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&DEG; and 480&DEG; C and between 630&DEG; and 930&DEG; 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 &SIM; 200&DEG; C and fully converted to an apatitic phase and amorphous CaO at 600&DEG; C, and a crystalline phase of CaO subsequently appeared around 800&DEG;-1200&DEG; C. Reconversion to TTCP was observed between 1200&DEG; and 1400&DEG; C. In contrast, crystalline TTCP remained stable up to 500&DEG; C and decomposed to an apatitic phase and CaO around 600&DEG;-1000&DEG; C.
|Pages (from-to)||1327 - 1330|
|Number of pages||4|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 1 Jan 2005|