Фазовая диаграмма системы H-Zn

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H-Zn (Hydrogen-Zinc) A. San-Martin and F.D. Manchester Only limited experimental data are available for the Zn-H system. The assessed diagram illustrates the known phases at atmospheric pressure. The left boundary of the solid Zn phase represents absorption of H at very low concentration, i.e., constitutes present limits on the maximum observed solubility and does not necessarily demarcate the range of existence of equilibrium phases. Because the amount of H dissolved in Zn is extremely small (at the pressures investigated to date), the net effect of hydrogen on lowering or raising the melting temperature of Zn (419.58 C) should be scarcely measurable, under these conditions. [10Sie] concluded that Zn does not dissolve hydrogen up to temperatures of 600 C, but [23Dem] and [29Hen] found that under atmospheric pressure Zn was permeable to hydrogen at temperatures between 305 C and the melting point. [57Hof] found that molten Zn (99.995%) at a temperature of 516 C dissolves only around 1 x 10-5 at.% H. This value should be considered only as a lower limit, because the high vapor pressure of Zn limits the time available for degasification of the melt, and only a partial extraction of the hydrogen is possible [57Hof]. From a study of hydrogen diffusion in Zn, [71Moo] derived a solubility value of 3 x 10-5 at.% H at 200 C. This value was used to delineate the solubility boundary at atmospheric pressure suggested in the assessed diagram. ZnH2 has not yet been prepared by an equilibrium reaction of the metal with the hydrogen gas, but it has been obtained by [51Bar] from the interaction of dimethylzinc with a diethyl ether solution of AlH3 and by [51Wib] from the reaction of zinc iodide with an ether solution of LiAlH4. ZnH2 is a white, nonvolatile powder insoluble in ether, and it was separated from the by- products of the reaction either by filtration [51Bar] or by centrifuge [51Wib]. ZnH2 decomposes slowly to Zn and hydrogen gas (under atmospheric pressure) at temperatures of 25 [51Bar] or 90 C [51Wib]. [85Mik] also observed that the thermal decomposition of ZnH2 is accelerated by preliminary UV irradiation. [ 82Bas] reported that samples of ZnH2 subjected to high pressures decompose completely at temperatures below 100 C. 10Sie: A. Sieverts and W. Krumbhaar, Ber. Dtsch. Chem. Ges., 43, 893-900 (1910) in German. 23Dem: H.G. Deming and B.C. Hendricks, J. Am. Chem. Soc., 45, 2857-2864 (1923). 29Hen: B.C. Hendricks and R.R. Ralston, J. Am. Chem. Soc., 51, 3278-3285 (1929) . 51Bar: G.D. Barbaras, C. Dillard, A.E. Finholt, T. Wartik, K.E. Wilzbach, and H.I. Schlesinger, J. Am. Chem. Soc., 73, 4585-4590 (1951). 51Wib: E. Wiberg, W. Henle, and R. Bauer, Z. Naturforsch., 6B, 393 (1951). 71Moo: In.H. Moon, Kunmsok Hakhoe Chi, 9(3/4), 158-164 (1971) in Korean. 82Bas: I.O. Bashkin, I.T. Belash, N.S. Kedrova, N.N. Mal'tseva, and E.G. Ponyatovskii, Zh. Neorg. Khim., 27, 1915-1920 (1920) in Russian; TR: Russ. Inorg. Chem., 27, 1080-1082 (1982). 85Mik: Yu.I. Mikhailov, N.N. Mal'tsev, N.S. Kedrova, A.B. Brosalin, N.T. Kuznetsov, and V.V. Boldyrev, Akad. Nauk SSSR, Neorg. Mater., 21, 1329-1331 ( 1985) in Russian; TR: Inorg. Mater., 21, 1165-1167 (1985). Published in Bull. Alloy Phase Diagrams, 10(6), Dec 1989. Complete evaluation contains 1 figure, 1 table, and 17 references. 1