https://repositorio.ufba.br/handle/ri/4907 2026-05-03T20:35:36Z https://repositorio.ufba.br/handle/ri/18089 Título: The structural role of Ti in a thermally-treated Li2O − B2O3–Al2O3 glass system Autor(es): Silva, V. A.; Nascimento, M. L. F.; Morais, P. C.; Dantas, Noelio Oliveira Abstract: A 50Li2O·45B2O3·5Al2O3 (LBA, in mol%) glass matrix doped with increasing TiO2 content was synthesized and its physical properties were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and Raman spectroscopy. The thermograms showed typical vitreous curves with two clear crystallization peaks that are related to major crystalline phases in this glass system and in agreement with XRD results. The higher temperature crystallization peak (TC2) shifted towards the lower temperature peak (TC1) as TiO2 content increased. After specific heat treatments, the XRD measurements revealed the α-LiBO2, γ-LiAlO2 and LiTiO2 crystalline phase formations and the predominance of the first phase. The γ-LiTiO2 phase was particularly responsible for the variation in the second peak crystallization kinetics. In addition, crystal growth phase competition between γ-LiAlO2 and LiTiO2 occurred as TiO2 content increased; however, the main α-LiBO2 phase did not change. Raman spectra showed typical phonon modes associated with crystalline phases observed in XRD and main phases observed in DTA. Phonon modes were also associated with the LiTiO2 crystalline phase that was first observed in the glassy matrix. Tipo: Artigo de Periódico 2014-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/17180 Título: Solubility and solubility modeling of polycyclic aromatic hydrocarbons in subcritical water Autor(es): Teoh, Wen Hui; Mammucari, Raffaella; Melo, Silvio Alexandre Beisl Vieira de; Foster, Neil R. Abstract: A static analytical equilibrium method was used to measure the binary and ternary solubilities of anthracene and p-terphenyl in subcritical water between 393 and 473 K and at 50 and 150 bar. Temperature was found to have the most significant effect on the solubility of polycyclic aromatic hydrocarbons (PAHs) in subcritical water. The effect of pressure, and the combined effect of temperature and pressure on solubility were found to be insignificant, particularly when the range of pressure considered is relatively small. The solubilities of PAHs were found to be governed primarily by sublimation pressure, and only secondarily by the dielectric constant of water. The Peng–Robinson equation of state was used to correlate the aqueous solubilities of PAHs under subcritical conditions, with good agreement between experimental and calculated values obtained for binary systems. Tipo: Artigo de Periódico 2013-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/17175 Título: Evaluation of the chemical stability of a landfilled primary lead smelting slag Autor(es): Lima, Luiz Rogério Pinho de Andrade; Bernardez, L. A. Abstract: A primary lead smelter operating in Santo Amaro, Bahia, Brazil, from 1960 to 1993 generated a large amount of slag that was landfilled close to the former smelter and used in roads and houses as a construction material. To evaluate the stability of the slag classical leaching procedures (TCLP, SWEP and SPLP) were applied. In addition, samples of the slag were placed in contact with HCl, HNO3, HOAc and NaOH solutions for about 24 h at room temperature to simulate acidic and alkaline environments over a wide pH range. In the acidic environment Ca, Fe and Si are strongly solubilized, and Pb and Zn solubilization was significant only below pH 3. The lead slag was also in contact with purified water for a period of 30 days. The results show that Ca and Si were solubilized and Pb, Fe, and Zn were not detected in the solution. The solubilization kinetics are second order processes for both Ca and Si. The initial solubilization rate for Ca and Si are 4.6 and 0.6 mg/L/day, respectively. The main implication of these results is that the major potentially toxic elements of the lead slag landfilled at Santo Amaro were stabilized for a short contact time with pure water and for alkaline and acidic solutions to a pH of about 3 and the groundwater and the surface water contamination found at Santo Amaro smelter region cannot be directly attributed to the landfilled lead slag. Tipo: Artigo de Periódico 2013-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/16249 Título: Cassava sarch-based films plasticized with sucrose and inverted sugar and reinforced with cellulose nanocrystals Autor(es): Silva, Jania B. A. da; Pereira, Fabiano V.; Druzian, Janice Izabel Abstract: Bionanocomposites films of cassava starch plasticized with sucrose and inverted sugar and reinforced by cellulose nanocrystals (CNCs) were prepared by solution casting method incorporating 0.1 to 5 wt% of eucalyptus CNCs. The nanocrystals were characterized using transmission electron microscopy, whereas the bionanocomposites properties were studied using Fourier transform infrared spectroscopy, tensile measurements, water solubility, swelling behavior, and water activity (aw). The water resistance properties (solubility and swelling behavior) of the nanocomposites were enhanced with the addition of cellulose nanofillers. These results were explained in terms of the high crystallinity of the nanocrystals and the formation of a rigid network with the nanofillers, which provide physical barriers to the permeation of water within the hydrophilic cassava matrix. The addition of CNCs in the bionanocomposites decreases aw linearly, reaching values below 0.5 (for CNCs concentration higher than 4 wt%), a reference value for no microbial proliferation for food product design. The presence of small concentrations of CNCs (0.1–0.3 wt%) also effectively increased the maximum tensile strength (more than 90%) and elastic modulus (more than 400%), indicating the formation of a suitable percolation network in this concentration range. Because the cellulose nanofillers enhanced the mechanical and water stability properties of the nanocomposites, the obtained results in this work may be applied to the development of biodegradable packaging or coatings to enhance shelf life of food products. Tipo: Artigo de Periódico 2012-01-01T00:00:00Z