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

authors	Brazete, D; Torres, PMC; Abrantes, JCC; Ferreira, JMF
nationality	International
journal	CERAMICS INTERNATIONAL
author keywords	Powders: chemical preparation; Thermal properties; Alpha - Tricalcium phosphate; Biomedical applications
keywords	BETA-TRICALCIUM PHOSPHATE; SETTING REACTION; HIGH-TEMPERATURE; ALPHA-TCP; BEHAVIOR; CRYSTALLINITY; DIFFRACTION; STABILITY
abstract	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.
publisher	ELSEVIER SCI LTD
issn	0272-8842
year published	2018
volume	44
issue	7
beginning page	8249
ending page	8256
digital object identifier (doi)	10.1016/j.ceramint.2018.02.005
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000428974300116