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The CaO–P2O5–SiO2–MgO system presents several compounds used as biomaterials such as hydroxyapatite (HA), tricalcium phosphate (TCP) and TCP with magnesium substituting partial calcium (TCMP). The β-TCMP phase with whitlockite structure has interesting biological features and mechanical properties, meeting the requirements of a bioactive material for bone restoration. In this work, the production of Mg-doped TCP, β-TCMP, has been investigated by crystallization from a glass composed of 52.75 wt% 3CaO·P2O5, 30 wt% SiO2 and 17.25 wt% MgO (i.e., 31.7 mol% CaO, 10.6 mol% P2O5, 26.6 mol% MgO and 31.1 mol% SiO2) using heat treatments between 775 ℃ and 1100 ℃ for up to 8 h. The devitrification process of the glass has been accompanied by differential scanning calorimetry (DSC), high-resolution X-ray diffraction (HRXRD), relative density and bending strength measurements. The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation, a transient non-cataloged silicate between 800 ℃ and 1100 ℃, and the formation of diopside in samples treated at 1100 ℃ as crystalline phases. The overall crystalline fraction varied from 26% to 70% depending on the heat treatments. Furthermore, contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments, which were attributed to the β-TCMP formation with the partial substitution of Ca2+ by Mg2+. Relative densities near 99% and 97% for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment. Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975 ℃ for 4 h, respectively.


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Development and characterization of 3CaO·P2O5–SiO2–MgO glass-ceramics with different crystallization degree

Show Author's information Juliana Kelmy M. F. DAGUANOaPaulo A. SUZUKIaKurt STRECKERbJosé Martinho Marques de OLIVEIRAcMaria Helena Figueira Vaz FERNANDESdClaudinei SANTOSa,e,*( )
Universidade de São Paulo - Escola de Engenharia de Lorena, USP-EEL - Pólo Urbo-Industrial, s/n, Gleba AI-6, Lorena-SP, CEP 12600-000, Brazil
Universidade Federal de São João del-Rei, – UFSJ-CENEN, Campus Sto Antônio - Praça Frei Orlando 170 – Centro, S. J. del-Rei-MG. CEP 36307-352, Brazil
Escola Superior Aveiro Norte, Edifício Rainha, 3720-232 O. Azeméis, Portugal
Universidade de Aveiro, Campus Universitário de Santiago3810-193 Aveiro, Portugal
Universidade do Estado do Rio de Janeiro – Faculdade de Tecnologia de Resende – UERJ-FAT – Rod. Presidente Dutra, km, 298, Resende-RJ, CEP 27537-000, Brazil

Abstract

The CaO–P2O5–SiO2–MgO system presents several compounds used as biomaterials such as hydroxyapatite (HA), tricalcium phosphate (TCP) and TCP with magnesium substituting partial calcium (TCMP). The β-TCMP phase with whitlockite structure has interesting biological features and mechanical properties, meeting the requirements of a bioactive material for bone restoration. In this work, the production of Mg-doped TCP, β-TCMP, has been investigated by crystallization from a glass composed of 52.75 wt% 3CaO·P2O5, 30 wt% SiO2 and 17.25 wt% MgO (i.e., 31.7 mol% CaO, 10.6 mol% P2O5, 26.6 mol% MgO and 31.1 mol% SiO2) using heat treatments between 775 ℃ and 1100 ℃ for up to 8 h. The devitrification process of the glass has been accompanied by differential scanning calorimetry (DSC), high-resolution X-ray diffraction (HRXRD), relative density and bending strength measurements. The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation, a transient non-cataloged silicate between 800 ℃ and 1100 ℃, and the formation of diopside in samples treated at 1100 ℃ as crystalline phases. The overall crystalline fraction varied from 26% to 70% depending on the heat treatments. Furthermore, contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments, which were attributed to the β-TCMP formation with the partial substitution of Ca2+ by Mg2+. Relative densities near 99% and 97% for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment. Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975 ℃ for 4 h, respectively.

Keywords:

glass-ceramics, heat treatment, high-resolution X-ray diffraction (HRXRD), bending strength
Received: 09 September 2013 Revised: 23 October 2013 Accepted: 30 October 2013 Published: 04 December 2013 Issue date: December 2013
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Publication history

Received: 09 September 2013
Revised: 23 October 2013
Accepted: 30 October 2013
Published: 04 December 2013
Issue date: December 2013

Copyright

© The author(s) 2013

Acknowledgements

The authors would like to thank LNLS - Laboratório Nacional de Luz Síncrotron for technical support, and FAPESP for financial support, under grant No. 07/50510-4. We also acknowledge Prof. E. D. Zanotto and the LaMaV, UFSCar, for melting of glass and DSC analysis.

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