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

• Autor(a) principal: Daguano, Juliana Kelmy M. F.
• Data de Publicação: 2013
• Outros Autores: Suzuki, Paulo A., Strecker, Kurt, Marques de Oliveira, Jose Martinho, Figueira Vaz Fernandes, Maria Helena, Santos, Claudinei
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/20144
• topic: glass-ceramics; heat treatment; high-resolution X-ray diffraction (HRXRD); bending strength

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 beta-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, beta-TCMP, has been investigated by crystallization from a glass composed of 52.75 wt% 3CaO center dot 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 degrees C 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 degrees C and 1100 degrees C, and the formation of diopside in samples treated at 1100 degrees C 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 beta-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 degrees C for 4 h, respectively.