Фазовая диаграмма системы C-Li

К оглавлению: Другие диаграммы (Others phase diargams)

C-Li (Carbon-Lithium) H. Okamoto The assessed C-Li phase diagram is based on review of the experimental data [ 55Her, 57Fed, 65Juz1, 65Juz2, 66Bag] and was obtained by thermodynamic calculations. The equilibrium phases are (1) the liquid, L; (2) the terminal solid solutions, (C); (3) a series of C-rich lamellar compounds, CmLi (m = 6, 12, 18, 36, 72); (4) the intermetallic compound CLi, probably with two polymorphic forms; and (5) the terminal solid solutions (bLi) and (aLi). No homogeneity range is known for any phase. A number of C-rich lamellar compounds are formed by the reaction of Li vapor with graphite [65Juz2, 66Bag] or by treating graphite in Li aryl solutions [ 65Gol] or in liquid Li [68Sal]. The most Li-rich compound is C6Li. [65Juz2] and [66Bag] reported C12Li and C18Li. C36Li and C72Li were observed by [66Bag]. These compounds may not be true equilibrium phases, because in 2 to 55 at.% Li alloys heat treated below 700 C, the equiatomic compound CLi is in equilibrium with pure (C) [62Sec1, 62Sec2, 62Sec3]. The presence of C4Li [ 55Her] was postulated, but this compound has not been confirmed by other investigators. The equiatomic compound CLi was discovered by [55Her]. [57Fed] considered there to be four polymorphic forms in CLi, with transformation temperatures at 560, 440, and 410 C (see [Elliott]). [62Sec3], on the other hand, found only one type of phase in quenched specimens after annealing at 325 to 800 C. [ 67Sec] suspected that the observation of polymorphs by [57Fed] was induced by such contamination as nitride skin formed on Li or by hydrolyzation of CLi. The presence of allotropic forms, however, cannot be ruled out. These two different types are distinguished tentatively in this evaluation as aCLi and bCLi. If CLi is actually bimorphic, the transition temperature is probably close to 800 C. Further investigation is needed. The van't Hoff relation suggests that the L = CLi + (Li) eutectic temperature is ~6 C below the melting point of bLi at most, corresponding to no solubility of C in (bLi) and the eutectic composition at 99 at.% Li. Therefore, the eutectic temperature is shown at 175 C in the assessed diagram. 55Her: A. Herold, Bull. Soc. Chim. Fr., (7-8), 999-1012 (1955) in French. 57Fed: P.I. Fedorov and M.T. Su, Acta Chim. Sin. (China), 23(1), 30-39 (1957) in Chinese. 62Sec1: D.R. Secrist, USAEC Rep. KAPL-2182, 33 p (1962). 62Sec2: D.R. Secrist and W.J. Childs, USAEC Rep., TID-17149, 21 p (1962). 62Sec3: D.R. Secrist and L.G. Wisnyi, Acta Crystallogr., 15(10), 1042-1043 ( 1962). 65Gol: J. Gole and C. Stein, Compt. Rend., 260, 6351 (1965) in French. 65Juz1: R. Juza and V. Wehle, Naturwissenschaften, 52(19), 537 (1965) in German. 65Juz2: R. Juza and V. Wehle, Naturwissenschaften, 52(19), 560 (1965) in German. 66Bag: M. Bagouin, D. Guerard, and A. Herold, Compt. Rend. C, 262(7), 557-559 ( 1966) in French. 67Sec: D.R. Secrist, J. Am. Ceram. Soc., 50(10), 520-523 (1967). 68Sal: F.J. Salzano, S. Aronson, and A. Ingraham, J. Am. Ceram. Soc., 51(7), 465 (1968). Published in Bull. Alloy Phase Diagrams, 10(1), Feb 1989. Complete evaluation contains 1 figure, 3 tables, and 17 references. 1