engleski

The comparison of precipitation conditions and physical chemical properties of salts relevant for biomineralization, calcium phosphates and calcium carbonates

Many classes of organic, inorganic or hybrid materials are produced by process of precipitation (crystallization) in which the size, morphology, chemical and structural composition could be tuned by the strict control of formation conditions. In fact, the synthesis of materials that resemble complex properties of natural biominerals is one of key fields in biomimetic science. Calcium carbonates (CaCO3) and calcium phosphates (Ca- PO4) are optimal selection for precipitation model system in biomineralization, because calcium carbonates are the most abundant biominerals that appear in invertebrates, like mollusks, sponges, corals, crustaceans. On the other hand, calcium phosphates (hydroxyapatites) are mostly the constituents of the vertebrate bones and teeth. Calcium carbonates and calcium phosphates appear in a variety of solid phases such as amorphous or crystalline, metastable and stable. The role of the amorphous phase is not completely resolved. The goal of this research is to develop precipitation diagrams of calcium carbonate and calcium phosphate in the concentration relevant for biomineralization of these salts and make their comparison. The precipitated diagrams are performed through screening precipitation experiments in model systems with increased complexity (from basic to physiological systems). Solutions of reagents are mixed together in strictly controlled hydrodynamic and thermodynamic conditions. Precipitation processes are continuously monitored by measuring the pH over time. The resulting solids are separated by filtration at the end of each experiment (1 h, 25 ºC) and analyzed by advanced physical-chemical characterization (XRD, FT-IR, SEM, TEM, EPR, TG). The results of this research give detailed inset to precipitation boundaries and domains in which different solid phases of CaCO3 and Ca-PO4 are precipitated. The formation of amorphous/metastable phases in both carbonate and phosphate system is predominantly influenced by increasing complexity of model systems.

calcium carbonate ; calcium phosphate

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