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Insight into Metastable Lifetime of α‐Calcium Sulfate Hemihydrate in CaCl 2 Solution
Author(s) -
Jiang Guangming,
Mao Jingwei,
Fu Hailu,
Zhou Xu,
Guan Baohong
Publication year - 2013
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.12451
Subject(s) - metastability , chemistry , calcium , gibbs free energy , phase (matter) , crystallography , mineralogy , thermodynamics , physics , organic chemistry
Alpha calcium sulfate hemihydrate (α‐ HH ), an important kind of cementitious material, is a metastable phase in CaSO 4 – H 2 O system. In CaCl 2 solution, thermodynamic metastable window for α‐ HH preparation from calcium sulfate dihydrate is constructed as a function of CaCl 2 concentration (0–4.0 m ) and temperature (60°C–130°C), and then the metastability of α‐ HH is characterized by the metastable lifetime ( MLT ). As the concentration of CaCl 2 is raised from 1.5 to 4.0 m and temperature from 80°C to 110°C, MLT of α‐ HH decreases gradually from 2920 to 60 min. The reducing effect of CaCl 2 on MLT arises from its contribution to lowering the total interfacial Gibbs free energy required for the subsequent phase transition of α‐ HH to anhydrite, the thermodynamic stable phase. This work establishes a method to evaluate the phase metastability and provides a potential approach to optimize the reaction time in metastable material synthesis according to the MLT value for purity control.