Abstract The photoluminescent behavior of Eu-doped Sr3Al2O6 obtained by highly efficient solution combustion synthesis is reported. In order to understand the influence of the fuel on the synthesis, the stoichiometric quantity and an excess of fuel were evaluated. By adjusting the amount of fuel, different luminescence responses were obtained, allowing europium cations incorporation into the Sr3Al2O6 lattice to serve as effective luminescence activators in such a short time during the rapid combustion synthesis process. The higher amount of fuel in the presence of the oxidizing agent produced Sr3Al2O6:Eu particles with higher phosphorescence brightness, owing to the increase of the reduction process from Eu3+ to Eu2+. The synthesized phosphor showed an intense band emission centered at 515 nm and could be excited over a broad spectral range in the UV-visible region. Particles having nanostructured flake-type morphology were obtained, which was considered a micro-nanofunctional candidate for practical applications.

Abstract The objective of this work was to produce brushite cement for orthopedic applications, based on the system wollastonite/phosphoric acid with the incorporation of polyethylene glycol (PEG) as a setting and processing additive. Brushite/PEG cement was obtained by the dissolution-precipitation method and its physicochemical properties were characterized by X-ray diffraction, compressive strength, porosimetry, and biological behavior (cell adhesion and bioactivity tests). The results indicated the formation of brushite cement with 21.4 MPa of compressive strength and 30% porosity, similar to human trabecular bone. The surface was shown to be adequate for cell adhesion and growth and bioactive with the formation of apatite layers. The incorporation of PEG improved working conditions without causing undesirable changes in the physicochemical properties and biological behavior of developed cement, thus promising for the repair of bone tissue injuries.

Resumo A hidroxiapatita (HAp) é um biomaterial cerâmico com ampla aplicação na regeneração óssea. Pode ser obtida por diferentes rotas e diferentes precursores. Neste estudo, a síntese da HAp foi realizada por precipitação e tratamento térmico subsequente utilizando diferentes precursores de cálcio: hidróxido de cálcio de origem sintética e óxido de cálcio obtido da casca do ovo. Os materiais obtidos foram caracterizados por difração de raios X (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia no infravermelho com transformada de Fourier (FTIR). Por MEV, foram observadas variações do tamanho dos cristais e da concentração de aglomerados. Análises por FTIR e DRX comprovaram a formação de HAp e como os precursores (mineral e biológico) influenciaram a microestrutura. O processo de decomposição térmica do óxido de cálcio obtido da casca do ovo mostrou-se mais efetivo para a síntese da hidroxiapatita, resultando em morfologia e microestrutura mais estáveis.

Abstract The hydroxyapatite (HAp) is a ceramic biomaterial with wide application in the bone regeneration. It can be obtained by different routes and different precursors. In this study, the synthesis of HAp was carried out by precipitation and subsequent thermal treatment using different calcium precursors: calcium hydroxide from synthetic origin and calcium oxide obtained from the eggshell. The obtained materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. By SEM, variations of the crystal size and the concentration of agglomerates were observed. FTIR and XRD analyses proved the formation of HAp and how the (mineral and biological) precursors affected the microstructure. The thermal decomposition process of the calcium oxide obtained from the eggshell showed to be more effective for the synthesis of the hydroxyapatite, resulting in more stable morphology and microstructure.

O crescimento da hidroxiapatita - HA, tanto no meio biológico quanto em soluções aquosas como a Synthetic Body Fluid - SBF, ocorre em meio contendo, além dos elementos Ca e P, elementos-traços essenciais tais como: Mg2+, HCO3-, K+ e Na+. Alguns destes elementos são conhecidos como inibidores do crescimento da HA, como Mg2+ e HCO3-. Neste trabalho, estudou-se a influência dos íons K+ e Mg2+ na formação de apatitas sobre substratos metálicos de Ti c.p. previamente tratados com NaOH 5M. Os efeitos destes íons no recobrimento obtidos, antes e após o tratamento térmico a 800ºC, foram analisados por microscopia eletrônica de varredura - MEV, espectroscopia de energia dispersiva de raios-X - EDX, difratometria de raios-X - DRX e espectroscopia no infravermelho - IV e mostraram que o efeito inibitório do Mg2+ na formação da HA se manifesta após o tratamento térmico. Diferentemente, o crescimento cristalino da HA não foi afetado pela presença do íon K+. Além disso, a formação de apatita carbonatada se deu também em soluções que não continham o íon CO3(2-) em sua composição.

The growth of the hydroxyapatite - HA, as much in the biological agent as in watery solutions as the Synthetic Body Fluid - SBF, occurs agent containing, beyond calcium and phosphate elements, essential element-traces such as: Mg2+, HCO3-, K+ and Na+. Some of these elements are known as inhibiting of the growth of the HA, as Mg2+ and HCO3-. In this work, it was studied the influence of ions K+ and Mg2+ in the formation of apatites, mainly of the HA, on metallic substrate of Ti c.p. previously treated with NaOH 5M. The effects of these ions in the obtained covering, before and after the thermal treatment at 800ºC, were analyzed by scanning electron microscopy - SEM, energy dispersive X-rays - EDX, X-ray diffractometer - XRD and Fourier transformation infrared - FT-IR, and they showed that the inhibitory effect of the Mg2+ in the formation of the HA happens after the thermal treatment. Differently, the crystalline growth of the HA was not affected by the presence of the K+ ion. Moreover, the carbonated apatite formation also happened in solutions that did not contain the CO3(2-) ion in its composition.