Benefits of rapid solidification processing of modified LaNi_5 alloys by high pressure gas atomization for battery applications

摘要

A high pressure gas atomization approch to rapid solidification has been employed to investigate simplified prcessing of Sn modified LaNi_5 powders that can be used for advanced Ni/metal hydride (Ni/MH) batteries. The current industrial practice involves casting large ingots followed by annealing and griding and utilizes a complex and cotly alloy design. This investigation is an attempt to produce owders for battery cathode fabrication that can be used in an as-atomized condition without annealing or grinding. Both Ar and He atomization gas were tried to investigate rapid solidification effects. Sn alloy additions wer tested to promote subsmbient pressure absorption/desorption of hydrogen at ambient temperature. The resulting fine, spherical powders were subject to microstructural analysis, hydrogen gas cycling, and annealing experiments to evaluate suitability for Ni/MH battery applications. The results demonstrate that a brief anneal is required to homogenize the as-solidified microstructure of both Ar and He atomized powders and to achieve a suitable hydrogen absorption behavior. The Sn addition also appears to suppress cracking during hydrogen gas phase cycling in particles smaller than about 25 mu m. These results suggest that direct powder prcessing of a LaNi_(5-x)Sn_x alloy has potential application in rechargeable Ni/MH batteries.