Reversible alloys

Due to its high energy density (3,860 mAh/g) and low voltage, lithium is the most attractive metal of the periodic table for battery application. Unfortunately lithium metal, and most of its alloys cannot be used in rechargeable batteries because of their poor cyclability. Therefore, lithium intercalation compounds and reversible alloys are among today s materials of choice for subject application. The most common active materials for the negative electrodes in lithium-ion battery applications are carbonaceous materials. The ability of graphitized carbonaceous materials to... 

In the next paper by Y. Illin et al., capabilities of Sn anodes are considered as a possible alternative to carbon. Thin films of Sn were deposited onto current collector in vacuum, and tested in the coin cells. Authors were able to obtain reversible alloying reaction, which stabilized at 100 mAh/g between cycle number 100 and 400. The stability of Sn and its characteristics upon cycling was seen to be a function of the current collector material. The best results were achieved with non-copper-based substrates. 

It was indicated that the structure that allows Li and Sn, Sn and Ni to reversibly alloy/dealloy is the key to gain high-capacity longlife anode materials. 3804 phase may have been able to realize such reversible reactions, hence resulting in the high capacity of... 

There is current interest in hydrogen sponge alloys containing lanthanum. These alloys take up to 400 times their own volume of hydrogen gas, and the process is reversible. Every time they take up the gas, heat energy is released therefore these alloys have possibilities in an energy conservation system. 

Storage as Hydrides. The discovery of metal compounds that reversibly absorb hydrogen is relatively recent. In the 1970s, the AB and AB family of alloys, which reversibly absorb hydrogen at room temperature and low pressure, were identified (205). Both A and B are metals. As of this writing many such compounds are known LaNi and TiFe are examples. 

The lanthanides can form hydrides (qv) of any composition up to LnH. Lanthanide hydrides can desorb hydrogen reversibly with temperature. Therefore, the lanthanides and some of thek alloys ate good candidates for hydrogen (qv) storage, of which LaNi is probably the most promising (see... 

Fig. 1. Schematic of the hysteresis loop associated with a shape-memory alloy transformation, where M. and Afp correspond to the martensite start and finish temperatures, respectively, and and correspond to the start and finish of the reverse transformation of martensite, respectively. The physical property can be volume, length, electrical resistance, etc. On cooling the body-centered cubic (bcc) austenite (parent) transforms to an ordered B2 or E)02...

As of this writing the 2inc alloys are too new to have actual corrosion resistance data, except for that based on accelerated tests. Zinc—nickel usually shows better results than 2inc-cobalt in salt spray tests. The reverse is tme when the Kesternich test is used. Tin—2inc performs well in both salt spray and Kesternich tests, but appears only to equal 2inc plating and 2inc—nickel in humidity tests. 

Pitting and Crevice Corrosion The general literature for pre-dic ting pitting tendency with the slow scan reviews the use of the reverse scan if a hysteresis loop develops that comes back to the repassivation potential below the FCP (E ) the alloy will pit at... 

Shock-recovery experiments by Gray [10] were conducted to assess directly if the strain-path reversal inherent to the shock contains a traditional microstructurally controlled Bauschinger effect for a shock-loaded two-phase material. Two samples of a polycrystalline Al-4 wt.% Cu alloy were shock loaded to 5.0 GPa and soft recovered in the same shock assembly to assure identical shock-loading conditions. The samples had two microstructural... 

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