Фазовая диаграмма системы B-Si

К оглавлению: Другие диаграммы (Others phase diargams)


B-Si (Boron-Silicon) R.W. Olesinski and G.J. Abbaschian The assessed Si-B phase diagram includes a peritectic reaction at 2020 C, involving the B-rich intermediate phase SiBn (n ~ 23), a peritectic reaction involving the intermediate phase SiB6 at 1850 C, a eutectic reaction at 8 at.% B and 1385 C, and a peritectoid reaction involving the intermediate phase SiB3 around 1270 C. The present diagram is based primarily on evaluation of the work of [63Sam], [ 68Hes], [80Via], [81Arm], and [81Mal]. Various computational techniques were used to calculate the phase diagram by utilizing the enthalpy function given by [78Esi]. The calculated coordinates of the eutectic and SiBn peritectic points agree well with the experimental data. The calculations were done by assuming Henrian behavior for the solid solutions, and thermodynamically identifying the SiBn phase with the (B) solid solution. The calculated liquidus curve agreed with the experimental features of the diagram only upon weighting the solubility data. It is generally agreed that SiB3, sometimes erroneously identified as SiB4, is unstable above 1200 to 1400 C. The homogeneity range of SiB3 is probably between SiB2.89 [62Mag] and SiB3.651 [70Ett]. Under equilibrium conditions, up to 1.6 at .% Si can dissolve in (B) at 1600 C, 2.4 at.% Si at 1900 and 2000 C, and 3.0 с 0.4 at.% Si at the peritectic temperature of 2020 C [81Arm]. [80Via] studied X-ray powder patterns of Si-B mixtures containing up to 14.3 at.% Si that were reacted at 1600 C in an argon atmosphere and rapidly cooled. They indicated that the single-phase solid solution can contain up to 5.6 at.% Si at this temperature, and the solid solubility limit extends to 6.13 at.% Si at a peritectic temperature of 1850 C. Somewhat larger solubilities have also been reported. Recently obtained thermal analysis results in conjunction with X-ray, microprobe, and microhardness analyses have been interpreted by [81Mal] and [ 81Arm] as evidence of the formation of a B-rich solid phase, SiBn, distinct from, although isotypic with, the solubility of Si in (B). 62Mag: B. Magnusson and C. Brosset, Acta Chem. Scand., 16, 449-455 (1962). 63Sam: G.V. Samsonov and V.M. Sleptsov, Zh. Neorg. Khim., 8, 2009-2011 (1963) in Russian: TR: Russ. J. Inorg. Chem., 8, 1047-1048 (1963). 68Hes: J. Hesse, Z. Metallkd., 59, 499-502 (1968) in German. 70Ett: P. Ettmayer, H.C. Horn, and K.A. Schwetz, Mikrochim. Acta Suppl., 4, 87- 95 (1970) in German. 78Esi: Yu.O. Esin, S.P. Kolesnikov, V.M. Baev, and A.F. Ermakov, Tezisy Nauchn. Soobshch. Vses. Konf. Str. Svoistvam Met. Shlakovykh Rasplavov, 3rd Ed., Vol. 2, 182-183 (1978). 80Via: J.C. Viala and J. Bouix, J. Less-Common Met., 71, 195-206 (1980). 81Arm: B. Armas, G. Male, and D. Salanoubat, J. Less-Common Met., 82, 245-254 ( 1981). 81Mal: G. Male and D. Salanoubat, Rev. Int. Hautes Temp. R‚fract., 18, 109-120 (1981). Published in Bull. Alloy Phase Diagrams, 5(5), Oct 1984. Complete evaluation contains 1 figure, 4 tables, and 50 references. Special Points of the Si-B System