A New Investigation of the Cl--CO(3)2-Substitution in AFm Phases

作者：Me**ah Adel; Cau dit Coumes Celine; Frizon Fabien; Leroux Fabrice; Ravaux Johann; Renaudin Guillaume^*

来源：Journal of the American Ceramic Society, 2011, 94(6): 1901-1910.

DOI：10.1111/j.1551-2916.2010.04305.x

Chloride to carbonate substitution in AFm phase of general formulae [Ca2Al(OH)(6)]center dot[Cl1-x center dot(CO3)(x/2)center dot(2+x/2)H2O] (or 3CaO center dot Al2O3 center dot(CaCl2)(1-x)center dot(CaCO3)(x)center dot(10+x)H2O written in cement notation) has been characterized by studying 12 powdered samples synthesized at 25 degrees and at 85 degrees C. The existence of a solid solution has been highlighted. It forms one stable rhombohedral [Ca2Al(OH)(6)]center dot[Cl1-x center dot(CO3)(x/2)center dot(2+x/2)H2O] solid solution with 0.25 < x < 0.95, isotypic with the recently described <file name="jace_04305_mu5.gif" type="gif"/> chloro-carboaluminate of [Ca2Al(OH)(6)]center dot[Cl-0.5 center dot(CO3)(0.25)center dot 2.25H(2)O] composition. A second metastable monoclinic [Ca2Al(OH)(6)]center dot[Cl1-x center dot(CO3)(x/2)center dot(2+x/2)H2O] solid solution has also been identified in a less extended x domain. The structural relationship between these two stable and metastable chloro-carboaluminate polymorphs shows similarities with the structural transition of the Friedel's salt (from rhombohedral high-temperature-structure to monoclinic low-temperature-structure at about 35 degrees C). The two [Ca2Al(OH)(6)]center dot [Cl1-x center dot(CO3)(x/2)center dot(2+x/2)H2O] solid solutions are simultaneously present, in quite equivalent weight amounts, in samples synthesized at room temperature, whereas only the stable rhombohedral polymorph is observed for samples synthesized at 85 degrees C. Raman spectroscopy has been successfully used to locate carbonate in the structure. The [CO3] symmetric stretching mode is observed at 1068 cm-1 for monocarboaluminate (x=1) for carbonate directly bonded to main layer, while it is observed at 1086 cm-1 for both chloro-carboaluminate polymorphs, which is characteristic of interlayer carbonate.

• 出版日期2011-6
• 单位中国地震局