MARIANA SILVA DE ARAUJO
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Artigo IPEN-doc 28337 In vitro bioactivity and antibacterial capacity of 45S5 Bioglass®-based compositions containing alumina and strontium2021 - ARAUJO, M.S.; SILVA, A.C.; CABAL, B.; BARTOLOME, J.F.; MELLO-CASTANHO, S.A modified 45S5 Bioglass® containing 2 mol% alumina and 2 mol% strontium oxide was prepared. In vitro bioactivity in powder and monolithic samples was conducted. Fourier transform infrared analysis and pH change in simulated body fluid were investigated for powder samples after 480 min of immersion. Additionally, X-ray diffraction and scanning electron microscopy after 7 and 14 days of immersion in simulated body fluid were investigated for monolithic samples. The formation of phosphate and carbonate phase precursors of hydroxycarbonate apatite was observed after 480 min for powder samples, and the hydroxycarbonate apatite pattern and morphology were confirmed after 7 days of immersion for monolithic samples. It seems that changes in composition did not affect reactivity but caused a decrease in the maxima of pH. Cytotoxicity and cell viability obtained by using the NCTC clone 929 cell line did not show any significant loss of cell viability or cytotoxicity. Moreover, after overnight incubation, the samples demonstrated safe disinfection for Escherichia coli. For these reasons, the use of these new bioactive glasses can be considered a promising alternative for the reconstruction of bone defects and even for the treatment and suppression of bone infections.Artigo IPEN-doc 27172 Tribological and mechanical behaviour of 45S5 Bioglass®-based compositions containing alumina and strontium2020 - ARAUJO, M.S.; BARTOLOMÉ, J.F.; MELLO-CASTANHO, S.Although bioactive glasses have been widely used for the surfaces of orthopaedic and dental implants, its limited mechanical strength, low toughness and wear resistance have prevented their use as load-bearing devices. Considering that even a small variation in the composition of such materials can deeply modify their features, inducing very different physicochemical or mechanical properties, the present research was conducted by modifying the glass network of 45S5 Bioglass® by adding Al2O3 and SrO to obtain a highly bioactive glass with improved mechanical and tribological performance for biomedical applications. The addition of 2% Al2O3 and 2% SrO produced a dense material with the same elastic modulus as 45S5 (~50 GPa). Moreover, the bending strength increased by 60% and the toughness doubled. The wear rate obtained against steel was found to be three times lower than that of 45S5. From the results, it can be assumed that both alumina and strontium synergistically play crucial roles in the mechanical and tribological properties of these new bioactive glasses.Artigo IPEN-doc 27160 Structural and thermal behavior of 45S5 Bioglass®-based compositions containing alumina and strontium2020 - ARAUJO, MARIANA S.; SILVA, ANTONIO C.; BARTOLOMÉ, JOSÉ F.; MELLO-CASTANHO, SONIAThe present research exposes the influence of 2 mol% of Al2O3 and 2 mol% SrO in 45S5 Bioglass®-based compositions. Four compositions were produced to elucidate the difference in how both oxides influence structure and thermal behavior separately and their synergy when together. Thermal properties, crystallization tendency, and sintering behavior was evaluated by differential scanning calorimetry, hot stage microscopy, and dilatometry. Changes of medium-range structures were characterized by Qn distribution of Raman spectroscopy and evaluation of 31P, 27Al, 23Na, and 29Si environment obtained by magic angle spinning nuclear magnetic resonance. Despite Qn distribution was predominantly Q2 in all samples, the composition criteria used enabled improved processing and stabilibity characteristics. The addition of Al2O3 and SrO promoted larger sinterability parameter (Sc) which indicates better sintering behavior, the glass stability against crystallization doubled (KH) compared to 45S5 and the processing window enlarged from 106 to 171.Artigo IPEN-doc 26431 Double line waveguide amplifiers written by femtosecond laser irradiation in rare-earth doped germanate glasses2020 - SILVA, DIEGO S. da; WETTER, NIKLAUS U.; KASSAB, LUCIANA R.P.; ROSSI, WAGNER de; ARAUJO, MARIANA S. deWe report the production of active double waveguides in Er/Yb doped GeO2-PbO glasses, by direct femtosecond laser writing. The glasses were produced using the melt-quenching technique and the active waveguides were written using 30 fs laser pulses, at 800 nm, with writing speed of 0.06 mm/s and pulse energy of 32 μJ. The photo-induced negative refractive index change was of 7.4 � 10 3. The Er/Yb doped sample showed a relative gain (signal enhancement of 7.5 dB/cm, for 105 mW of 980 nm pump power. The relative gain compensates both, the propagation losses and the absorption losses, and a positive maximum internal gain of 4.6 dB/cm can be obtained at the signal wavelength of 1550 nm. The results obtained in present work demonstrate that Er/Yb glasses are promising materials for the fabrication of integrated amplifiers, lossless components and lasers based on germanate glasses.