A hydrogen storage system includes a hydrogen storage alloy containment vessel comprising an external pressure containment vessel and a thermally conductive compartmentalization network disposed within the pressure containment vessel. The compartmentalization network creates compartments within the pressure vessel within which a hydrogen storage alloy is disposed. The compartmentalization network includes a plurality of thermally conductive elongate tubes positioned within the pressure vessel forming a coherent, tightly packed tube bundle providing a thermally conductive network between the hydrogen storage alloy and the pressure vessel. The hydrogen storage alloy is a non-pyrophoric AB.sub.2-type Laves phase hydrogen storage alloy having: an A-site to B-site elemental ratio of not more than 0.5; and an alloy composition including (in at %): Zr: 2.0-5.5, Ti: 27-31.3, V: 8.3-9.9, Cr: 20.6-30.5, Mn: 25.4-33.0, Fe: 1.0-5.9, Al: 0.1-0.4, and/or Ni: 0.0-4.0.

A hydrogen storage system includes a hydrogen storage alloy containment vessel comprising an external pressure containment vessel and a thermally conductive compartmentalization network disposed within the pressure containment vessel. The compartmentalization network creates compartments within the pressure vessel within which a hydrogen storage alloy is disposed. The compartmentalization network includes a plurality of thermally conductive elongate tubes positioned within the pressure vessel forming a coherent, tightly packed tube bundle providing a thermally conductive network between the hydrogen storage alloy and the pressure vessel. The hydrogen storage alloy is a non-pyrophoric AB.sub.2-type Laves phase hydrogen storage alloy having: an A-site to B-site elemental ratio of not more than 0.5; and an alloy composition including (in at %): Zr: 2.0-5.5, Ti: 27-31.3, V: 8.3-9.9, Cr: 20.6-30.5, Mn: 25.4-33.0, Fe: 1.0-5.9, Al: 0.1-0.4, and/or Ni: 0.0-4.0.

A rare-earth magnet containing Sm, Fe, and N contains an Me and B serving as additive elements, the Me representing at least one element selected from elements in groups 4, 5, and 6 of the periodic table, and a nanocomposite microstructure including an Fe phase, a SmFeN phase, and an MeB phase, in which the SmFeN phase includes at least a Sm.sub.2Fe.sub.17N.sub.x phase selected from the Sm.sub.2Fe.sub.17N.sub.x phase and a SmFe.sub.9N.sub.y phase, the volume percentage of the SmFe.sub.9N.sub.y phase in the microstructure is 65% or less by volume, the atomic percentage of the total content of the Me and B is 0.1 at % or more and 5.0 at % or less with respect to the total amount of Sm, Fe, the Me, and B, and the atomic percentage of Fe in all phases of compounds each containing at least one of the Me and B is 20 at % or less.

A non-pyrophoric AB.sub.2-type Laves phase hydrogen storage alloy and hydrogen storage systems using the alloy. The alloy has an A-site to B-site elemental ratio of no more than about 0.5. The alloy has an alloy composition including about (in at %): Zr: 2.0-5.5, Ti: 27-31.3, V: 8.3-9.9, Cr: 20.6-30.5, Mn: 25.4-33.0, Fe: 1.0-5.9, Al: 0.1-0.4, and/or Ni: 0.0-4.0. The hydrogen storage system has one or more hydrogen storage alloy containment vessels with the alloy disposed therein.

To provide a steel and a manufacturing method thereof that can contribute to achieving both high strength and hydrogen embrittlement resistance. The steel has a chemical composition represented by: C: 0.15% to 0.35%; Si: 0.8% to 2.5%; Mn: 0.8% to 2.5%; Al: 0.03% to 2.0%; N: 0.002% to 0.010%; P: 0.01% or less; S: 0.01% or less; O: 0.01% or less; B: 0.0001% to 0.005%; Nb: 0.0% to 0.05%; Ti: 0.0% to 0.2%; V 0.0% to 0.05%; Mo: 0.0% to 1.0%; Cr: 0.0% to 1.0%; Ni: 0.01% to 1.0%; Cu: 0.05% to 1.0%; at least one of Ca, Mg and REM: 0.0005% to 0.01%; and the balance: Fe and impurities, and has a martensite phase or/and a bainite phase in which ?-carbide is dispersedly precipitated.

A nickel hydrogen secondary battery comprises an outer can and an electrode group accommodated in a hermetically sealed state together with an alkaline electrolyte solution in the outer can, wherein the electrode group comprises a positive electrode and a negative electrode stacked through a separator, wherein the negative electrode contains a hydrogen absorbing alloy powder that is an aggregate of particles of a hydrogen absorbing alloy, wherein the hydrogen absorbing alloy powder is such that when an average particle size of the particles is represented by M; a particle size of of the M is represented by P; and a particle size of of the M is represented by Q, a content of the particles having a particle size equal to or smaller than the P is lower than 20% by mass of the whole of the hydrogen absorbing alloy powder; and the content of the particles having a particle size equal to or smaller than the Q is lower than 10% by mass of the whole of the hydrogen absorbing alloy powder.

A nickel hydrogen secondary battery comprises an outer can and an electrode group accommodated in a hermetically sealed state together with an alkaline electrolyte solution in the outer can, wherein the electrode group comprises a positive electrode and a negative electrode stacked through a separator, wherein the negative electrode contains a hydrogen absorbing alloy powder that is an aggregate of particles of a hydrogen absorbing alloy, wherein the hydrogen absorbing alloy powder is such that when an average particle size of the particles is represented by M; a particle size of of the M is represented by P; and a particle size of of the M is represented by Q, a content of the particles having a particle size equal to or smaller than the P is lower than 20% by mass of the whole of the hydrogen absorbing alloy powder; and the content of the particles having a particle size equal to or smaller than the Q is lower than 10% by mass of the whole of the hydrogen absorbing alloy powder.

A range of alloys of Mg and at least one of Cu, Si, Ni and Na alloys that is particularly suitable for hydrogen storage applications. The alloys of the invention are formed into binary and ternary systems. The alloys are essentially hypoeutectic with respect to their Cu and Ni contents, where one or both of these elements are present, but range from hypoeutectic through to hypereutectic with respect to their Si content when that element is also present. The terms hypoeutectic and hypereutectic do not apply to Na if it is added to the alloy. The alloy compositions disclosed provide high performance alloys with regard to their hydrogen storage and kinetic characteristics. They are also able to be formed using conventional casting techniques which are far cheaper and more amenable to commercial use than the alternative ball-milling and rapid solidification techniques which are much more expensive and complex. Each of the individual binary Mg-E systems, where E=Cu, Ni or Si, forms a eutectic comprising of Mg metal and a corresponding Mg.sub.xE.sub.y intermetallic phase.

A surface treatment method for a hydrogen absorbing alloy powder of the present disclosure is used for a surface treatment on a hydrogen absorbing alloy powder containing rare earth elements and nickel as constituent elements, including an immersion process in which the hydrogen absorbing alloy powder is immersed in an aqueous alkaline solution; and a removal process in which a liquid containing the hydrogen absorbing alloy powder immersed in the aqueous alkaline solution is introduced into a liquid cyclone, and undesired substances having a smaller specific gravity than the hydrogen absorbing alloy powder adhered to the surface of the hydrogen absorbing alloy powder are removed.

A hydride secondary battery includes: a pressure vessel; a positive electrode disposed in the pressure vessel; a negative electrode disposed in the pressure vessel; and hydrogen gas with which the pressure vessel is filled. The negative electrode contains a hydrogen-absorbing alloy. In a pressure-composition-temperature diagram, a desorption curve at 25 C. of the hydrogen-absorbing alloy has a plateau pressure of 0.15 MPa or more and 10 MPa or less. The hydrogen gas has a pressure equal to or higher than the plateau pressure at 25 C. of the hydrogen-absorbing alloy.