Фазовая диаграмма системы Hg-Pt

К оглавлению: Другие диаграммы (Others phase diargams)

Hg-Pt (Mercury-Platinum) C. Guminski The Hg-Pt phase diagram is based primarily on the work of [73Jan1]. The present evaluator believes that the most reliable value of Pt solubility in liquid Hg at 25 C is that established by [83Gum], 5 C 10-4 at.%. Hg is easily dissolved in (Pt) at elevated temperatures; however, at room temperature, the corresponding solubility is very small. Stability of this solution is significant because, even at 800 C, a small amount of Hg still remains in Pt foil [68Aff]. There are some rather vague indications about the existence of metastable Hg- Pt intermetallics. [40Pla] and [45Pla] postulated the formation of HgPt3 and HgPt2, decomposing at 485 and 236 C, respectively. The former compound was never confirmed and investigators [53Bau2, 61Sta, 73Jan1, 73Jan2] found only mixed crystals of Pt and PtHg. The existence of HgPt2 was confirmed in electrochemical experiments. [73Has] and [81Yos] observed the formation of HgPt2 in the initial step of electrode position of Hg on Pt, when less than one monolayer of Hg covered Pt. When a larger amount of Hg was deposited, Hg2Pt2 (which appears to be a different form from HgPt) represented the main component of the surface layer [81Yos]. Unfortunately, these surface-formed compounds were postulated after electroanalytical [73Has, 81Yos] and thermogravimetrical [66Aff, 68Aff, 81Yos] measurements, which gave only indirect information concerning the composition and structure of these metastable phases. Inclusion of H into the Hg-Pt alloys is always possible, so HgPt3 and HgPt2 may be only apparent formulae. After investigation of the vapor pressure of Pt amalgams, [73Jan1] retracted the earlier postulate of Hg3Pt formation in the system of [65Jan]. 40Pla: I.N. Plaksin and N.A. Suvorovskaya, Acta Physicochim. URSS, 13, 83-96 ( 1940) in Russian; TR: C.R. Acad. Sci. URSS, 27, 460-463 (1940). 45Pla: I.N. Plaksin and N.A. Suvorovskaya, Izv. Sekt. Platiny, 18, 67-76 (1945) in Russian. 53Bau1: E. Bauer, H. Nowotny, and A. Stempfl, Monatsh. Chem., 84, 211-212 ( 1953) in German. 53Bau2: E. Bauer, H. Nowotny, and A. Stempfl, Monatsh. Chem., 84, 692-700 ( 1953) in German. 61Sta: H.H. Stadelmaier and W.K. Hardy, Z. Metallkd., 52, 391-396 (1961) in German. 65Jan: G. Jangg and F. Steppan, Z. Metallkd., 56, 172-178 (1965) in German. 66Aff: S. Affrossman and W.G. Erskine, Trans. Faraday Soc., 62, 2922-2927 ( 1966). 68Aff: S. Affrossman, W.G. Erskine, and J. Paton, Trans. Faraday Soc., 64, 2856-2863 (1968). 69Rob: G.D. Robbins and C.G. Enke, J. Electroanal. Chem., 23, 343-349 (1969). 73Has: M.Z. Hassan, D.F. Unterker, and S. Bruckenstein, J. Electroanal. Chem., 42, 161-181 (1973). 73Jan1: G. Jangg and T. D”rtbudak, Z. Metallkd., 64, 715-719 (1973) in German. 73Jan2: G. Jangg and E. Lugscheider, Monatsh. Chem., 104, 1269-1275 (1973) in German. 80Lah: S.K. Lahri and D. Gupta, J. Appl. Phys., 51, 5555-5560 (1980). 81Yos: Z. Yoshida, Bull. Chem. Soc. Jpn., 54, 556-561 (1981). 83Gum: C. Guminski, H. Roslonek, and Z. Galus, J. Electroanal. Chem., 158, 357- 368 (1983). Published in Bull. Alloy Phase Diagrams, 11(1), Feb 1990. Complete evaluation contains 2 figures, 6 tables, and 25 references. Special Points of the Hg-Pt System