Thermal Performance of Mechanically Activated Tetracalcium Phosphate
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.
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Document Type: Research Article
Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, D-97070 Würzburg, Germany
Biomaterials Unit, School of Dentistry, University of Birmingham, St. Chad's Queensway, Birmingham B4 6NN, U.K.
Publication date: May 1, 2005