Navegando por Palavras-chave "Óxido De Nióbio"

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    Avaliação do biovidro 45S5 modificado com Nb+5 na fabricação de arcabouço para engenharia tecidual
    (Universidade Federal de São Paulo (UNIFESP), 2019-02-18) Siqueira, Lilian De [UNIFESP]; Triches, Eliandra De Sousa [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Currently, various types of alloplastic grafts, known as scaffolds, have been developed for the treatment of bone defects caused by trauma and/or infection. Among the materials used to manufacture scaffolds, the 45S5® Bioglass stands out due to its excellent bioactivity and ease of preparation. This bioglass has the ability to form chemical bonds with both soft tissues (cartilages) and hard tissues (bones). Among the various processing methods cited in the literature for the production of bioactive glass scaffolds, gelcasting is a method that produces macroporous structures with interconnected and spherical pores and good mechanical strength. However, there are few reports in the literature about bioactive glass scaffolds produced by the gelcasting method. In the present work, bioglass derived from 45S5® (BG45S5) and 45S5® modified with niobium (Nb+5) (BGNb5 and BGNb10) were manufactured by fusion/cooling technique and used to manufacture scaffolds by gelcasting method for tissue engineering applications. The obtained bioglass were characterized by X-ray fluorescence (FRX), particle size by laser diffraction and differential scanning calorimetry (DSC). The obtained bioglass showed chemical composition close to the nominal ones and exhibited particle size ˂ 7 μm. A change in the profile of the DSC curves in relation to Tg and Tc of the bioglass can be observed due to the addition of Nb2O5 in the bioglass composition. Then, different thermal treatments (500 - 1000 ºC) were carried out in the bioglass to study the effect of the addition of Nb2O5 on the structural properties of the BG45S5 bioglass during the calcination process. To this end, the following investigations were performed: X-ray diffractometry (XRD), Fourier Transform Infrared (FTIR) spectroscopy and RAMAN spectroscopy. The MTT test was performed to select the best composition for the scaffolds. The bioglass presented a vitreous characteristic after the synthesis process, as well as the formation of the main crystalline phases: Na2CaSi2O6 and NaNbO3 after heat treatment. FTIR and Raman spectroscopy allowed a detailed understanding of the bioglass structure. For the BGNb's, the NbO6 octahedron enters the silicate network, sharing its vertices with the silicon tetrahedra to form O-Si-O-Nb-O-Si-O chains. The results of in vitro bioglass studies on the viability of osteoblasts show significant differences between BG45S5 and BGNb's. The BGNb10 bioglass presented better cell viability compared to BG45S5 and BGNb5. Thus, BG45S5 and BGNb10 bioglass scaffolds were prepared by the gelcasting method, where different amounts of foaming agent (0.1, 0.2 and 0.3% by mass) were tested. The obtained scaffolds were characterized by scanning electron microscopy (SEM), X-ray microtomography, X-ray diffractometry (XRD),mechanical resistance to compression and in vitro biological assays. The scaffolds produced presented macroporous structures, with interconnected and spherical pores. The BG45S5 bioglass scaffolds showed porosity between 70.7 ± 0.8 – 86.0 ± 1.2 % and compressive strength of 1.22 ± 0.7 and 0.78 ± 0.4 MPa, while BGNb10 bioglass scaffolds showed 89.2 ± 1.4 % porosity and compressive strength of 0.18 ± 0.03 MPa. In in vitro biological studies, all scaffolds showed cytocompatibility for human osteoblastic cells and bioactive properties using the SBF assay. However, BGNb10 bioglass scaffolds show a tendency for higher alkaline phosphatase activity (ALP) and higher degradation than BG45S5 bioglass scaffolds. Thus, the biological evaluation suggests a viable application of the macroporous scaffolds of BGNb10 bioglass for applications in the regeneration of the bone tissue.
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    Síntese, caracterização e aplicações de materiais híbridos de óxido de nióbio (Nb2O5)
    (Universidade Federal de São Paulo (UNIFESP), 2021) Santos, Marconi Da Cruz [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São Paulo
    The objective of this thesis was to propose new methods of producing hybrid materials of niobium oxide. In the first chapter, the preparation of hybrid materials of niobium oxide and conducting polymers was investigated using an unconventional niobium precursor, the niobium peroxo-oxalate complex. The hybrid materials obtained from the oxidation of aniline are composed of polyaniline in its most conductive form (the emeraldine salt form), containing oxalate as a doping anion, with Nb2O5 nanoparticles homogeneously dispersed in the polymeric matrix. The electrical conductivity ranged from 10-2 to 10-3 S cm-1 , which is three orders of magnitude greater than that observed for pure Nb2O5. The photocatalytic activity was investigated using the standard decolorization reaction of the methylene blue dye (MB) in aqueous solution. The hybrids showed better MB adsorption capacity and were more effective in discoloring the solution under visible light than pure Nb2O5. In the second chapter, the preparation of nonmodified cellulose membranes containing niobium oxide nanoparticles was proposed. In this approach, ionic liquids were used in the nanoscale synthesis of niobium oxide and in the immobilization of these particles in cellulose membranes. Using a simple methodology, transparent cellulose membranes containing nanostructured niobium oxide without segregation of organic and inorganic phases were obtained. The hybrid membranes were evaluated as photocatalysts for degradation of methylene blue dye in aqueous medium, showing a greater capacity for adsorption of the dye and later the discoloration of the solution under UV light irradiation.