Method for sintering La-Mg-Ni based type AB3 hydrogen storage alloy in magnetic field

Abstract

The invention relates to a method for preparing La-Mg-Ni based AB3 type hydrogen storage alloy by magnetic field sintering, which belongs to the technical field of metallic functional material and powder metallurgy. The method mainly comprises the following steps: firstly, mixing La and Mg metal powder or master alloy La2Mg prepared by a molten salt method with one or two of Ni powder, Co powder or Cu powder according to the atom molar mass proportion of AB3, and pre-ball milling the mixture by adopting proper technology; secondly, pressing the milled and mixed raw material powder under a pressure of between 200 and 500MPa into a cake of Phi 15mmx(3-5)mm, putting the cake into a self-made high-pressure reaction kettle and filling 0.5MPa argon after repeated vacuum pumping; and finally putting the high-pressure kettle into a steady high magnetic field of between 1 and 8T and heating to between 610 and 850 DEG C, sintering the cake and slowly reducing the temperature to obtain the La-Mg-Ni based AB3 type hydrogen storage alloy. The material prepared by the method has the advantages of high activity, even compositions, low impurity content and the like. Electrochemistry and PCT tests find that the hydrogen storage material has high capacity and better comprehensive performance.

Description

technical field [0001] The invention relates to a method for preparing La-Mg-Ni-based AB by sintering under a magnetic field 3 The invention discloses a method for a type hydrogen storage alloy, which belongs to the technical field of metal functional materials and powder metallurgy. Background technique [0002] Since 1990, based on rare earth AB 5 A small Ni / MH battery with a type hydrogen storage alloy as the negative electrode material is commercialized in Japan. Compared with Ni-Cd batteries, Ni-MH secondary batteries have many advantages such as high specific energy, fast charge and discharge speed, resistance to overcharge and overdischarge, no memory effect, and no environmental pollution. But affected by CaCu 5 type structure constraints, rare earth based AB 5 The discharge capacity of the type hydrogen storage electrode alloy is generally only about 300~320mAh / g, which cannot meet the development requirements of Ni / MH batteries to further increase the energy de...

AI Technical Summary

Problems solved by technology

However, since the volatilization of magnesium cannot be predicted and controlled, and the smelting time is short, the uniformity of the alloy composition cannot be guaranteed. The alloy needs to undergo multiple remelting and long-term homogenization annealing, or rapid quenching after remelting, and the process is relatively complicated. ;Another commonly used method is the solid state reaction sintering method - mixing rare earth, magnesium, nickel and other raw metal powders, pressing them into tablets, and sintering at 600~1100 °C

But there are also problems in this method: (1), when the temperature is low, it takes a long time to sinter, and the energy consumption is large and the cycle is long

However, when using this method to smelt alloys, the sintering time is also very long, and more than two kinds of intermediate alloys are required, which makes the process complicated and increases the cost

In addition, AB 3 The composition of the alloy is limited by the master alloy

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