Abstract Automotive windshield represents a large volume of solid waste due to limited recycling. Glass-ceramics were produced from discarded windshields with Nb2O5 as a nucleating agent at concentrations of 0, 5, 10, and 15 wt% at 700 and 800 °C sintering temperatures. Mechanical and electrical characterizations of glass-ceramics were performed. Equibiaxial flexural strength was performed and related to porosity. At 700 °C, Nb2O5 favors the monoclinic NaNbO3 phase with perovskite structure. At 800 °C, high Nb2O5 content formed crystalline phases of perovskite and quartz. Dielectric constant and electrical conductivity increased with the addition of Nb2O5, reaching 64 and 4.3 μS/m for 15 wt% Nb2O5 at 700oC. At 800oC, niobium pentoxide reduces the biaxial flexural strength from 28.7 to 14.4 MPa; while increasing the electrical conductivity from 0.10 to 0.33 µS/m for samples with 0 and 15 wt%.

In this work we synthesized pigments capable of developing dental shades when mixed with dental porcelain and fired at appropriate temperatures. TiO2-xCeO2 pigments (x = 2, 6, 10, 13 and 18 mol%) were synthesized by the Pechini method. Characterization by thermal analysis revealed the stability of the material at temperatures up to 1200 ºC. X-ray diffraction showed stable crystalline phases (rutile to TiO2 and cerianite to CeO2) for all pigments studied. Color of pigments was characterized by colorimetric coordinates according to the CIELAB method and reflectance measurements in the visible region. Through colorimetric analysis it was possible to verify the potential use of these pigments in dental ceramics.

Soluções simuladoras do fluido corpóreo (SBFs) são usadas em avaliação de biocompatibilidade de biomateriais e também como processo de recobrimento alternativo à aspersão por plasma. Processos biomiméticos ocorrem heterogeneamente sobre superfícies metálicas; portanto, o uso da técnica de microeletrodo é muito recomendável para detectar mudanças na superfície. Neste trabalho, o pH local foi monitorado durante as primeiras 44 h de deposição de fosfato de cálcio em amostras de titânio com uma solução SBF simplificada. Dados tridimensionais (pH local, coordenadas x-y) foram empregados para simular as concentrações de equilíbrio para todas as espécies químicas. Baseadas nestas quantidades, foram calculadas as supersaturações relativas e variações de energia de Gibbs para hidroxiapatita e fosfato octacálcico. A abordagem experimental e teórica conjunta sugere que nem a alcalinidade local nem a concentração de cálcio livre fornecem um cenário adequado sobre a condição de precipitação, mas o uso simultâneo produz resultados interessantes não obtidos com somente uma delas.

Simulated body fluids (SBFs) are largely used as biocompatibility screening and also as an alternative process to the plasma spray coating. Biomimetic processes occur heterogeneously on metallic surface; therefore, the use of a microelectrode technique is highly advisable to detect surface changes. In this work, the local pH was monitored during the first 44 h of deposition of calcium phosphates on titanium samples with a simplified SBF solution. Three-dimensional data (local pH, x-y coordinates) were used to simulate equilibrium concentrations of all species. Based on these quantities, relative supersaturations and Gibbs energy variations of hydroxyapatite and octacalcium phosphate were evaluated. The conjoint experimental and theoretical approach suggested that neither local alkalinity nor free calcium concentration alone produces an adequate scenario of precipitation conditions, but the use of both procedures results in interesting findings not achieved using only a single approach.