Rare earth-nickel-type alloys

Much of this study was conducted on LaNi5-based alloys [13-20] and TiNir-based alloys [21-23], Sanyo Electric, Matsushita Battery and most other battery manufacturers have been using LaNi5-based rare earth-nickel-type alloys [24,... 

Figure 2.16 shows the charge-discharge cycle characteristics of alloys in which part of the nickel component was replaced with cobalt. Misch metal (Mm), which is a mixture of rare earth elements such as lanthanum, cerium, praseodymium, and neodymium, was used in place of lanthanum. It was found that the partial replacement of nickel with cobalt and the substitution of the lanthanum content with Mm was very useful in improving the charge-discharge cycle life. However, such alloys have insufficient capacity, as shown in Figure 2.17 [18]. From study of the effect that their compositions had on the charge-discharge capacity, it was concluded that the best alloy elements were Mm(Ni-Co-Al-Mn)This alloy led to the commercialization of sealed nickel-M H batteries. All the battery manufacturers who use a rare earth-nickel-type alloy for the negative electrode material employ similar alloys with slightly different compositions.

Two types of metallic alloys are used a) rare-earth (misch metal) alloys, known as AB5, based on lanthanum and nickel (LaNis plus some substituents) b) alloys based on titanium and nickel, plus V, Zr, Cr, known as AB2. The first type is the most widely used. A hydrogen-absorbing alloy must allow quantitative absorption-desorption at relatively high rates and for hundreds of cycles. 

Two types of metallic alloys are generally used. These are the rare-earth (Misch metal) alloys based on lanthanum nickel (LaNij), known as the ABj class of alloys and alloys consisting of titanium and zirconium, known as the AB2 class of alloys. In both cases, some of the base metals are replaced by other metals to improve performance characteristics. 

Alloy Compositions and Product Forms. SteUite 21, an early type of cobalt-base high temperature alloy, is used primarily for wear resistance. The use of tungsten rather than molybdenum, moderate nickel contents, lower carbon contents, and rare-earth additions typify cobalt-base high temperature alloys of the 1990s as can be seen from Table 5. 

EEI has used both commercially sintered silver powder with 1-mm-thick electrodes and sintered silver powder with in-house electrodes made from an ABj-type metal-hydride alloy (also known as lanthanum-nickel alloy) using rare earth material for initial laboratory cell test evaluations. Introduction of rare earth material improves the oxidation resistance during the alloy manufacturing process. The ABj-type metal-hydride alloy should be widely used in sealed Ni-MH batteries. The use of rare earth metal lanthanum will provide improved electrical performance, enhanced reliability, and ultra-high longevity for the sealed Ni-MH and Ag-MH battery systems. 

The stony-iron meteorites are intermediate between chondrites and irons. These very rare meteorites are equal mixtures of iron/nickel alloys and silicate minerals. Pallasites are striking examples of this type of meteorites, consisting of green olivine crystals in a matrix of metallic iron. Another type of stony-iron meteorite, called mesosiderites, contain pyroxene and plagioclase feldspars, minerals that are common on Earth. 

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