Фазовая диаграмма системы C-Sc

К оглавлению: Другие диаграммы (Others phase diargams)


C-Sc (Carbon-Scandium) K.A. Gschneidner, Jr. and F.W. Calderwood [67Ras] prepared scandium carbide samples by heating mixtures of powdered Sc and reactor grade C(graphite) under a high vacuum at 1200 to 1350 C. Between 55 and 60 at.%, the phase relationships in the Sc-C phase diagram may be quite similar to those observed in the Y-C system. Only limited structural data are available and they are sometimes in conflict. Scandium carbide samples containing 85 to 95% Sc were found to be heterogeneous and consisted of Sc and a fcc phase [67Ras]. Samples containing 60 to 80% Sc had the fcc structure and were practically single phase. A sample with 42 at.% C had a nearly pure Pu2C3-type structure. Samples with 50 at.% or more C produced a phase high carbon with a complex structure. Thus, [67Ras] concluded that a series of peritectic reactions takes place in the Sc-C system. [68Ato] reported that the data for Sc2<310>3C was in better agreement with a trigonal Y2C-type cell than with the proposed fcc cell. [69Kri] confirmed the existence of Sc2-3C as well as the trigonal Sc2C phase isostructural with Y2C. [69Kri] reported that Sc4C3 has a narrow range of homogeneity. This phase is bcc with the I43d space group. The Sc4C3 phase remains stable when heated at 1500 C, but an unidentifiable patter results upon heating to 1600 C. Another phase, in the composition range ScC1.2 to ScC1.3, had a complex X-ray pattern. Cooling curves for this complex phase in equilibrium with free carbon indicated a eutectic at 1780 C. Editor's note: The Sc-C phase diagram is redrawn from [87Gor] (as quoted in [ 89Vel]). 67Ras: H. Rassaerts, H. Nowotny, G. Vinck, and F. Benesovsky, Monatsh. Chem., 98, 460 (1967). 68Ato: M. Atoji and M. Kikuchi, ANL-7441, Chemistry Division, Argonne National Laboratory, Argonne, IL (1968). 69Kri: N.H. Krikorian, A.L. Bowman, M.C. Krupka, and G.P. Arnold, High Temp. Sci., 1, 360 (1969). 87Gor: O.V. Gordiichuk, Author's Abstract of Candidate's Thesis, Chemical Sciences, Kiev (1987). 89Vel: T.Ya. Velikanova, V.N. Eremenko, L.V. Artyukh, A.A. Bondar, and O.V. Gordiichuk, Poroshk. Metall., (9), 49-57 (1989) in Russian; TR; Sov. Powder Metall., Met. Ceram., 28(9), 711-718 (1989). This updates the evaluation by K.A. Gschneidner, Jr. and F.W. Calderwood published in Bull. Alloy Phase Diagrams, 7(6), Dec 1986, which contains 1 table and 13 references. 1