Effect of nitrogen incorporation on the phase structure, thermal behaviour and structural properties of apatite wollastonite (AW) bioactive ceramics

What is it about?

A powder mixture of SiO2–P2O5–CaO–CaF2–MgO–Al2O3 compound was prepared, and the melt quenching process was employed to obtain apatite wollastonite (AW) bioactive glasses. The mixture was melted in an alumina crucible at a temperature exceeding 1500 ◦C for 1 h under both ambient and protective nitrogen (N2) atmosphere conditions. By using a melt-quenching method, the melted glass was cooled over a critical cooling rate into a graphite crucible. The protective N2 atmosphere resulted in an increase in the indentation fracture toughness (IFT), from 1.54 to 1.72 MPa m1/2, while the hardness of glasses slightly increased from 5.98 to 6.00 GPa. The findings demonstrate that nitrogen not only contributes to the structural organisation but also plays a critical role in driving the thermodynamic stability and microstructural evolution of the system, significantly influencing the specific phase transformation occurring from β-wollastonite to pseudo-wollastonite. This could be considered a critical parameter for future material design and functional applications.

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