DANILO LOPES COSTA E SILVA
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Resumo IPEN-doc 25492 Structural reinforcement of Nb2O5 in soda-lime borosilicate glasses for nuclear waste immobilization2018 - SILVA, D.L.C.; SILVA, A.C.; ARAUJO, M.S.; MELLO-CASTANHO, S.R.The vitrification process has been used for high level nuclear waste (HLW) immobilization for more than 40 years around the word. However, there are still many difficulties involving the radiation effects in the glass matrixes as, for example, crackings that reduce their mechanical and chemical resistance. The impact of Nb2O5 addition in the CaO-Na2O-SiO2-B2O5 glass system was investigated. The glass samples, produced by melting method, were submitted to extreme chemical attacks like the alkaline ISO 695-1984 (E), the acid DIN 12116-1976 and characterized by X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR) and Raman Spectroscopy. XRD diffraction patterns obtained before the chemical attacks confirmed the vitreous character of the samples. Raman spectra and FTIR spectra obtained after the chemical attacks indicated that the Nb2O5 is well connected to the glass network, supported by the decrease in mass loss after the chemical attacks, as the the Nb2O5 content was raised in the samples. These results are indicative that the chemical resistance of the studied glasses can be improved by increasing the Nb2O5 content. These results show that the process is a promising alternative to produce new family of the appropriate glasses for nuclear wastes immobilization.Resumo IPEN-doc 25491 Variations of Qn distribution in bioactive glasses containing strontium oxide and alumina2018 - ARAUJO, M.S.; SILVA, A.C.; SILVA, D.L.C. e; MELLO-CASTANHO, S.R.The complexity in designing brand-new compositions as 45S5 Bioglass® is mainly due to the fact the more components you have, the more difficult it is to trace the relationship between composition, structure and bioactivity. Also, the properties of bioactive compositions reflect their ability to release a critical amount of different ions in the surrounding host tissue, creating or not favorable conditions to stimulate cellular processes. Since these properties and process of interaction are directly related to the glass network connectivity, which can be evaluated by Qn distribution and other medium-range structural techniques, the present research studied two series of compositions based on 45S5 however adding amounts of Al2O3 and SrO, to verify the impact of subtle compositional changes in the Qn distribution. The samples were obtained by melting (1500°C) and quenching and characterized by X-ray diffraction (XRD), differential thermal analysis (ATD), Fourier transform infrared (FTIR) and Raman spectroscopy. The initial results indicates that the matrix of typical bioactive phospho-silicate glasses which consists to be mostly Q², with some Q³, structures have been maintained in samples containing only SrO (0-2,7%mol). However, the samples containing both Al2O3 (2%mol) and SrO (0-2,7%mol) indicates that the addition of 1%mol SrO there is an increase of Q² in detriment of Q³, but then when the addition is up to 2,7%mol there is a decrease of Q² inversely proportional to Q³. Although these changes have been presented, none of the samples of both series presented cytotoxicity. Furthermore, studies on biocompatibility are being conducted to evaluate its impacts on their bioactivity.Resumo IPEN-doc 22914 Multifunctional bioactive glasses for tissue regeneration: compositions modified with strontium oxide2017 - ARAUJO, M.S.; SILVA, A.C.; SILVA, D.L.C. e; MELLO-CASTANHO, S.R.H.The complexity in designing brand-new compositions as 45S5 Bioglass® is mainly due to the fact the more components you have, the more difficult it is to trace the relationship between composition, structure and bioactivity. Also, the properties of bioactive compositions should reflect directly their ability to release a critical amount of different ions in the surrounding host material, creating or not favorable conditions for the cellular processes. The present research was conducted by modifying the glass network of 45S5 by adding Al2O3 and SrO in order to obtain a multifunctional glass for biomedical applications, i.e. a not only with bioactive properties as osteoinductive and also biocidal. Three series of compositions were produced to optimized the amounts of both oxides, thus, minimizing undesirable effects and enhancing the mobility of Ca2+ cations due to the rearrangement of the glass network. The samples were obtained by melting (1500°C) and quenching and characterized by X-ray diffraction (XRD), differential thermal analysis (ATD), Fourier transform infrared (FTIR) and Raman spectroscopy. The initial results indicates that the vitreous network is predominantly of Q3 arrangements in detriment of the typical 45S5 Q2 structure. And, the FT-IR and Raman spectra are similar to glasses with adequate solubility and bioactivity for the interaction between the implant and the host.