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The objective of this work is the production and characterization of glass-ceramic with recycled glass powder and 4% (w/w) of cerium dioxide. Eleven groups were defined with conformation pressure of 11.6 and 25.8 MPa, and cerium dioxide addition. The sintering temperatures of 650, 675, 700 and 750 °C were used. The raw material was formed into a mold with a uniaxial pressure. The density was measured by the Archimedes principle. The water absorption of the groups was also determined, as linear contraction percentage and the crystalline structure. The flexural strength was obtained by the three-point bending test and the results analyzed by the Weibull analysis. The specimens presented density ranging from 1.99 to 2.38 g/cm3. Increasing the temperature provided an increase in the density of the specimens and the flexural strength. At higher sintering temperature, this behavior was not observed. The highest flexural strength was 63.55 MPa, obtained at the sintering temperature of 700 oC, conformed with 25.8 MPa, only glass powder. The increase in the forming pressure favored crystallization. The addition of cerium dioxide favored for the increase density and the Weibull modulus, but decrease of the flexural strength. Keywords: Glass-ceramic, Flexural Test, Weibull Analysis, Wasted Glass recycling and Cerium Dioxide.

Composite cellulose acetate (CA) membranes are widely used but their multiphase nature results in additive losses, poor mechanical strength, low chemical resistance and thermal stability, limiting their separation/purification yields. To overcome this, we fabricated monophasic hybrid membranes using a modified phase inversion technique, where tetraethylorthosilicate and 3-(aminopropyl)triethoxysilane were added to the CA casting solution. The resulting co-polymerization between CA, silanols and amine-functionalized silica groups, through sol-gel chemistry, was proved by ATR-FTIR (1118 cm−1, ν(Si O C)). The presence of propyl-amine groups increases the hydraulic permeability (3×), the rupture elongation (×1.5), and decreases the Young modulus (×1/2), due to the disruption of the CA-silica 3D network. For high propyl-amine contents this behaviour is reversed due to intensive cross-linking between CA-silica chains (decrease in 903 cm−1, ν(CH3COOC-)). The addition of silica- and amine-based structures to the CA framework increases the system degrees of freedom, opening the door to the design of new CA membranes.

Bioceramics used in biomedical applications must exhibit specific behaviors. In scaffolds, for instance, the degradability of bioceramics is important to allow the cell ingrowth. Therefore, the dissolution of calcium phosphates increases the ionic concentrations around the interface implant–bone, favoring a more rapid bone apposition to the graft surface. The dissolution takes place under static or dynamic conditions, but the latter is usually not performed under rigorous hydrodynamic control. In the present work, two bioceramics, β-tricalcium phosphate and β-tricalcium phosphate substituted by magnesium, were produced by pressing and sintering to form disks. They were characterized by XRD, Raman, ICP, SEM, AFM and photometric test. The influence of chemical composition in the dissolution test was conducted through strict control of the hydrodynamic conditions. The disks were rotating in a precise speed, in order to produce a dissolution under the well-controlled mass transfer. Subsequently, the calcium release was evaluated in a simulated infectious environment using pH equals to circa 4. Thus, it was possible to evaluate the fraction of dissolution related to mass transfer or surface reactions for a large rotation speed range. The magnesium added to the bioceramic inhibits the total dissolution when compared to pure tricalcium phosphate, probably related to more dense and less soluble ceramic. Moreover, the mass transfer affects relatively less the magnesium tricalcium phosphate than pure tricalcium phosphate.

Simulated body fluids — SBF solutions are useful to evaluate bioactivity as well as to change the surface response of materials not considered fully bioactive. Several simulated body fluids produce similar results during precipitation stage, and an attempt to standardize a specific solution was recently made [T. Kokubo, H. Takadama, Biomaterials. 27, [T. Kokubo, H. Takadama, How useful is SBF in predicting in vivo bone bioactivity?, Biomaterials. 27, (2006) 2907–2915.]]. Moreover, several protocols include buffers as Tris or Bistris to maintain pH near physiological range. Using buffered solutions, two additional reactions may occur for each alkaline earth ion, namely protonation and alkaline earth metal ion complexation. Therefore, the new species Ca(Tris) 2+ and Ca(Bistris) 2+ modify the free Ca content in fluid and consequently the Ca(free)/P ratio, influencing the stoichiometry of precipitated phosphate. In this paper, we theoretically investigated calcium/buffer interactions for two types of SBF, standard and simplified, in terms of thermodynamic parameters such as activity coefficients, ion activities, and free Gibbs change energy for hydroxyapatite precipitation. Our results show that Tris and Bistris buffers reduce the content of available calcium ion, with a stronger trend towards Bistris. Besides, high pH increases the calcium complexation effects.