Production of mixed carbonate phases using ammonium carbonate-metal acetate reactions

Materials such as bone, nacre, and fish scales have unique structures that give the material strength as well as ductility. The ultimate goal of our research is to develop new composite materials that have improved strength and ductility compared to conventional materials. The US Army Engineer Research and Development Center is incorporating these design principles to develop hierarchical materials for structural applications. In the present study, the mineralogy and morphology of calcium-containing carbonates precipitated by reacting (NH4)₂CO₃ with mixed Ca, Sr, Mg, and Mn-acetates was investigated. As the proportion of the non-Ca component increased, the products shifted toward double carbonates and mixtures of double carbonates with single carbonates. Characterization by scanning electron microscopy and X-ray diffraction to determine crystal sizes, morphology, and structure of precipitated phases indicated a potential for re-crystallizing the products to form new composite materials. Ongoing research efforts are focused on using information obtained in the present study to develop composites by hydrothermal recrystallization of metastable phases.