resumo
Glass and glass-ceramics with the compositions 1Fe(2)O(3)-99SiO(2) (1Fe), 2Fe(2)O(3)-98SiO(2) (2Fe), 1MnO-99SiO(2) (1Mn), 2MnO-98SiO(2) (2Mn), 1MnO-1Fe(2)O(3)-98SiO(2) (2MnFe), 2MnO-2Fe(2)O(3)-96SiO(2) (4MnFe) (mol%) were prepared using the sol-gel method. The gel samples were heat treated between 120 and 1000 degrees C. Thermogravimetric and differential thermal analysis (TG-DTA), ultraviolet, visible and near infrared spectrophotometry (UV-Vis-NIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (SEM-EDS) were used to study the structural changes that occur during the gel to glass and glass-ceramic conversions. Many of the prepared glass and glass-ceramics present brown or black colorations. These dark colorations are due to the presence in the samples of maghemite-C, magnetite, hematite, Mn3O4 (bixbyite) and Mn2+(Mn3+)(14)SiO24 (braunite) or simultaneously more than one of these crystalline phases. These nano particles give to the samples very interesting magnetic and optical properties of great importance in several medical fields. Furthermore, the study contributed to understanding the formation mechanism of some MnO and/or Fe2O3-containing silicate glasses and glass-ceramics prepared by the sol-gel method. (C) 2016 Elsevier B.V. All rights reserved.
palavras-chave
THERMAL-DECOMPOSITION; IRON; NANOCOMPOSITES; PRECIPITATION; FERRIHYDRITE; PRECURSORS; MECHANISM; GOETHITE; FE2O3; OXIDE
categoria
Materials Science
autores
da Silva, MGF
nossos autores
Maria Gracinda Ferreira da Silva
Professor AuxiliarGrupos
agradecimentos
I would like to thank Carlos Capela (student) for the help in the preparation of the dried gel samples. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the YI2020 Partnership Agreement.