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Phase transitions of silver and silver–palladium alloys immersed in mercury
Author(s) -
CHERN LIN J. H.,
YUAN J. Y.,
HO W. F.,
JU C. P.
Publication year - 2007
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/j.1365-2842.2007.01202.x
Subject(s) - stoichiometry , mercury (programming language) , palladium , crystallography , materials science , phase (matter) , analytical chemistry (journal) , chemistry , catalysis , organic chemistry , computer science , programming language , biochemistry , chromatography
summary A series of Ag–Hg and Ag–Pd–Hg phases have been prepared by immersion in mercury and subsequent heat treatment of pure Ag and a series of Ag–Pd alloys. Phase transitions, along with the changes involved in morphology and chemistry, are investigated. Experimental results indicate that when mercury‐immersed Ag discs are heat‐treated at 90 °C for 12 h, large (>50 μm) crystals with Ag/Hg atomic ratios close to those of stoichiometric AgHg 2 form on the Ag surface. Heat treatment for 36 h causes these crystals to disintegrate into smaller (majority <10 μm) Ag 2 Hg 3 (γ 1 ) crystals. After 60 h, the stoichiometric γ 1 crystals further breakdown into even smaller stoichiometric AgHg( β 1 ) crystals. The oft‐referenced β 1 phase Ag 1·1 Hg 0·9 is not supported in the present study. Addition of Pd to Ag has a dramatic effect on the morphology of the γ 1 phase. With more addition of Pd, large‐faceted and elongated γ 1 crystals tend to grow in the midst of smaller matrix γ 1 crystals. All three different Pd‐containing crystals have (Ag + Pd)/Hg ratios very close to those of the stoichiometric γ 1 phase, indicating that added Pd tends to replace Ag, rather than Hg, in the γ 1 phase.