resumo
Alpha and beta-tricalcium phosphates are allotropic phases which play a very important role as bone graft substitutes, namely in calcium phosphate cements. Despite extensive research efforts, contradictory reports exist on the importance of quenching for maintaining alpha-TCP purity. The role of calcium pyrophosphate impurities derived from a certain calcium-deficiency, hydroxyapatite impurities derived from calcium excess, and various ionic substitutions on thermal stability of these phases was not yet fully disclosed. The present work reports on the kinetics of alpha <->beta-TCP phase transformations of calcium-deficient TCP powders with different Mg-doping extents (0-5 mol%) prepared by precipitation. Mg clearly enhanced the thermal stability of beta-TCP. The effect of cooling rate was more complex and interdependent on the Mg content and the heat treatment schedule. High alpha-TCP contents were retained upon cooling at 5 degrees C min(-1) for Mg <= 1 mol% or upon quenching from 1550 degrees C for Mg contents <= 2 mol%. (C) 2015 Elsevier Ltd. All rights reserved.
palavras-chave
BETA-TRICALCIUM PHOSPHATE; NEUTRON POWDER DIFFRACTION; X-RAY-DIFFRACTION; ALPHA-TRICALCIUM; SETTING REACTION; HIGH-TEMPERATURE; BONE; SYSTEM; SUBSTITUTION; CEMENT
categoria
Materials Science
autores
Torres, PMC; Abrantes, JCC; Kaushal, A; Pina, S; Dobelin, N; Bohner, M; Ferreira, JMF
nossos autores
Ajay Kaushal
Bolseiro de pós-Doutoramento
João Carlos de Castro Abrantes
Professor Adjunto
José Maria da Fonte Ferreira
Professor(a) Jubilado(a)
Paula Maria da Costa Torres
Investigador Auxiliar
Sandra Cristina de Almeida Pina
Bolseiro de pós-DoutoramentoGrupos
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos
G5 - Materiais Biomiméticos, Biológicos e Vivos
agradecimentos
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, www.ciceco.ua.pt) and by Mathys Ltd. Bettlach (Switzerland). P.M.C. Torres (SFRH/BD/62021/2009), Ajay Kaushal (SFRH/BPD/77598/2011) and S. Pina (SFRH/BPD/64119/2009) acknowledge the respective fellowship Grant by FCT.; The authors would also like to acknowledge Professor J.J.C. Cruz Pinto A. Barros-Timmons and Sandra Magina for the Thermal Analysis. Thermal Analysis Laboratory was funded by FEDER Funds through 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.