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Thermal treatment method for rare earth nickel based AB5 type hydrogen storage alloy

A heat treatment method and hydrogen storage alloy technology are applied in the field of heat treatment of rare earth nickel-based AB5 type hydrogen storage alloys, which can solve the problems affecting the powder performance of hydrogen storage alloys, the growth of alloy grains, and the difficulty in eliminating and improving the composition segregation of hydrogen storage alloys. And other issues

Inactive Publication Date: 2009-05-13
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the hydrogen storage alloy is kept at a higher temperature, if the holding time is short, it is difficult to eliminate and improve the composition segregation of the hydrogen storage alloy and reduce the segregation of manganese in the alloy; if the holding time is longer, the alloy grains will merge and grow , increase the grain size, that is, lead to the coarsening of the metallographic structure of the alloy, thus affecting the pulverization performance of the hydrogen storage alloy

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] 1. Production of hydrogen storage alloy:

[0019] Using cerium-rich mixed rare earth, electrolytic nickel, cobalt, manganese, aluminum as raw materials, according to MmNi 3.55 co 0.75 mn 0.4 al 0.3The chemical composition of the alloy is compounded, wherein the weight composition of the cerium-rich mixed rare earth is 27.28wt% La, 50.41wt% Ce, 5.03wt% Pr, 17.04wt% Nd, and the purity of other metal raw materials is greater than 99.9wt%.

[0020] The prepared alloy raw material is placed in a medium frequency induction melting furnace (produced by Jinzhou Electric Furnace Co., Ltd., with a capacity of 500kg), melted at 1300°C to 1500°C for 2 to 4 hours, and cast to obtain an alloy ingot. Elemental analysis shows that the composition of the obtained hydrogen storage alloy block is MmNi 3.55 co 0.75 mn 0.4 al 0.3 .

[0021] The above MmNi 5 Rare earth nickel base AB 5 Type hydrogen storage alloy ingots were put into a vacuum high-temperature resistance furnace (pr...

Embodiment 2-11 and comparative example 1-10

[0030] Except that heat treatment temperature and time are different from Example 1, other conditions are all the same as Example 1. Specifically as shown in Table 1,

[0031] Table 1. Electrochemical properties of alloys under different heat treatment conditions

[0032]

serial number

heat treatment conditions

discharge capacity

(mAh / g)

200 cycles

Environmental Protection

Holding rate (%) Comparative example 1 300℃*4h, 1000℃*2h 289 86 Example 1 400℃*4h, 1000℃*2h 315 94 Example 2 500℃*4h, 1000℃*2h 314 95 Example 3 600℃*4h, 1000℃*2h 324 96 Example 4 800℃*4h, 1000℃*2h 318 94 Comparative example 2 900℃*4h, 1000℃*2h 311 88 Comparative example 3 600℃*1h, 1000℃*2h 294 87 Example 5 600℃*2h, 1000℃*2h 317 93 Example 6 600℃*5h, 1000℃*2h 320 96 Comparative example 4 600℃*7h, 1000℃*2h 314 86 Comparative Example 5 600℃*4h,...

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PUM

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Abstract

The invention relates to a thermal processing method for rare earth nickel base AB5 type hydrogen storage alloy for the negative electrode of a nickel hydrogen cell. A staged thermal processing method using low-temperature treatment before high-temperature treatment is adopted for the rare earth nickel base AB5 type hydrogen storage alloy in the inert or reducing atmosphere after smelting and casing the rare earth nickel base AB5 type hydrogen storage alloy into ingots. The staged thermal processing method comprises the following steps: firstly keeping the rare earth nickel base AB5 type hydrogen storage alloy within the temperature range of 400 to 800 DEG C for 2 to 5 hours; and then increasing the temperature to 950 to 1100 DEG C and keeping the rare earth nickel base AB5 type hydrogen storage alloy for 0.3 to 5 hours. The staged thermal processing of the rare earth nickel base AB5 type hydrogen storage alloy can remove and improve the component segregation, the lattice stress and the lattice distortion of the hydrogen storage alloy without the merging and growing of the crystal grains of the alloy, thereby improving the anti-atomization capability of the alloy, improving the gradient of the P-C-T curve of the hydrogen storage alloy, reducing the platform pressure, improving the hydrogen absorption and desorption amount, the electrochemical content and the cycle life of the alloy, and consequently truly improving the electrochemical performance and the cycle life of the cell.

Description

【Technical field】 [0001] The invention relates to a rare-earth nickel-based AB for negative electrodes of nickel-hydrogen batteries 5 Heat treatment method of type hydrogen storage alloy. 【Background technique】 [0002] Rare earth nickel base AB 5 The type hydrogen storage alloy has good activation performance and high electrochemical capacity, and has been widely used as the negative electrode material of Ni-MH battery. Conventional casting AB 5 Type hydrogen storage alloys are prone to intragranular segregation and lattice defects, and the uniformity of composition and microstructure is poor and the lattice stress is large. Although increasing the cooling rate can reduce segregation and improve composition uniformity, it also increases lattice defects and lattice stress. At the same time, some elements of the alloy such as nickel, cobalt, manganese, aluminum, etc. will be deposited on the surface of the grain boundary, making the alloy easy to be corroded, thereby redu...

Claims

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Application Information

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IPC IPC(8): C22F1/10
Inventor 尤聿媛
Owner BYD CO LTD
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