Thermal Performance of Mechanically Activated Tetracalcium Phosphate

Abstract

Prolonged high‐energy ball milling of tetracalcium phosphate (TTCP) resulted in a mechanical activation with the formation of nanocrystalline or amorphous domains within the compound. This mechanically activated material demonstrated a completely different thermal behavior compared with highly crystalline TTCP. Differential scanning calorimetry (DSC) measurements indicated the presence of exothermic reactions between 370° and 480°C and between 630° and 930°C for 24 h‐milled TTCP, which could be related to conversion to an apatitic phase and calcium oxide (CaO) and crystallization of these products during heating. X‐ray diffraction analyses showed that mechanically activated TTCP began converting to an apatitic phase at ∼200°C and fully converted to an apatitic phase and amorphous CaO at 600°C, and a crystalline phase of CaO subsequently appeared around 800°–1200°C. Reconversion to TTCP was observed between 1200° and 1400°C. In contrast, crystalline TTCP remained stable up to 500°C and decomposed to an apatitic phase and CaO around 600°–1000°C.

Tetracalcium phosphate: Synthesis, properties and biomedical applications

“…However, single-component TTCP cements can be obtained after prolonged ball-milling, leading to partial amorphization (mechanical activation) of the material [12,[31][32][33]. This strongly increases both the kinetic solubility (rate of dissolution) as well as the thermodynamic solubility product, such that setting occurs even at room or body temperature.…”

“…At low temperatures, this apatitic phase may be phosphate deficient as a result of the incomplete decomposition. Thermal analysis using differential scanning calorimetry (DSC) showed an endothermic peak at 750°C in the pattern of mechanically activated TTCP, which may be attributed to a combination of the transformation of this non-stoichiometric apatite phase to stoichiometric HA and crystalline CaO [32]. In order to confirm further that mechanical activation was responsible for the decomposition of TTCP at temperatures as low as 200°C, DSC measurements were performed on mechanically activated TTCP which had been hydrolysed to CaO and HA at room temperature in water.…”

Amorphous Calcium Orthophosphates: Nature, Chemistry and Biomedical Applications

“…Other authors have shown that a prolonged high-energy ball milling of either α-TCP, β-TCP powder in ethanol or a dry mixture of ACP and DCPD powders lead to ACP formation after 24 h [156][157][158]. Furthermore, prolonged high-energy ball milling of TTCP was found to result in a mechanical activation with the formation of undisclosed nanocrystalline and/or amorphous domains within the compound [159]. However, there is a non-negligible risk of powder contamination (ball wear) when using this processing route over extended periods to obtain an ACP [31].…”

Amino acid containing amorphous calcium phosphates and the rapid transformation into apatite

“…7 However, because the additives have limited solubilities, amorphous calcium phosphates with Ca/P molar ratios similar to and/or larger than that of apatite are needed for the preparation of intelligent calcium phosphate cement. Although a few research groups have actually proposed synthetic routes for amorphous calcium phosphates with large Ca/P molar ratios, 26,27 a facile synthetic approach is needed for the further design of such materials.…”