Effects of nitrogen on properties of oxyfluoronitride bioglasses

Bioglasses are used as bone substitutes and prosthetic coatings. Following implantation, they are predisposed to generate a series of physicochemical reactions at the glass-bone interface. Bioglasses with molar composition: 55SiO2–8.5CaO–31.5Na2O–5CaF2 have been synthesized and characterized. However, because of their poor strength, doping with nitrogen was performed on these glasses to increase their mechanical properties. These glasses were chemically analyzed to verify the amount of nitrogen introduced and structurally characterized by 29Si and 19F MAS NMR. The fluorine complexes with calcium and sodium and is present as mixed calcium sodium fluoride and sodium fluoride species. The addition of fluorine to bioglasses reduces the melting temperature which helps to minimize nitrogen loss and bubble formation. So the fluorine facilitates the dissolution of nitrogen into the melt. Nitrogen substitutes for oxygen in the silicate network and is present as SiO3N and SiO2N2 structural units. The density, glass transition temperature, Young's modulus, hardness and fracture toughness all increase with the content of nitrogen introduced into the glasses. These changes are a result of greater cross-linking of the silicate network due to the higher coordination of nitrogen compared to oxygen.

► Bioglasses are used such as bone substitutes.
► Doping with nitrogen of oxyfluoronitride glasses allows to increase the mechanical properties.
► Nitrogen substitutes for oxygen in the glass network as SiO3N and SiO2N2 units.
► SiO3N and SiO2N2 units are responsible for improving the properties mechanical.