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Biomaterials
Published in Chander Prakash, Sunpreet Singh, J. Paulo Davim, Functional and Smart Materials, 2020
At 1125°C, β-TCP transforms into α-TCP (high melting temperature) phase, β-TCP is less soluble in water than α-TCP. Pure β-TCP never occurs in organic calcification. Whitlockite (β-(Ca, Mg)3(PO4)2), magnesium-containing form is found in dental calculi, urinary stone, dental caries salivary stone, arthritic cartilage and some soft tissue deposits (Le Geros, 1994). α-TCP is a metastable phase at room temperature (Dorozhkin and Epple, 2002).
Crystallization of struvite in the presence of calcium ions: Change in reaction rate, morphology and chemical composition
Published in Cogent Engineering, 2022
D. S. Perwitasari, S. Muryanto, J. Jamari, A. P. Bayuseno
Additionally, XRPD diffractograms of precipitating solids at Ca/Mg ratios are shown in Figure 5. Each peak profile has been checked using the Rietveld refining method and linked to the standard mineral database. With Ca/Mg ratios of 1 and 2, the formation of struvite, struvite-(K), sylvite, hydroxyapatite (Ca5(PO4)3OH), dolomite (CaMg(CO3)2), portlandite (CaOH), Mg-whitlockite (Ca9Mg(PO4)6PO3OH), newberyite (MgPO3OH)•3(H2O) could be affirmed. It may also include amorphous calcium precipitate, which could not be fully identified with the XRPD method. However, this suggestion would be later justified by the EDX analysis. When the chemistry solution has a molar ratio of Ca:Mg > 0.5:1, there is evidence of the formation of hydroxyapatite, dolomite, and portlandite associated with the presence of Ca2+ ions, which competes with phosphate ions in crystallization processes (Le Corre et al., 2005). As a result, the interaction of calcium with phosphate ions in wastewater systems can typically produce poorly crystallized hydroxylapatite based on the following reaction (Equation 4):