Influence of the Ca/P ratio and cooling rate on the allotropic alpha <->beta-tricalcium phosphate phase transformations


Alpha-tricalcium phosphate (alpha-TCP) is a component of particular interest in the formulation of apatitic calcium phosphate based bone cements. During the setting reaction of this type of cements, a calcium deficient hydroxyapatite with composition similar to bone hydroxyapatite is formed. But the purity levels of the commercially available products based on alpha-TCP are generally low, and their prices are prohibitive. Such stringent conditions are pushing most of the researchers in the area of bone cements towards preparing alpha-TCP in their own laboratories. The low degree of purity of alpha-TCP based products is generally due to an incomplete beta-TCP -> alpha-TCP phase transformation and/or to a partial alpha-TCP -> beta-TCP reversal during cooling. Despite extensive research efforts, contradictory reports exist about the effects of composition of the starting material, cooling rates and the importance of quenching for maintaining alpha-TCP purity. The present work aims at shedding further light on this issue by controlling the relevant parameters of wet synthesis of the starting beta-TCP powders and their heat treatment schedule in order to transform them in high purity alpha-TCP products. The key experimental variables investigated included the composition of the starting beta-TCP powders, namely the Ca/P ratio, the maximum heat treatment temperatures, and the cooling rates.




Materials Science


Brazete, D; Torres, PMC; Abrantes, JCC; Ferreira, JMF

nossos autores


This work was supported by the European Regional Development Fund (FEDER) through the COMPETE, by the Portuguese Government through the Portuguese Foundation for Science and Technology (FCT), in the scope of the projects UID/CTM/50011/2013 (Aveiro Institute of Materials, CICECO, The Thermal Analysis Laboratory was funded by the Programa Operacional Factores de Competitividade-COMPETE and by National Funds through FCT under the project REEQ/515/CTM/ 2005. The XRD facility was funded by FEDER funds through QREN-Aviso SAIECT-IEC/2/2010 and Operacao NORTE-07-0162-FEDER-000050.

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