storage capacity and excellent room temperature kinetics
A hydrogen storage composite material having a Mg—Ni based alloy with a coating of a catalytically active metal deposited on at least a portion of a surface of said Mg—Ni based alloy. The coating is less than about 200 angstroms thick and preferably is formed from iron or palladium. The composite material is capable of adsorbing at least 3 weight percent hydrogen and desorbing at least 1 weight percent hydrogen at 30° C. The Mg—Ni based alloy has a microstructure including both a Mg-rich phase and a Ni-rich phase, micro-tubes having an inner core of Ni-rich material surrounded by a sheathing of Mg-rich material, amorphous structural regions and microcrystalline structural regions.
1. A hydrogen storage alloy comprising:
an Mg—Ni based alloy;
said alloy having a two-phase microstructure comprising both a Mg-rich phase and a Ni-rich phase;
said microstructure further comprising micro-tubes having an inner core of Ni-rich material surrounded by a sheathing of Mg-rich material.
2. The hydrogen storage alloy of claim 1 , wherein said two phase microstructure comprises amorphous structural regions and microcrystalline structural regions.
3. The hydrogen storage alloy of claim 1 , wherein said Mg—Ni based alloy has a magnesium content ranging from 40 to 65 atomic percent of the alloy.
4. The hydrogen storage alloy of claim 3 , wherein said Mg—Ni based alloy has a magnesium content ranging from 45 to 65 atomic percent of the alloy.
5. The hydrogen storage alloy of claim 1 , wherein said Mg—Ni based alloy has a nickel content ranging from 25 to 45 atomic percent of the alloy.
6. The hydrogen storage alloy of claim 5 , wherein said Mg—Ni based alloy has a nickel content ranging from 30 to 40 atomic percent of the alloy.
7. The hydrogen storage alloy of claim 1 , wherein said Mg—Ni based alloy further contains manganese and cobalt.
8. The hydrogen storage alloy of claim 7 , wherein said Mg—Ni based alloy has a cobalt content of between 1 and 10 atomic percent of the alloy.
9. The hydrogen storage alloy of claim 8 , wherein said Mg—Ni based alloy has a cobalt content of between 2 and 6 atomic percent of the alloy.
10. The hydrogen storage alloy of claim 7 , wherein said Mg—Ni based alloy has a manganese content of between 1 and 10 atomic percent of the alloy.
11. The hydrogen storage alloy of claim 10 , wherein said Mg—Ni based alloy has a manganese content of between 3 and 8 atomic percent of the alloy.
12. The hydrogen storage alloy of claim 7 , wherein said Mg—Ni based alloy further contains at least one element selected from the group consisting of Fe, Al, Zr, Zn, Cu, Ag, Cu, B, La, Ru, Re, Li, Cr, Pd, Si, V, Sr, Misch Metal, and mixtures thereof.
13. The hydrogen storage alloy of claim 12 , wherein said at least one element is incorporated into the alloy in a total amount of less than about 5 atomic percent of the alloy and each individual element is incorporated into said alloy in an amount of less than about 3 atomic percent.
14. The hydrogen storage alloy of claim 1 , wherein said microstructure is prepared by a process comprising the steps of:
forming a melt of the alloy;
melt quenching said melt onto a chill roller to form melt-quenched alloy ribbons, wherein the parameters of said melt-quenching are controlled such that said melt-quenched alloy ribbons have a two phase microsrturcture comprising a Mg-rich phase and a Ni-rich phase;
grinding said melt-quenched ribbons in an attritor to for a time sufficient to obtain a hydrogen storage alloy comprising the following:
1) a powder formed from said melt-quenched ribbons;
2) micro-tubes; and
3) a mixture of amorphous structural regions and microcrystalline regions.