This paper presents a historical of the Biosilicate®, a bioactive glass-ceramic developed at the Vitreous Materials Laboratory of the Federal University of São Carlos, Brazil. After decades of study accomplished with bioactive glasses and glass-ceramics, Biosilicate® results from a natural evolution and has similar bioactivity index, but far superior mechanical properties than of all bioactive glasses. Biosilicate® is almost fully crystalline and also exhibits much higher bioactivity than all the currently commercially available bioactive glass-ceramics. Due to its special characteristics, Biosilicate® has been successfully tested for several medical and dental applications as we thoroughly discuss in this review paper

This study reports the oxidation behavior of a Ni-based alloy used in the manufacture of valve seats for automotive engine exhaust systems. Isothermal thermogravimetric analyses were carried out at temperatures of 660, 740, 860, and 900 °C under an oxygen atmosphere for up to 1 h. At 660 and 740 °C, only one stage was observed during the whole time studied. At this stage, the oxide layer was formed mainly by NiO + Cr₂O₃, following a linear oxidation law with a rate constant (K_l) on the order of magnitude of 10⁻⁶ kg/m²s and an apparent activation energy (E_a) of ~47 kJ/mol. At 860 and 900 °C, an identical first stage was observed with a transition to a different stage. In the second stage, the oxidation layer was composed of Cr₂O₃, and a parabolic oxidation law was followed with a rate constant (K_p) on the order of 10⁻⁸ kg²/m⁴s and E_a of ~128 kJ/mol. Moreover, the Ni-based alloy formed a dense and compact oxide layer after oxidation, with no apparent cavities, pores, or microcracks. Characterization techniques such as Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Raman Spectroscopy were carried out to characterize the formed oxide layer.