Efeito do manganês sobre a estrutura cristalina da hidroxiapatita

• Ano de defesa: 2021
• Autor(a) principal: Oliveira Júnior, Paulo Henrique
• Orientador(a): Santos, Euler Araujo dos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Ciência e Engenharia de Materiais
• Palavras-chave em Português: Ciência dos materiais; Hidroxiapatita; Óxidos de manganês; Nanopartículas magnéticas; Óxido de manganês; Estrutura cristalina
• Palavras-chave em Inglês: Hydroxyapatite; Manganese oxide; Magnetic nanoparticles; Crystalline structure
• Área do conhecimento CNPq: ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: https://ri.ufs.br/jspui/handle/riufs/15077

Manganese (Mn) can develop magnetic properties in substituted hydroxyapatites (HA), as well as iron, copper, cobalt and samarium, but with the advantage of controlling several cellular activities. The occupation of the HA sites by Mn and its segregation from HA structure during heat treatments can affect magnetic properties. For this reason, the objective of this work was to study the accommodation of Mn into a carbonated HA, and its segregation mechanism at temperatures above 800°C yielding Mn3O4 nanoparticles. HAs with five different concentrations of Mn in relation to calcium were synthesized by the aqueous precipitation method: (Mn/(Mn+Ca) = 0, 5, 10, 15 and 20 at. %. Using wavelength dispersion X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, it was possible to demonstrate that Mn was inserted into the HA structure in all concentrations, strongly compromising its crystalline structure. The regions around the hydroxyl channels were affected the most, with clear evidence of preferential Ca2 sites occupation, especially in the samples with a high content of CO3 2- replacing PO4 3- . When carbonate was released at high temperature and the crystallinity increased, the Ca1 sites seemed more susceptible to occupation by Mn. At temperatures above 1000°C, Mn segregated from the HA structure in the form of Mn3O4 nanoparticles, via hydroxyl channels, preferentially occupying Ca2 sites at the final segregation stage. The presence of Mn in several oxidation states also suggested that, in addition to the cationic substitutions, there were also anionic substitutions such as MnO4 3- at the PO4 3- sites. No cytotoxicity was detected for the lower concentration of Mn regarding osteoblastic cells. These results contributed to clarify the Mn behavior into HA and its segregation, being fundamental to the development of new strategies to synthesize magnetic-active hydroxyapatite-based scaffolds in the future.